Clinical History
A 9-year-old boy with learning disabilities and facial dysmorphism in the form of brachyturricephaly, a flat forehead, hypertelorism, epicanthal folds, low-set broad ears, upturned nose, high arched palate, maloccluded teeth, right simian crease, and bilateral parietal alopecia underwent an MRI to document any associated structural brain anomalies.
Imaging Findings
Brain MRI showed an absence of cerebellar vermis with transversely oriented cerebellar folia and continuity of the cerebellar white matter across the midline with fusion of dentate nuclei (Fig.2) and middle cerebellar peduncles (Fig.3). On axial sections, a diamond shaped rostral 4th ventricle was noted (Fig.3). Large massa intermedia (Fig.4) with partial fusion of thalami (Fig.5) was also noted. The remainder of the supratentorial brain parenchyma was normal.
Discussion
Gomez-Lopez-Hernandez syndrome (GLHS) or cerebello-trigeminal-dermal dysplasia is a rare syndrome characterized by the triad of rhombencepalosynapsis (RS), parietal alopecia and trigeminal anaesthesia. Other typical findings are skull abnormalities, craniofacial dysmorphism, short stature and intellectual impairment [1-3].
Rhombencepalosynapsis is a rare brain malformation, characterized by vermian agenesis or hypogenesis, fusion of cerebellar hemispheres and apposition or fusion of dentate nuclei with or without fusion or apposition of cerebellar peduncles and colliculi [3, 4]. Supratentorial midline anomalies may also be seen, of which the most common is ventriculomegaly due to the abnormal orientation of fourth ventricle or aqueductal stenosis, which is also common in RS. Absence of septum pellucidum and fusion of thalami are common; hypoplasia of the commissural system, absence of olfactory tracts and agenesis of the posterior lobe of the pituitary gland may also be occasionally seen. The corpus callosum may be normal, hypoplastic or dysplastic [4].
Vermian agenesis with dentate fusion, inferior colliculi fusion and aqueductal stenosis may be due to an abnormality in the isthmus, which is a band of neuroepithelium between metencephalon and mesencephalon. This insult may occur prior to the development of the vermis. The cause of this is unknown and no teratogenic factor has been identified so far [4].
It is difficult to detect cerebellar abnormalities on CT imaging. However, the diagnosis of RS may be suggested if posterior pointing of the fourth ventricle, large lateral ventricles and absence of septum pellucidum are seen. Rarely, the fourth ventricle may assume the configuration of a keyhole or heart shape [4].
MRI which is definitely better than CT to delineate abnormality at the posterior fossa is the imaging method of choice. It is also better than CT for small key structures like dentate nuclei, cerebellar peduncles and colliculi. Moreover, the midline abnormalities commonly associated with RS can also be better assessed. MRI also bears no radiation risk and should be the first choice imaging modality [4].
Neuroimaging is not useful to distinguish isolated RS from GLHS. If RS is diagnosed by imaging, clinical signs of GLHS should be sought. The diagnosis of GLHS can only be made by the combination of trigeminal anaesthesia, dermal dysplasia and the typical dysmorphic features along with neuroimaging in children [2]. However, GLHS cannot be diagnosed prenatally by imaging as alopecia, trigeminal anaesthesia and subtle dysmorphism cannot be picked up.
Differential Diagnosis List
Gomez-Lopez-Hernandez syndrome
Joubert syndrome
Dandy Walker malformation
Final Diagnosis
Gomez-Lopez-Hernandez syndrome
