A c t a l~eurochirurgica 30, 95--109 (1974) 9 b y Springer-Verlag 1974

Division of Neurosurgery of The Children's Hospital of Philadelphia and

The University of Pennsylvani~

Diagnosis of Posterior Fossa Tumors with Angiography in Children By H. E. J a m e s a n d L. Sehut ~Vith 14 :Figures

Summary The differential diagnosis of posterior fossa tumors with cerebral angiography in children is presented with diagrams and illustrations. The literature is reviewed and the angiographic landmarks are discussed. The advantage of this form of examination over other methods of contrast studies is emphasized. I t is concluded t h a t the detailed analysis of the anglographic findings in posterior fossa tumors in children can be of locMizing and of diagnostic vMue in the m a j o r i t y of cases, and surgery can then be, performed without additional contrast studies.

P r e s e n t l y t h e r e is a b u n d a n t l i t e r a t u r e in reference to t h e differen~ial diagnosis of i n f r a t e n t o r i a l t u m o r s w i t h v e r t e b r o b a s i l a r angiog r a p h y l , 2, 5, 6, 7, s, 9, 10, 13, 17. However, t h e m a j o r i t y of these descriptions relate to findings in adults. T h e diagnosis becomes even m o r e i m p o r t a n t in children, due to t h e g r e a t e r incidence of neoplasms in this l o c a t i o n in t h e p e d i a t r i c p o p u l a t i o n , when c o m p a r e d to a d u l t s 12, 14, 18, 19 T h e a d v a n t a g e of o b t a i n i n g t h e diagnosis w i t h a n g i o g r a p h y r a t h e r t h a n w i t h p n e u m o v e n t r i c u l o g r a p h y is t h a t t h e surgeon is n o t pressed following t h e f o r m e r s t u d y b y t h e fear of d e c o m p e n s a t i o n t h a t can occur when air studies are p e r f o r m e d 14, 17. Thus, surgery can t h e n be c a r r i e d o u t on a n " e l e c t i v e " a p p r o a c h , r a t h e r t h ~ n i m m e d i a t e l y following t h e diagnostic p r o c e d u r e n.

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Angiographic Landmarks We have found that the majority of the vascular findings that are present in the literature in reference to infratentorial tumors in adults, can be applied to neoplasms in childhood. In the arterial phase, as well as the basilar and superior eerebellar arteries, the PICA (posterior

inferior eerebellar artery) and its branches and the transverse pontine arteries are of marked localizing significance 1~, 16, 17 (Fig. 1). The variations of the P I C A both in normal and abnormal situations have been extensively reviewed by Greitz a and by Margolis and Newton 15. Of practical value have been the descriptions of Huang and Wolf% 10, not only because of the angiographic findings in the differential diagnosis between fourth ventricle and brain stem tumors, but also because of the nomenclature of the different portions of the PICA (Fig. 1). We have found this nomenclature useful in the surgical considerations. The transverse pontine arteries by outlining the ventrolateral pens will permit at times the differential diagnosis of extra-axial tumors, with exophitie extensions of pontine gliomas (Fig. 3). The venous phase of the angiogram is just as important in m a n y eases for the differential diagnosis 1, 2, 4, 5, 6, 7, 10. We have found that in children the pontomesencephalie, preeentral eerebellar, vermian and superior retrotonsillar veins are of particular value (Fig. 2). The pontomeseneephalic vein in its distal portion outlines the ventral pens, and in brain s t e m t u m o r s will be ventrally displaced. The precentral cerebellar vein courses between the c011ieuli ventrally and the

Fig. 1. Anterioposterior and lateral diagrams of the arterial phase of a posterior fosse angiogram. A C anterior culminate segment. A M anterior medullary segment. B A basilar artery. C ehoroidal artery. L M lateral medullary segment. P c precentral eerebellar artery. P M posterior medullary segment. P c pontine artery. S G superior cerebellar artery. S R t superior retrotonsillar segment. S t supratonsillar segment. S V superior vermian segment. T h tonsillo-hcmispherie branch. T p thalamo-perf0rating arteries. V vermian segment. V A vertebral artery. (Modified from Huang et el.) Fig. 2. Diagram of the normal venous pattern in a posterior fosse angiogram. AM anterior medullary vein. APM anterior pontomesencephalie vein. AS anterior spinal vein. B brachial tributary. // hemispheric vein. I V inferior vermian vein.

