Monitoring superficial peroneal nerve somatosensory evoked potential during L4-5 lumbar root decompression.

Background Context: Posttibial nerve somatosensory evoked potential (PTN-SSEP) often fails to detect individual nerve root dysfunction, whereas dermatomal somatosensory evoked potential (DSSEP) can be difficult to obtain in anesthetized patients.

Purpose: The main aim of this study is to investigate whether the superficial peroneal nerve SSEP (SPN-SSEP), a cutaneous nerve SSEP derived from L4-5 roots, can be relied on as an intraoperative neurophysiological assessment for L4-5 roots.

Study Design/setting: Retrospective review of consecutive case series.

Patient Sample: Thirty-five consecutive patients who underwent lumbar root microdecompression were reviewed. The control group consisted of 11 patients who underwent anterior cervical discectomy and fusion (ACDF).

Outcome Measures: Intraoperative SSEP measures defined outcome measures.

Methods: Data from 35 patients undergoing SPN-SSEP, PTN-SSEP, and sural nerve SSEP (SN-SSEP) monitoring during lumbar surgeries were analyzed and compared with the control group of patients underwent ACDF surgery.

Results: Cortical SPN-SSEP could be readily recorded in more than 90% patients from both groups. The waveforms of SPN-SSEP were about 30% smaller than PTN-SSEP, but very similar to SN-SSEP. Importantly, SPN-SSEP was capable of detecting intraoperative L4-5 root dysfunction without the corresponding PTN-SSEP or SN-SSEP alterations. Overall, SPN-SSEP displayed twofold greater sensitivity over PTN-SSEP or SN-SSEP.

Conclusions: SPN-SSEP was a more sensitive measure for intraoperative L4-5 nerve root dysfunction in comparison with PTN-SSEP and SN-SSEP.