Time to Revisit a Low-Cost Alternative? Palpation Assessment Nerve Monitoring (PANM) for Recurrent Laryngeal Nerve to Predict Postoperative Vocal Cord Function—a Validation Study Using an In-House Neuromonitoring Device

Neuromonitoring has proved to be a useful technique in reducing nerve injury during thyroid surgery; however, costs continue to limit its use in resource-constrained settings. This study was done to assess the functional integrity of the recurrent laryngeal nerve (RLN) during thyroid surgery using palpation assessment of posterior cricoarytenoid muscle twitch in response to RLN stimulation. Between August 2016 and July 2017, 24 patients with 47 nerves at risk (NARs) underwent thyroid surgery with visual identification and testing of 44 RLNs. The functional integrity of the RLN was checked by stimulation of the RLN. Intraoperative assessment showed 100% sensitivity and positive predictive value in predicting postoperative vocal cord function. The postoperative vocal cord assessment confirmed all 44 nerves tested to be normally functioning. The mean (standard deviation) peak-to-peak amplitude and latency of the CMAP were 0.889 (0.740)/1.336 (1.660) mV and 2.295 (0.319)/2.217 (0.393) ms for left/right side NARs, respectively, with no statistically significant difference (P > 0.05). Palpation assessment of the posterior cricoarytenoid muscle provides a simple and reliable technique for confirming integrity of the RLN. Combining palpation assessment with CMAP from the inferior constrictor muscle may help reduce potential false negative results. With the use of our in-house built device which is significantly cheaper than the commercial ones, this could be considered a low-cost alternative to current established techniques.