Parkinsonism in bipolar disorder: a clinical-neuroimaging study

Abstract

Background: Parkinsonism is a frequently encountered symptom in individuals with bipolar disorder (BD). It can be drug-induced, co-occurring with Parkinson's disease (PD), or a genuine motor abnormality of BD itself. This study aims to clarify the primary pathophysiology of parkinsonism in BD. Methods: Sixteen patients with BD and parkinsonism were recruited from consecutive patients who were referred to a neurology clinic at a tertiary psychiatric center. The patients underwent clinical assessments, dopamine transporter single-photon computed tomography (DAT-SPECT), cardiac MIBG scintigraphy, and morphometric MRI. The positivity or negativity of Lewy body disease (LBD) biomarkers was determined based on the visual assessment of DAT-SPECT and heart-to-mediastinum ratio on cardiac MIBG scintigraphy. Four out of the 16 participants received 300-600mg of levodopa. Results: Thirteen patients were diagnosed with BD type 1, and 12 had experienced > 5 previous mood episodes. Parkinsonism developed more than 10 years after the onset of BD and after the age of 50 years in all patients. Four cases were positive for LBD biomarkers. Six patients with negative LBD biomarkers showed reduced striatal uptake with z-scores below -2.0. MRI morphometry revealed varying degrees of brain atrophy in most patients. Three of the 4 patients did not respond to 600mg of levodopa. Conclusions: This study suggests that the majority of parkinsonism in BD is not due to PD/LBD. Parkinsonism may be a genuine motor abnormality of BD in late life.