Radiol med (2014) 119:694–704 DOI 10.1007/s11547-014-0387-y
PAEDIATRIC RADIOLOGY
Identification of skull base sutures and craniofacial anomalies in children with craniosynostosis: utility of multidetector CT Rosalinda Calandrelli • Gabriella D’Apolito • Simona Gaudino • Maria Carmela Sciandra • Massimo Caldarelli • Cesare Colosimo
Received: 11 May 2013 / Accepted: 13 August 2013 / Published online: 8 February 2014 Ó Italian Society of Medical Radiology 2014
Abstract Purpose Craniosynostosis is a condition characterised by the premature fusion of one or more of the cranial sutures. The aim of the study was to identify, by multidetector computed tomography (CT), the involvement of vault sutures as well as of the skull base sutures (named ‘‘minor’’ sutures). The latter ones are involved in development of craniofacial and skull base deformities. Materials and methods We retrospectively reviewed 27 children with complex synostosis (n = 21) and anterior synostotic plagiocephaly (n = 6). High-resolution CT images with bone definition algorithm and tridimensional volume rendering reconstructions were assessed. Results In 27 children we found different sutures involved in the synostotic process, including both major and minor skull suture synostosis, and synostosis of synchondroses. Superior orbital rim deformity, nasal root deviation, anterior endocranial axis deviation (ethmoidal axis) are found in children with coronal arch synostosis, while reduced size of the posterior fossa and Chiari 1 malformation are noted in children with lambdoid arch synostosis. Conclusions High-resolution CT allows an accurate identification of both ‘‘major’’ and ‘‘minor’’ skull base suture synostosis and it represents the gold standard for the
R. Calandrelli (&) G. D’Apolito S. Gaudino M. C. Sciandra M. Caldarelli C. Colosimo Institute of Radiology, Universita` Cattolica Sacro Cuore, L.go A. Gemelli 8, 00168 Rome, Italy e-mail:
[email protected] S. Gaudino M. Caldarelli Institute of Neurosurgery, Universita` Cattolica Sacro Cuore, L.go A. Gemelli 8, 00168 Rome, Italy
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diagnosis of craniostenosis and for planning the proper surgical approach. Keywords Craniosynostosis Coronal arch Minor sutures
Introduction The deformity of the skull in the newborn represents a common and significant diagnostic problem, particularly in distinguishing positional plagiocephaly from deformity caused by craniostenosis [1, 2]. Positional plagiocephaly is an alteration of the morphology of the skull in the absence of premature cranial suture synostosis caused by a dynamic distortion of the skull secondary to pre- and/or postnatal external forces without malformative alterations [3, 4]. Craniostenosis, by contrast, is a pathological condition of skull deformity caused by premature sutural closure of the vault and/or skull base, occasionally associated with early closure of cranial fontanels [5, 6]. Sutures are fibrous bands of tissue that connect the bones of the skull, allowing their growth from the inside to the outside during development, whereas the fontanels are membranes covering parts of the skull where the bones have not yet settled, allowing the skull bones to adapt to brain expansion (‘‘functional mobility’’ during the birth and during the first year of life) [7]. Normally, sutures and fontanels ossify (that is, they form synostoses) at different times after the birth. Specifically the metopic suture normally ossifies between 9 and 11 months, and the other sutures (sagittal, coronal and lambdoid) close completely at approximately 30–40 years of age. The anterior fontanel (bregmatic fontanel) typically ossifies within the second year of life, the posterior fontanel (lambdoid fontanel)
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Fig. 1 Sagittal arch a this is composed of the metopic suture (white arrow in b1 patent suture; black arrow in b2 synostotic suture), the sagittal suture (white arrows in c1 patent suture; black arrows in c2 synostotic suture) and the ethmoido-frontal (minor sutures) (white arrows in d1 patent sutures; black arrows in d2; synostotic sutures). It is responsible for the lengthening of the skull
Fig. 2 Coronal arch a this begins at the bregma and is composed of coronal sutures (b white arrow patent suture on the right side; black arrow synostotic suture on the left side), each divided into an anterior branch composed of the fronto-sphenoidal (minor sutures) (c white arrow patent suture on the left side; black arrow synostotic suture on the right side) and ethmoido-sphenoidal (minor sutures) synchondrosis (black arrow synostotic suture in d1; white arrow patent suture in
d2), and a posterior branch composed of the spheno-squamous (minor sutures) (e white arrow patent suture on the right side; black arrow synostotic suture on the left side), the spheno-parietal (minor sutures) (f white arrow patent suture on the left side; black arrow synostotic suture on the right side) and spheno-petrosal (minor sutures) synchondrosis (g white arrow patent suture on the right side; black arrow synostotic suture on the left side)
is no longer palpable after the first 3 months of life, the sphenoid fontanels (pteric fontanels) close after the first year of life, and the mastoid fontanels (asteric fontanels) ossify more often within the first 18 month of life [7, 8].
