Effects of Pallidal Stimulation on Speech in Three Men with Severe Parkinson's Disease

This project examined the effects of pallidal stimulation and medication on speech in three men with severe Parkinson's disease. Two participants had bilateral pallidal stimulation and one had unilateral stimulation contralateral to a prior pallidotomy. Measures included general motor function, auditory perceptual characteristics of speech, intelligibility, interpause speech rate, and speech aerodynamics. All three participants had improved motor function (better mobility, reduced tremor and dyskinesia), but responses for speech varied widely. The participant with a prior unilateral pallidotomy and contralateral pallidal stimulation had alleviation of painful facial-mandibular dystonia so that he was more willing and better able to talk. One participant developed marked hypophonia postoperatively from a presumed pallidotomy or chronic stimulation effect as this result was not altered by deactivating the bilateral stimulators. The third participant demonstrated improved overall speech characterized by reduced vocal strain and tremulousness in the medication-on condition when the stimulators were activated. In the medication-off condition, he developed abnormal speech dysfluencies with bilateral pallidal stimulation, but this impairment was eliminated with medication or when the stimulators were deactivated. Careful exploration of speech sequelae after pallidal stimulation is essential to develop risk/benefit data for future neurosurgical candidates.