Sensory perception changes induced by transcranial magnetic stimulation over the primary somatosensory cortex in Parkinson's disease

Sensory symptoms are common nonmotor manifestations of Parkinson's disease. It has been hypothesized that abnormal central processing of sensory signals occurs in Parkinson's disease and is related to dopaminergic treatment. The objective of this study was to investigate the alterations in sensory perception induced by transcranial magnetic stimulation of the primary somatosensory cortex in patients with Parkinson's disease and the modulatory effects of dopaminergic treatment. Fourteen patients with Parkinson's disease with and without dopaminergic treatment and 13 control subjects were included. Twenty milliseconds after peripheral electrical tactile stimuli in the contralateral thumb, paired-pulse transcranial magnetic stimulation over the right primary somatosensory cortex was delivered. We evaluated the perception of peripheral electrical tactile stimuli at 2 conditioning stimulus intensities, set at 70% and 90% of the right resting motor threshold, using different interstimulus intervals. At 70% of the resting motor threshold, paired-pulse transcranial magnetic stimulation over the right primary somatosensory cortex induced an increase in positive responses at short interstimulus intervals (1-7 ms) in controls but not in patients with dopaminergic treatment. At 90% of the resting motor threshold, controls and patients showed similar transcranial magnetic stimulation effects. Changes in peripheral electrical tactile stimuli perception after paired-pulse transcranial magnetic stimulation over the primary somatosensory cortex are altered in patients with Parkinson's disease with dopaminergic treatment compared with controls. These findings suggest that primary somatosensory cortex excitability could be involved in changes in somatosensory integration in Parkinson's disease with dopaminergic treatment.