Development of In-Office Laryngeal Nerve Conduction Studies: Computed Tomography and Cadaveric Study

In-office recurrent laryngeal nerve conduction studies (NCSs) are a technique that can potentially provide information about laryngeal innervation. NCS is essential in the management of other neuropathies including carpal tunnel syndrome and spinal cord injury. We hypothesize that laryngeal NCS may have similar utility in managing patients with vocal fold paralysis, atrophy, and neurodegenerative disease. NCSs are technically challenging because they require transcervical stimulation of the recurrent laryngeal nerve (RLN). This study combines radiographic data with cadaveric dissection to describe the anatomic parameters for optimal RLN stimulation.

Radiographic and Cadaveric Study.

Fifty computed tomography scans were reviewed to determine the dimensions for ideal needle electrode placement. These values were compared to measurements from 12 fresh human cadaveric neck dissections. Ultrasound imaging was utilized in select cases. The neck was dissected to assess the accuracy of electrode placement.

Radiographically, the mean transcervical depth to the RLN was 33.2 mm ± 8.3 mm in males versus 29.4 mm ± 9.4 mm in females. The working space between the lateral trachea and carotid artery was 15.3 mm ± 3.6 mm on the right and 14.1 mm ± 2.9 mm on the left. After placement of stimulating electrodes into the cadaveric neck, the electrode tips were consistently within 8 mm of the RLN. Ultrasound guidance improved placement accuracy of the stimulating electrode.

Laryngeal NCSs can provide detailed and objective information about laryngeal innervation that could dramatically improve the management of various neuropathies. In-office NCSs require technical precision, and this study describes anatomic factors that may affect the feasibility of performing this technique.

NA Laryngoscope, 131:1566-1569, 2021.