To the Editor We read with interest the article by Gratwicke et al1 that described deep brain stimulation of the nucleus basalis of Meynert (NBM DBS) and the potential symptomatic effects in patients with Parkinson disease dementia. No consistent improvements were observed in the primary cognitive outcomes. However, the authors found evidence of improvements in neuropsychiatric symptoms, probably driven by a reduction in complex visual hallucinations. Although modest, these findings encourage further DBS research in this subgroup of patients.