No electrophysiological evidence for Onuf's nucleus degeneration causing bladder and bowel symptoms in Huntington's disease patients

Aims In several degenerative neurologic diseases degeneration of Onuf's nucleus has been demonstrated using histologic and electromyographic (EMG) methods. Although Huntington's disease (HD) patients also frequently complain of bladder and bowel symptoms, degeneration of Onuf's nucleus has not been systematically studied in this group. Methods From our inventory of patients with genetically confirmed HD, all patients willing and capable of participating in the study, which utilized several standard questionnaires, were included. The patients reporting bladder/bowel symptoms were also asked to participate in anal sphincter EMG and sacral reflex studies. Results Of 52 patients (23 men) with genetically confirmed HD, 34 reported bladder/bowel symptoms, and 16 (8 men) of them consented to anal sphincter EMG and sacral reflex studies. Complete pattern of urinary and fecal urgency with incontinence reported 6 (38%), and incomplete 3 (19%) patients, accompanied with episodic diarrhea in another 3 (19%) patients. No patient exhibited quantitative anal sphincter EMG or sacral reflex abnormalities. However, in 81% of patients, decreased tonic anal sphincter activity and/or decreased voluntary activation were found on qualitative EMG. Lower sacral sensory thresholds and shorter reflex latencies were also found in HD patients compared to controls. Conclusions We found no EMG signs of Onuf's nucleus degeneration in HD patients. The observed decreased anal sphincter tonic activity and voluntary activation, lower sacral sensory thresholds and shorter reflex latencies as well as the reported bladder/bowel symptoms, are probably caused by degeneration of other central nervous system structures. Neurourol. Urodynam. 33:524–530, 2014. © 2013 Wiley Periodicals, Inc.