Association of Chiari I malformation and Williams syndrome.

Two Williams syndrome patients are presented who had neurologic symptoms secondary to Chiari malformation type I. Both patients had many of the well-known medical problems found in Williams syndrome. In addition, Patient 1 developed headache, diplopia, and tinnitus at 26 years of age. Neurologic examination revealed intermittent nystagmus and brisk reflexes. Magnetic resonance imaging demonstrated Chiari malformation type I; neurologic symptoms abated following surgery. Patient 2 had a normal neurologic examination at 2 years of age except for hyperreflexia and tight heel cords. At age 10 years, she had generalized contractures, decreased strength and wasting of hand musculature, and hyperreflexia. Magnetic resonance imaging documented Chiari malformation type I. Both patients have significant dysphagia and fusion of cervical spine segments noted on radiography. Morphometric analyses of intracranial contents based on midsagittal magnetic resonance images were performed. This analysis suggests that, compared to age-matched controls, the posterior fossa size is selectively diminished in Williams syndrome, whereas the cerebellum is normal in size. This "mismatch" between the size of the posterior fossa bony compartment and its neural contents may place Williams syndrome patients at high risk for developing Chiari malformation type I.