I-123-metaiodobenzylguanidine myocardial scintigraphy in Parkinson's disease

Objectives-I-123-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is clinically used to estimate local myocardial sympathetic nerve damage in so me forms of heart disease, autonomic nerve disturbance in diabetic neuropat hy, and disturbance of the autonomic nervous system in neurodegenerative di sease. In the present study, examinations were performed to clarify (1) the proportion of cardiac sympathetic nerve disturbance in Parkinson's disease , (2) the usefulness of I-123-MIBG myocardial scintigraphy to detect sympat hetic nerve disturbances compared with autonomic function tests, (3) cardia c function in patients who have a decreased MIBG uptake in I-123-MIBG myoca rdial scintigraphy, (4) the usefulness of I-123-MIBG myocardial scintigraph y to differentiate Parkinson's disease from the other neurological diseases mimicking it. Methods-I-123-MIBG myocardial scintigraphy was performed, together with aut onomic function tests and cardiac examinations in 46 patients with Parkinso n's disease and 25 patients with vascular parkinsonism, essential tremor, o r multiple system atrophy. Results-In an anterior image study, the average count per pixel in heart to mediastinum (HIM) ratio decreased in 80% of the patients with Parkinson's disease in the early phase and 84% in the late phase. The mean HIM ratio in Parkinson's disease was significantly lower than that in controls and the other diseases. The HIM ratio tended to decrease with the disease progressi on. In almost half of the patients in Hoehn and Yahr stage I, the HIM ratio was already decreased. The sympathetic skin response in upper and lower li mbs, head up tilt test, and coefficient of variation of R-R interval were a bnormal in 17%, 31%, 30%, and 17% of the patients, respectively. All the pa tients with abnormal autonomic functions were in Hoehn and Yahr stage III, IV, or V. Echocardiography showed normal left ventricular function. Twenty four hour Holter electrocardiography detected no serious arrhythmias except for one patient with non-sustained ventricular tachycardia. Conclusion-I-123-MIBG myocardial scintigraphy might detect early disturbanc es of the sympathetic nervous system in Parkinson's disease and might give useful diagnostic information to differentiate vascular parkinsonism, essen tial tremor, and multiple system atrophy from Parkinson's disease.