Intraoperative neuromonitoring (IONM) for recurrent laryngeal nerve protection: comparison of intermittent and continuous nerve stimulation.

Clinical results comparing intermittent intraoperative neuromonitoring (Int-IONM) and continuous IONM (Cont-IONM) for recurrent laryngeal nerve protection are lacking. Int-IONM has been routinely applied in thyroid resection since January 2008. Cont-IONM was added in November 2008 (ISIS; Inomed, Emmendingen, Germany). Rates of vocal cord palsies (VCPs) and the corresponding IONM signals of both methods are compared. Int-IONM was applied in 458 patients and Cont-IONM in 667 patients. Early postoperative VCPs were diagnosed in 4.0% (34/850 NaR) of the Int-IONM group and in 2.9% (34/1184 NaR) of the Cont-IONM group (p = n.s.). The permanent palsy rate was 0.7% (n = 6) for the Int-IONM group, while all VCPs of the Cont-IONM group except one recovered within 1 to 5 months (p = 0.01). First mobilizing the gland is an early risk point for loss of signal (LOS) in 19.1% of cases. VCPs were identified in 58.8% to 85.3% by intraoperative LOS. Recognition of the nerve-threatening surgical action is significantly better for Cont-IONM (67.7% vs. 20.6%; p = 0.0008). In this clinical setup the Cont-IONM method reduces permanent VCP rates significantly in comparison with Int-IONM. The continuous evaluation of signals during the various dissection steps reduces and limits irreversible damage and allows the surgeon to pay increased attention to the functioning of the nerve.