L M V lateral meseneephalic vein. L R vein of the lateral recess of the IV ventricle. M P S median posterior spinal vein. M T medial tonsillar vein. P e V precentral eerebellar vein. P M V posterior meseneephMie vein. P V petrosal vein. R B vein of the restiform body. S c ~ supraculminate vein. S R t superior retrotonsillar vein. S t supratonsillar vein. S V superior vermian vein. T P transverse pontine vein. Tp thalamoperforating vein. (Modified from Huang.:et el,)

Diagnosis of Posterior Fossa Tumors

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superior vermis (central lobule) dorsally; therefore, mass lesions involving this area will cause its displacement and modify its configuration (Fig. 4). The v e r m i a n veins course on the vermis at each side of the midline (Fig. 2). The superior retrotonsillar vein corresponds to the initial portion of the vermian vein, and it delineates the lateral portions of the cerebellar tonsil and roof of the fourth ventricle (Fig. 2).

Case Presentations F o u r patients are now presented to illustrate the differential diagnosis t h a t can be entertained with angiography. T h e y correspond to a pontine glioma, a f o u r t h ventricle tumor, a cystic a s t r o c y t o m a of the cerebellum and a t u m o r involving the ventromedial cerebellar hemisphere. These four locations are c o m m o n l y encountered sites in t u m o r s of childhood 12, 14. 1. Pontine Glioma

1%. C. is a 4-year-old, b.m. who for two years demonstrated personality changes and gait disturbance. One week prior to admission he manifested falling to the left and complained of headaches. On examination he was lethargic and presented horizontal nystagrnus, internuclear ophthalmoplegia, right V I I nerve palsy and bilateral disdiadokokinesis. Plain films of the skull were normal, and the E E G showed bilateral symmetrical slowing. A right braehial ~rteriogram was performed. On the arterial phase the lateral view revealed ventral displacement of the basilar artery against

Fig. 3. Diagram of the arterial phase of a posterior fosse angiogram, in a pontine gliom a. A C anterior culminate segment. A L M anterior lateral marginal branch. A M anterior medullary segment. B A basilar artery. L M lateral medullary segment. P I C A posterior inferior cerebellar artery. P M posterior medullary segment. P c pontine arteries. S C A superior eerebellar artery. Sp suprapyramidal branch. S R t supraretrotonsillar segment. St supratonsillar segment. S V superior vermian segment. Th tonsillohemispherie branch. T p thalamo-perforating arteries. V vermian segment. V A vertebral artery. (Modified from 1-Iuang et el.) Fig. 4. Diagram of the venous phase of a posterior fosse angiogram, in a pontine glioma. A M anterior medullary vein. A P M anterior pontomesencephalie vein. A S anterior spinal vein. B brachial tributory. Dc declival vein. 1 V inferior vermian vein. L M V lateral mesencephalie vein. L R vein of the lateral recess of the IV ventricle. M P S medial posterior spinal vein. P c V precentral cerebellar vein. P V - P M V posterior mesencephalic vein. P V petrosal vein. R B vein of the restiform body. Rt retrotonsillar veins. Scu supraculminate tributary. Sp suprapyrarnidal vein. SiPS superior petrosal sinus. St supratonsillar vein. SV superior vermian veins. (Modified from Huang et el.)

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the clivus (Fig. 6). The transverse pontine arteries are accompanying the displacement, thus confirming a pontine mass or a forward displacement (large arrow). The P I C A shows a ventrally displaced anterior medullary (lowermost arrow) segment and a very stretched lateral medullary segment,

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Fig. 5. Diagram of the arterial phase of posterior fossa angiogram, in a I V ventricle tumor. A C anterior culminate segment. AL2VI anterior lateral marginal branch. A M anterior medullary segment. B A basilar artery. L M lateral medullary segment. Pc preeentrM eerebellar artery. P3// posterior medullary segment. S - S V superior vermian segment. SC superior eerebellar artery. Sp suprapyramidal braneh. S R t supraretrotonsillar segment. St supratonsillary segment. Th tonsillohemispherie branch. Tp thalamo-perforating arteries. V vermian segment. V A vertebral artery. (Modified from I t u a n g et al.)

