Hereditary essential myoclonus is a disease in which segmental myoclonus is the sole clinical abnormality and whose cause is unknown. It is characterized by an early onset, a benign course, an autosomal dominant pattern of inheritance, the absence of any other neurologic dysfunction, and normal results of auxiliary tests. Cerebral blood flow studies of a father and son with this disease showed a cortical blood flow reduction contralateral to the myoclonus symptoms. We postulate the cause to be a focal unilateral subcortical cerebral lesion, either in the basal ganglia or in the brain stem, with subsequent cortical deafferentation.
Delecluse F, Waldemar G, Vestermark S, Paulson OB. Cerebral Blood Flow Deficits in Hereditary Essential Myoclonus. Arch Neurol. 1992;49(2):179–182. doi:10.1001/archneur.1992.00530260081025