Cognitive outcome following staged bilateral pallidal stimulation for the treatment of Parkinson's disease.

As neurosurgical treatment of parkinsonian symptoms has become increasingly popular, concern about the cognitive morbidity which may result from such interventions has risen proportionately. Previous reports of cognitive difficulties associated with pallidotomy and thalamotomy, especially in bilateral cases, have provided the impetus for research into chronic electrical deep brain stimulation procedures which are believed to be safer than ablation. Given the lack of neurobehavioral research following bilateral deep brain stimulation procedures, this preliminary study of six Parkinson's disease patients undergoing staged bilateral pallidal stimulation was undertaken. A battery of tests assessing attention, executive function, visuomotor coordination, language, visuoperceptual function, learning memory and mood revealed no significant change in overall level of cognitive functioning after either unilateral or bilateral pallidal deep brain stimulation. No significant declines were observed about three months following bilateral stimulation, and in fact, significant gains in delayed recall and relief of anxiety symptoms were noted. It was concluded from this preliminary data that bilateral pallidal stimulation for the treatment of Parkinson's disease, at least in the absence of operative complications, offers a cognitively safe alternative to ablation.