In craniostenosis, the welding of the skull sutures, which is sometimes associated with premature closure of the fontanels, occurs in the prenatal period, perinatal epoch, or during early infancy [1, 5]. The deformity, resulting from
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Fig. 3 Lambdoid arch a this starts at lambda and it is composed of the lambdoid sutures (b white arrow patent suture on the left side; black arrow: synostotic suture and a copper-beaten appearance of the skull on the right side), the spheno-occipital (minor sutures) synchondrosis (c white arrow) and occipito-mastoid (minor sutures) (d white arrow patent suture on the right side; black arrow synostotic suture on the left side)
pathological and premature sutural closure, progresses over time; therefore, timely diagnosis and immediate treatment are required. The incidence of craniostenosis is 1 in 2,100–2,500 newborns without any ethnic predilection [8]. Traditionally craniostenosis has been classified according to the sutures involved, the deformity of the head, the presence or absence of a skull-facial syndrome and the degree of progression of the anomaly [5, 8, 9]. Therefore, craniostenosis can be classified as simple (monosutural) or complex (multisutural) or as a primary defect of ossification or secondary to systemic disorders (endocrine, haematological, metabolic alterations) or iatrogenic causes. Most cases of craniostenosis (84 %) are found as an isolated defect (non-syndromic craniostenosis), although 15 % of cases are part of a syndromic condition (syndromic craniostenosis) [5, 8, 9]. Non-syndromic craniostenoses occur more commonly with the premature closure of a single or two major sutures, whereas cases of syndromic craniostenosis more frequently involve the fusion of several sutures and are often associated with facial deformities and brain anomalies [10]. However, it is
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important to note that the severity of the cranial deformity does not reflect the severity or the extent of the synostotic process; indeed, skull symmetry can be preserved when multiple sutures are symmetrically fused [11, 12]. Since its introduction, computed tomography (CT) has emerged as the technique of choice to confirm the clinical diagnosis, to define the extent of the synostosis and to exclude any associated anomalies and, consequently, to determine a prompt and accurate treatment. Therefore, CT with three-dimensional (3D) reconstructions represents the gold standard in the evaluation of skull sutures but is used, for radioprotective reasons, with a low-dose technique and only when it is deemed clinically necessary. Several studies have reported the high sensitivity (96.4 %) and specificity (100 %) of 3D CT in the identification of the vault sutures involved by the synostotic process, but no study has ever evaluated the accuracy and utility of spiral CT (low-dose technique) in identifying the extension of the synostotic process towards the skull base in children with a clinical suspicion of craniosynostosis [5, 9].
