Reversal of a Virtual Lesion in Human Pharyngeal Motor Cortex by High Frequency Contralesional Brain Stimulation

BACKGROUND & AIMS: Excitatory brain stimulation with repetitive transcranial magnetic stimulation (rTMS) has been proposed as a treatment for dysphagia after stroke. Moreover, 1-Hz rTMS can induce a "virtual lesion" in the human pharyngeal motor cortex that suppresses brain activity and temporarily disrupts swallowing. We thus examined if rTMS could reverse the disrupted brain and swallowing functions following a unilateral virtual lesion in the pharyngeal motor cortex, such that rTMS might be developed as a therapy. METHODS: Healthy subjects (n = 23) were given varying conditions of 5-Hz rTMS over the pharyngeal motor cortex to determine the most effective excitatory parameters. Thereafter, a unilateral virtual lesion was made in the pharyngeal motor cortex using 1-Hz rTMS, followed by contralateral active or sham 5-Hz rTMS. Motor evoked potentials and serial swallowing reaction times were recorded before and for 60 minutes postlesion to assess reversibility of the disruption to the brain and swallowing. RESULTS: The greatest increase in pharyngeal motor cortex excitability was seen following 250 pulses of 5-Hz rTMS (F(1, 11) = 10.3, P = .008), an effect that lasted over 2 hours. In contrast to sham rTMS, active contralateral 5-Hz rTMS completely abolished the cortical suppression induced by the virtual lesion, with effects occurring for up to 50 minutes in both unlesioned (F(1, 11) = 6, P = .03) and lesioned (F(1,11) = 67, P < .001) hemispheres. Active rTMS also reversed. the changes in swallowing behavior (F(1,8) = 9, P = .018), restoring function to prelesional levels. CONCLUSIONS: Contralesional-targeted neurostimulation modulates brain activity and swallowing motor behavior after experimental disruption and might be usefully applied in stroke-affected patients as a therapy for dysphagia.