The relationship between the dopaminergic system and depressive symptoms in cervical dystonia

Cervical dystonia (CD) is associated with tremor/jerks (50%) and psychiatric complaints (17-70%). The dopaminergic system has been implicated in the pathophysiology of CD in animal and imaging studies. Dopamine may be related to the motor as well as non-motor symptoms of CD. CD is associated with reduced striatal dopamine D-2/3 (D2/3) receptor and increased dopamine transporter (DAT) binding. There are differences in the dopamine system between CD patients with and without jerks/tremor and psychiatric symptoms. Patients with CD and healthy controls underwent neurological and psychiatric examinations. Striatal DAT and D2/3 receptor binding were assessed using [I-123]FP-CIT and [I-123]IBZM SPECT, respectively. The ratio of specific striatal to non-specific binding (binding potential; BPND) was the outcome measure. Twenty-seven patients with CD and 15 matched controls were included. Nineteen percent of patients fulfilled the criteria for a depression. Striatal DAT BPND was significantly lower in depressed versus non-depressed CD patients. Higher DAT BPND correlated significantly with higher scores on the Unified Myoclonus Rating Scale (UMRS). The striatal D2/3 receptor BPND in CD patients showed a trend towards lower binding compared to controls. The D2/3 BPND was significantly lower in depressed versus non-depressed CD patients. A significant correlation between DAT and D2/3R BPND was found in both in patients and controls. Alterations of striatal DAT and D2/3 receptor binding in CD patients are related mainly to depression. DAT BPND correlates significantly with scores on the UMRS, suggesting a role for dopamine in the pathophysiology of tremor/jerks in CD.