Cauda Equina Conduction Time Determined by F-Waves in Normal Subjects and Patients With Neurogenic Intermittent Claudication Caused by Lumbar Spinal Stenosis

Factors associated with improvement in tibialis anterior weakness due to lumbar degenerative disease

BACKGROUND

The weakness of the tibialis anterior remains to be a controversial topic. There has been no study that used electrophysiological assessment of the function of the lumbar and sacral peripheral motor nerves. The aim is to evaluate surgical outcomes in patients with weakness of the tibialis anterior using neurological and electrophysiological assessments.

METHODS

We enrolled 53 patients. Tibialis anterior weakness was quantified by muscle strength, as assessed using a manual muscle test on a scale of 1 through 5, with scores <5 indicating weakness. Postoperative improvement in muscle strength was classified as excellent (5 grades recovered), good (more than one grade recovered), or fair (less than one grade recovered).

RESULTS

Surgical outcomes for tibialis anterior function were categorized as "excellent" in 31, "good" in 8, "fair" in 14 patients. Significant difference in outcomes were observed depending on diabetes mellitus status, type of surgery, and the compound muscle action potentials amplitudes of the abductor hallucis and extensor digitorum brevis (p < 0.05). Surgical outcomes were classified into two groups, patients with excellent and good outcomes (Group 1) and patients with fair outcome (Group 2). Using the forward selection stepwise method, sex and the compound muscle action potentials amplitudes of the extensor digitorum brevis were identified as significant factors for their positive association with Group 1 status. The diagnostic power of the predicted probability was as high as 0.87 in terms of area under curve of the receiver operating characteristic curve.

CONCLUSIONS

There was a significant correlation between the prognosis of tibialis anterior weakness and sex and the compound muscle action potentials amplitude of extensor digitorum brevis, suggesting that recording the compound muscle action potentials amplitude of extensor digitorum brevis will aid the outcome assessment of future surgical interventions for tibialis anterior weakness.

Transcranial Magnetic Stimulation in the Diagnosis of Compressive Myelopathy at the Thoracolumbar Junction

PURPOSE

The disc level in the thoracolumbar junction at which measurement of the central motor conduction time in the lower limbs (CMCT-LL) is useful for a diagnosis remains unclear. Therefore, this study investigated the spinal vertebral level at which compressive myelopathy due to ossification of the ligamentum flavum in the thoracolumbar junction is detectable using CMCT-LL.

METHODS

We preoperatively measured CMCT-LL in 57 patients (42 men, 15 women; aged 35-85 years) with a single ossification of the ligamentum flavum from the T10-11 to T12-L1 disc levels and in 53 healthy controls. Motor evoked potentials after transcranial magnetic stimulation, compound muscle action potentials, and F waves were recorded from the abductor hallucis. Central motor conduction time in the lower limbs was calculated as follows: Motor evoked potential latency - (compound muscle action potential latency + F latency - 1)/2 (ms). Central motor conduction time in the lower limbs was compared between patients and controls.

RESULTS

Compressive lesions were located at the T10 to 11 level in 27 patients, the T11 to 12 level in 28, and the T12-L1 level in 2. Central motor conduction time values in the lower limbs at the T10 to 11 level (19.9 ± 4.7 ms) and T11 to 12 level (18.1 ± 3.4 ms) were significantly longer than control values (11.8 ± 1.1 ms; P < 0.01). Central motor conduction time in the lower limbs was not calculated at the T12-L1 level because motor evoked potentials were not recorded in any patient.

CONCLUSIONS

We confirmed that CMCT-LL was significantly longer in patients with ossification of the ligamentum flavum at the T10 to 11 and T11 to 12 levels because the S2 segment of the spinal cord is caudal at the T12 vertebral body level. Therefore, CMCT-LL is useful for diagnosing thoracolumbar junction disorders proximal to the T12 vertebral body level.

Risk factors for sleep quality disturbances in patients with lumbar spinal stenosis before operation

PURPOSE

We aimed to explore the risk factors of preoperative sleep quality in patients with lumbar spinal stenosis (LSS) and the association of sleep-related beliefs with sleep quality in these patients.

