Trans-Kambin Oblique Lateral Lumbar Interbody Fusion With a Low Neurostimulation Threshold and Transient Intraoperative Neuromonitoring Changes Without Postoperative Neurological Deficits

Trans-Kambin oblique lateral lumbar interbody fusion (OLLIF) is a minimally invasive lumbar fusion technique that relies heavily on intraoperative neuromonitoring (IONM) to reduce the risk of neural injury. Triggered electromyography (tEMG) stimulation thresholds below 3-4 mA are traditionally considered to indicate increased neural risk; however, the clinical implications of isolated low thresholds remain incompletely defined. We report the case of a 44-year-old female who underwent L5-S1 trans-Kambin OLLIF. During probe placement, triggered EMG responses were elicited at 2 mA, indicating close proximity to neural elements. Free-run EMG remained quiet, and baseline motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) were stable during dilation and cage insertion. Approximately 10 minutes after final cage positioning, an ~80% reduction in left L5 MEP amplitude occurred, which persisted until extubation. Despite these transient IONM changes, post-extubation neurological examination was normal, with no motor or sensory deficits. The patient remained neurologically intact at follow-up with improvement in preoperative symptoms. This case demonstrates that isolated low neurostimulation thresholds and transient IONM changes do not inevitably predict postoperative neurological deficit, highlighting the importance of interpreting multimodal neuromonitoring in the clinical context and emphasizing that patient-specific risk-benefit analysis and surgical judgment remain paramount.