Parkinson's disease and depression: evidence for an alteration of the basal limbic system detected by transcranial sonography

OBJECTIVES—Depression is a frequent symptom inParkinson's disease. Compelling evidence suggests a role of thebrainstem in the control of mood and cognition. In patients withunipolar depression transcranial sonography (TS) studies have shownstructural alteration of the mesencephalic brainstem raphe which couldsuggest an involvement of the basal limbic system in the pathogenesisof primary mood disorders. The objective of the present study was toevaluate whether a similar alteration could be found in depressedpatients with Parkinson's disease using TS.
METHODS—Thirty patients with Parkinson's diseaseand 30 age and sex adjusted controls were examined by TS. Rapheechogenicity was rated semiquantitatively. The severity of motorsymptoms and depression was rated using standard research instruments.
RESULTS—Raphe echogenicity was significantlyreduced in depressed patients with Parkinson's disease compared withnon-depressed patients with Parkinson's disease and control subjects.Raphe echogenicity correlated negatively with degree of motorimpairment, and differences in raphe echo between depressed andnon-depressed patients with Parkinson's disease were upheld when motorimpairment was controlled for.
CONCLUSION—These preliminary findings suggestthat, as in unipolar depression, a morphological alteration of thebrainstem raphe might be involved in the pathogenesis of depression inParkinson's disease. This raphe alteration may reflect involvement inthe basal limbic system in the pathogenesis of secondary depression.This concept is in line with current knowledge on the pathogenesis ofboth depression in Parkinson's disease and primary depressive disorders.