Balance function in patients with Williams syndrome.

Impaired control of balance has been described in Williams syndrome (WS). The aim of this study was to investigate balance function by means of clinical and instrumental tests in order to measure postural sway in people with WS in an objective way. 23 WS patients (11 males, 12 females, mean age 17.52 ± 8.33 years) and 23 healthy subjects (11 males, 12 females, mean age 17.74 ± 8.93 years) performed static posturography with eyes open and closed, on a firm surface and on foam pads. The WS patients had higher mean length, velocity and surface values than controls under all of the test conditions, and their length and surface values were significantly higher in the eyes open test. The cognitive abilities of the WS patients were not related to their stabilometric performance. The greatest differences between the WS patients and the controls were found mainly in the older subjects. WS patients are more unstable than healthy subjects of the same age, particularly when they use visual information to maintain their balance: i.e. under conditions of normal everyday life. Possible explanations may be the ophthalmologic problems and the visuospatial difficulties attributed to a neural processing abnormality involving the dorsal stream impairment model. The balance function of WS patients is different from that of normal developing subjects, especially after adolescence when postural control is generally complete. This suggests an atypical developmental trajectory.