STRIATAL [F-18] DOPA UPTAKE IN FAMILIAL IDIOPATHIC DYSTONIA

It is known that most cases of idiopathic torsion dystonia (ITD) are i nherited in an autosomal dominant fashion. Despite clarification of th e underlying genetic defect, no consistent structural lesion has been identified in ITD, and it is probable that a biochemical disturbance i s the basis of the disorder. To determine whether there is impaired fu nction of the nigro-striatal dopaminergic terminals in ITD we studied 11 subjects with generalized ITD and a positive family history using [ F-18]dopa and PET scanning. Of these 11 patients, eight had putamen [F -18]dopa uptake within the lower half of the normal range, while three had uptake reduced by >2 SDs below the normal mean. The lowest putame n [F-18]dopa influx constants were found in the most disabled patients . As these reductions were mild it is unlikely that abnormalities of t he nigro-striatal dopaminergic pathway are the primary determinant of either the nature or the severity of dystonic symptoms. In addition, w e studied three presumed carriers of the ITD gene. These subjects all had normal striatal [F-18]dopa influx constants suggesting that [F-18] dopa PET is unsuitable as a screening tool for ITD.