Fig. 6. Lateral view of the arterial phase of ~ right braehiM arteriogram, in a pontine glioma. The large arrow points to the pontine arteries which transversely surround the ventral aspect of the enlarged pens. The small arrows point to the ventrally displaced anterior medullary segment and the dorsally displaced posterior medullary segment. (See text) Fig. 7. Lateral

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pontine glioma. The pontomeseneephalie vein is displaced against the clivus (white arrows). The preeentral eerebellar vein has lost its normal concavity forward and is displaced posteriorly (top black arrow). The superior retrotonsillar vein is displaced dorsally outlining the inferior aspect of the enlarged brain stem (low black arrow). (See text)

Diagnosis of Posterior Fossa Tumors

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with dorsally displaced retromedullary (small right arrow) and superior retrotonsillar segments (compare with Fig. 3). These findings favor a markedly enlarged brain stem, and they are confirmed b y the changes in the venous phase (Fig. 7). The pontomesencephalie vein is displaced ventrally against the clivus (white arrows), and the precentral cerebellar vein is dorsally displaced and has lost its normal curvature (top black arrow). The superior retrotonsillar vein is also shifted dorsally (lower black

Fig. 8. Lateral view of the arterial phase of a brachiM arteriogram, in a IV ventricle tumor. The premedullary, lateral medullary, and retromedullary segments are displaced ventrally (small arrow). The supratonsillar segment is marked elongated and enlarged (large arrow). (See text) arrow). Both these veins outline the dorsal limits of the mass (compare with Fig. 4). The enlargement of the brain stem indicating a "pontine glioma" was well demonstrated on the pneumoencephalogram which was subsequently performed. This study revealed marked dorsal displacement of the aqueduct and the fourth ventricle floor, and obliteration of the prepontine cistern.

2. Fourth Ventricle Tumor 1~. L., a 6-year-old, w.f., was seen because of recurrent headaches of several months duration, and two weeks prior to admission was noticed to have difficulty walking. On examination her only findings were that of gross bilateral papilledema. Plain films of the skull were normM, and an E E G revealed bilateral symmetrical slowing. The brain scan showed a midline area of increased uptake in the posterior fossa. A right brachial

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arteriogram revealed on the lateral view of the arterial phase ventrM displaeement of the basilar artery and distortion of the PICA (Fig. 8). The premedullary, lateral medullary and retromedullary segments are ventrMly displaced (small arrow), and the superior tonsillar portion is markedly stretched (large arrow). The superior retrotonsillar and vermian segments are dorsally shifted. Also, the lateral medullary segment is caudally displaced in the foramen

Fig. 9. Anteroposterior view of a brachial arteriogram, in a IV ventricle tumor. The posterior inferior eerebellar artery is shown markedly displaced away from the midline in all its portions, primarily in the supratonsillar segment (arrow). (See text) magmml, suggesting herniation. The stretched superior tonsillar segment together with the displaced other segments of the PICA indicate a mass effect in the fourth ventricle (see Fig. 5). These findings are confirmed in the anteroposterior view (Fig. 9), in which tim right PICA is stretched a,wo~y from th~ midline (bl~ck an'ow). At surgery tonsillar herniation was confirmed, and the fom'th ventriele was occupied and distended by an astrocytoma, growing into this structure from the most, ventral vermis.

3. Cystic Astrocytoma o/ the Cerebellum A. P. is a 9-year-old, w.m., who was admitted with a history of headaches and vomiting of several months' duration. A few days prior to admission he manifested double vision, On examination double vision was confirmed, and gross papilledema was found together with mild changes in muscle

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tone of the left extremities. Plain films of the skull revealed suture separation, and the E E G manifested bilateral symmetrical slowing. A brain scan was interpreted as being normal. A left brachial arteriogram revealed

Fig. 10. Anteroposterior view of the arterial phase of a brachial arteriogram, in a left cerebellar hemisphere tumor. The PICA is shifted from left to right (small white arrow). The vermian segment is also similarly displaced across the midline (large white arrow). The hemispheric branches are markedly elongated and stretched (black arrows). (See text) in the Towne projection (Fig. 10) a shift from left to right of the superior tonsillar and vermian segments (white arrows), with stretching of the hemispheric branches (black arrows). The venous phase (Fig. 11) confirms the mass effect of the left cerebellar hemisphere, because the vermian vein shows a similar displacement (white arrow). The lateral view (Fig. 12) reveals the basilar artery displaced against the clivus, as well as stretched

