Altered bulbocavernosus reflex in patients with multiple system atrophy

Multiple system atrophy (MSA) is characterized by a combination of symptoms including autonomic dysfunction, parkinsonism, cerebellar ataxia, and cortico-spinal disorders. The disease can have either predominant parkinsonism or cerebellar features (MSA-P and MSA-C, respectively). The measurement of the bulbocavernosus reflex (BCR) and pudendal nerve somatosensory-evoked potentials (PSEPs) was originally developed to diagnose diabetic cystopathy and other neuropathologic diseases that share similar symptoms with MSA. We investigated the relationship between abnormalities of neurophysiological parameters and MSA, and estimated the potential value of BCR.

Fifty-one MSA patients (28 and 23 MSA-P and 23 MSA-C patients, respectively) and 30 healthy controls who were seen at the Department of Neurology were included in the study. A Keypoint EMG/EP system was used to test BCR and PSEPs, and the latencies and amplitudes were recorded for statistical analyses.

The BCR was elicited in 78.4% patients with MSA (22/28 MSA-P, 18/23 MSA-C). Prolonged BCR latencies were found in patients with MSA compared with healthy controls (p < 0.001). BCR amplitudes were significantly lower in the MSA group than the control group (p < 0.001). PSEP P41 amplitudes were not significantly different between the MSA and control groups in males (p = 0.608) or females (p = 0.897). There were no significant differences in PSEP latencies among the MSA-P, MSA-C, and control groups (p = 1.0, p = 0.263, and p = 0.060, respectively).

MSA patients exhibit prolonged BCR latencies and lower amplitudes, which provides a rough anatomical localization of nervous system lesions in MSA patients.