CHANGES IN PERFUSION PATTERN USING ECD-SPECT INDICATE FRONTAL-LOBE AND CEREBELLAR INVOLVEMENT IN EXERCISE-INDUCED PAROXYSMAL DYSTONIA

The clinical features of exercise-induced paroxysmal dystonia (EPD) ar e delineated in a pedigree including two affected members (both male) showing an autosomal-dominant inheritance trait. Gait analysis using k inematic electromyography during the motor attacks revealed coactivati on of antagonistic calf muscles characteristic of dystonia. In the int erval, impaired muscular alternation was observed. To characterize fur ther the pathophysiological basis of the condition, ictal and interict al cerebral perfusion SPECT studies using technetium 99m-ethyl cystein ate dimer (ECD) were performed to establish whether cortical hyperacti vity indicative of epilepsy is present during the motor attacks and to identify regional changes in the ictal perfusion pattern that could i ndicate an anatomic structure relevant to the disease. During the moto r attacks, decreased ictal perfusion of the frontal cortex was found i n both patients. In contrast, increased cerebellar perfusion was obser ved. The perfusion of the basal ganglia also decreased. No cortical hy perperfusion indicative of an epileptic nature was seen. Cerebellar hy peractivity in connection with prominent frontal hypoactivity has also been described in both the idiopathic and the symptomatic forms of dy stonia. Our findings therefore suggest that EPD represents a paroxysma l movement disorder rather than epilepsy. It is concluded that changes in frontal and in cerebellar function are relevant to the pathophysio logy of EPD.