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Objective: To evaluate the efficacy of routine intraoperative neuromonitoring (IONM) in preventing recurrent laryngeal nerve (RLN) injury during thyroidectomy.
Design: Retrospective chart review.
Setting: Academic institution.
Patients: Consecutive patients undergoing thyroidectomy at a single institution by experienced endocrine surgeons between 2006 and 2009 following adoption of routine IONM.
Interventions: Intraoperative IONM.
Main Outcome Measures: RLN injury.
Results: Between 2006 and 2008, 296 subjects underwent thyroid lobectomy or total thyroidectomy by an experienced endocrine surgeon. One patient was excluded because of preoperative documentation of RLN injury. IONM was used in 253 (88%) cases during adoption of this technology (with 403 nerves at risk of injury). Loss of RLN signal following surgical dissection occurred in 13 cases, prompting a change in surgical plan in one case. Three patients with RLN signal loss had transient post-operative voice changes. Post-operative laryngoscopy was performed in eight patients with persistent hoarseness, documenting vocal cord paralysis in one patient who had clear intraoperative anatomic evidence of RLN injury. In no case did loss of RLN signal after dissection lead to persistent voice change without anatomical evidence of injury detected by the surgeon. IONM had a one-time cost for reusable equipment of $29,536, and an average disposable cost of $420 to $437 per case.
Conclusions: In our early experience, routine IONM did not appear to increase protection of the RLN over visual identification. Loss of IONM signal did not reliably predict post-operative voice changes. Furthermore, IONM added equipment cost of around $450 per case.

	N	(%)
Female	194	(77%)
Mean age (years)	49	--
Procedure
Total thyroidectomy	152	(60%)
Right lobectomy	43	(17%)
Left lobectomy	39	(16%)
Completion thyroidectomy	19	(7%)
Reoperation	25	(10%)
Signal lost after dissection	13	(5%)
Signal loss prompted change in surgical plan	1	(0.3%)
Post-operative voice change	14	(5%)
Immediately	14	(5%)
2 weeks	14	(5%)
6 weeks	3	(1%)
2 years	1	(0.3%)
Laryngoscopy performed	8	(3%)
Normal	7	(1%)
Cord paralysis	1	(0.3%)
Visual identification of RLN injury	1	(0.3%)
Malfunction of IONM system	17	(7%)
Fixed Cost
Main unit	$29,536
Variable Cost
Endotracheal tube	$230-247
Stimulator probe	$103
Electrodes	$87