Early verbal fluency decline after STN implantation: Is it a cognitive microlesion effect?

BackgroundsWorsening of verbal fluency is reported after subthalamic nucleus deep brain stimulation in Parkinson's disease. It is postulated that these changes could reflect microlesion consecutive to the surgical procedure itself.MethodsWe evaluated verbal fluency, in 26 patients (mean age, 57.9 ± 8.5 years; mean disease duration, 11.4 ± 3.5 years) both before surgery (baseline) and, after surgery respectively the third day (T3), the tenth day (T10) just after STN implantation before turning on the stimulation and at six months (T180).ResultsNumber of total words and switches was significantly reduced at T3 and T10, while average cluster size was unchanged. Repeated post-operative neuropsychological testing demonstrated reliable improvement from T3 to T180 on verbal fluency.ConclusionThis study provides evidence of transient verbal fluency decline consecutive to a microlesion effect. Further studies needed to determine a putative relationship between early and long-term verbal fluency impairment.