Protocol for neurophysiological studies of the pelvic floor to appraise anorectal dysfunction in patients with multiple sclerosis

Patients with multiple sclerosis (MS) frequently develop anorectal dysfunction. The neuromuscular structures of the pelvic floor and the mechanisms of voluntary control over defecation can be compromised by the patchy lesions of MS or secondary to the patient's disability. The involvement of multiple factors limits understanding of the pathophysiology of anorectal dysfunction in MS. Specific neurophysiological tests assess the functionality of the elements of the central and peripheral nervous system involved in anorectal dysfunction. To propose a diagnostic protocol of standardised neurophysiological studies of the pelvic floor in order to characterise the pathophysiology of anorectal dysfunction in patients with MS. The following studies were conducted on 16 patients with defined MS and who met criteria for constipation or faecal incontinence: external anal sphincter electromyography (EAS-EMG), somatosensory evoked potentials (SSEP) of the internal pudendal nerve, recording of ano-sacral reflexes and pudendal nerve neurography. The clinical and neurophysiological characteristics were heterogeneous. Nine patients presented constipation; two had isolated faecal incontinence; and five, a combination of both. Abolition or delay in the latency of the SSEP was the most frequent finding (n = 12), followed by the detection of paradoxical contraction (n = 11) and deficient recruitment (n = 8) in the EAS-EMG. The correct interpretation of each available neurophysiological test and the correlation of the findings as a whole enable us to understand the pathophysiology of anorectal dysfunction. The implementation of a protocol for neuro-physiological studies of the pelvic floor makes it possible to adjust the diagnosis by identifying the central or peripheral nervous lesion determining anorectal dysfunction in patients with MS.