Neuroradiology 1,4-19(I970)

Differential Diagnosis of Fourth Ventricle Tumors from Brain Stem Tumors in Angiography* Yu~ PENG HuA~O and BERNARD S. WOLF Department of Radiology, Mount Sinai Hospital and Mount Sinai School of Medicine, New York, N.Y. 10029 Summary. 1. Normal arteriographic and venographie anatomic landmarks of the posterior fossa are described. 2. Differential diagnostic features between fourth ventricle tumors and brain stem tumors are described with illustrations of aetual eases. 3. If angiographie features are inconclusive, air or positive contrast studies may be performed expeditiously for further elucidation of the specific problem. Angiographie features of fourth ventricle tumors and of brain stem tumors have previously been described in some detail [12, 13]. Differential diagnosis is of great clinical importance since direct operative treatment is often feasible in fourth ventricle tumors and contraindicated in brain stem turnouts. Differential diagnosis must be based not only on displacements of larger arteries but also of small arteries and veins in the posterior fossa. Therefore, excellent visualization of posterior fossa vessels is a pre-requisite in angiographic diagnosis in these eases. Satisfactory opaeification with minimal complications can usually be achieved by performing bilateral retrograde braehial angiography using two pressure injectors, one on each side, with a quarter-second delay on the left side and with manual compression of the.right carotid artery in the neck. Angiographic Anatomic Landmarks in the Arterial Phase Arteries of importance in diagnosis (Fig. I) include : (1) basilar artery, (2) distal portion o f t h e vertebral artery, (3) various segments of the posterior inferior cerebellar artery [2, 4, 12, 16] (especially the posterior medullary, supratonsillar, superior retrotonsillar segments and the posterior medullary segment of the tonsillo-hemispheric branch), (4) various segments of the superior eerebellar artery [10] (the prepontine, lateral pontine, anterior superior marginal, anterior culminate and vermian segments), (5) the precentral cerebellar artery [10] (especially its fissural segment), (6) eircum-mesencephalie portion of the posterior cerebral artery, (7) eisternal and parenehymal segments of the thalamo-perforating arteries [5], (8) transverselyrunning pontine arteries, (9) medial posterior ehoroidal arteries [3, 13] (especially its eireumpeduneular, tectal and preteetal segments), and (10) the anterior and posterior spinal arteries. Of these, arteries which outline the anterior aspect of the brain stem are the anterior spinal arteries, distal portion of vertebral artery, basilar artery, pontine arteries, thalamo-perforating arteries and proximal portions of the superior eerebellar, the posterior eere* Contribution of the 1st European Colloquium for Neuroradiology, September 6, 1969 Colmar

bral, and medial posterior ehoroidal arteries. Arteries which outline the posterior aspect of brain stem include the posterior spinal arteries, posterior medullary segments of the posterior inferior eerebellar artery and of the tonsillo-hemispheric branch, and the tectal segment of the medial posterior ehoroidal artery. The precentral eerebellar artery, a branch of the superior eerebellar artery, outlines the roof of the upper part of the fourth ventricle and together with the anterior culminate segment [10] of the superior eerebellar artery, constitutes a landmark for the anterior superior aspect of the superior vermis and posterior border ol the inferior colliculi. The distance (lateral view) between the superior retrotonsillar and posterior medullary segments of the posterior inferior eerebellar artery, also indicated by the bridging supratonsillar segment, is a measure of the antero-posterior diameter of the body of the eerebellar tonsil and corresponds to the height of the fourth ventricle, or more exactly the height of the posterior superior recess of the fourth ventricle [12]. Occasionally, the supra-tonsillar segment of the posterior inferior eerebellar artery may be replaced by a more medially and inferiorly located medial tonsillar segment [12]. This anatomical variant should not be confused with an inferiorly displaced supratonsillar segment. The basilar artery, in most eases, lies immediately on the anterior aspect of the pons. It may, however, be located within the pontine cistern and be considerably separated from the anterior aspect of the brain stem [9]. In such cases, transverse pontine arteries and the eisternal segments of the thalamo-perforating arteries may outline the anterior aspect of the brain stem and interpeduneular fossa more accurately. In some eases, the vermian branch of the superior eerebellar artery may not run in the midline and therefore appears unusually separated from the straight sinus in the lateral view. It should be emphasized that the lateral medullary segment of the posterior inferior eerebellar artery may be located anywhere in the eerebello-medullary fissure. It may be located in the upper end of the cerebellomedullary fissure or as far down as the upper cervical canal. When it is located high, it takes a more lateral areuate course as it goes around the wider upper part of the medulla oblongata. The course of the posterior medullary segment in relation to the posterior medullary aspect of the tonsil is somewhat variable from side to side. I t may run laterally near the junction between the posterior medullary and lateral medullary aspects of the cerebellar tonsil. It may run medially near the valleeular ridge, the junction between the vallecular and posterior medullary aspects of the eerebellar

Y.P. Huang and B.S. Wolf: Differential Diagnosis of F o u r t h Ventricle Tumors

tonsil. Similarly, the supratonsillar segment may run over or around, medial or lateral to, the superior pole of the eerebellar tonsil These segments, therefore, may be located at varlous distances frQm the midsagittal plane in the Towne projection.

5

Angiographic Anatomic Landmarks in the Venous Phase Veins of i m p o r t a n c e in diagnosis" (Fig. 2) include: (1) t h e a n t e r i o r p o n t o - m e s e n e e p h a l i c vein [9] a n d its inferior continuation, the a n t e r i o r m e d u l l a r y a n d ante-

/MPC

\

BA]

"/

Fig. I A/B Fig.1. Diagrammatic representation showing normal course of major arteries of importance in angiographie diagnosis Labeled structures include: the anterior culminate segment (AC), anterior lateral marginal branch (ALM), anterior medullary segment (AM), basilar artery (BA), choroidal arteries (C), circumpeduncular segment (ep), lateral medullary segment (LM), medial posterior choroidal artery (MPC), preeentral eerebellar a r t e r y (Pc), posterior inferior cerebellar a r t e r y (PIC), plexal segment (pl), posterior medullary segment (PM), pontine artery (Pc), pretectal segment (pt), superior eerebellar a r t e r y (SC), sup r a p y r a m i d a l branch (Sp), superior retrotonsillar segment (SRt), supratonsillar segment (St), vermian segment (SV) of the superior eerebellar artery, 'bonsillo-hemispheric branch (Th), thalamo-perforating arteries (Tp), vermian segment (V) of the posterior ~nfericr eerebellar artery, vertebral a r t e r y (VA). The course of the medial posterior choroidal a r t e r y (MPC) is shown b y a line of dots. Segments Of arteries covered b y overlying structures and intra-parenehymal portions of arteries are dashed Fig. 1 A. Lateral view. Vessels located on the anterior aspect of the brain stem include the basilar a r t e r y (BA), distal portion of the vertebral artery (VA), the eisternal portion of the thalamo-perforating arteries (Tp), prepontine portions of the superior cerebellar (SC) and posterior cerebral arteries (not illustrated), and proximal portion of the eircumpeduncular segment (ep) of the medial posterior ehoroidal artery. Vessels located behind the brain stem include the tectal segment (t) of the medial posterior choroidal artery, posterior medullary segments of the

