Autonomic Function Tests and MIBG in Parkinson's Disease: Correlation to Disease Duration and Motor Symptoms

Aims: Disorders of the autonomic nervous system (ANS) have a variable degree of clinical relevance in patients with Parkinson's disease (PD). Here, we assessed whether subclinical autonomic dysfunction, as evaluated by a complete battery of autonomic function tests (AFTs), correlates with PD progression.

Methods: A series of 27 consecutive patients with PD underwent extensive ANS investigations including the head-up tilt test (HUTT), Valsalva maneuver, deep-breathing test, and handgrip test (HG); further, they performed 123I-meta-iodobenzylguanidine (MIBG) scintigraphy.

Results: Seven of the 27 patients showed orthostatic hypotension (OH) at HUTT and pathological responses to the deep-breathing and HG test and Valsalva maneuver. The majority of the remaining 20 patients with PD showed pathological responses to deep-breathing (n = 13) and/or HG (n = 11). Only 3 of 27 suffered relevant OH. MIBG uptake of myocardium was decreased in 19 patients with PD (H/M ratio 1.3 ± 0.2). Prolonged clinical observation (>3 years), persistent response to levodopa, and MIBG repetition allowed us to exclude negative MIBG as attributable to atypical Parkinsonism. MIBG uptake did not correlate with OH and other AFTs. Both HG test response and MIBG did correlate with the Unified Parkinson's Disease Rating Scale (UPDRS) motor score and disease duration. A positive correlation emerged between diastolic blood pressure (DBP) response to HG test and MIBG and with systolic blood pressure (SBP) response at tilt test.

Conclusions: Our investigation suggests that ANS impairment affects the majority of patients with PD, even those PD patients showing negative MIBG, irrespective of clinical neurovegetative symptoms. The strict correlation that has been revealed with disease progression supports the routine utilization of AFTs as a reliable and inexpensive tool for monitoring peripheral sympathetic dysfunction in PD and optimizing therapy.