Fig. 11. Anteroposterior view of the venous phase of a brachial arteriogram, in a left cerebellar hemispheric tumor. The vermian vein is shifted across the midline from left to right (arrows). (See text) Fig. 12. Lateral view of the arterial phase of a brachial arteriogram, in a left eerebellar hemispheric tumor. The superior eerebellar arteries are markedly elongated and stretched (black arrows). The PICA shows a ventrally displaced anterior medullary, lateral and retromedullary segments (small white arrow). The supratonsillar portion is markedly shifted towards tile foramen magnum (large white arrow). (See text)

Diagnosis of Posterior Fossa Tmnors

Fig. 11

Fig. 12

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superior cerebellar arteries (black arrows). The distorted left PICA aids in locating the lesion. The premedullary, lateral medullary and retromedullary segments are ventrally and caudally displaced (small white arrow). The superior tonsillar segment is caudally and ventrally displaced (large white arrow). These findings, together with the changes seen in the Towne view, indicate a mass effect of the left cerebellar hemisphere. At surgery a very large cystic astroeytoma occupying the left cerebellar hemisphere was found.

Fig. 13. Anteroposterior view of the arterial phase of braehial arteriogram, in a tumor involving in the ventromedial left cerebellar hemisphere. The left PICA is markedly shifted from left to right not only in its initial portions b u t in its supratonsillar segment (small white arrow), and in the vermlan segment (large white arrow). The hemispheric branches are somewhat stretched but differ from those seen in Fig. 10. (See text)

4. Tumor Involvinff the Ventromedial CerebeUar Hemisphere S . W . is a 7-year-old, w.f., who was admitted because of recurrent headaches, papilledema and vomiting. Examination revealed lethargy, papilledema, nystagmus on left lateral gaze and left arm ataxia. Plain fihns of the skull were unremarkable, and the E E G revealed bilateral symmetrical slowing. A brain scan revealed an area of increased uptake in the posterior fossa, just off the midline to the left side. The Towne projection of the left brachial arteriogram (Fig. 13) reveals a shift from left to right of the lateral, retromedullary, supratonsillar (small arrow) and vermian segments (large arrow) of the left PICA. The lateral view (Fig. 14) shows the basilar artery displaced forward and confirms

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the displacement of the left PICA. The premedullary segment is ventrally displaced (high small arrow), and the lateral medullary segment has descended into the cervical spine (low small arrow). The retromedullary segment is both caudally and ventrally displaced, indicating t h a t the mass effect is located behind it. This same finding is present for the superior retrotonsillar segment (large arrow) which suggests t h a t the mass effect involves the cerebellar hemisphere in t h a t area, confirming the findings of the Towne projection.

Fig. 14. Lateral view of the arteriM phase of a braehial arteriogram, in a ~umor involving ~he ventrolateral lef~ eerebellar hemisphere. The premedullary, lateral medullary, and retromedullary segments are not only ventrally displaced, b u t m a r k e d l y shifted down into the upper cervical spine (small white arrows). The retrosupratonsillar segment is markedly shifted and herniated into the foramen magnum (large white arrow). (See text) A t surgery a markedly herniated and necrotic eerebetlar tonsil was found on the left, together with an astrocytoma involving the ventromediM cerebellar hemisphere.

Conclu sions A d e t a i l e d analysis of t h e a n g i o g r a p h i e findings in posterior fossa t u m o r s in children can be localizing a n d diagnostic v a l u e in t h e m a j o r i t y of eases. S u r g e r y can be t h e n p e r f o r m e d w i t h o u t p n e u m o v e n t r i e u l o g r a p h y . This is a d v a n t a g e o u s because it allows s u r g e r y to be carried o u t on a n " e l e c t i v e " a p p r o a c h , r a t h e r t h a n i m m e d i a t e l y following

