Changes in nerve root motion and intraradicular blood flow during intraoperative femoral nerve stretch test

Abstract

Object. It is not known whether changes in intraradicular blood flow (IRBF) occur during the femoral nerve stretch test (FNST) in patients with lumbar disc herniation. An FNST was conducted in patients with lumbar disc herniation to observe the changes in IRBF, and results were then compared with clinical features. Methods. The study was composed of four patients with L3–4 disc herniation who underwent microdiscectomy. Patients were placed prone immediately before surgery, so that their knee flexed on the operating table with the hip joint kept in hyperextension, and the FNST was performed to confirm at which region pain developed in the anterolateral thigh. During the operation, the hernia-affected nerve roots were visualized under a microscope. The needle sensor of a laser Doppler flowmeter was then inserted into each nerve root immediately above the hernia, and the change in IRBF was measured during the intraoperative FNST. After removal of the herniated disc, a similar procedure was repeated and IRBF was measured again. The intraoperative FNST showed that the hernia compressed the nerve roots and there was marked disturbance of gliding, which was reduced to only a few millimeters. During the test, IRBF decreased by 92.8 to 100% (mean 96.9 ± 3.7% [± standard error of the mean]) relative to the blood flow before the test. This study demonstrated that the blood flow in the nerve root is reduced when the nerve root is compressed in vivo. Conclusions. The intraoperative FNST showed that the hernia compressd the nerve roots and there was marked disturbance of gliding, which was reduced to only a few millimeters. During the test, IRBF decreased by 92.8 to 100% (96.9 ± 3.7% [mean ± standard error of the mean]).