Complex sentence: The affected siblings have a form of nonprogressive congential cerebellar ataxia with brain impairments including cerebellar hypoplasia, mild cerebral cortex atrophy and a reduced corpus callosum.
Split into simpler sentences: The affected siblings have a form of nonprogressive congential cerebellar ataxia. The brain impairments include cerebellar hypoplasia, mild cerebral cortex atrophy and a reduced corpus callosum.