Clinical neurophysiologic findings in patients with rapidly progressive familial parkinsonism and dementia with pallido-ponto-nigral degeneration

Objective: To present clinical electrophysiologic studies performed on the pallido-ponto-nigral degeneration (PPND) family linked to chromosome 17q21–22.

Methods: Nine patients from this kindred were studied with 11 electroencephalograms (EEGs), 4 electroencephalographic background frequency analysis (BFA) studies, 4 electromyographic recordings (EMGs) including nerve conduction studies (NCSs), 4 electromyographic multichannel surface recordings (MSRs), one pattern visual evoked potential (VEP) study and one median nerve somatosensory evoked potential (SEP) study.

Results: EEGs revealed normal findings early in the disease and diffuse slowing which became more prominent with disease progression. BFA studies demonstrated rapid decrease in mean parietal frequencies with disease progression. EMGs and NCSs showed no abnormalities. MSRs revealed action myoclonus and a dystonic process. Long loop reflexes were absent in resting hand muscles. VEPs and SEPs were normal.

Conclusions: Clinical neurophysiologic studies were consistent with a cortical and subcortical degenerative process. With clinical deterioration, there is a progressive decline in the mean parietal frequency and background rhythms. Tremor studies were consistent with action myoclonus and a dystonic process and did not show parkinsonian features of resting tremor or agonist-antagonist cocontraction. There was no evidence of peripheral nerve involvement or slowing in central sensory pathways. Electrophysiologic findings are characteristic for this illness.