The role of dopamine and serotonin in cervical dystonia

Cervical dystonia (CD) is a movement disorder accompanied by non-motor symptoms like depressive symptoms and anxiety. Neuroimaging has been used to investigate brain regions involved in the pathophysiology of focal dystonia, including CD. We describe the used neuroimaging techniques and why focal dystonia is considered a network disorder with suggested abnormalities mainly in the basal ganglia, thalamus, cerebellum and cortical areas. The basal ganglia are hypothesized to play the most important role in this network. Dopamine has been considered to be one of the most important neurotransmitters involved in the pathophysiology of dystonia. We investigated tracer binding to both the presynaptic dopamine transporter (DAT) and postsynaptic dopamine D2/3 receptor (D2/3R) in the striatum of patients with CD. We showed that abnormalities in tracer binding to striatal DAT and D2/3R are mainly related to depression and jerks/tremor. It is known that depression and anxiety are related to alterations of the serotonergic system and that the dopaminergic and serotonergic systems are closely related. We performed the first SPECT study investigating the presynaptic serotonin transporter (SERT) in the midbrain of patients with CD. We showed that abnormalities in tracer binding to SERT are also mainly related to psychiatric symptoms. In addition we performed an intervention study with escitalopram, a selective serotonin reuptake inhibitor (SSRI). No add-on effect of escitalopram was found for the treatment of motor or non-motor symptoms in CD, despite adequate occupancy of SERT. We did show that patients with highest SERT occupancy were more optimistic about their symptoms.