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Fig. 20.12 Schematic drawing of Arnold-Chiari malformation. (Reprinted from ellepigraca/alamy.com with permission)
B. Homann et al.
There is general agreement on timing of surgery in cases of craniosynostosis with Chiari malformation and hydrocephalus: these cases should
be treated by ventricular shunting prior to correction of craniosynostosis. A controversial discussion remains for the best timing of craniocervical
decompression or the appropriate timing and technique of surgery for syringomyelia [40–42]. Some
authors recommend craniocervical decompression
at the time of craniosynostosis correction [41], but
there were also observations of improvement of
tonsillar herniation after craniosynostosis surgery.
Other groups even propose craniocervical decompression prior to craniosynostosis repair [40].
So all kinds of surgical techniques of craniosynostosis imply signicant stress for the small patients
Fig. 20.13 Patient with Crouzon syndrome after fronto-
orbito- nasal advancement. Mild Chiari malformation with
tonsillar herniation and signicant syringomyelia
including anesthesia, articial ventilation, bleeding
with blood transfusions, and other interventions.
Craniocervical decompression is far away to be a
small intervention as well, we prefer surgery on
ataxia, and disorders of the vegetative functions.
A typical symptom in children is the appearance
of scoliosis of the cervical spine. All of the
symptoms are difcult to evaluate in small children, so it needs neuropediatric expertise to
detect the clinical state for further decisions on
therapy [20, 22].
craniosynostosis rst, followed by surgery of
Chiari syndrome later depending on the clinical
course of the patient and follow-up MRT controls.
This includes the coincidence with syringomyelia,
because not all of the cases improve after surgery
and need extended decompression of the syrinx by
drainage into the spinal subarachnoid space.
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20.9 Summary
Neurosurgical investigation of patients with craniofacial malformations needs a reliable interdisciplinarity between neurosurgeons, neuropediatric
specialists, as well as ophthalmologists and cranio-maxillo-facial surgeons. Diagnostics must not
only precisely dene the diagnosis and its expression in an individual case but must also respect
pathophysiological mechanisms to develop a
therapeutic concept for the patient including an
appropriate timing for surgical interventions. If
cases of nonsyndromic single- suture synostosis
of the sagittal suture with scaphocephaly may be
sufciently diagnosed by anamnesis, clinical
examination, and sonography, complex cases of
syndromic pansynostosis require an interdisciplinary diagnostic concept including molecular
genetics, developmental state, and CAT and
MRT scans.
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Radiological Investigations
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ofCraniofacial Malformations
ChristophMönningho
21
Abbreviations
2D two-dimensional
3D three-dimensional
4D four-dimensional
CBCT cone beam computed tomography
CT computed tomography
DVT digital volume tomography
MDCT multidetector computed tomography
MPR multiplanar reconstruction
MRI magnetic resonance imaging
OAVS oculo-auriculo-vertebral spectrum
TCS Treacher Collins syndrome
US ultrasound, ultrasonography
VRT volume rendering technique
21.1 Radiological Imaging
Modalities forCraniofacial
Malformations
Imaging of craniofacial malformations is crucial
for the precise pre- and postnatal diagnosis, surgical therapy planning, therapy monitoring, and
for the exclusion of intracranial pathology and
other complications associated with these malformations. Interdisciplinary diagnosis and treatment of these craniofacial developmental
disorders by pediatricians, neurosurgeons, maxillofacial surgeons, and radiologists is based not
only on clinical examination but also on US, conventional X-rays, CT, and MRI.The optimal use
of these different imaging modalities for the visualization of craniofacial bone structures and soft
tissues requires knowledge of the normal anatomy and the diagnostic advantages and disadvantages of the different methods.
