Rhombencephalosynapsis

A rare cerebellar malformation characterized by congenital complete or partial fusion of the cerebellar hemispheres, dentate nuclei, and middle cerebellar peduncles, and complete or partial absence of the vermis. It may occur as an isolated anomaly or together with other malformations of the brain and is associated with variable clinical manifestations including developmental delay, ataxia, dysarthria, oculomotor abnormalities, seizures, and involuntary head movements, among others.

Epidemiology

The exact prevalence is unknown. A value of 4 in 3000 paediatric magnetic resonance imaging (MRI) scans was reported in one study and around 50 cases have been reported in the literature.

Clinical description

Other cerebral anomalies often associated with RS include fusion of the dentate nuclei, deformation of the fourth ventricle, and fusion of the cerebral peduncles. Supratentorial findings include hydrocephalus, fusion of the thalami, anomalies of the corpus callosum and septo-optic dysplasia. Extracerebral anomalies are also sometimes present: mild dysmorphism, anomalies of the hands and/or feet; ophthalmologic, cardiac, renal, uterine and anal abnormalities and Hirschsprung disease. Syndromic associations have also been reported: Gomez-Lopez-Hernandez syndrome (or cerebellotrigeminodermal dysplasia), RS with bilateral temporoparietal alopecia, anaesthesia in the trigeminal territory and craniostenosis.

Etiology

The aetiology remains to be confirmed.

Management and treatment

Management is symptomatic, requiring medical, educative, psychological and social care.

Prognosis

The neurological prognosis is variable, ranging from a normal IQ to more or less severe intellectual deficit with ataxia, dysarthria, strabismus and/or nystagmus, behavioural problems (such as obsessive-compulsive and auto-aggressive behaviour).