Researchers established normative values for bilateral lumbar and sacral-anorectal motor evoked potentials (MEPs) using translumbosacral anorectal magnetic stimulation (TAMS), a novel non-invasive test for identifying anorectal neuropathy. Findings were reported at the American College of Gastroenterology (ACG) Annual Scientific Meeting 2019, held October 25 to 30, 2019, in San Antonio, Texas.
Assessing anal neuropathy previously relied upon anal electromyography and pudendal nerve latency. However, neither test comprehensively assessed nerves from their origin in the spinal cord to anal innervation. This, among other significant deficiencies, has kept the American Gastroenterology Association from endorsing either test for the diagnosis of anorectal neuropathy.
This study explored the use of TAMS — a noninvasive test that evaluates the neuronal integrity of the lumbar and sacral plexus nerves from their origin in the spinal cord to their innervation in the rectum and anus by measuring latencies of MEPs — in identifying anorectal neuropathy. Investigators sought to establish baseline values for TAMS and examine potential age and gender discrepancies in rectal and anal MEP latencies.
Bilateral translumbar and transsacral magnetic stimulation was recorded in 48 healthy subjects (aged 18 to 59 years; female/male = 32/16). Using 2 pairs of bipolar ring electrodes, MEP was recorded simultaneously from the rectum and anus. Mean latency across 8 MEP sites (left and right lumbo-rectal; left and right lumbo-anal; left and right sacrorectal; left and right sacroanal) was measured and gender differences were compared.
Overall, no difference was reported between the lumbar and sacral nerve latencies, right and left side latencies, or the anal and rectal latencies. Moreover, no difference in MEP latency between men and women was found for any of the 8 sites examined. Except for a weak association in the right sacrorectal MEP (r, 0.386; P =.009), age was not significantly associated with anal or rectal MEP latency (r, 0.09 to 0.326).
The researchers concluded that “this study provides normative values for the bilateral lumbar and sacral-anorectal MEPs in healthy subjects” with no age or gender influence on rectal or anal MEP latency. They added that “these data will provide the basis for comparing the novel TAMS test findings in patients with those from suspected anorectal or pelvic neuropathy.”
Yan Y, Xiang X, Sharma A, Herekar A, Parr R, Rao S. Translumbosacral anorectal magnetic stimulation (TAMS): novel anorectal neurophysiology test, normative values, and effects of gender. Abstract presented at American College of Gastroenterology 2019 Annual Scientific Meeting; October 25-30, 2019; San Antonio, Texas. Abstract P2160.