MR demonstration of cerebral hemimegalencephaly associated with cerebellar involvement (total hemimegalencephaly).

Hemimegalencephaly or unilateral megalencephaly is a rare malformation characterized by overdevelopment of all or part of one cerebral hemisphere. Although previous pathological studies noted an associated overdevelopment of the ipsilateral cerebellar hemisphere in a few cases, to the best of the author's knowledge, such an association has not yet been reported in the radiological literature. This paper reports a 1-yr-old patient with hemimegalencephaly of the right cerebral hemisphere, and hemimegalencephaly of the ipsilateral cerebellar hemisphere. The ipsilateral half of the brainstern was also enlarged. This condition is suggested to be labelled as "total hemimegalencephaly".