posterior inferior eerebellar artery (PIC) and of its tonsillohemispheric branch (Th), and choroidal arteries (C) of the fourth ventricle. The precentral cerebellar artery (Pc) runs behind and parallel to the roof of the upper p a r t of the fourth ventricle and, together with the anterior culminate (AC) and vermian segments (SV) of the superior eerebellar artery, outlines the size and shape of the superior vermis. The superior retrotonsillar segment (SRt) of the posterior inferior cerebellar artery outlines the posterior border of the upper half of the eerebellar tonsil. The distance between this segment and the posterior medullary segment (PM) of this artery indicates the anteroposterior diameter of the cerebellar tonsil and roughly corresponds to the height of the posterior superior recess of the fourth ventricle. The circumpeduncular segment (cp) of the medial posterior ehoroidal artery runs usually parallel and medial to the posterior cerebral artery Fig. 1 B. Towne view. Although the lateral medull ~ry segment (LM) of the posterior inferior cerebellar artery is in relation to the lateral aspect of the medulla oblongata, the distance between this segment of the artery and the midsagittal plane is variable since this segment m a y be located high or low in the cerebello-medullary fissure. The supratonsillar segment (St) m a y be in relation to the medial, superior, or lateral aspect of the superior pole of the cerebellar tonsil. Similarly, the posterior medullary segment (PM) m a y run close to the vallecular ridge or in the medullary impression [12]. I n the Towne projection, these segments m a y therefore appear somewhat more medial!y or laterally located t h a n illustrated. Usually the anterior culminate segment (AC) runs in or adjacent to the superior paravermian suleus

Y.P. ]:Iuang and B.S. Wolf: Differential Diagnosis of F o u r t h Ventricle Tumors rior spinal veins, (2) t r a n s v e r s e p o n t i n e vein [9], (3) p e d u n c u l a r t r i b u t a r i e s of the basal vein of g o s e n t h a l or of t h e p o s t e r i o r mesencephMic vein [7], (4) l a t e r a l meseneephalic vein [15] a n d its inferior extension, t h e i n t e r b r a e h i a l vein [7], (5) b r a c h i a l t r i b u t a r y of the p e t r o s a l vein [9], (6) p r e c e n t r a l cerebellar vein [6], (7) c u l m i n a t e t r i b u t a r i e s of t h e superior v e r m i a n vein [7],

Neuroradiology

(8) m e d i a n posterior spinal vein [13] a n d its superior extension, t h e vein of t h e restiform b o d y [9, 13], (9) vein of t h e l a t e r a l recess of t h e f o u r t h ventricle [8] a n d its s u p r a t o n s i l l a r a n d m e d i a l tonsillar t r i b u t a r i e s , (10) inferior v e r m i a n vein [11] a n d its superior a n d inferior retrotonsillar tributaries. The a n t e r i o r ponto-mesencephMic, a n t e r i o r me-

Fig. 2 A/B Fig. 2. DiagTammatie representation showing normal course of major veins of importance in angiographie diagnosis Labeled structures are anterior medullary vein (AM), anterior ponto-meseneephalic vein (AMP), anterior spinal vein (AS), brachial t r i b u t a r y (B) of the petrosal vein, braehial t r i b u t a r y (B') of the precentral cerebellar vein, deelival vein (De), hemispheric vein (H), inferior retrotonsillar vein (IRt), inferior vermian vein (IV), lateral mesencephalie vein (LMV), vein of the lateral recess of the fourth ventricle (LR), median posterior spinal vein (MPS), medial tonsillar vein (MT), preeentral eerebellar vein (PoV), peduncular vein (Pt, P2), posterior meseneephalie vein (PMV), petrosal vein (PV), vein of the restiform body (RB), supraculminate vein (Seu), suprapyramidM vein (Sp), superior retrotonsillar vein (SRt), supratonsillar vein (St), superior vermian vein (SV), thalamo-perforating vein (Tp) transverse pontine vein (TP) Fig. 2A. Lateral view. Veins outlining the anterior aspect of the brain stem and upper cervical cord are various segments of the anterior ponto-meseneephalic vein (APM), anterior medullary vein (AM), anterior spinal vein (AS), transverse pontiac vein (TP), peduncular vein (unlabeled arrowhead), and cisternal portion of the thalamo-per forating veins (Tp). Vessels outlining the posterior aspect of the upper cervical cord and brain stem are the median posterior spinal vein (MPS), vein of the restiform b o d y (RB), and medial tonsillar vein (MT). Superior and inferior retrotonsillar 'tributaries (SRt, I R t ) of the inferior vcrmian vein (IV) outline the posterior margin of the cerebellar tonsil. The distance between these retrotonsillar

tributaries and those which outline the posterior aspect of the brain stem and the upper cervical cord indicates the antero-posterior diameter of the cerebellar tonsil and roughly corresponds to the height of the posterior superior recess of the fourth ventricle The preeentral cerebellar vein (PcV) together with culminate tributaries, especially supraculminate tributary(Scu), of the superior vermian vein (SV) outline the superior vermis. The distance between the straight sinus and supraculminate vein (Scu) or declival vein (Dc) roughly indicates the width of the superior cerebellar cistern Fig. 2B. Towne view. Brachiat tributaries (B') of the precentral cerebellar vein (PeV) join to form a single trunk at a variable level. They are usually in line with the brachial tributaries (B) of the petrosaI vein (PV). When the lateral mesencephalie vein (LMV) is visualized on both sides, the distance between these two vessels indicates the transverse width of the tegmenta. Peduncular veins m a y be multiple (P1, P2) and outline various portions of the basis of the cerebral peduncle. They are often connected with the anterior ponto-mesencephalic vein (APM) in the interpeduncular fossa. The distance .between the transverse pontine vein (TP) and the clivus is variable depending on the precise location of this vein in relation to the anterior aspect of the pens. The vein of the lateral recess of the fourth ventricle (LR) m a y drain into the petrosal vein (on reader's right) or into the inferior petrosal sinus or into the sigmoid sinus (reader's left). The posterior portion of the posterior mesencephalic vein (PMV) takes a variable course and is often not in direct contact with the brain stem

Vol.l, No. 1, 1970 Y.P. Huang and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors dullary and anterior spinal vein and peduncular tributaries of the basal vein of Rosenthal or the posterior meseneephalie vein are located on the anterior aspect of the brain stem. The preeenfrM cerebellar vein outlines the posterior aspect of the roof of the upper part of the fourth ventricle. Veins which outline the posterior aspect of the upper cervical cord and lower brain stem include the median posterior spinal vein and the vein of the restiform body. The junction between the supratonsillar and medial tonsillar tributaries of the vein of the lateral recess of the fourth ventricle is located at the tonsillar ineisura and corresponds to the location of the lateral angle of the fourth ventricle. This lies opposite the restiform body at this level. The antero-posterior diameter of the body of the cerebellar tonsil is indicated by the distance between vessels outlining the posterior aspect of the medulla oblongata and those located behind the cerebellar tonsil in the retrotonsillar fissure -- retrotonsillar tributaries of the inferior vermian vein. This distance, as in the arterial phase, roughly corresponds to the height of the posterior superior recess of the fourth ventricle. The veins of the lateral recess of the 4th ventrielff run parallel to and below the laterat recesses of the fourth ventricle. The distance between these veins in the semi-axial projection is an indication of the width of the brain stem at the ponto-medullary junction. Similarly the width of the lateral medullary cistern or the transverse width of the medulla oblo~gata at lower levels m a y be estimated by finding the retro-olivary (lateral medullary) vein [9] on one or both sides. Supratonsillar tributaries of the vein of the lateral, recess of the 4th ventricle and of the inferior vermian vein outline the superior pole of the tonsil. The width of the meseneephalon can also be measured when lateral mesencephalic veins are visualized on both sides. The culminate tributaries of the superior vermian vein outline the superior vermis.

