Life with only one half of the cerebellum: Outcome in children with severe unilateral cerebellar hypoplasia
Aims: Complete or subtotal absence of one cerebellar hemisphere is exceptional and only few cases have been described. We report a large patient series focussing on clinical and MR findings as well as on cognitive functions.
Materials and methods: We reviewed the MR findings of 8 and the clinical records of 7 patients with severe unilateral cerebellar hypoplasia. Two patients had prenatal MRI at 21 gestational weeks, in one case the pregnancy was terminated. The mean age of the patients at the last follow-up was 7.3 years (range 2.3–14.9 years).
Results: The left cerebellar hemisphere was affected in 6, the right in 2. The hypoplasia was severe in 5 patients, in 3 children a subtotal aplasia was present. The vermis was involved in 5 cases and in all patients a contralateral brainstem asymmetry was present. The volume of the posterior fossa was reduced ipsilateral to the cerebellar hypoplasia in 4, normal in 3, and enlarged in one case. In both prenatal MRI at 21 gestational weeks a unilateral cerebellar hypoplasia was already present. A mild truncal ataxia was present in 3 patients, a mild limb ataxia in 5 (in 3 patients only ipsilateral to the cerebellar hypoplasia). Other symptoms were muscular hypotonia and head tilt in 4 patients. Three patients had a global developmental delay (moderate in 2 cases, mild in 1), requiring special class. Four patients had predominantly expressive language impairment, one patient severe behavioral disorder as obsessive-compulsive disorder.
Conclusion: Severe unilateral cerebellar hypoplasia represents a residual change following a disruptive prenatal cerebellar insult, likely hemorrhagic (or ischemic). The outcome of these children is variable, ranging from almost normal development to marked developmental impairment. Risk factors for poor outcome could not be found.