21.1.1 Cranial Ultrasonography
C. Mönninghoff (*)
Department of Radiology, Neuroradiology and Nuclear
Medicine, Johannes Wesling University Hospital,
Ruhr University Bochum, Minden, Germany
Institute for Diagnostic and Interventional Radiology
and Neuroradiology, University Hospital Essen,
Essen, Germany
e-mail: christoph.moenninghoff@
muehlenkreiskliniken.de
© Springer Nature Switzerland AG 2021
U. Meyer (ed.), Fundamentals of Craniofacial Malformations,
https://doi.org/10.1007/978-3-030-46024-2_21
A basic principle of pediatric radiology is to keep
exposure to X-rays for children as low as possible.
Ultrasound (US) is always the rst study of choice
in the fetus and nearly always the rst in neonates
[1, 2]. This imaging technique requires no ionizing
radiation, is noninvasive, inexpensive, and mostly
available. US examinations can be performed
repeatedly pre- and postnatal without sedation [3,
4]. In recent years, high-quality US examinations
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a
c
Fig. 21.1 Ultrasonographic image of a closed metopic
suture (a) of a 3-month-old girl. The outer layer of the
cortical bone of the skull is already closed. A transversal
sonogram of the lambdoid suture reveals it as an open
hypoechoic gap between the hyperechoic frontal bones (b
markedly improved by the introduction of highfrequency transducers, high- bandwidth tissue harmonic imaging techniques, and the use of multiple
acoustic windows with competitive results for cranial exams in newborns compared to MRI [5]
(Fig.21.1). After the rst months of life, the closing fontanels and sutures limit the applicability for
cerebral and spinal imaging of infants, making
MRI the imaging method of choice [1]. A welltrained sonographer can verify the results of US
examinations by the targeted use of multiple transducers functioning at variable frequencies, a combination of vector, curved, and linear array
b
SSS
d
right, c left side). The sagittal suture (d) is still patent
revealing the superior sagittal sinus (SSS) and underlying
interhemispherical ssure between the frontal lobes.
Courtesy of Dr. Ulrike Materna, Clemenshospital
Muenster, Germany
transducers used with adjusted frequencies
(between 8 and 17MHz). All sutures and regions
of the brain can be analyzed via the anterior and
posterior fontanels and the temporal, mastoid, and
occipital synchondroses. Changes in echogenicity
can be monitored in real time and at several examination time points [6]. Doppler techniques reveal
peak systolic velocities, end-diastolic velocities,
and resistive indices of larger physiological and
pathological vessels. It is a helpful imaging technique to differentiate vascular malformations, e.g.,
arteriovenous malformations, hemangioblastomas, and lymphangiomas [7, 8].
21 Radiological Investigations ofCraniofacial Malformations
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21.1.2 Magnetic Resonance Imaging
(MRI)
Diagnostic neuroimaging performed with MRI is
often dependent on sedation to acquire diagnostic
images in children. In the hospital setting, permanent monitoring and MR-compatible life-support
equipment has to be available for pediatric
patients [9]. In general, MRI is the imaging study
of choice in children older than 4 months [6].
Cerebrospinal and soft tissue anatomy can be well
depicted in high anatomical resolution with
detailed soft tissue contrast. The use and dosage
of gadolinium has to be determined, and imaging
protocols have to be adapted to compensate for
the smaller size of the pediatric brain, the different
water content, and the varying status of myelinization. Besides multiplanar anatomical imaging
of the craniofacial region, specic MR sequences
allow for vascular, microstructural, and metabolic
imaging. MRI with tailored imaging protocols
can add valuable diagnostic information and
greatly improve the medical care of children with
neurological and craniofacial disorders.
facial malformations involving bony structures.
For radiation protection reasons, it is only used at
the end of the rst year of life and as late as possible in children with diagnosed complicated types
of craniosynostosis [18]. With modern multidetector CT scanners, 3D scans of the skull can be
acquired in diagnostic image quality with approximately 0.2–2mSv effective doses [19–21]. In combination with model-based iterative reconstruction
algorithms, 3D CT scans of the head with
0.008 mSv are reported without reduced image
quality [22]. In phantom studies, ultralow-dose CT
protocols of the head have been acquired with
0.02mSv dose equal to the exposure to radiation of
a plain skull radiography ranging from 0.01 to
0.04mSv [
tor CT (MDCT), also known as medical CT, has an
important role in the diagnosis and management of
craniofacial injuries and pathology. Microcomputed tomography (micro-CT) has accelerated
craniofacial biology research by allowing higherresolution scanning of teeth beyond the capabilities
of MDCT and CBCT [23].
