Familial cortical myoclonus is an autosomal dominant neurologic condition characterized by adult onset of cortical myoclonus manifest as involuntary jerks or movements affecting the face and limbs. Affected individuals can also experience falls without seizure activity or loss ... Familial cortical myoclonus is an autosomal dominant neurologic condition characterized by adult onset of cortical myoclonus manifest as involuntary jerks or movements affecting the face and limbs. Affected individuals can also experience falls without seizure activity or loss of consciousness (summary by Russell et al., 2012).
Russell et al. (2012) reported a large 4-generation Canadian Mennonite family in which 11 individuals had adult-onset, slowly progressive cortical myoclonus variably affecting the face and upper and lower extremities. Onset of multifocal myoclonus occurred between the second ... Russell et al. (2012) reported a large 4-generation Canadian Mennonite family in which 11 individuals had adult-onset, slowly progressive cortical myoclonus variably affecting the face and upper and lower extremities. Onset of multifocal myoclonus occurred between the second and seventh decade. Myoclonus was triggered by action, sudden movements, and/or by inadvertent somatosensory stimuli, but not by light, noise, or startle. Symptoms reportedly were aggravated by fatigue, exertion, sleep deprivation, emotion, and hunger. Alcohol reportedly had no consistent effect. Most patients experienced multiple sudden falls without loss of consciousness. Four patients developed mild cerebellar ataxia, usually later in life, and some older patients became wheelchair-bound. None had seizures. Somatosensory evoked potentials confirmed the cortical origin of myoclonus. Myoclonus was suppressed by clonazepam or valproic acid.
In 11 affected members of a large Canadian Mennonite family with familial cortical myoclonus, Russell et al. (2012) identified a heterozygous mutation in the NOL3 gene (E21Q; 605235.0001). In vitro functional expression studies suggested that the mutation may ... In 11 affected members of a large Canadian Mennonite family with familial cortical myoclonus, Russell et al. (2012) identified a heterozygous mutation in the NOL3 gene (E21Q; 605235.0001). In vitro functional expression studies suggested that the mutation may alter posttranslational modification of NOL3. The mutation was found by genomewide linkage analysis followed by massively parallel and Sanger sequencing. Direct sequencing of the NOL3 gene in 5 additional kindreds with cortical myoclonus did not reveal any pathogenic mutations.