Differential Diagnostic Features Both fourth ventricle tumors (Fig. 3, 4) and brain stem tumors (Figs. 5, 6) displace vessels toeated on the anterior aspect of the brain stem forward. In fourth ventricle tumors, the major bulk of tumor is located within the ballooned fourth ventricle, flattens the brain stem, and invariably projects downward into the valleeula between two laterally displaced and flattened tonsils (Figs. 7, 8, 9, 10). On the other hand, in brain stem tumors, the main bulk of the tumor is located anterior to the fourth ventricle, ,enlarges the brain stem in all directions and extends variably upward into the mid-brain and downward into the medulla oblongata (Figs. 11, 12, 13). In brain stem tumors, the thalamo-perforating arteries and veins and the segments of the anterior pontomeseneephalie vein which outline the interpeduncular fossa are flattened from below and behind and the fossa is often tilted upward in its

7

posterior portion. The angle formed by the mesencephalic and pontine segments of the anterior pontomesencephalic vein at the superior foramen caecum is often blunted or increased and i{s apex elevated in brain stem tumors, whereas this angle is usually more acute or decreased in fourth ventricle tumors [13, 14]. In brain stem tumors, tumor nodules often fungate from the surface of the enlarged pons and bulge forward into the pontine cistern lateral to the basilar artery [14]. Upon reaching the elivus, these pseudoextra-axial nodules displace the enlarged pons backward, carrying the basilar artery and the midline anterior pontomeseneephalie vein with it. The distance between these vessels and the elivus therefore is often paradoxically increased rather than decreased. In some cases, the basilar artery may be so markedly posteriorly displaced as to simulate an extra-parenehymal tumor [13]. Tile less rigid and less tmtsatile transverse pontine veins and small transversely running pontine arteries are much more easily displaced forward toward tile clivus by these tumor nodules (Figs. 11, 12, 13). This paradoxical phenomenon has, in our experience, been seen only in cases of brain stem tumors, more specifically, in astroeytoma and perhaps glioblastoma multiforme [1]. I t does not occur with fourth ventricle tumors. With ballooning of the fourth ventricle in fourth ventricle tumors, the roof of the upper portion of the fourth ventricle is markedly elevated and forms a defifiite obtuse angle with the dilated aqueduct in the lateral view (Figs. 3, 4). In brain stem tumors, on the other hand, the floor of the fourth ventricle, aqueduct and of the 3rd ventricle usually form a continuous arch (Figs. 5, 6). The junctional area between the inferior colliculi and the upper part of the central lobule of the cerebellum is displaced mainly upward and slightly backward in fourth ventricle tumors, whereas this area is mainly displaeed backward and only slightly upward in brain stem tumors. Fissural portions of precentral cerebellar arteries and veins are displaced and flattened backward towards the straight sinus and run more or less parallel to the clivus in brain stem tumors. The eoltieulo-eentral point, is therefore displaced backward and its angle is markedly increased. In fourth ventricle tumors, the fissural portions of these vessels are markedly elevated and run almost horizontally. The eollieulo-eentral point is markedly elevated and the eollieulo-central angle is markedly decreased. The superior vermis outlined by the precentral eerebellar artery and vein, vermian artery and culminate tributaries of the superior vermian vein is squeezed backward in brain stem tumors, whereas in fourth ventricle tumors, it is displaced markedly upward and backward (Figs. 8, 10C, l l A . l l B , 12,

laA, 13C). In fourth ventricle tumors, the brain stem is bowed and displaced anteriorly. The eerebellar tonsils are elongated antero-posteriorly, flattened and displaced laterally in areuate fashion. The posterior me-

Neuroradiology

Y.P. t l u a n g and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors d u l l a r y segment of t h e posterior inferior eerebellar a r t e r y is therefore displaced forward, t h e r e t r o t o n s i l l a r segment b a c k w a r d a n d the i n t e r v e n i n g s u p r a t o n s i l l a r segment stretched, elongated a n d a p p e a r s to t a k e a large sweep in t h e l a t e r a l view (Fig. 7A). The supra-

tonsillar segment is displaced l a t e r a l l y in a r c u a t e fashion in the Tow~e p r o j e c t i o n a n d often forms a single continuous curve w i t h the a d j a c e n t portions of the posterior m e d u l l a r y a n d retrotonsillar segments (Figs. 7B, 10B). I n b r a i n stem tumors, on t h e o t h e r

sv l...

_pf' o

:

tv

x4, i s ,

:,<.,. ""

))))/;j;)~,

" PC

\, .. si[-AM # Fig. 3 A]B Fig. 3. Diagrammatic representation showing changes in the arterial phase in fourth ventricle tumors Labeled structures include: the anterior culminate segment (AC), anterior latgral marginal branch (ALM), anterior medullary segment (AM), basilar artery (BA), eireumpeduneular segment (ep), lateral medullary segment (LM), a medial posterior choroidal artery (MPC), precentral cerebellar a r t e r y (Pc), plexal segment (pl), posterior medullary segment (PM), pontine artery (Po), pretectal segment (pt), suprapyramidal branch (Sp), superior retrotonsillar (SRt), superior eerebellar artery (SC), supratonsillar segment (St), vermian segment (SV) of the superior eerebellar artery, tectal segment (t), tonsillo-hemispherie branch (Th), thalamo-perforating arteries (Tp), vermian segment (V) of the posterior inferior cerebellar artery, vertebral artery (VA). The fourth ventricle tumor ballooning the fourth ventricle and projecting into the val!eeula is horizontally shaded Fig. 3 A. Lateral view. The basilar artery and distal portion of the vertebral artery are displaced forward and downward. The proximal portion of the posterior inferior eere~ bellar artery, especially its posterior medullary segment (PM), is m a r k e d l y anteriorly displaced indicating the anterior displacement and bowing of the lower brain stem. The superior retrotonsillar segment (SRt) and, to a lesser degree, the suprapyramidal branch (Sp) are m a r k e d l y displaced posteriorly. The intervening supratonsillar segment (St) of the artery is m a r k e d l y stretched, elongated and somewhat elevated. The proximal portion of t h e superior eerebellar artery (SC) is somewhat stretched and

its anterior lateral marginal branch (ALM) m a y be minimally anteriorly and superiorly displaced. The preeentral eerebellar branch (Pc) of the superior cerebellar artery is markedly elevated and slightly posteriorly displaced. The vermian segment (SV) of the artery is also displaced toward the straight sinus indicating narrowing of the superior eerebellar cistern. I t is often elevated upward in the region of the apex. The posteriorly and superiorly displaced anterior culminate (AC) and vermian segments (SV) and the preeentral cerebellar branch (Pc) of the superior eerebellar artery outline the superiorly and posteriorly squeezed superior vermis. Except for a slight elevation of the eireumpeduneular (ep) and tectal segments (t), the medial posterior ehoroidal artery shows little change. The eisternal segments of the thalamo-perforating arteries m a y be elevated although the parenehymal segments (Tp) show little change Fig. 3B. Towne view. The posterior medullary (PM), supratonsillar (St), and the superior retrotonsillar (SRt) segments of the posterior inferior eerebellar artery are displaced markedly laterally in arcuate fashion. I n addition, the supratonsillar segment (St) is markedly stretched in the antero-posterior direction. I t therefore appears elongated upward in this view. The course of the superior eerebellar (SC) and medial posterior choroidal arteries (MPC) shows little change, except for a somewhat more rounded course. Although difficult to detect in this view, the anterior lateral marginal branch (ALM) m a y show minimal lateral and anterior displacement. The thalamoperforating vessels (Tp) are stretched upward and crowded toward the midline