11]. Current state-of-the-art multidetec-
21.1.3 Computed Tomography (CT)
In the pediatric population, the use of CT carries a
signicantly increased risk of malignancy in later
life. Hence, the exposure of children should be limited to the diagnostic minimum necessary to prevent radiation-associated diseases, e.g., radiation
cataract after repeated CTs of the eye lens. The perception of this problem has led to the denition of
low-dose protocols including iterative reconstructions. Especially children with craniofacial malformations may benet from these low-dose CTs, if
repetitive CT examinations are unavoidable for
posttreatment monitoring [10–15]. Multidetector
CT (MDCT) technology has signicantly accelerated acquisition times. Fewer than 1.5% of pediatric patients now require sedation with this imaging
modality [16]. With adapted protocols for midface
structures, radiation dose can be reduced by 89%
compared with conventional craniofacial CT scans
with adequate diagnostic quality [17]. Two- and
three-dimensional CT still play a prominent role in
the diagnostic and preoperative imaging of cranio-
21.1.4 Digital Volume Tomography
(DVT)
Digital volume tomography (DVT), based on 3D
cone beam CT (CBCT) and the principles of rotational tomography, was introduced in 1998in preoperative dental and craniofacial imaging [24].
This imaging technique produces similar 3D
images to CT with faster image acquisition but at
a radiation dose comparable with panoramic radiography and at lower cost [25]. For high-contrast
structures of the midface, DVT can be considered
as the gold standard for imaging the oral and maxillofacial area and as an alternative imaging
modality to CT for midface structures [25–27].
21.1.5 Plain Radiography
Digital X-ray detectors use X-ray-sensitive plates
to directly capture data during the patient examination, immediately transferring it to a computer
system without the use of an intermediate cassette [28]. In pediatric patients, plain radiogra-
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C. Mönningho
phy, including computed radiography (CR) and
digital radiography (DR), is only used for specic
diagnostic questions, e.g., for nondepressed linear skull fractures or single-suture craniosynostosis [29–31]. The latter may depict as a linear
sclerotic line, which correlates with a bony ridge
on CT images. Digital radiography causes much
lower radiation exposure than CT, but spatial
resolution and detailed depiction of bone structures is also very limited in plain radiography.
Therefore, plain radiographs are usually postponed to the date of surgery or the end of the rst
year [30].
21.2 Craniosynostosis
Craniosynostosis is based on a premature fusion
of one or more cranial sutures that exist along
adjacent cranial bones, namely, the frontal, parietal, temporal, and occipital bones [18]. If left
untreated, premature fusion may cause skull
deformities, facial asymmetry combined with
pathologically increased intracranial pressure,
deafness, visual impairment, and cognitive
decline [18, 32–37]. The incidence is about
1–2000 live births [38]. Craniosynostosis can be
subdivided into two categories. Primary craniosynostoses are the premature fusions of one or
more cranial sutures based on a developmental
defect during embryogenesis. Secondary craniosynostoses include the premature ossication and fusion of the skull sutures due to other
causes such as teratogens, intrauterine cranial
compression, extrauterine positional deformity,
or insufcient cerebral growth. Craniosynostoses
may occur sporadically in single individuals as
nonsyndromic craniosynostosis in 85% of all
cases or as a manifestation of syndromes in
combination with other developmental anomalies (syndromic craniosynostosis) in 15% of
cases [39, 40]. The cranial vault may be variably
deformed, depending on the fused sutures with
compensatory growth of the skull in the regions
that are not restricted by prematurely closed
sutures. Single- suture synostosis occurs as
scaphocephaly from premature sagittal synostosis along the sagittal suture, as trigonocephaly
caused by premature metopic synostosis along
the metopic suture, and as plagiocephaly secondary to unilateral premature coronal or lambdoid suture synostosis [
After clinical examination, US is the rst-line
imaging modality for neonates and infants
younger than 8–12 months with suspected craniosynostosis [1, 42, 43]. Compared to CT, cranial US is an effective and reliable technique for
the diagnosis of closed sutures with 100% sensitivity and 86–100% specicity before the age of
12months [3] (Fig.21.1). In children with abnor-
mal or asymmetric skull shape, e.g., from deformational plagiocephaly, US has proven to be an
effective screening tool for craniosynostosis [
43, 44]. Two- and three-dimensional (2D/3D) US
are successfully applied for skull deformities
even in the prenatal period [4, 45, 46].
