Electrophysiological diagnosis using sensory nerve action potential for the intraforaminal and extraforaminal L5 nerve root entrapment

Abstract

Background The diagnosis of lumbar intraforaminal and extraforaminal stenosis (lumbar foraminal stenosis) is sometimes difficult. However, sensory nerve action potential (SNAP) decreases in amplitude when the lesion is at or distal to the dorsal root ganglion. Therefore, the amplitude of SNAP with lumbar foraminal stenosis should be decreased. In this cohort study, the usefulness of SNAP for the preoperative diagnosis of L5/S foraminal stenosis was assessed. Methods In 63 patients undergoing unilateral L5 radiculopathy, bilateral SNAPs were recorded for the superficial peroneal nerve (L5 origin). The patients were divided into two groups according to the results of imaging examinations. Group A (37 patients) included patients whose lesion was located only at the intraspinal canal. In group B (26 patients), the lesion was located only at the intra-or extraforaminal area. All patients received surgery and the symptoms were diminished. The ratios of the amplitudes of SNAPs on the affected side to that on the unaffected side were compared between groups A and B. Results SNAPs could not be elicited bilaterally in four patients. The amplitude ratio for group B (median 0.42, max 1.17, min 0) was significantly lower than that in group A (median 0.85, max 1.43, min 0) (p \ 0.001 by MannWhitney U test). Using a cut-off value of 0.5 for the amplitude ratio, the sensitivity for the diagnosis of lumbar foraminal stenosis was 91.3 % with a specificity of 85.7 %. Conclusions Measurement of SNAP could be useful to diagnose a unilateral L5/S foraminal stenosis.

Diagnosis of Lumbar Foraminal Stenosis using Diffusion Tensor Imaging

“…Nerve conduction studies are tests that are used to detect nerve conduction disorders peripheral to the knee, but lumbar nerve injuries are localized to the foramen. If Waller degeneration does not extend to the region below the knee, there is the possibility of a false-negative result [ 26 ].…”

The prevalence of tarsal tunnel syndrome in patients with lumbosacral radiculopathy

“…Furthermore, radiculopathy group patients with suspected extreme lateral lumbosacral hernia or suspected intervertebral foraminal stenosis identified by radiologic evidence were also excluded from the study because the LR caused by these two conditions might affect the sensory ganglion or more distal sensory nerves, which may cause the abnormal sensory nerve action potential in LR, particularly in L5 radiculopathy [18,19], although some author suggests that this condition is very rare [20], and amplitudes of sensory nerve action potential may be the only parameters that would be affected by LR [21].…”

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Dffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography

“…Traditional imaging studies do not allow a determination of whether the compressing lesion is inside or outside of the spinal canal, or if a doublecrush lesion is responsible, which leads to poor surgical success rates. The distal latency of L5 has been measured electrophysiologically; however, this is an invasive approach, and noninvasive diagnostic methods are virtually nonexistent 68,69) . Diagnosis of L5 nerve damage double-crush lesions by DTI was studied.…”