Vol. 1, No. 1, 1970

Y . P . Huang and B.S. Wolf: Differential Diagnosis of F o u r t h Ventricle Tumors

h a n d , t h e floor of t h e f o u r t h ventricle is d i s p l a c e d b a c k w a r d . The b o d y of the cerebellar tonsil is squeezed a n d displaced b a c k w a r d with r e s u l t a n t m a r k e d posterior d i s p l a c e m e n t of t h e p o s t e r i o r m e d u l l a r y segment, a n d t o a lesser degree, t h e supratonsillar, superior retro-

9

tonsillar a n d v e r m i a n segments of the posterior inferior cerebellar a r t e r y . These changes are best seen in the l a t e r a l view (Figs. 12A, 13A). I n t h e Towne projection, however, unlike f o u r t h ventricle tumors, the distal p o r t i o n of t h e posterior m e d u l l a r y segment and the

Fig. 4 A/B Fig. 4. Diagrammatic representation showing venographie changes in fourth ventricle tumors Labeled structures include the anterior medullary vein (AM), anterior pontomeseneephalie vein (APM), anterior spinal vein (AS), braehial t r i b u t a r y (B) of the petrosal vein, braehial t r i b u t a r y (B') of the preeentral cerebellar vein, declival vein (De), inferior retrotonsillar vein (II~t), inferior vermian vein (IV), lateral mesencephalie vein (LMV), vein of the lateral recess of the fourth ventricle (LR), median posterior spinal vein (MPS), medial tonsillar vein (MT), preeentral cerebellar vein (PcV), posterior mescneephalie vein (PMV), petrosal vein (PV), vein of the restiform body (P,B), supraculminate vein (Seu), superior retrotonsillar vein (SRt), supratonsillar vein (St), superior vermian vein (SV), thalamo-perforating vein (Tp), transverse pontine vein (TP) Fig. 4 A. LaterM view. The anterior ponto-meseneephalie vein (APM) and anterior medullary vein (AM) are displaced forward and downward. The portion of the anterior ponto-meseneephalic vein outlining the interpeduncular fossa is displaced upward. The fissural portion (Pe) of the preeentral eerebellar vein is m a r k e d l y elevated producing angulation of the vein at the collieulo-central point between the inferior eollieuli and central lobule. The supraeulminate t r i b u t a r y (Sou) of the superior vermian vein is also displaced backward and upward toward the straight sinus. The superior and inferior retrotonsillar tributaries (SRt, I R t ) of the inferior vermian vein (IV) are m a r k e d l y posteriorly displaced. The supratonsillar tribut a r y (St) of the vein of lateral reeess of the fourth ventricle (LR) is m a r k e d l y elevated, stre~tehed and its june-

tion with the stretched medial tonsillar vein (MT) (the location of the tonsillar incisura) is anteriorly displaced. The vein of the restiform body (RB) is anteriorly displaced due to anterior bowing and displacement of the lower brain stem. Slight elevation, anterior and superior displacements of the braehiM tributaries (B) of the petrosal vein (PV) and slight elevation of the posterior mesencephalic vein (PMV) m a y also be seen in this view Fig. 4B. Towne view. The braehial tributaries (B') of the precentral cerebellar vein (PeV) run more horizontally. Although the stem of the inferior vermian vein (IV) is not laterally displaced, its superior and inferior retrotonsillar veins (SRt, I R t ) are often m a r k e d l y displaced and rotated laterally producing an increased copular angle (*). The eopular point ( t ) m a y be elevated, especially when the mass within the eisterna magna is large. The lateral meseneephalic veins (LMV) are slightly laterally displaced and elevated. This is due to the ballooning of the fourth ventricle and ventricularization of the lower part of the acueduet. Slight elevation and lateral displacement of the braehial tributaries (B) of the petrosal vein (PV) may also be seen. The vein of lateral recess of the fourth ventricle (LR), including its supratonsillar (-+ ~ ) and medial tonsillar tributaries ( ~ ) , is invariably markedly laterally displaced. When the tumor extends into the lateral recess of the fourth ventricle, there m a y be extreme lateral displacement of this vein, resulting in a more lateral location of the vessel than the brachial t r i b u t a r y (B) of the petrosal vein (reader's left). The transverse pontine vein (TP) may appear close to the elivus. Peduncular veins (P1, P2) outlining the anterior aspect of the cerebral peduncle are tinchanged

10

Y.P. Hua/ng and B.S. Wolf: Differential Diagnosis of F o u r t h Ventricle Tumors

Fig. 5. Diagrammatic representation showing possible urteriographic changes in extensive brain stem tumors. The brain stem tumor is shaded. Hypertrophied nodules protruding from the surface of the enlarged brain stem are more d a r k l y shaded. Labeled structures include the anterior culminate segment (AC), anterior lateral marginal branch (ALM), anterior medullary segment (AM), basilur artery (BA), cireumpeduncular segment (cp), lateral medullary segment (LM), medial posterior ehoroidal a r t e r y (MPC), preeentral eerebellar branch (Pc), peduncular veins (PI, P2), posterior inferior eerebellar artery (PICA), plexal segment (pl), posterior medullary segment (PM), pontine branches (Po), pretectul segment (pt), superior cerebellar artery (SCA), suprapyrumidal branch (Sp), superior cerebellar a r t e r y (SCA), suprupyrumidal brunch (Sp), superior retrotonsillur segment (SRt), supratonsillur segment (St), vermian branch (SV) of the superior eerebellur artery, tectal segment (t), tonsillo-hemispherie branch (Th), thalamo-perforuting arteries (Tp), vermian segment (V) of the posterior inferior eerebellar artery and vertebral artery (VA) Fig. 5A. Lateral view. The basilar artery (BA) is markedly straightened but is not directly applied to the scalloped clivus. The pontinc branch (Po) is, however, closer to the elivus. The distal portions of the ~;ertebral arteries are displaced forward and come close to the lower p a r t of the clivus. The proximal portion of the posterior inferior eerebellar artery (PICA), including its anterior medullary (AM) and lateral medullary segments (LM) is m a r k e d l y stretched posteriorly. The distal part of the posterior medullary segments (PM) of this artery and its tonsillo-hemispherie branch are displaced markedly, posteriorly. Similarly, b u t to a lesser degree, the supratonsillar segment (St), sxlperior retrotonsillar segment (SEt), suprapyramidal branch (Sp) and vermian segment (V) are displaced backward. The superior pole of the ecrebellar tonsil, outlined by theposterior medullary, supratonsillar and superior retrotonsillar segments, is tilted posteriorly. The proximal portion of the superior cerebellar artery (SCA) is stretched and somew h a t elevated. The precentral cerebellar branch (Pc), anterior culminate (AC) and vermian segments (SV) of the superior eerebellar artery, are flattened and displaced backward toward the straight sinus indicating posterior crowding of the superior vermis. The eireumpeduncular segment (cp) of the medial posterior choroidal artery is elevated and the angle formed b y this segment and pretectal segment (pt) adjacent to the teetum is decreased. The tectal segment (t) is compressed from below. The thalamo-perforating arteries (Tp) are arched and displaced forward. This is often associated with elevation of the floor of the fourth ventricle and is seen in eases of tumor infiltration and upward herniation of a brain stem tumor Fig. 5 B. Towne view. The proximal portions of the superior cerebellar (SC) and medial posterior choroidul arteries (MPC) are displaced medially and backward due to paradoxical displacement of pseudo-extra-axial t y p e (curved arrow). Posteriorly, the tectal (t) and pretectal segments (pt) of the medial posterior choroidal artery are displaced outward and take a large sweep. The precentral cerebellar branch (Pc) is displaced laterally and backward. The anterior lateral marginal branch (ALM) of the superior eerebellur artery is displaced upward and laterally due to enlargement of the bruin, stem and brachium pontis. The thulumo-perforuting arteries (Tp) originating from the proximal .portion of posterior cerebral arteries are shown displaced to the left side indicating gre~ter involvement on the right. The lateral medullary segment (LM) of the posterior inferior cerebellar artery is slightly laterally displaced. However, this is difficult to recogmze because of variations in the course of this segment. The oosterior