In children older than 12 months, MRI
becomes increasingly important to assess sutures
and underlying cerebral pathologies as fontanels
and sutures get closed and sound windows for
ultrasonography shrink. A black bone MR
sequence performed as a 3D low ip angle
gradient- echo MRI sequence may have the potential to replace CT for the diagnosis and monitoring of craniosynostosis [47]. MR imaging is the
imaging modality of choice in infants with congenital midface masses and craniofacial syndromes [48]. Despite radiation exposure, cranial
CT with 3D reconstructions of the calvarium is
requested by many surgeons in order to plan individualized reconstructive operations (Fig.21.2).
Two-dimensional reformatted images of highresolution CT scans in axial, coronal, and sagittal
orientation, which are obtained at a slice thickness of 3mm or less with a bone algorithm, are
suitable to assess osseous midface and calvarial
deformities easily. Anomalies of the external and
middle ear resulting from the abnormal formation of the skull base are best depicted on 1mm
CT sections acquired with bone algorithm
through the petrous pyramids supplemented by
coronal reformations to reveal possible asymmetries [18]. Both CT and MR imaging are required
to comprehensively assess skull, brain, and soft
tissue disorders of midface anomalies and craniofacial syndromes [48].
41].
2,
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a
c
b
d
Fig. 21.2 Transversal CT images of a 10-month-old boy
with metopic craniosynostosis (white Arrow) in brain
window (a, c) and in bone window (b, c). The coronal and
lambdoid sutures (b, black arrows) are regularly open,
whereas the prematurely fused metopic suture (white
arrow) forms palpable ectocranial ridge with trigonoceph-
aly and parieto-occipital bossing due to the constricted
growth of the frontal bone. After neurosurgical correction
with opened metopic and coronal sutures (c, d) a normal
oval head form was reconstructed. Courtesy of Dr. Claudia
Moeller-Hartmann, University Hospital Essen, Germany
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C. Mönningho
21.2.1 Nonsyndromic
Craniosynostosis
In 85% of cases, craniosynostosis is not accompanied by other developmental disorders
(nonsyndromic) [49]. Recent analysis of exome
sequence data from nonsyndromic craniosynostosis has underlined the impact of genetic mutations in one-quarter of sporadic cases with
detected mutations in two genes, TCF12 and
ERF [50, 51]. Depending on which suture is
affected, nonsyndromic craniosynostosis occurs
as sagittal, coronal, metopic, lambdoid, or multisuture synostosis. Ultrasonographic key features of craniosynostosis are the loss of the
hypoechoic brous gap between the hyperechoic
bony plates, an irregular sclerosed inner sutural
margin, the loss of a beveled edge, and asymmetric fontanels [52]. Isolated single-suture craniosynostosis or positional plagiocephaly is
diagnosed clinically and may be conrmed by
digital X-ray images of the skull. Cross-sectional
imaging studies are not indicated to assess single,
nonsyndromic sutures. Especially, CT scanning
should be indicated carefully for the assessment
of single-suture craniosynostosis taking into
account that there is a quantiable risk of developing cancer in further lifetime [30]. If inevitable, low-dose CT images (20–30 mAs) with
three-dimensional reformations depict prematurely closed sutures as sclerotic bony bridges
with reduced serration linearly along the affected
suture. The complete absence or pathological
shortening of a suture on plain radiographs of the
skull and on “black bone” MRI indicates craniosynostosis [18, 40, 53].
