IMAGING THE PRE-SYNAPTIC AND POSTSYNAPTIC SIDE OF STRIATAL DOPAMINERGIC SYNAPSES IN IDIOPATHIC CERVICAL DYSTONIA - A SPECT STUDY USING [I-123] EPIDEPRIDE AND [I-123] BETA-CIT

There is increasing evidence that a dysfunction of the dopaminergic sy stem may be involved in the pathogenesis of idiopathic dystonia. To vi sualize possible alterations of the pre-and postsynaptic side of stria tal dopaminergic synapses, SPECT studies using the radiotracers [I-123 ] epidepride and [I-123] beta-CIT were performed in 10 patients with i diopathic cervical dystonia. Eleven age-and sex-matched subjects serve d as controls. [I-123] Epidepride is a new highly affine marker of D2 receptors, and [I-123] beta-CIT binds to dopamine transporters on dopa minergic nerve endings. [I-123] Epidepride binding was significantly r educed 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.