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Fig. 4 Parieto-squamosal arch a this is the junction of the coronal and lambdoid arches and it is responsible for the vertical growth of the skull. Parieto-squamous (b white arrow patent suture on the right side; black arrow synostotic suture on the left side) and parieto-mastoid (minor sutures) (c white arrow patent suture on the right side; black arrow synostotic suture on the left side) are a part of this arch
The lack of CT data in the involvement of the skull base sutures contradicts scientific reports that the synostotic process progresses over time along the four ‘‘sutural arches’’ of the skull [13–15]. These ‘‘arches’’ are formed by the sutures of the vault and the base (‘‘major’’ and ‘‘minor’’) as well as three synchondroses (Figs. 1, 2, 3, 4). The ‘‘minor’’ sutures and the synchondroses represent the extension of the vault sutures towards the skull base; synchondroses differ from the sutures because they are immovable joints, composed of hyaline cartilage between the two articular surfaces. There are seven synchondroses of the skull base, but only three of them make up the four ‘‘sutural arches’’ of the skull. The synchondroses normally ossify (i.e., they form synostoses) before or after birth at different times. In particular, the intra-sphenoidal synchondrosis (is) ossifies before or immediately after the birth; the spheno-ethmoidal synchondrosis (se) ossifies by the age of 6 years; and the spheno-occipital (so) between the 17th and 20th year. The anterior intra-occipital synchondrosis (io a) begins to ossify by year 1–2 and finishes by year 7–10, and the posterior intra-occipital synchondrosis (io p) begins to close by year 1–2 and finishes by year 4–7. The temporo-occipital or petrooccipital (to = po) and the spheno-petrosal (sp) synchondroses, however, exhibit residual cartilage throughout adolescence (Fig. 5) [7, 16]. Furthermore, in
the synchondroses, the cartilage can sometimes undergo early ossification, resulting in premature synostosis. This process has been demonstrated in experimental studies where genetic mutations have been considered the cause of the non proliferation of chondrocytes and, consequently, the cause of the synostosis of the synchondroses [17]. The sagittal arch (Fig. 1a) is composed of the sagittal and metopic sutures (major sutures) (Fig. 1b, c, arrows) as well as the ethmoido-frontal sutures (minor sutures) (Fig. 2d, arrows). The coronal arch (Fig. 2a) consists of the coronal sutures of both sides (major sutures) (Fig. 2b, arrows). The extension of each coronal suture toward the skull base is divided into an anterior and a posterior branch. The anterior branch (BA) is composed of the fronto-sphenoidal (fs) sutures (minor sutures) and the ethmoido-sphenoidal (es) synchondrosis (Fig. 2c, d, arrows), whereas the posterior branch (BP) consists of the spheno-parietal (spa) and spheno-squamous (sq) sutures (minor sutures) as well as spheno-petrosal (sp) synchondrosis (Fig. 2e–g, arrows). The lambdoid arch (Fig. 3a) consists of the lambdoid sutures (major sutures) (Fig. 3b, arrows) extending to the minor sutures of the skull base, including the occipito-petrosal or occipito-mastoid sutures (op = om), and the sphenooccipital synchondrosis (so) (Fig. 3c, d, arrows). The parieto-squamosal arch (Fig. 4a) represents the joint
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Fig. 5 Cranial base synchondroses. Anterior intra-occipital synchondroses (white arrows in a patent synchondroses); posterior intraoccipital synchondroses (white arrow in b patent synchondrosis; black arrow in b synostotic synchondrosis); temporo-occipital synchondroses (white arrows in c patent synchondroses); anterior intra-sphenoidal synchondroses (white arrow in d1 patent synchondrosis; black arrow
in d2: synostotic synchondrosis); spheno-ethmoidal synchondrosis (white arrow in e1 patent synchondrosis; black arrow in e2 synostotic synchondrosis); spheno-petrosal synchondroses (white arrows in f1 patent synchondroses; black arrows in f2 synostotic synchondroses); spheno-occipital synchondrosis (white arrow in g1 patent synchondrosis; black arrow in g2 synostotic synchondrosis)
between the coronal and lambdoid arches. This arch is responsible for the vertical growth of the skull and consists of the parieto-squamous (ps) and parieto-mastoid (pm) sutures (Fig. 4b, c, arrows) [13–15]. Our study, based on the recognition of the key role of these four ‘‘sutural arches’’ of the skull, demonstrates that 3D reconstructions of spiral CT in conjunction with bone algorithms and volume rendering allow for identification of the minor sutures and synchondroses of the skull base. In addition, we demonstrate that both the minor sutures and the synchondroses play a remarkable role in determining asymmetries of the cranial fossae and alterations of the facial skeleton [18].
Materials and methods
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Patients We retrospectively reviewed high-resolution CT images of 27 children with cranio-facial deformities secondary to craniosynostosis. Twenty-one children (14 males, 7 females) 1–67 months old (average, 18 months old) exhibited complex or multisutural synostoses (14 syndromic and 7 non-syndromic children), whereas six children (four males, two females) between the ages of 7 and 114 months old (average 37 months old) exhibited anterior synostotic plagiocephaly (Table 1).
