Cardiac uptake of [I-123]MIBG separates Parkinson's disease from multiple system atrophy

Objective: To improve the differential diagnosis between patients with mult iple system atrophy (MSA) and idiopathic PD (IPD) with autonomic failure. B ackground: Some patients diagnosed with IPD are discovered to have alternat ive diseases such as MSB, despite the application of stringent diagnostic c riteria. This differentiation is particularly difficult if patients with IP D also show symptoms of autonomic failure. In IPD, autonomic failure is cau sed by damage of the postganglionic part of the autonomic nervous system, w hereas in MSA, degeneration of preganglionic and central autonomic neurons is revealed histopathologically. Methods: Scintigraphy with [I-123] metaiod obenzylguanidine (MIBG) enables the quantification of postganglionic sympat hetic cardiac innervation. Fifteen patients with IPD and 5 patients with MS A underwent standard autonomic function tests and scintigraphy with MIBG. R esults: In all patients, cardiovascular testing showed evidence of autonomi c failure of varying severity. In all patients with IPD, the heart-mediasti num (H/M) ratio of MIBG uptake was pathologically impaired, independent of duration and severity of autonomic and parkinsonian symptoms. All patients with MSA had a regular H/M ratio. Each patient could be assigned to the cor rect diagnostic group based on the results of the MIBG scintigraphy, even i f the duration of the disease was only 2 years or less. Conclusions: This p opulation assessment of the heart-mediastinum ratio of [I-123]metaiodobenzy lguanidine uptake showed a high sensitivity for the detection of autonomic involvement in patients with idiopathic IPD and also a high specificity for the discrimination between idiopathic PD and MSA.