Neuroradiology

medullary segment (PM) is displaced backward and there.fore its distal end appears high in this projection. Al: though difficult to detect, the supratonsillur segment (St) is somewhat foreshortened and posteriorly displaced. Unlike fourth ventricle tumors, the posterior medullary. supratonsillar and superior retrotonsillar segments of the artery usually show no or little lateral displacement Fig. 6A. Diagrammatic representation showing possible venographie changes in extensive brain stem tumors Labeled structures include the anterior medullary vein (AM), anterior pontomesencephalic vein (APM), anterior spinal vein (AS), braehial t r i b u t a r y (B) of the petrosal vein, braehial t r i b u t a r y (B') of the precer.tral eerebellar vein, deelival vein (De), inferior vermian vein (IV), lateral meseneephalie vein (LMV), vein of the lateral recess of the fourth ventricle (LP~), posterior spinal vein (MSP), precentral eerebellar vein (PeV), peduncular veins (P1, P2). posterior meseneephalic vein (PMV), petrosal vein (PV), vein of the restiform body (RB), superior and inferior r etrotonsillar veins (SRt and IRt, or Rt), supraeulminate vein (Scu), suprapyramidal vein (Sp), superior petrosal sinus (SPS), supratonsillar vein (St.), superior vermian vein (SV), thalamo-perforating veins (Tp), transverse pontine vein (TP). The medial tonsillar vein (-~) is also indicated Fig. 6A. Medial view. The interpeduneular fossa outlined b y the anterior ponto-meseneephalie vein shows upward compression and displacement. Like tile basilar artery, the midline pontine segment of the anterior p.onto-mesencephalic vein is straightened and separated from the elivus. More laterally located transverse pontine veins (TP) reach closer to the elivus and dorsum sellae. The anterior medullary vein (AM) is anteriorly displaced. The posterior meseneephalie vein (PMV) and lateral mesencephalie vein (LMV) are slightly elevated. The brachial t r i b u t a r y (B) of the petrosal vein (PV) is elevated and anteriorly displaced. The portion of the vein of the lateral recess of the fourth ventricle (LR) which runs parallel to the lateral recess of the fourth ventricle is markedly displaced downward in ureuate fashion. The supratonsillar (St) and medial tonsillar tributaries (unlabeled arrowhead) of the vein of the lateral recess, the vein of the restiform body (RB), the median posterior spinal vein (MPS) and, to a lesser degree, the retrotonsillar (Rt) und supratonsillar tributaries (St) of the inferior vermian vein (IV) are posteriorly displaced. The preeentral cerebellar vein (PcV) is markedly flattened and displaced posteriorly and the colliculocentral angle is increased. Culminate tributaries, including the supraculminute t r i b u t a r y (Seu), of the superior vermian vein (SV) and the declival t r i b u t a r y (Dc) of the inferior vcrmiun vein (IV), are posteriorly displaced toward the straight sinus. The thalamo-perforating ,reins (Tp) are slightly arched forward. I n some eases, the posterior portion of the internal cerebral vein m a y be elevated, in the absence of obvious hydrocephalus, as the result of upward displacement of the posterior third ventricle by the brain stem tumor Fig. 6B. Towne view. Paradoxical medial and posterior displacements of the peduncular tributaries (P1, P2) of the posterior mesencephalie vein (PMV) are demonstrated in this diagram. The posterior meseneephalie vein on the right side is displaced outward. The intcrpeduneular fossa ( f ) outlined by the peduncular vein (P2) and mesencephalie portion of the anterior ponto-meseneephalic vein (APM) is displaced to the left. Braehial tributaries (B') of the preeentral eerebellar vein (PeV) are displaced upward and ulso toward the left. Lateral meseneephMie veins (LMV) are laterally displaced and separated from each other due to enlargement of the mid-brain. Due to involvement of the braehium pontis, the braehial tributaries (B) of the petrosal veins (PV) are laterally and superiorly displaced. The veins of the lateral recess of the fourth ventricle (LI:I)

Vol. 1, No. 1, 1970

Y.P. t f u a n g and B.S. Wolf: Differential Diagnosis of Fourth. Ventricle Tumors

,c

p,.[

r "~..~A ~ S

"-

11

C

A

~

/ ~

/

"Ir/~ ..,,,~h

.

z

Fig. 5 A/B

(

Fig. 6 A/B

are displaced downward and medially. This is much more marked on the right due to extensive involvement of the braehium pontis, restiform body and adjacent cerebellar hemisphere. The supeNor and inferior retrotonsillar tri-

butaries (SRt, IRt) of the inferior vermian vein (IV) are displaced slightly to the left. The transverse pontine vein (TP) is displaced anteriorly and comes close to the bone

12

Y.P. Huang and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

supratonsillar segment show little if a n y lateral displacement in brain stem tumors (Fig. 13B). An exception to this m a y occur if a t u m o r infiltrates into the cerebellar hemisphere through the cerebellar peduncles. I t should however be emphasized t h a t the posterior medullary segment of the posterior inferior cerebellar artery m a y appear displaced posteriorly in a fourth ventricle t u m o r in the lateral view simulating a brain stem tumor (Fig. 10A). This is presumably due to a more medial location of the posterior medullary segment before development of the fourth ventricle tumor. Distinction in the Towne projection in these cases is not difficult since in fourth ventricle tumors, as described above, the posterior medullary, supratonsillar and superior retrotonsillar segments are markedly displaced laterally (Fig. 10B). Deformities of the cerebellar tonsils described above are also demonstrated in the venous phase. I n brain stem tumors, the junction between the supratonsillar and medial tonsillar tributaries of the vein of the lateral recess of the fourth ventricle and, to a lesser degree, the retrotonsillar tributaries of the inferior vermian vein are displaced markedly b a c k w a r d (Fig. 6 A, 11 B, 13 C). The first or peduncular segment of the vein is often elongated and m a y even be displaced downward in arcuate fashion when there is an extension of the t u m o r into the cerebellar hemisphere t h r o u g h brachium pontis and restiform b o d y [13]. I n fourth ventricle tumors, the supratonsillar and medial tonsillar tributaries of the vein of the lateral recess of the fourth ventricle are m a r k e d l y stretched elongated and laterally displaced in ~rcuate fashion, and their junction (the lateral angle of the fourth ventricle) is markedly anteriorly and laterally displaced (Figs. 4, 8, 9). I n fourth ventricle tumors, the peduncular or first segment of the vein of the lateral recess of the fourth ventricle is displaced forward and foreshortened (Figs. 4B, 8). I t m a y be displaced markedly laterally, when there is an extension of the t u m o r into the lateral

