Spasticity (neuromuscular hypertonia) primarily in the muscles of the legs, hips, and pelvis.

Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time.

Hypoplasia of the cerebellum, pontine nuclei, and inferior olivary nucleus.

A generalized myoclonic seizure is a type of generalized motor seizure characterized by bilateral, sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus.

Head circumference below 2 standard deviations below the mean for age and gender.