INTRODUCTION:Linked Quadripolar Stimulation (LQP) is a recent adaptation of transcranial electric motor evoked potential stimulation, with proposed advantages over traditional Bipolar (BP) stimulation. This study aims to comprehensively compare BP and LQP stimulation to validate the efficacy of LQP. METHODS:BP and LQP stimulation were performed on 30 patients undergoing anterior cervical discectomy and fusion. A comprehensive assessment involved conducting four trials for each technique on each patient. An Accelerometer placed over the right masseter region recorded movement. A Mann-Whitney U test and Pearson Correlation Coefficient were used to quantitatively compare patient movement, compound muscle action potential (CMAP) response amplitude, and area under the curve (AUC) values. RESULTS:TCMEP recordings were successfully obtained from the entire sample. No statistical significance was found between patient movement, amplitude, or area under the curve (AUC) between BP and LQP stimulation. A weak correlation was found between patient movement and stimulation intensity for both techniques. A strong correlation was found between amplitude and AUC values. CONCLUSION:Patient movement and stimulation parameters showed similar outcomes between BP and LQP. LQP did not demonstrate reduced movement compared to BP stimulation. This study contributes valuable insights into the effectiveness of BP and LQP stimulation in anterior cervical discectomy and fusion surgery.
Injury to the recurrent laryngeal nerve (RLN) during anterior cervical spine surgery is an uncommon yet impactful sequela. This study evaluates the feasibility and intraoperative behavior of laryngeal adductor reflex (LAR) and motor-evoked potentials with vocalis recordings (MEP-VC) during anterior cervical spine surgery. LAR and MEP-VC were employed for 13 patients undergoing anterior cervical spine surgery. LAR alerts were issued when clinically correlated reductions in amplitude, typically ≥20% in previously stable, non-habituating recordings, and/or temporal dispersion of the LAR waveform occurred. MEP-VC alerts were issued for a ≥50% isolated decrease in amplitude or any amplitude reduction that occurred concurrently with an LAR amplitude decline. LAR alerts were observed in five surgeries, with four showing recovery to baseline. In one case, with no LAR recovery, this patient demonstrated post-operative hoarseness. Conversely, another case showed persistent MEP-VC deterioration, despite LAR recovery following the intervention. This patient exhibited right vocal fold paralysis, diagnosed with incomplete glottic closure by an otolaryngologist. All other patients exhibited no RLN deficits post-surgery. Our proof-of-concept study demonstrates the feasibility of LAR and MEP-VC monitoring and suggests that these modalities may provide physiologically relevant information regarding RLN function during anterior cervical spine surgery.