Radiol med (2014) 119:694–704 Table 1 Classification craniosynostosis
of
699 27
Synostosis
patients
Patients
diagnosed
Sex (n)
The CT scan was performed using a multidetector scanner (LightSpeed Pro 64, GE Medical System, Milwaukee USA) without the injection of contrast medium. The scanner was equipped with automatic tube current modulation techniques. In most children, the algorithm AutomA 3D was used, although in the last two patients, the adaptive statistical iterative reconstruction (ASIR) algorithm was used. CT was performed under spontaneous sleeping or under sedation in a small number of cases.
Age (months)
M
F
14
8
6
12
Non-syndromic pansynostosis
7
6
1
27
Anterior synostotic plagiocephaly
6
4
2
37
Syndromic pansynostosis
CT
with
m male, f female
Table 2 Distribution of synostoses in patients with craniosynostosis Patients
Sagittal arch
Coronal arch
Lambdoid arch
Major
Major
Major
Minor
Minor BA
Parieto-squamosal arch Minor
Major
Minor
BP
Syndromic pansynostosis 1-Pfeiffer
S, M
efr-l
Cr–l
–
sp, sqr–l, spar–l
Lr–l
omr–l
pqr–l
pmr–l
2-Crouzon
S, M
efr–l
Cr–l
fsr–l, es
sp,sqr–l, spar–l
Lr–l
omr–l so
pqr–l
pmr–l
3-Crouzon
S, M
efr–l
Cr–l
–
spr, sqr–l, spar–l
–
omr–l
pql
pmr–l
4-Crouzon
–
–
Cd-s
–
spar
–
–
psd-s
–
5-Apert
–
efr-l
Cr–l
fsr–l, es
spl, sql, spal
–
–
–
–
6-Not specified
M
–
Cr
–
–
Lr–l
–
–
–
7-Crouzon
S, M
efr–l
Cr–l
fsr–l, es
spl, sql, spar-l
Lr–l
omr–l
pql
pmr–l
8-Not specified
S, M
–
Cr–l
fsr–l, es
spar–l
–
oml
pql
pmr–l
9-Crouzon
M
–
Cr
–
–
–
–
pqr–l
–
10-Crouzon
S
–
–
fsr
sqr, spar
–
omr–l
–
pmr
11-Pfeiffer 12-Not specified
– –
– –
Cl Cr–l
fsl –
– –
– Lr–l
– –
– –
– –
13-Apert
–
–
Cr–l
fsl
–
–
–
–
pmr
14-Crouzon
–
–
–
–
sqr–l
–
–
–
pmr
Non-syndromic pansynostosis 1
S, M
–
Cr–l
2
S
–
–
–
3
S, M
–
–
–
4
S, M
efr–l
Cr–l
fs, esr–l
5
S, M
–
Cr–l
6
M
efr–l
7
M
fsr, es
–
Lr–l
–
–
–
–
Lr
–
–
–
–
Lr–l
–
–
–
spr,sqr–l, spar–l
Lr–l
omr–l
pqr–l
pmr–l
–
–
Lr–l
–
–
–
Cl
fsl
–
–
–
pql
–
–
Cl
–
–
Lr
–
pql
pml –
Anterior plagiocephaly 1
M
–
Cr
fsr
–
–
–
–
2
–
–
–
fsl
–
–
–
–
–
3 4
M –
– –
Cr Cr
– –
– –
– –
– –
– –
– –
5
M
–
Cl
fsr–l
–
–
–
–
–
6
–
–
Cl
–
–
–
–
–
–
Major sutures: C coronal, M metopic, S sagittal, L lambdoid, pq parieto-squamosal Minor sutures: sagittal arch: ef ethmoido-frontal, coronal arch: BA anterior branch (fs fronto-sphenoidal, es ethmoido-sphenoidal), BP posterior branch (spa spheno-parietal, ss spheno-squamous, sp spheno-petrosal), lambdoid arch: om occipito-mastoid or occipito-petrosal, so sphenooccipital, parieto-squamosal arch: pm parieto-mastoid, r–l right–left
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Table 3 Synostoses of fontanel and synchondroses in patients with craniosynostosis Patients
Age (months)
Fontanel
Synchondroses
A
P
S
M
so
is
to
io (a)
io (p)
se
sp
Syndromic pansynostosis 1-Pfeiffer
19
–
Yes
Yesr–l
Yesr–l
–
Yesr–l
–
–
Yesr–l
–
Yesr–l
2-Crouzon
34
–
Yes
Yesr–l
–
Yes
Yesr–l
–
–
–
Yes
Yesr–l
r–l
–
Yesr
3-Crouzon
22
Yes
Yes
Yes
–
–
Yes
4-Crouzon
2
–
–
5-Apert
8
–
–
–
–
–
Yesr–l
yesl
–
6-Not specified 7-Crouzon
3 36
– Yes
Yes Yes
– Yesr–l
– Yesr–l
8-Not specified
9
Yes
–
Yesr–l
Yesl
r–l
r–l
r–l
r–l
–
–
Yes
–
–
–
–
–
–
–/Yesr–l
–
–
–
Yes
Yess
– –
– Yesr–l
– –
– –
– –
– Yes
– Yess
–
–/Yesr–l
–
–
–
yes
–
–
Yesr–l
–
–
–
–
– –
9-Crouzon
30
Yes
Yes
Yes
10-Crouzon
3
–
–
–
–
–
–
–
–
–
11-Pfeiffer
6 days
–
–
–
–
–
–
–
–
–
–
–
12-Not specified
4
–
Yes
–
–
–
–
–
–
–
–
–
13-Apert
3
–
–
–
–
–
–
–
–
–
–
–
14-Crouzon
5
–
–
–
–
–
–/Yesr–l
–
–
–
–
–
–
–
–
–
–
Yesr–l
Yes
Non-syndromic pansynostosis 1
48
–
–
Yesr–l
r–l
yes
–
2
8
–
Yes
–
–
–
–/Yes
–
–
–
–
–
3
8
–
Yes
–
–
–
–/Yesr–l
–
–
–
–
–
–
–
–
Yes
Yesd
–
–
– –
– –
4
40
Yes
Yes
Yes
r–l r–l
Yes
r–l
Yes
r–l
–
Yes
r–l r–l
–
–
Yes
– –
– –
– Yesl
5
67
Yes
Yes
Yes
–
Yes
6 7
14 7
– –
– –
Yesl Yesl
– –
– –
Yesr–l –
r-l
Anterior plagiocephaly 1
