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.