The electromyographic silent period is reduced in individuals at risk for huntington's disease

Huntington's disease (HD) is an invariably fatal condition having an autosomal dominant mode of inheritance. Although the pathological gene has a high penetrance, its presence in at risk individuals cannot usually be detected until obvious neurological or behavioral signs are manifest. Consequently, several electrophysiological parameters have been studied in an attempt to predict the presence of the gene for HD before the onset of the clinical syndrome. Despite the lack of an effective treatment for the disorder such information is vital to the genetic counseling of at risk individuals. Thus, the R₂ response of the blink reflex has been reported abnormal in 41% of descendants of HD patients (Esteban et al., 1981), while 73% of children born to HD affected parents show EEG abnormalities similar to those found in overt cases of HD (Patterson et al., 1948). It has recently been demonstrated that the electromyographic silent period (ESP) is shortened in patients with HD (Sandyk, 1982; Hufschmidt & Linke, 1977). Here we have examined the ESP in 24 individuals considered to be at risk for HD.