Recurrent Laryngeal Nerve (RLN) EMG Monitoring during Cervical Spine Surgeries

October 30, 2019

Faisal R. Jahangiri, M.D., CNIM, D.ABNM, FASNM, FASET¹, Eloise Faust, CNIM¹

¹Axis Neuromonitoring LLC, Richardson, TX, USA;

A 33-year-old female with a history of bilateral arm pain, left arm numbness/tingling, and neck pain was admitted with cervical disc displacement and radiculopathy.

Magnetic Resonance Imaging (MRI) of the patient showed a C5-C6 mild left disc bulge causing mild to moderate compression on the C6 nerve root. Cervical X-ray revealed no dynamic instability. Pre-operative electromyogram (EMG) studies demonstrated a left C6 cervical radiculopathy. The surgeon decided to proceed with a one-level anterior cervical discectomy and fusion (ACDF) procedure at the C-C6 level to treat the herniated cervical disc.

A multimodality Intraoperative Neurophysiological Monitoring (IONM) protocol was planned to include bilateral median nerve, ulnar nerve and posterior tibial nerve Somatosensory Evoked Potentials (SSEPs) [1], bilateral upper and lower limb Transcranial electrical Motor Evoked Potentials (TCeMEPs), bilateral upper extremity EMG and Train of Four (TOF).  The Recurrent Laryngeal Nerve (RLN) EMG was also included to prevent any RLN palsies, which has been previously reported in the literature during anterior cervical spine surgeries [2].

The procedure was performed by a fellowship-trained orthopedic spine surgeon, with a CNIM [3] certified technologist providing the neuromonitoring in the operating room, and a D.ABNM [4] board-certified neurophysiologist available via remote-monitoring. A board-certified neurologist with a specialty in IONM was also present online for remote monitoring during the entire surgical procedure [5].

During the surgical procedure, there was an EMG activity noted in the left recurrent laryngeal nerve after the surgeon placed the retractors (Figure 1). The surgeon was immediately alerted of the RLN irritation and activity. The surgeon readjusted the retractors to remove the pressure on the nerve, resulting in EMG returning to the baseline quite mode (Figure 2).

Figure 1: Abnormal EMG activity in the left recurrent laryngeal nerve recorded during an anterior cervical discectomy and fusion surgery.

Figure 2: EMG returned to baseline in the left recurrent laryngeal nerve after readjusting the retractors.

There was a change in RLN EMG during the procedure with no changes in SSEP or TCeMEP. The surgeon was immediately informed, and he released the retractors, and the EMG came back to baselines within a few minutes. Postoperatively, the patient had no neurological deficits due to early identification of EMG changes as well as quick intervention.

Damage to the RLN during the anterior cervical procedure has been reported in the literature, which may result in vocal cord paralysis, hoarseness, and dysphagia. The injury may result either due to direct sectioning or indirect compression. The common cause of indirect injury is retraction and compression [6].

References