Purpose: Magnetospinography provides a noninvasive and detailed visualization of neural currents. We previously reported that magnetospinography can be used to evaluate neural function in the lower lumbar spine in response to tibial, peroneal, and sciatic nerve stimulation. However, evaluating the neural function of the upper and middle lumbar spine is often difficult due to lower current intensity. We aimed to visualize the neural activity of the upper and middle lumbar spine using new stimulation methods and assess the foraminal current. Methods: Neural magnetic fields in 10 healthy volunteers were recorded after stimulation of the lateral femoral cutaneous nerve, saphenous nerve, femoral nerve, and peroneal nerve. The conduction velocity and current intensity in the spinal canal and intervertebral foramen were calculated and compared for each type of nerve stimulation. Results: Magnetospinography visualized the evoked magnetic fields in the lumbar region after each nerve stimulation method in all volunteers. The current intensity in the upper lumbar spine was significantly greater after femoral nerve stimulation. Magnetospinography revealed that action current flowed mainly along the L2 nerve root after lateral femoral cutaneous nerve stimulation and the L4 nerve root after saphenous nerve stimulation. Conclusions: Using a new stimulation method, magnetospinography enabled the noninvasive visualization of neural currents in the upper and middle lumbar spine. Femoral nerve stimulation is suitable for evaluating the spinal canal of the upper lumbar spine, and lateral femoral cutaneous nerve and saphenous nerve stimulations are suitable for evaluating the upper and middle lumbar intervertebral foramina, respectively.
Higashikawa et al. (Thu,) studied this question.