18
yes
–
Yesr
–
–
Yesr–l
–
–
–
–
–
2
7
–
–
–
–
–
–
–
–
–
–
–
3
15
–
–
–
–
–
–/Yesr–l
–
–
–
–
–
4
26
–
–
–
–
–
–
–
–
–
–
–
5
114
Yes
Yes
Yesrl
Yesr–l
–
Yesr–l
–
–
Yesr–l
–
–
–
r–l
–
–
–
–
–
6
44
–
–
Yes
l
–
Yes
A anterior or bregmatic, P posterior or lambdoid, S sphenoidal or pterica, M mastoid or asterica, so spheno-occipital, is inter- or intra-sphenoidal, to temporo-occipital or petro-occipital, io(a) anterior intra-occipital, io(p) posterior intra-occipital, se spheno-ethmoidal, sp spheno-petrosal, l left, r right, – patent, yes synostosis, –/yes partial synostosis
Table 4 Findings regarding cranio-facial abnormalities in children with craniosynostosis Synostosis
Patients
Skull shape deformity
Superior orbital fissure displacement
Ethmoidal axis deviation
Nasal root deviation
Forehead deformation
Syndromic pansynostosis
14
14
13
10
8
13
Non-syndromic pansynostosis
7
7
5
4
4
4
Anterior plagiocephaly
6
6
6
6
3
6
After the acquisition of a topogram (scout view), a spiral scan was acquired from the lower limit of the C2 soma up to 1 cm cranial of the vertex without inclination of the scanning planes. Image acquisition was performed with the following parameters: 100–120 KVp,
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50–280 mAs, scan time 1 s, small field of view (FOV 18–20 cm), slice thickness 1.25 mm and convolution filter for soft tissue. Beginning from the native axial images, the data were processed using multiplanar reconstructions with bone
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Table 5 Orbital rim deformity in patients with coronal arch synostosis Synostosis
Coronal arch
Orbital rim deformity
Coronal suture
Coronal and fs sutures
fs
None
Elevated (‘‘harlequin’’ deformity)
Depressed and recessed
Syndromic pansynostosis
6
6
1
1
7
1
Non-syndromic pansynostosis
2
3
–
2
3
–
Anterior plagiocephaly
3
2
1
–
5
1
fs fronto-sphenoidal Table 6 Chiari 1 malformation in patients with lambdoid arch synostosis Synostosis
Lambdoid arch
Low insertion of the tentorium
Chiari 1
Major sutures
Minor sutures (om)
Major and minor sutures
Syndromic pansynostosis
2
3
3
7
5
Nonsyndromic pansynostosis
5
–
1
4
4
children exhibited synostosis of the sutures of the coronal arch, five children exhibited ‘‘harlequin’’ deformity of the orbit, and one child exhibited superior orbital roof displacement (Table 5). In the group of newborns with complex craniostenosis (syndromic and non-syndromic), in which the synostotic process involves the sutures of the lambdoid arch, 11 out of 15 children exhibited a low insertion of the tentorium. Of these 11 children, nine exhibited caudal herniation of the cerebellar tonsils towards the magnum foramen (Chiari 1) (Table 6).
om occipito-mastoid
algorithms with a thickness of 0.65 mm and 3D volume rendering reconstructions (3D VR). Using complementary 2D multiplanar images with bony algorithm and 3D VR reconstructions, all of the sutures (minor and major), the synchondroses of the four sutural arches and any synostosis were assessed in each child. Moreover, the remaining synchondroses of the skull base and cranial fontanels were also identified.
Results The results of our study are presented in Tables 2, 3, 4, 5 and 6. All of the examined children with craniosynostosis exhibited synostosis of both the ‘‘major’’ and ‘‘minor’’ sutures of the four ‘‘sutural arches’’ of the skull (Table 2) as well as synostosis of the synchondroses and the fontanels (Table 3). The patients consequently exhibited craniofacial alterations (cranial deformity, superior orbital rima deformity, nasal root deviation, ethmoidal axis deflection) (Table 4). Facial alterations were observed in the majority of children with synostosis of the coronal arch. In the group of children with complex craniostenosis (syndromic and nonsyndromic), 18 out of 21 children exhibited synostosis of the sutures of the coronal arch, 10 children exhibited ‘‘harlequin’’ deformity of the orbit, and only one child exhibited superior orbital roof displacement (Table 5). In the group with anterior synostotic plagiocephaly, all
