P063 Disinhibition of motor cortex in post-stroke paresthesia

Abstract

Pain or paresthesia is one of the major symptoms after stroke. Nonpharmacological treatments including motor cortex electric stimulation or repetitive transcranial magnetic stimulation have been applied to treat such symptoms. However, the underlying pathomechnism of post-stroke pain/paresthesia, especially the excitability of motor cortex, has not been fully elucidated. Here we enrolled thirteen patients (11 men, age 58.8 ± 9.0 years-old) with persistent post-stroke paresthesia or pain but without motor weakness in the contralateral limbs (duration = 4.0 ± 4.9 years). The locations of stroke were pontine, lateral medulla or thalamus. We investigated the short-interval intracortical inhibition and the intracortical facilitation of the motor cortex in the stroke and healthy side of each patient. Paired stimuli of short (3, 5 and 7 ms) and medium (10, 15 and 20 ms) interstimulus intervals (ISI) were pseudo-randomly mixed with a single stimulus. The motor evoked potentials were recorded from the first dorsal interosseous muscle. There was no difference in the rest motor threshold ( p = 0.72). The intracortical inhibition at ISI of 3 ms were absent ( p = 0.045), and there was significant facilitation at ISI of 5, 7, 10, 15, 20 ms in stroke side ( p p p = 0.087) and a trend of facilitation at ISI of 10 and 15 ms ( p = 0.057 and 0.077 respectively) in the healthy side. These findings suggested impairment of intracortical inhibition in the motor cortex of stroke side in patients with post-stroke paresthesia or pain.