Dominantly inherited hypoplasia of the vermis.

A mother and her two daughters with presumed dominantly inherited, non-progressive, congenital cerebellar ataxia are reported. Magnetic resonance imaging revealed vermal hypoplasia in one case, and generalized hypoplasia of the cerebellum, predominating at the vermal level, in another case. These patients are identical to those previously published, except for a slowly progressive improvement of motor abilities observed during evolution.