Discussion The evaluation of cranial deformities in newborns necessitates that clinicians be able to distinguish, above all, between positional plagiocephaly and craniostenosis. In ambiguous cases or cases with a clinical suspicion of craniostenosis, diagnostic imaging plays a key role in the diagnosis. In particular, 3D CT has revolutionised the diagnostic evaluation, the planning of surgical procedures, the post-surgical evaluation and the follow-up [5, 18]. Diagnostic imaging is useful to evaluate the involvement of the sutures in the synostotic process and to assess intracranial alterations that can be associated with craniostenosis. However, it should be emphasised that the use of the CT, although it allows the rapid acquisition of images without the use of anaesthesia, exposes newborns to a nonnegligible dose of radiation [5]. Brenner et al. have reported the noticeable and quantifiable risk of ionising radiation exposure in children in developing cancer in advanced age. Brenner et al. [19, 20] have also demonstrated that this risk dramatically decreases with increasing age, especially during the first year of life. The diagnostic technique of choice in children with craniostenosis remains a point of controversy and is partially dependent on the skull-facial malformations of the child. Some authors have suggested the utility of alternative techniques to CT, such as ultrasound and conventional radiography of the skull, in children with cranial deformities associated with a lower clinical suspicion of
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craniosynostosis or in children with the clinical suspicion of simple monosutural craniostenosis [19]. Nevertheless, other authors underline the high sensitivity (96.4 %) and specificity (100 %) of low-dose CT with 3D maximum intensity projection (MIP) reconstructions for the identification of synostosis of the vault sutures in newborns with craniosynostosis associated with serious skull-facial deformities (complex craniostenosis) [18, 21]. In this regard, almost all of the modern MDCT scanners are currently equipped with some type of automatic exposure control (AEC) or automatic tube current modulation (ATCM) technique [22]. In our study, in most of the patients, we used the dose modulation technique called AutomA 3D, whereas more recently in two cases, the default ASIR algorithm was used. These systems permit further reduction of the radiation dose to the newborn by predicting the dose length product (DLP) and calculating the effective dose (E) that reflects the stochastic risk from exposure to ionising radiation (Table 7). Vannier et al. have reported differences in the diagnostic performance of 3D CT between experienced and less experienced radiologists. Specifically, the authors have described a lower specificity of 3D CT (83.3 %) among less experienced radiologists. The authors have also described other 3D reconstruction algorithms, including surface projection rendering (SPR) for craniostenosis, although this algorithm is not as widely available as 3D MIP [21, 23]. To date, however, no study has considered the effectiveness and the importance of low-dose spiral CT in identifying and assessing the vault sutural extension toward the skull base [18, 24]. Our study demonstrates the utility of spiral tomography with a multidetector scanner (64-slice MDCT) using bone algorithms as well as 2D and 3D VR reconstructions in identifying the suture/synchondroses that form the four arches of the skull, the remaining synchondroses of the skull base and, consequently, the identification of possible synostosis.