Fig. 7. Cholesteatoma of the fourth ventricle Fig. 7 A. Left braehial angiogram, arterial phase, lateral view (subtraction). The clivus and sella are retouched. The basilar artery, the distal portion of *':~ vertebral artery and proximal portion of the left posterior inferior cerebellar artery (LPIC) including its anterior medullary (AM), lateral medullary (LM), and posterior medullary segments (PM) are displaced forward indicating anterior bowing and displacement of the brain stem. The superior retrotonsillar segment (black arrowhead), the copula pyramidis (*) and vermian segment (V) of the artery are markedly displaced backward and upward. The intervening left supratonsillar segment (LSt) is stretched, elongated and elevated. The tortuous tonsillar-hemispheric branch ( 1, 1, 2, 4, I-I) is elongated and stretched backward. The faintly visualized right posterior inferior cerebellar artery ( t ) is also seen. The supratonsillar segment of this vessel (row of white arrowheads) is also elongated and elevated. Its medial tonsillar branches (a, b) are stretched and elongated. The superior eerebellar and posterior cerebral arteries (large white arrowhead) are slightly elevated

Neuroradiology

Fig. 7B. Arterial phase, Towne view (same case). The most striking findings on the left side (reader's right) are lateral arcuate displacement of the posterior inferior cerebellar artery (LPIC), especially its posterior medullary (PM), supratonsillar (St), superior retrotonsillar (black arrowhead), and vermian segments (V). The tortuous tonsillo-hernispheric branch ( ], 1, 2, ~, H) is markedly laterally displaced. On the right side, the right posterior inferior cerebellar artery (RPIC) originates from the lower part of the basilar artery and runs laterally along the lower border of the pons and brachium pontis. It enters (~) the upper end of the cerebello-medullary fissure and continues posteriorly over the superior pole of the cerebellar tonsil (row of white arrowheads). Portions of the vessel which run in the fissure are markedly laterally displaced. Its medial tonsillar branches (a, b) are markedly stretched and laterally displaced. The posterior cerebral and superior cerebellar arteries (SCA) which run around the brain stem are displaced outward. More posteriorly, the superiorcerebellar and the posterior cerebral arteries (~) are somewhat separated from each other presumably due to upward herniation of the posterior fossa contents (Reproduction of Fig. 7 through the courtesy of Charles C. Thomas, Publisher)

Fig. 8. Another ease of cholesteatoma of the fourth ventricle. Left brachial angiogram, venous phase, lateral view. The pontine segment of the anterior pontomesencephalic vein (APlV[) is displaced forward. The interpeduncular fossa (black arrow) outlined by various segments of the vein is narrowed from below and displaced upward. The colliculo-central point (CCP) of the precentral cerebellar vein (Pc) is elevated and its first segment (1) is arched upward and backward. The collicuJo-centrM angle formed by the 1st and 2nd segments (1, 2) of this vein is markedly diminished. Narrowing of the superior cerebellar cistern is indicated by the close relationship of the prominent supraculminate vein (Scu) to the straight sinus. The supratonsillar (arrowhead, St) and medial tonsillar tributaries (MT) of the vein of the lateral recess of the fourth ventricle are markedly stretched and elongated and their junction (large arrow) is displaced forward indicating antero-posterior 'elongation of the cerebeltar tonsil and forward bowing and displacement of the brain stem. The superior retrotonsillar tributary (SRt) and, to a lesser degree, the suprapyramidal tributary (Sp) of the inferior vermian (IV) are displaced backward. The eopular point is displaced backward and downward. The transverse pontine (TP) and anastomotic lateral mesencephalie vein (ALM) are also labeled. (Reproduction of Fig. 8 through courtesy of Charles C. Thomas, Publisher. Amer. J. Roentgenol. - Ref. 12)

Fig. 9. Ependymoma of the fourth ventricle. Right braehial angiogram, venous phase, modified Towne view The brachial tributaries (unlabeled arrowheads) of the precentral vein and the superior retrotonsillar tributary (SRt) of the inferior vermian vein (IV) are markedly laterally displaced. The copular angle (*) is increased. The vein of the lateral recess of the fourth ventricle (LR) is arched and markedly laterally displaced. The anastomotie lateral mesencephalic vein (ALM) is also laterally displaced. These findings indicate presence of a midline mass in the vallecula and fourth ventricle. The copular point (CP) is also labeled (Reproduction of Fig. 9 through courtesy of Charles C. Thomas, Publisher. Amer. J. Roentgenol. -l~ef. 12)

Vol. 1, No. 1, 1970

Y.P. I-tttang and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

Fig. 7 A

Fig. 7 B

Fig. 8

Fig. 9

13

14

Y.P. Huang and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

recess of the fourth ventricle (Fig. 4B). I n the lateral view, the junction between tire first and second segments of the vein at the eerebello-ponto-medullary junction is often widened in brain stem tumors whereas in fourth ventricle tumors, this angle is often maintained (Figs. 4A, 6A). The median posterio r spinal vein and the vein of the restiform b o d y are markedly anteriorly displaced in fourth ventricle tumors whereas t h e y are posteriorly displaced i n brain stem tumors [13]. Evidence of deep grooving on the anterior aspect of a brain stem a s t r o c y t o m a seen in the arterial phase can also be observed in the venous phase. Not infrequently, in such cases, the midline or near midline anterior pontomesencephalic vein m a y be considerably posteriorly located in relation to the more laterally located pontine veins (Fig. 12B). There m a y be a discrepancy angiographically as to the location of the anterior aspect of the brain stem outlined by the veins and arteries (Figs. 11 A, 11 B). These changes indicative of hypertrophic nodules fungating from the brain stem are not seen in fourth ventricle tumors. Sizeable protrusion of a fourth ventricle t u m o r into the vallecula produces not only posterior b u t also frequently superior displacements of the copula pyramidis (Figs. 7A, 10C). The copular point in the course of the inferior vermian vein or of the posterior inferior cerebellar artery is often displaced backward in brain stem tumors whereas in fourth ventricle tumors, it m a y in addition, be displaced upward. I n a large low brain stem tumor, however, the copular point m a y be displaced upward as well. Distinction is not difficult since lateral displacements of the superior retrotonsillar t r i b u t a r y of the inferior vermian vein and superior retrotonsillar segment of the posterior inferior cerebellar a r t e r y are usually n o t observed in brain stem tumors (Fig. 13D). Vascular deformities and displacements are in general symmetrical in both brain stem tumors and fourth ventricle tumors. Marked a s y m m e t r y or unilateral involvement is highly suggestive of a brain stem tumor. Extensions of t u m o r into upper brain stem, hypothalamic area, the medulla oblongata and upper cervical cord are not seen in p r i m a r y fourth ventricle tumors. Paradoxical displacement m a y involve the basilar, superior cerebellar, posterior cerebral, vertebral, anterior and posterior inferior cerebellar arteries. These are, as described above, features of brain stem tumors and are not seen in fourth ventricle tumors. Distinction of a fourth ventricle tumor, which has extended into the lateral recess and appeared in the cerebell0-ponto-medullary angle on one side, from a brain stem t u m o r with large pseudo-extra-axial nodules on one side m a y be exceedingly difficult. I n these cases, visualization of the vein of the lateral recess of fourth ventricle is of assistance in distinguishing these two conditions. The vein of the lateral recess of the fourth ventricle in the former case will "show marked lateral and posterior displacement, whereas in the latter case, the vein of the lateral recess of the fourth ventricle is usually displaced downward, medially and posteriorly.

