Measurement of the Local Pressure of the Intervertebral Foramen and the Electrophysiologic Values of the Spinal Nerve Roots in the Vertebral Foramen.

Morishita, Yuichiro MD; Hida, Shinichi MD, PhD; Naito, Masatoshi MD, PhD; Arimizu, Jun MD, PhD; Matsushima, Ushio MD; Nakamura, Atsuhiko MD

To investigate the neurophysiologic changes of the spinal nerve roots in the vertebral foramen. The intraoperative findings of the local pressure of the intervertebral foramen and the electrophysiologic values of the spinal nerve roots were evaluated. The local pressure of the intervertebral foramen was continuously measured while the lumbar spine posture was changed in 66 vertebral foramens. In addition, 20 L5 nerve roots were electrophysiologically evaluated using the compound muscle action potentials (CMAPs) from tibialis anterior (TA) muscle after L5 nerve root stimulation. The results showed that local pressure of the intervertebral foramen was significantly increased during lumbar spine extension (P < 0.001); moreover, the latency and amplitude of the CMAPs both significantly deteriorated in line with the increasing local pressure. The authors conclude that a double compression of the nerve root exists in lumbar spinal stenosis with lumbar spine extension, which includes the spinal canal and the vertebral foramen.

Spine. 31(26):3076-3080, December 15, 2006.

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