Table 7 Mean values of radiation dose for unenhanced computed tomography (CT) of the brain in patients with craniosynostosis Volume coverage
From the soma of C2 to 1 cm cranial to the vertex
Scan parameters
100–120 kVp; 50–280 mAs
Dose modulation
On: Smart–mAp (x–y–z axis dose modulation); ASIR
CTDIvol (mGy)
12.09–43.11
DLP (mGy 9 cm)
90–375
Effective dose (mSv)
1.0–1.2
CTDIvol volume CT dose index, DLP dose length product, ASIR adaptive statistical iterative reconstruction
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Thus, starting from the functional meaning of the 4 four sutural arches of the skull (sagittal arch, coronal arch, lambdoid arch and parieto-squamous arch), we identified, for each arch, the sutures/synchondroses that were prematurely fused in 21 children with complex craniostenosis (syndromic and non-syndromic) and in six children with anterior synostotic plagiocephaly (Tables 2, 3). All of the examined children with craniosynostosis exhibited, with variable distribution, synostoses of both the ‘‘major’’ and ‘‘minor’’ sutures and synchondroses of the four arches (Table 2) as well as of the skull base (Table 3), resulting in skull-facial deformity. Consistent with many previous studies [14, 25–29], our data confirmed the high frequency of facial alterations and the hemibase asymmetry of the anterior cranial fossa in all of the newborns in whom the synostotic process involved the sutures of the coronal arch, especially the coronal and the fronto-sphenoidal sutures [13]. Indeed, most of studied children with craniostenosis exhibited synostosis of one or more sutures of the coronal arch (24 out of 27) and consequently skull shape deformity, median axis deviation of the anterior skull base (ethmoidal axis) and orbit deformation (Table 4). In agreement with current data, our results confirm that the orbital ‘‘harlequin’’ deformity is present both in children with isolated synostosis of the coronal suture (‘‘major’’ suture of coronal ring), and in children with associated ipsilateral synostosis of the coronal and frontosphenoidal sutures (‘‘major’’ suture and ‘‘minor’’ suture of the BA of the coronal ring) [30]. Children with isolated synostosis of the coronal suture (n = 8) exhibited a more pronounced orbital ‘‘harlequin’’ deformity than did children with associated ipsilateral synostosis of the coronal and fronto-sphenoidal sutures (n = 7). The recessed orbital rim is a rare and exclusive finding in children with isolated synostosis of the fronto-sphenoidal suture [13, 25]; indeed, in our study, this finding was identified in 2 out of 27 children (Table 5; Fig. 6). Nevertheless, unlike anterior synostotic plagiocephalies, in newborns with multiple synostosis (syndromic and nonsyndromic synostosis) in which coronal ring synostosis was identified, the severity of the facial deformity (particularly orbital dysmorphism) and the asymmetry of the anterior skull base was not very evident; this may be a result of the symmetry of the synostotic process along the sutures of the coronal ring or the time course of the synostotic process. To date, different authors have confirmed the utility of low-dose spiral CT in children with complex or multisutural synostosis in avoiding irradiation in newborns with the clinical diagnosis of monosutural synostosis [18, 19, 21]. However, we believe that low-dose spiral CT can be suitable in children with anterior synostotic plagiocephaly because high-resolution CT has the ability to identify the ‘‘minor’’ sutures of the coronal arch and, therefore, to