2Veuroradiology

Fig. 10. Hemangi0blastoma of the fourth ventricle with a small attachment to the obex Fig. 10A. Right brachial angiogram with manual compression of the carotid artery in the neck, arterial phase, lateral view. The basilar artery and the distal portion of the vertebral artery are displaced forward. The proximal portion (AM) of the posterior inferior cerebellar artery is tortuous and dips down into the cervical canal (Ce). The posterior medullary segment (PM) of the artery, especially its lower part, is markedly posteriorly displaced simulating a low brain stem tumor. The supratonsillar segment (St) is however stretched, elongated and elevated, and the distance between the superior retrotonsillar segment (SRt) and the posterior medullary segment (PM) is increased. The copular angle (*) is diminished and the vermian segment (V) of the artery is posteriorly displaced. The anterior superior marginal (large arrowhead) and vermian segments (small arrowhead) of the superior cerebellar artery are elevated. The precentral cerebellar artery is not identified

Fig. 10B. Arterial phase, Towne view (same case). The posterior inferior cerebellar artery (arrowheads) on the left side, which originates from the vertebral artery (VA), is markedly laterally displaced in arcuate fashion convex laterally. On the right side, the course of the posterior inferior cerebellar artery is more difficult to trace because of superimposition of the right carotid artery and its anterior cerebral (ACA) and other branches. Nevertheless, it is clearly displaced laterally (row of arrows). The basilar artery (BA) and faint tumor stain (T) due to a hemangioblastoma are also labeled

Fig. IOC. Venous phase, lateral view (same case). Veins (Pc) on the anterior aspect of the pons are unusually close to the clivus. The distance between the deelival vein (De) and the straight sinus is decreased. The eolliculo-central point (~) of the preeentral cerebellar vein (Pc) is markedly elevated and the first segment of this vein (black arrowhead) is angulated superiorly and posteriorly. The superior retrotonsillar segments (SRt) of the inferior vermian veins (IV) are markedly posteriorly displaced. A tumor stain with a large draining vein of lateral recess (unlabeled arrows | ) which enters the petrosal vein and superior petrosal sinus (SPS) can be identified

Fig. 10D. Late venous phase, Towne view (same case). A large tumor stain (T) located in the midline with greater extension toward the left side is noted. The large vein of the lateral recess ( 1 ) opening into the petrosal vein (PV) and superior petrosal sinus (SPS) is clearly seen

Vol. 1, No. 1, 1970

Y.P. Huang and 13. S. Wolf: Differential Diagnosis of F o u r t h Ventricle Tumors

Fig. 10 A

Fig. 10 C

Fig. 10 B

Fig. 10 D

15

16

Y. 1°. H u a n g and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

Fig. l l A Fig. 11. Pontine astrocytoma showing angiographic evidence of grooving of the anterior aspect of the enlarged pens by the basilar artery Fig. 11 A. Left brachial angiogram, arterial phase, lateral view. The precentral cerebellar branch (Pc) of the superior cerebellar artery is markedly posteriorly displaced. The basilar artery comes close to the clivus. Transversely running pontine arteries (Po) originating from the basilar artery, are however, displaced more anteriorly toward the elivus ( ~) than the basilar artery. The course of the posterior inferior cerebellar artery (black arrows) is unusual. There is no posterior medullary segment. The retrotonsillar segment (A) is displaced backward. The vermian seg-

Fig. 11 C

Neuroradiology

Fig. l l B ment (V) of the posterior inferior cerebellar artery is tortuous. The vermian branch (unlabeled white arrow) of the superior cerebellar artery appears elevated. Temporal branches of the posterior cerebral artery (1) must be distinguished from transverse pontine arteries Fig. 11 B. Venous phase, lateral view (same case). A transverse pontine vein (TP) which outlines the anterior aspect of the mid-pens comes unusually close to the elivus indicating marked narrowing of the pontine eisten. The precentral eerebellar vein (Pc) is faintly visualized and displaced backward indicating enlargement of the upper brain stem. Inferiorly, the median posterior spinal and medial tonsillar veins (row of arrowheads) which outline the posterior aspect of the upper cervical cord and anterior aspect of the cerebellar tonsil are displaced markedly posteriorly. The superior and inferior retrotonsillar tributaries (SRt, IRt) of the inferior vermian vein (IV) are also displaced backward but to a lesser degree. A peduncular vein outlining the anterior aspect of the basis pedunculi ( ~.) is also labeled. The posterior tubercle of C1 is retouched

Fig. 1 1 C. Pneumoencephalogram, lateral view, erect position (same case). The floor of the fourth ventricle (4V) is flattened backward. The aqueduct (Aq) is displaced backward and upward. The' interpeduncular (I) and pontine cisterns (&) arc narrowed by the enlarged pens

Vot. 1, No. 1, 1970

Y.P. H u a n g and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

17

Fig. 12. Another case of brain stem astroeytoma showing deep grooving of the anterior aspect of the pens by the basilar artery Fig. 12A. Left retrograde brachial angiogram, arterial phase, lateral view. The basilar artery (~) is straightened and lies at some distance from the clivus (~). Pontine arteries (Po) are seen closer to the clivus. The distal portion of the vertebral artery is also separated from the anterior margin of the foramen m a g n u m (F). The thalamo-perforating arteries (Tlo) are stretched upward and arched forward indicating indentation of the floor of the posterior portion of the 3rd ventricle. The eireumpeduncular segment of the medial posterior choroidal artery (row of arrows) is somewhat elevated and the angle formed by this segment (~) and the pretectal segment ( ~ ) is decreased. This is due to upward herniation of the enlarged brain stem. Similarly, the portion of the lateral posterior ehoroidal artery which runs in the infra-pulvinar portion of the ehoroid fissure (~) is also slightly elevated. The proximal portion of the superior eerebellar artery (SC) is displaced forward. The anterior culminate segment (AC) and, to a lesser degree, the vermian segment (SV) of the superior cerebellar artery are displaced backward. The anterior lateral marginal branch (row of white arrowheads) of the superior cerebellar artery is markedly elevated and anteriorly displaced due to involvement of the brachium pontis. The precentral cerebellar artery (row of black arrowheads) is flattened backward. The posterior medullary segment (PM) and, to a lesser degree, the superior retrotonsitlar segment (SRt) and vermian segment' (V) of the posterior inferior cerebellar artery are crowded backward. Note the increased distance between the posterior medullary segment of the inferior cerebellar artery and the anterior margin of the foremen magnum (F)

