The incidence, cause, and prevention of recurrent laryngeal nerve palsies during anterior cervical spine surgery

Study Design. A retrospective review of contemporaneously acquired clinical data supplemented by experimental cadaver dissection. Objective. To establish the incidence and mechanism of vocal cord paralysis after anterior cervical spine surgery and to determine whether controlling for endotracheal tube (ET)-laryngeal wall interactions induced by the cervical retraction system could decrease the rate of paralysis. Summary of Background Data. Vocal cord paralysis is the most common otolaryngologic complication after anterior cervical spine surgery. However, the quoted frequency of this varies considerably, and the cause of the injury is not clearly defined. As a result, various, and at times contradictory, recommendations to prevent this are presented without data to support their effectiveness. Methods. Data gathered at the time of surgery and during follow-up visits on 900 consecutive patients who underwent anterior cervical spine surgery with plating during a 12-year interval were entered into a computerized database and reviewed for complications and procedural risk factors. After the first 250 cases an intervention consisting of monitoring ET cuff pressure and release of pressure after retractor replacement or repositioning was used; which allowed the ET to recenter within the larynx. The ET-laryngeal wall relation also was studied in fresh intubated cadavers using videofluoroscopic images, before and after retractor placement. Results. Thirty incidences of vocal cord paralysis consistent with recurrent laryngeal nerve (RLN) injury were :identified: 27 temporary and 3 permanent. The rate of temporary paralysis decreased from 6.4% to 1.69% (P = 0.0002) after institution of the described maneuver. The findings confirmed that the retractor displaced the larynx against the shaft of the ET, allowing impingement on the vulnerable intralaryngeal segment of the RLN. Conclusions. The most common cause of vocal cord paralysis after anterior cervical spine surgery is compression of the RLN within the endolarynx. Monitoring of ET cuff pressure and release after retractor placement may prevent injury to the RLN during anterior cervical spine-surgery.