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Fig. 6 Orbital rim deformity in children with anterior synostotic plagiocephaly. Child with right coronal suture synostosis. Threedimensional computed tomography (3D CT) (a1, a2) and axial CT image (a3, a4) show, on the right side, coronal synostosis (black arrows in a2, a3) and a patent fronto-sphenoidal suture (arrow heads in a2, a4). Note the elevation and relative vertical overgrowth of the right sphenoid, especially in the lateral portion of the greater wing, creating the harlequin’s eye (a1). Coronal and fronto-sphenoidal sutures are patent on the left side (white arrows in a3, a4) Child with left fronto-sphenoidal suture synostosis. 3D CT scan (b1, b2) and axial CT images (b3, b4) show, on the left side, an absent fronto-
sphenoidal suture (arrow heads in b2–b4) and a patent coronal suture (black arrows in b2, b3). The roof of the left orbit is depressed with obvious retrusion of the lateral part of the supraorbital rim (b1). Coronal and fronto-sphenoidal sutures are patent on the right side (white arrows in b3, b4) Child with left fronto-sphenoidal and coronal sutures synostosis. 3D CT scan (c1, c2) and axial CT image (c3, c4) show, on the left side, both fronto-sphenoidal suture (arrow head in c2–c4) and coronal suture synostosis (black arrow in c2, c3). Note the right orbital elongation but less than children with isolated coronal synostosis (c1). Coronal and fronto-sphenoidal sutures are patent on the right side (white arrow in c3, c4)
evaluate the extension of the synostotic process toward the skull base and the consequent asymmetric deformity of the anterior cranial base. These data can modify the therapeutic choice guiding toward timely and appropriate treatment. In our study of 15 children with complex craniostenosis in which the synostotic process involved the sutures of the lambdoid arch, 11 out of 15 children exhibited a low insertion of the tentorium, and 9 out of 15 exhibited caudal herniation of the cerebellar tonsils in the magnum foramen (Chiari 1 malformation) (Table 6). Different authors have described the frequent evidence of Chiari 1 malformation in children with syndromic multisutural or monosutural craniostenosis,
describing the main contribution of the synostosis of the lambdoid suture in this dynamic and complex process [31]. Other authors have explained the onset of the Chiari 1 malformation not only with the reduction in volume/ deformity of the posterior cranial fossa secondary to synostosis of the lambdoid suture but also with the altered fluid dynamics [32]. Our data confirm the importance of the lambdoid arch as well as the involvement of both the ‘‘major’’ and ‘‘minor’’ sutures (individually or in combination) in the onset of the Chiari 1 malformation. Therefore, we are proceeding to volumetrically evaluate, using magnetic resonance (MR) imaging, the posterior cranial fossa and the infra-tentorial compartment. In the
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same study, we are evaluating some of the morphometric parameters of the posterior cranial fossa (diameter of the foramen magnum, tentorial angle, and supraoccipital and basioccipital lengths) in children with craniostenosis and with other syndromic conditions in which Chiari 1 malformation is present to better explain the mechanisms of the cerebellar herniation and the variable timing of development. In conclusion, in the study of craniostenosis, low-dose CT with 3D VR reconstructions allows the prompt and precise identification of the extension of the synostotic process towards the skull base, which has important implications for surgical planning. Conflict of interest R Calandrelli, G. D’Apolito, S. Gaudino MD, M.C. Sciandra, M. Caldarelli, C. Colosimo declare no conflict of interests.
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