Complex intracranial venous circulatory disorder in Crouzon's syndrome

Preliminary notes
Crouzon's syndrome, which is a congenital ossification disorder of the skull (characterized by the association of craniosynostosis, ocular proptosis and facial deformity), can also be complicated by hydrocephalus. In fact, a similar mechanism as in achondroplasia has been suggested to explain hydrocephalus related to Crouzon's syndrome. As a part of the complete neuroradiological evaluation, MRA can be successfully employed in the assessment of clinical problems related to Crouzon's syndrome.

Clinical history
This 6-year-old girl was born at term with a head circumference of 34 cm. Bilateral synostosis of the coronal sutures was present on skull x-rays. The craniofacial deformity was suggestive of Crouzon's syndrome. At 10 months of age, head circumference was 46 cm, which corresponds to the 75th percentile, and the anterior fontanel was large and bulging.
MRI revealed communicating hydrocephalus, tonsillar herniation and cervical hydromyelia. A ventriculo-peritoneal shunt was placed at 11 months of age and the opening pressure of the CSF was at that time noted to be 25 cmH20. The craniosynostosis was corrected one month later by bilateral lateral canthal advancement. Her psychomotor development was normal during the following years.
She was readmitted for headache and the appearance of a pulsatile mass in the occipital region. Craniofacial examination revealed ocular proptosis with exophthalmos, maxillary hypoplasia, beaked nose, and the presence of a pulsatile and depressible subcutaneous mass in front of the inion. Cranial perimeter was 39.5 cm, which is above the third percentile. Cutaneous lesions suggestive of acanthosis nigricans were present. There were no signs of focal deficit at neurological examination.

Crouzon's syndrome 0.5 T
Complex intracranial venous circulatory disorder in Crouzon's syndrome
Fig.1 Plain skull X-ray films taken at the age of 6 years show a disproportionately developed skull and signs of surgical reconstruction, as well as ventricular shunt. Note also the abnormal pattern of the occipital bone in the midline (arrows).
Fig.2 T1-weighted sagittal and coronal spin echo images shows enlarged ventricles, despite the presence of the ventricular drain. Note also an occipital signal void structure involving the cranial vault, which corresponded to the pulsatile structure detected at physical examination (above image).
Fig.3 Sagittal T1-weighted spin echo image. Tonsillar herniation and hydromyelia are noted.
Fig.4 No interval change is appreciated when compared to the MRI examination performed at the age of 6 months.
Fig.5 The occipital signal void structure proved to be a vascular structure, suggesting a "sinus pericranii" on the sagittal 2D Phase Contrast image.
Fig.6 Compare the correspondence between the T1-weighted spin echo and the 2D Phase Contrast image. Note also the connecting venous channel (arrows) between the torcular and the sigmoid sinus, which is in fact an unusual occipital sinus.
Fig. 7 2D TOF (above) and 2D Phase Contrast (below) MR venograms of the base of the skull (transverse views). The former better depicts the entire basal venous network (the 2D TOF sequence is very sensitive to slow flow!). However, the previously mentioned occipital sinus (arrows) is somewhat more easy to evaluate on the 2D Phase Contrast image (Venc: 20 cm/s, probably to high to visualize the small veins of the basal foramina, so only the hemodynamically more important venous structures are identified). This image also demonstrates the absence of a sigmoid sinus on the left side.

Comments
This child had an unusual cerebral venous drainage network most likely related to the Crouzon's syndrome [30]. Intracranial venous blood was essentially drained through the "sinus pericranii" towards the suboccipital intramuscular venous plexus and by the right transverse and occipital sinuses, draining towards the right sigmoid sinus-internal jugular vein system. This system was probably insufficient and the baseline intracranial venous pressure increased, resulting in non-resorptive hydrocephalus. Persistent tonsillar ectopia and the hydromyelia, present on the initial MRI also worked in favor of this hypothesis [31]. The functional reserve of the venous draining system was presumably minimal. Dysfunction of the ventriculo-peritoneal shunt must have decompensated the system, resulting in further increase in the intracranial venous pressure and appearance of the clinical symptomatology, consistent with the transient benign intracranial hypertension syndrome. Shunt revision was performed which led to rapid normalization of the child's symptoms, probably due to reestablishment of the previous pressure equilibrium between the different intracranial compartments. The pulsatile occipital mass also significantly decreased in size.

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