Dystonia is a syndrome of intermittent or sustained involuntary muscle contractions that frequently causes twisting and repetitive movements producing abnormal postures. These involuntary movements can affect many parts of the body (generalized) or affect more limited areas (focal) such as the eyelids in blepharospasm or the hand and arm in hand cramp. The pathophysiology of these syndromes remain unclear but a variety of clues suggest abnormalities of central dopaminergic pathways. We hypothesize that patients with idiopathic focal dystonia have upregulation of striatal D2 receptors and that this upregulation is somatotopically organized depending upon the body part involved. We will test this hypothesis by measuring radioligand binding in vivo with positron emission tomography (PET) and [18F]spiperone (or the more specific radioligand [18F](N-methyl)benperidol, if this radioligand is available at the beginning of these studies) in patients with blepharospasm, hand cramp and age-matched normals. We will analyze the data to determine whether either group of patients has an elevation of receptor binding and also determine whether the location of maximal radioligand binding differs between patients with blepharospasm and hand cramp. These data should provide important information about the pathophysiology underlying these focal dystonias and lead to new avenues of investigation regarding pathophysiology and treatment of the idiopathic dystonias.
