Clinical-electrophysiological correlation of tremor and myoclonus in a kindred with the N279K tau mutation.

We used electrophysiological methods to study the hyperkinetic movement disorders in a pallido-ponto-nigral degeneration (PPND) family, which harbors the N279K tau gene mutation. Our purpose was to: (1). characterize the tremor patterns, (2). characterize the myoclonus physiology, (3). determine whether electrophysiology can detect abnormalities in asymptomatic cases. In PPND, we found that the activation tremors correlated with a semi-rhythmic 6-10 Hz electromyography (EMG) pattern, and the rest tremors showed a reciprocal 4-6 Hz pattern. At least two different myoclonus physiology patterns exist in PPND, most notably contrasted by the presence or absence of a demonstrable electroencephalography (EEG) correlate. Electrophysiology yielded remarkable findings in those asymptomatic at-risk individuals that carried the N279K tau mutation.