Dysfunction in the right putamen is associated with drooling in de novo Parkinson's disease

Drooling is a common and troublesome symptom in Parkinson's disease (PD), but the underlying pathophysiological mechanisms remain unclear. Studies in recent years have suggested each part of the striatum has different functions. Here, we investigated the association between drooling and dopaminergic dysfunction in each part of the striatum among patients with de novo PD. We retrospectively reviewed consecutive enrolled patients who had been diagnosed with de novo PD. Drooling was assessed using the Non-Motor Symptoms Questionnaire item 1. Uptake of ¹²³I-ioflupane in each part of the striatum bilaterally on single positron emission computed tomography was quantitatively evaluated in PD patients with or without drooling. We enrolled 44 PD patients, comprising 12 with drooling and 32 without drooling. Significantly lower uptake of ¹²³I-ioflupane was identified among patients with drooling compared to patients without drooling in the right anterior putamen (median 0.49 vs 0.74, p = 0.004) and right posterior putamen (median 0.23 vs 0.41, p = 0.02). These findings suggest that in PD patients, drooling is associated with dopaminergic dysfunction in the right putamen.