Sagittal synostosis results in scaphocephaly
with occipital protrusion and ridging of the fused
sagittal suture with frontal bossing. Also clinocephaly with attened calvarium and tall and narrow skull deformities (leptocephaly) can develop
from sagittal synostosis [18, 54]. Coronal synostosis causes a growth disturbance of the skull in
anterior-posterior direction along the coronal
suture with compensatory expansion of the skull
in parietal direction. Anterior plagiocephaly is a
result of unicoronal synostosis with diminished
anterior cranial fossa and contralateral frontal
bossing and elevated roof and lateral wall of the
ipsilateral orbit (“harlequin appearance”) [
The bicoronal craniosynostosis leads to a shortening of the skull (brachycephaly) and is often
associated with upper and midface hypoplasia
and craniofacial deformities in syndromic cases
(Fig.21.3).
Metopic synostosis, which is in one-third of
cases syndromic, results in a too small anterior
cranial fossa with a triangular pointed forehead
(Fig. 21.2). It needs to be distinguished from
metopic ridge, which is a physiological variant of
the closed metopic suture in 4% of children
between 0 and 18months of age without trigonocephaly or other symptoms [55].
Lambdoid synostosis may occur uni- or bilaterally. Unilateral lambdoid synostosis results in
posterior plagiocephaly (oblique deformity of the
posterior cranium), which is more often caused
by positional deformation (deformational or
positional plagiocephaly) than by premature
fusion of this cranial suture. The rst is based on
an asymmetric occipital attening of the skull
after preferred head positioning on one side during sleep. It can be treated conservatively,
whereas the latter needs surgical correction. If
the lambdoid suture synostosis occurs bilaterally,
a tower-like deformation of the skull (turricephaly, oxycephaly, or acrocephaly) results.
Multisuture craniosynostosis is mostly syndromic with variable patterns, depending on the
affected sutures. If coronal, lambdoid, and sagittal sutures simultaneously merge prematurely,
the resulting pansynostosis leads to oxycephaly
or a cloverleaf deformity of the skull (severe proptosis combined with dilated bitemporal regions
described with the German word “kleeblattschädel”) [18].
18].
21.2.2 Syndromic Craniosynostosis
More than 180 different syndromes are associated with craniosynostosis [38]. Roughly 15% of
all craniosynostoses occur with other developmental anomalies of the body [49]. The so-called
syndromic craniosynostoses comprise several
diagnoses and underlying genetic mutations,
ab
cd
21 Radiological Investigations ofCraniofacial Malformations
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Fig. 21.3 9-Month-old boy with coronal craniosynosto-
sis. Lateral plain skull radiography (a), lateral (b) and
coronal (d) 2D CT images in bone window, and lateral 3D
CT-image (VRT) (c) show premature bilateral fusion of
coronal sutures (white arrows) with resulting turricephaly.
which cause developmental malformations of the
skull, the face, and the central nervous system.
Syndromic craniosynostosis is usually combined
with developmental delay [34]. Gene mutations
encoding broblast growth factor receptors 1, 2,
and 3 (FGFR1, FGFR2, FGFR3), TWIST, and
MSX2 (muscle segment homeobox 2) have been
identied in syndromic craniosynostosis [56, 57].
The most frequent syndromic craniosynostoses
The anterior (asterix) and posterior fontanel (black
arrows) are not yet closed, typical for this age group.
Courtesy of Dr. Claudia Moeller-Hartmann, University
Hospital Essen, Germany
are Apert (FGFR2), Crouzon (FGFR2), Pfeiffer
(FGFR1 and FGFR2), Muenke (FGFR3), and
Saethre-Chotzen (TWIST) [34]. The severity of
the anomalies varies from mild suture involvement to severe pansynostosis with a spectrum of
extracraniofacial dysmorphic manifestations
[34]. The affection of the central nervous system
in these syndromes often affects intelligence,
prognosis, and outcome of these patients. Hence,
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