A Comparison of Interside Asymmetries of Lower Extremity Somatosensory Evoked Potentials in Anesthetized Patients with Unilateral Lumbosacral Radiculopathy.

STUDY DESIGN: Prospective cohort study.

PURPOSE: This study was to investigate interside asymmetries of three lower extremity somatosensory evoked potentials (SSEPs) in anesthetized patients with unilateral lumbosacral radiculopathy.

OVERVIEW OF LITERATURE: Although interside asymmetry is an established criterion of abnormal SSEP, little is known which of the lower SSEPs is more sensitive in detecting interside asymmetry in anesthetized patients.

METHODS: Superficial peroneal nerve SSEP (SPN-SSEP), posterior tibial nerve SSEP (PTN-SSEP), and sural nerve SSEP were obtained in 31 lumbosacral surgery patients with unilateral lumbosacral radiculopathy, and compared with a group of 22 control subjects.

RESULTS: The lumbosacral group showed significant larger interside asymmetry ratios of P37 latencies in SPN-SSEP and PTN-SSEP, and significant larger interside asymmetry ratio of P37-N45 amplitude in SPN-SSEP, when comparing with the control group. Within the lumbosacral group but not the control group, SPN-SSEP displayed significant larger interside asymmetry ratio in P37 latency. When referencing to the control group, more patients in the lumbosacral group displayed abnormal interside SPN-SSEP latency asymmetries which corroborated the symptom laterality.

CONCLUSIONS: The data suggested that SPN-SSEP was more sensitive in detecting interside latency asymmetry in anesthetized patients.