Imaging the pre- and postsynaptic side of striatal dopaminergic synapses in idiopathic cervical dystonia:: A SPECT study using [123I] epidepride and [123I] β-CIT

There is increasing evidence that a dysfunction of the dopaminergic system may be involved in the pathogenesis of idiopathic dystonia. To visualize possible alterations of the pre-and postsynaptic side of striatal dopaminergic synapses, SPECT studies using the radiotracers [I-123] epidepride and [I-123] beta-CIT were performed in 10 patients with idiopathic cervical dystonia. Eleven age-and sex-matched subjects served as controls. [I-123] Epidepride is a new highly affine marker of D2 receptors, and [I-123] beta-CIT binds to dopamine transporters on dopaminergic nerve endings. [I-123] Epidepride binding was significantly reduced in both striata of dystonia patients compared with controls (p < 0.05). In contrast, striatal [I-123] beta-CTT uptake did not differ from controls. We conclude that dopaminergic dysfunction in idiopathic focal dystonia mainly involves postsynaptic mechanisms and suggest a disturbance of the indirect pathway of the motor circuit resulting in a disinhibited thalamocortical stimulation.