Fig. 12 B Neuroradiology,Vol. 1

Fig. t2 A

Fig. 12B. Venous phase, lateral view (same ease). The mid-line anterior loonto-mesencephalie vein (row of arrowheads) can be identified ; its pontine segment is located at some dmtance from the elivus. More laterally located transverse pontine veins (~) are seen much closer to the elivus. The eolliculo-eentral point of the preeentral eerebellar vein (Pc) is displaced back and the eolliculo-eentral angle increased. Although the supraeulminate vein is close to the straight sinus, the distance between this vein and the preeentral eerebellar vein is decreased. The superior and inferior retrotonsillar tributaries (SRt, IRt) of the inferior vermian (IV) are displaced markedly backward. The copular angle (*) is diminished. The posterior portions of the posterior meseneephalie veins (black arrowheads) are somewhat elevated and straightened. The discrepancy in distance between the clivus and the anterior pontomeseneephalie vein and between the clivus and the more laterally located loontine veins indicates presence of hypertrophic nodules on the surface of the enlarged loons 2

i8

Y.P. Huang and B.S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

Fig. 13 A

Fig. 13 C

Fig. 13 B

Fig. 13 D

Neuroradiology

Vol. 1, No. 1, 1970

Y . P . H u a n g and B. S. Wolf: Differential Diagnosis of Fourth Ventricle Tumors

References

Fig. 13. Another case of brain stem astrocytoma Fig. 13A. Left brachial angiogram, arterial phase, lateral view. The distal half of the ba~ilar artery ( ~) is displaced backward. The thalamo-perforating arteries (Tp) are stretched and displaced forward in areuate fashion. The eircumpeduneular (cp), tectal (t), pretectal (pt), and plexal segments (pl) of the medial posterior' choroidal artery show no definite abnormalities. The anterior culminate (AC) and, to a lesser degree, superior vermian segments (SV} of the superior eerebellar artery are displaced backward. The precentral cerebellar artery (row of arrows) is displaced backward. The posterior inferior cerebellar arteries are visualized on both sides and their posteriQr medullary segments (PM) are markedly posteriorly displaced. The superior retrotonsillar branch (SRB) and superior retrotonsillar segments (SRt) of the posterior inferior cerebellar arteries are also displaced backward. Inferior retrotonsillar branches (two opposing arrowheads) are also visualized and are slightly displaced backward. The anterior lateral marginal branch (ALM) is slightly anteriorly displaced. Also labeled are hemispheric branches of the posterior inferior eerebellar arteries. The lateral medullary-segment of the posterior inferior eerebellar artery on the right side (RLM) runs higher than t h a t on the left (LLM). The anterior and posterior tubercles of C1 and dens are retouched

Fig. 13B. Arterial phase, Towne view (same case). The lateral medullary segment (LM) of the right posterior inferior cerebellar artery, which runs higher than t h a t on the left side in the lateral view (Fig. 13A), takes a more lateral course in the Towne projection. The medial tonsillar segments (LMT, RMT) which run on the medial aspects of the cerebellar tonsils considerably below the level of the superior poles, outline a normal vallecula. The superior retrotonsillar segment (black arrowheads) and the vermian segments are not laterally displaced. The precentral cerebellar artery (Pc) can be identified on the left side and is displaced laterally and posteriorly. The medial posterior ehoroidal artery (row of arrowheads} which originates from the posterior cerebral artery on the lateral aspect of the cerebellar peduncle takes an unusual lateral course. The tectal (t), pretectal (pt) and plexal segments (P1) can also be identified and are normally located

19

1. Anderson, P. : Personal communication. 2. Dilenge, D., David, M. : L'angiographie Ver%brale. Neuroehirurgie 13, 121 -- 156 (1967). 3. Galloway, J . R . , Greitz, T. : The medial and lateral ehoroid arteries -- an anatomic and roentgenographie study. Aeta radiol. 58, 353--366 (1960). 4. Greitz, T., Sj6gren, S.E.: The posterior inferior eerebellar artery. Acta radiol. 1,284--297 (1963). 5. Hare, K., Fujino: Thalamoperforate artery. Acta radiol. 5, 192--200 (1966). 6. Huang, Y.P., Wolf, B.S.: Precentral cerebellar vein in angiography. Actaradiol. (Diag.) 5,250--262 (1966). 7. -- -- Veins of the posterior fossa -- superior or Galenic draining group. Amer. J. goentgenol. 95, 808--821 (1965). 8. -- -- The vein of the lateral recess of the fourth ventricle and its tributaries -- Roentgen appearance and anatomic relationships. Amer. J. Roentgenol. 101, 1--21 (1967). 9.-- Antin S.P., Okudera, T.: The veins of the posterior fosse -- anterior or petrosal draining group. Amer. J. goentgenol. 1{}4, 36--56 (1968). 10.

Kim, I . H . . Angiographie features of aqueductal stenosis. Amer. J. Roentgenol. 104, 90-108 (1968).

1 1 . - -- Okudera, T.: Angiographie an at o m y of the inferior vermian vein of the cerebellum. Presented at the 8th International Neuroradiological Symposium, Paris, 1967. To be published in Acta Radiologica. 12. --, - - : Angiographic features of fourth ventricle tumors with special reference to the posterior inferior cerebellar artery. Amer. J. Roentgenol. 107, 543-- 564 (1969). 13. -- -- Angiographie features of brain stem tumors and differential diagnosis from fourth ventricle tumors. Amer. J. Roentgenol. Accepted for publication.

Fig. 13C. Venous phase, lateral view (same case). There is marked posterior displacement of the precentral cerebellar vein (Pc) and the superior retrotonsillar tributary (SRt) of the inferior vermian vein ( I V ) The suprapyramidal vein (Sp) is also visualized and is displaced backward. The vein of the lateral recess of the fourth ventricle (row of arrowheads) is stretched and displaced downward. The peduncular vein (Pd) and posterior mesencephalie vein (PM) are also labeled. The origin of the superior retrotonsillar tributary is labeled with a small arrow

14. Lef6bvre, J., Four6, C., Solomon, G.: ]~tude radiologique des gliomes infiltrants du trone e6r6bral. Acta radiol. 1, 343--357 (1963). 15. Wolf, B.S., Huang, Y.P., Newman, C.M.: The lateral anastomotie mesencephalic vein and other variations in drainage of the basal cerebral vein. Amer. J. Roentgenol. 89, 4 1 1 - 422 (1963). 16. -- Khilnani, M.T. : The posterior inferior eerebellar artery on vertebral angiography. Amer. J. Roentgenol. 87, 322--337 (1962).

Fig. 13D. Venous phase, Towne view (same case). The brachial tributaries of the preeentral cerebellar vein arrowheads) are separated. The superior retrotonsillar tributary (SRt) of the inferior vermian vein (IV) is foreshortened. However, its up]~r or anterior end (small arrow) is not laterally displaced

Y.P. Huang, M. D. Department of Radiology Mount Sinai Hospital and Mount Sinai School of Medicine New York, N.Y. 10029, U SA

2*