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t h e s t u d y . The s a m e does n o t h o l d for p n e u m o v e n t r i c u l o g r a p h y , due to t h e fear of d e c o m p e n s a t i o n t h a t can occur w i t h t h e s e studies n, la, 17, t h u s pressing t h e surgeon for t h e surgical i n t e r v e n t i o n . T h o u g h positive c o n t r a s t v e n t r i c u l o g r a p h y can be utilized i n s t e a d of air, t h e findings on these studies are l i m i t e d t o shifts or o b s t r u c t i o n s of t h e v e n t r i e u l a r system. A n g i o g r a p h y on t h e o t h e r h a n d can often outline t h e e x t e n t a n d gross limits of a t u m o r . P r e s e n t l y a t t h e Children's H o s p i t a l of P h i l a d e l p h i a , p a t i e n t s w i t h clinical evidence of p o s t e r i o r fossa t u m o r s are e v a l u a t e d w i t h p l a i n films of t h e skull, e l e c t r o e n c e p h a l o g r a p h y a n d section scans of t h e p o s t e r i o r fossa. F o l l o w i n g t h e s e p o s t e r i o r fossa a n g i o g r a p h y is perf o r m e d ; a n d if t h i s s t u d y is s a t i s f a c t o r y , s u r g e r y is u n d e r t a k e n w i t h o u t p n e u m o v e n t r i c u l o g r a p h y . I f on t h e o t h e r h a n d s a t i s f a c t o r y i n f o r m a t i o n is n o t o b t a i n e d , v e n t r i c u l o g r a p h y is u n d e r t a k e n before t h e i n t e r v e n t i o n . References

1. Bradae, G . B . , The pontomeseneephalic vein. Neuroradiol. 1 (1970), 52--57. 2. Bull, J., and P. Kozlowski, The angiographic p a t t e r n of the petrosal veins in the normal and pathological. Neuroradiol. 1 ((1970), 20--26. 3. Greitz, T., and S . E . Sjogren, The posterior inferior cerebellar artery. Aeta Radiol. 1 (1963), 284~297. 4. I-Iuang, Y . P . , ]3. S. Wolf, S . P . Antin, and T. Okudera, The veins of the posterior fossa---Anterior or Petrosal group. Amer. J. goentgenol. 104, 1 (1968), 36--56. 5. - - Precentral cerebellar vein in angiography. Aeta Radiol. 5 (1966), 250--262. 6. - - Veins of the posterior fossa--Superior or GMenic group. Amer. J. Roentgenol. 95 (1965), 808--821. 7. - - Vein of the lateral recess of the F o u r t h Ventricle and its tributaries. Amer. J. Roentgenol. 101 (1967), 1--21. 8. - - Angiographic features of aqueductal stenosis. Amer. J. Roentgenol. 104 (1968), 90--108. 9.-Angiographic features of fourth ventricle tumors with special reference to the PICA. Amer. J. Roentgenol. 107 (1967), 543--564. 10. - - Differential diagnosis of I V ventricle tumors from brain stem tumors in angiography. Neuroradiol. 1 (1970), 4--19. 11. Jane, J. A., 13. Kaufman, F. Nulsen, I). u and I-I. Young, The role of angiography and ventriculovenous shunting in the t r e a t m e n t of Posterior Fossa Tumors. A e t a Neuroehir. 28 (1973), 13--27. 12. Noes, W. Th., and M. I-t. Miller, Introduction to tumors of infants and children. CV Mosby Co. 1971. 13. Kr~yenbiihl, t-I. A., and M . B . Ya~argil, Cerebral angiography. J . B . Lippineott Co. 1968. 14. Matson, D. D., Nenrosurgery of Infancy and Childhood. Ch. C Thomas. 1969. 15. Margolis, M . T . , and T. I-I. Newton, Borderlands of the normal and abnormal PICA. Aeta gadiol. Diagn. 13 (1972), 163--176.

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16. Megret, M., A landmark for the ehoroidM arteries of the fourth vent r i c l e - B r a n c h e s of the PICA. Neuroradiol. 5 (1973), 85--90. 17. Taveras, J. M., and E. I-I. Wood, Diagnostie Neuroradiology. 2nd Ed. The Williams Wilkins Co. 1969. 18. Russell, D. S., and L. J. Rubinstein, Pathology of tumors of the nervous system. 3rd Ed. Edward Arnold. 1971. 19. Ziileh, K. J., Brain Tumors. Their Biology and Pathology. 2nd Amer. Ed. Springer Publishing Co. 1965. Authors' address: I-I. E. James, M.D., Division of Neurosurgery, Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104, USA.