Faculty Bibliography

PURPOSE/OBJECTIVE:To determine whether changes in intraoperative neuromonitoring with saphenous nerve somatosensory evoked potential (SSEP) stimulation, preoperative assessment of  lumbar plexus location, and screw placement, are associated with thigh paresthesia development following an anterior-to-the-psoas (ATP) approach for vertebral body tethering (VBT) in adolescent idiopathic scoliosis (AIS) patients. METHODS:39 patients who underwent a thoracoabdominal ATP approach for VBT with a minimum 2-year follow-up were included. Neurologic monitoring variables, including saphenous nerve SSEPs and quadriceps motor evoked potentials (MEPs), psoas location, an indicator of lumbar plexus location, and screw placement were compared between patients with and without postoperative thigh paresthesia. Demographics and outcomes were analyzed using the Mann-Whitney U test and Fisher's exact test as appropriate, with statistical significance set at p < 0.05. RESULTS:41% of patients experienced postoperative thigh paresthesia. Additionally, 10% reported transient thigh numbness. No patients developed motor deficits. Lumbar plexus position and screw distance did not significantly differ between groups, and no neuromonitoring alarms occurred during psoas retraction. Although changes in quadriceps MEPs were not statistically associated with postoperative sensory symptoms, a higher proportion of patients with paresthesia demonstrated MEP changes (50% vs 19%, p = 0.063) and decreased MEP amplitudes (31% vs 13%, p = 0.077), representing a directional difference. All sensory symptoms resolved without intervention at a mean of 5.3 ± 5.6 weeks and a median of 2.5 (IQR 1-10). CONCLUSION/CONCLUSIONS:Changes in intraoperative neuromonitoring with saphenous nerve SSEP stimulation, psoas location, and screw positioning were not statistically associated with postoperative thigh paresthesia following the ATP approach for VBT in AIS patients. However, a directional difference was observed between quadriceps MEP changes and postoperative thigh paresthesia. These findings highlight the complexity of neurologic responses and support further investigation into patient-specific anatomy, surgical technique, and optimization of neuromonitoring strategies.

Peripheral nerve injuries are unusual in sport but impact an athlete's safe return to play. Nerve injuries result from either acute trauma (most commonly in contact/collision sports) or from repetitive microtrauma and overuse. Diagnosis of overuse nerve injuries includes nerve localization and surrounding soft-tissue anatomy, and must account for possible causes of repetitive microtrauma, including biomechanics, equipment, training schedule, and recovery. Prognosis is related to the type of nerve injury. Management should not simply be rest and gradual return to sport but should address biomechanical and training predispositions to injury. Understanding the type of injury and the tissues involved will guide appropriate rehabilitation decisions. Recognizing acute care considerations and implementing appropriate strategies can help minimize secondary trauma to an area following acute injury.

Intraoperative monitoring is performed to provide real-time assessment of the neural structures that can be at risk during spinal surgery. Somatosensory evoked potentials (SEPs) are the most commonly used modality for intraoperative monitoring. SEP stability can be affected by many factors during the surgery. This study is a prospective review of SEP recordings obtained during intraoperative monitoring of instrumented spinal surgeries that were performed for chronic underlying neurologic and neuromuscular conditions, such as scoliosis, myelopathy, and spinal stenosis. We analyzed multiple montages at the baseline, and then followed their development throughout the procedure. Our intention was to examine the stability of the SEP recordings throughout the surgical procedure on multiple montages of cortical SEP recordings, with the goal of identifying the appropriate combination of the least number of montages that gives the highest yield of monitorable surgeries. Our study shows that it is necessary to have multiple montages for SEP recordings, as it reduces the number of non-monitorable cases, improves IOM reliability, and therefore could reduce false positives warnings to the surgeons. Out of all the typical montages available for use, our study has shown that the recording montage Cz-C4/Cz-C3 (Cz-Cc) is the most reliable and stable throughout the procedure and should be the preferred montage followed throughout the surgery.

PURPOSE: Comparison of T1-T4 decrement between upper and lower extremity muscles can indicate differences between recovery time from neuromuscular blockade, which may have repercussions for neurophysiologic intraoperative monitoring. We investigated decrement between T1 and T4 hand and foot muscle responses on quantitative train-of-four (TOF) test. METHODS: Study analyzed differences between recovery of foot, abductor hallucis muscle, and hand, first dorsal interosseous muscle, by application of quantitative TOF test on 147 patients undergoing lumbar spine surgery. T1 to T4 decrements on hand and foot TOF were obtained and classified into different groups, depending on elapsed time after administration of neuromuscular blocking agents and its dose. RESULTS: There are significant differences between T1-T4 decrements obtained on hand and foot (P < 0.05). T1-T4 decrement determined on abductor hallucis muscle was lower indicating more rapid recovery than the first dorsal interosseous muscle (P < 0.05). Interestingly, quite opposite, more pronounced decrement in foot TOF than hand was showed in 4% (5 out of all 147 cases). CONCLUSIONS: The observed difference between recovery of hand and foot muscles suggests that quantitative TOF test should be performed on extremities for which accurate data about the level of neuromuscular blockade is sought. During lumbar spine surgery monitoring, in addition to hand TOF, foot TOF should be included.