Autonomic dysfunction in Machado-Joseph disease assessed by iodine (123)-labeled metaiodobenzylguanidine myocardial scintigraphy

Iodine(123)-labeled metaiodobenzylguanidine, a radioiodinated analogue of n orepinephrine, is a tracer for evaluating sympathetic Function. We used iod ine(123)-labeled metaiodobenzylguanidine myocardial scintigraphy and sympat hetic skin response to study autonomic nervous functions in 19 patients wit h Machado-Joseph disease (MJD) and 20 control subjects. Planar imaging of a ll the participants was done to evaluate myocardial scintigraphy. The ratio of average counts in the heart to average counts in the mediastinum was ca lculated For both early and delayed images, the latter of which reflects th e cardiac neural uptake of the tracer. Single photon emission computed tomo graphy also was done on 12 patients with MJD to examine regional tracer upt ake to the heart. The mean ratio of counts in the heart to counts in the me diastinum in the delayed images was lower for the patients with MJD than fo r the control subjects (p < 0.01). Abnormal sympathetic skin response was p resent in 6 patients with MJD whose mean ratio of counts in the heart to co unts in the mediastinum was lower than that of patients with MJD who had no rmal sympathetic skin response (p < 0.01). A single photon emission compute d tomography study showed significantly lower accumulation of the tracer in patients with MJD than in the control subjects in the anterior lateral sec tors predominantly innervated by sympathetic nerves but not in the inferior septal sectors reported to be under main innervation by parasympathetic fi bers. These results show that MJD is accompanied by cardiac sympathetic dys function, as detected by iodine(123)-labeled metaiodobenzylguanidine myocar dial scintigraphy, which appears to be correlated with sudomotor sympatheti c dysfunction.