METHODS

Sleep quality and related risk factors of sleep quality disturbances in patients with LSS preoperatively were assessed by questionnaires. Pittsburgh Sleep Quality Index (PSQI) for sleep quality, Oswestry Disability Index (ODI) for clinical outcomes, Visual Analog Scale for Pain (VAS Pain), Self-Rating Anxiety Scale (SAS) for anxiety level, and Dysfunctional Beliefs and Attitudes about Sleep (DBAS-16) for sleep-related beliefs were assessed. Bivariate logistic regression analysis was used to assess the risk factors of sleep quality disturbances.

RESULTS

A total of 227 patients were enrolled, mean age 64 years (SD 13.1), 119 women (52%). The incidence of sleep quality disturbances in patients was 37% (83/227). Increased DBAS-16 scores (OR = 0.781; 95% CI, 0.725-0.841; p < 0.001) significantly decreased the probability of developing sleep quality disturbances, while increased anxiety levels (OR = 1.241; 95% CI, 1.152-1.337; p < 0.001) significantly increased the probability of developing sleep quality disturbances in patients. Factors including educational level, increased age, sex, preoperative length of stay, VAS Pain scores, and ODI scores showed no significant association and were therefore excluded from the model.

CONCLUSIONS

High levels of anxiety and mistaken sleep-related beliefs were risk factors of sleep quality disturbances in patients with LSS before surgery. The more mistaken sleep-related beliefs were, the greater the probability of sleep disturbances.

Relationship Between Cauda Equina Conduction Time and Type of Neurogenic Intermittent Claudication due to Lumbar Spinal Stenosis

INTRODUCTION

This study investigated whether the prolongation of the cauda equina conduction time (CECT) was related to the type of neurogenic intermittent claudication due to lumbar spinal stenosis.

METHODS

In total, 149 patients who underwent surgery due to lumbar spinal stenosis with neurogenic intermittent claudication were classified into three groups as follows: cauda equina-type(n = 67), radicular-type(n = 29), and mixed-type(n = 53). Cauda equina conduction time was measured by placing disc electrodes on the abductor hallucis muscle, electrically stimulating the tibial nerve of the ankle and recording the compound muscle action potentials and F-waves. Motor evoked potentials from the abductor hallucis muscle were measured after magnetically stimulating the lumbosacral spine. Cauda equina conduction time was calculated from the latencies of compound muscle action potentials, F-waves, and motor evoked potentials. The measurement of the dural sac cross-sectional area were assessed using computed tomography myelography or MRI.

RESULTS

The values of CECT were as follows: cauda equina-type, 5.6 ± 1.1 ms; mixed-type, 5.1 ± 0.9 ms; and radicular-type, 4.0 ± 0.9 ms. The values of dural sac cross-sectional area were as follows: cauda equina-type, 42.8 ± 18.7 mm; mixed-type, 49.6 ± 20.9 mm; and radicular-type, 75.3 ± 19.1 mm. In the cauda equina-type and mixed-type patients, CECT was significantly prolonged and there were negative correlations between CECT and dural sac cross-sectional area.

CONCLUSIONS

Cauda equina conduction time differed according to the type of lumbar spinal stenosis. The prolongation of CECT may be caused by the demyelination of the CE. Cauda equina conduction time may be a useful measure for evaluating the dysfunction of the CE rather than radiculopathy for patients with lumbar spinal stenosis.

Visualization of the electrical activity of the cauda equina using a magnetospinography system in healthy subjects

OBJECTIVE

To establish a method to measure cauda equina action fields (CEAFs) and visualize the electrical activities of the cauda equina in a broadly aged group of healthy adults.

METHODS

Using a 124-channel magnetospinography (MSG) system with superconducting interference devices, the CEAFs of 43 healthy volunteers (22-64 years of age) were measured after stimulation of the peroneal nerve at the knee. Reconstructed currents were obtained from the CEAFs and superimposed on the X-ray image. Conduction velocities were also calculated from the waveform of the reconstructed currents.

RESULTS

The reconstructed currents were successfully visualized. They flowed into the L5/S1 foramen about 8.25-8.95 ms after the stimulation and propagated cranially along the spinal canal. In 32 subjects (74%), the conduction velocities of the reconstructed currents in the cauda equina could be calculated from the peak latency at the L2-L5 level.

CONCLUSIONS

MSG visualized the electrical activity of the cauda equina after peroneal nerve stimulation in healthy adults. In addition, the conduction velocities of the reconstructed currents in the cauda equina could be calculated, despite previously being difficult to measure.

SIGNIFICANCE

MSG has the potential to be a novel and noninvasive functional examination for lumbar spinal disease.