Somatosensory evoked potential recovery in Kii amyotrophic lateral sclerosis/parkinsonism–dementia complex (Kii ALS/PDC)

Objective: To evaluate the recovery function of the sensory cortex in patients with Kii amyotrophic lateral sclerosis/parkinsonism–dementia complex (Kii ALS/PDC) using somatosensory evoked potentials (SEPs) elicited by paired stimuli of the median nerve at the wrist. Methods: Five patients with Kii ALS/PDC were compared with 5 patients with classical ALS, 5 with Parkinsonʹs disease (PD), and 7 healthy normal volunteers. SEPs were recorded from the hand sensory area contralateral to the side of stimulation. Recovery functions of N20-P25 and P25-N33 components were evaluated by comparing the second SEPs elicited by paired pulse stimuli at various interstimulus intervals (ISIs, 20–300 ms) with the SEPs elicited by single stimuli. Results: Conventional SEPs to a single stimulus had a normal latency and size in all patients. The recovery function of the N20-P25 and P25-N33 components showed significantly less suppression at short ISIs without any facilitation at long ISIs in Kii ALS/PDC patients than in normal subjects, classical ALS or PD patients. Conclusions: In Kii ALS/PDC, the sensory cortex is disinhibited or hyperexcitable. These abnormalities may reflect cortical pathology in the sensory cortex and may be partly due to a secondary effect on the sensory cortex from the primary parkinsonian pathological changes.