A Dynamic Magnetic Resonance Imaging Study of Changes in Severity of Cervical Spinal Stenosis in Flexion and Extension

OBJECTIVE: To evaluate changes in the severity of cervical spinal stenosis (CSS) in flexion and extension and determine whether the rate of change with motion varied with severity. METHODS: The study included 92 symptomatic patients with a mean age of 57.80±10.41, who underwent cervical spine dynamic magnetic resonance imaging. The severity of stenosis was evaluated using a semi-quantitative CSS score, ranging from 0 (no spinal stenosis) to 18 (severe stenosis). Radiological evaluation included flexion, neutral, and extension measurements, as determined by the C2–C7 Cobb angle. The severity of stenosis was represented by the total CSS score. The total CSS score in flexion, neutral, and extension positions was compared using repeated measures one-way analysis of variance. The change rate of stenosis per angle motion (CRSPAM) was defined as change in total CSS score divided by change in Cobb angle. The correlation of CRSPAM with severity of stenosis, represented by total CSS score in neutral position, was evaluated using Pearson correlation analysis. RESULTS: The total CSS score was significantly higher in extension (6.04±2.68) than in neutral position (5.25±2.47) (p < 0.001), and significantly higher in neutral than in flexion position (4.40±2.45) (p < 0.001). The CRSPAM was significantly and positively correlated with total CSS score in neutral position in the flexion-extension range (r=0.22, p=0.04) and flexion-neutral range (r=0.27, p=0.01). CONCLUSION: In symptomatic CSS patients, the radiological severity of stenosis increases with extension and decreases with flexion. In patients with CSS, the rate of variation in spinal stenosis increases with increased severity.

Intraoperative Monitoring of Hypoglossal Nerve Using Hypoglossal Motor Evoked Potential in Infratentorial Tumor Surgery: A Report of Two Cases

The hypoglossal nerve (CN XII) may be placed at risk during posterior fossa surgeries. The use of intraoperative monitoring (IOM), including the utilization of spontaneous and triggered electromyography (EMG), from tongue muscles innervated by CN XII has been used to reduce these risks. However, there were few reports regarding the intraoperative transcranial motor evoked potential (MEP) of hypoglossal nerve from the tongue muscles. For this reason, we report here two cases of intraoperative hypoglossal MEP monitoring in brain surgery as an indicator of hypoglossal deficits. Although the amplitude of the MEP was reduced in both patients, only in the case 1 whose MEP was disappeared demonstrated the neurological deficits of the hypoglossal nerve. Therefore, the disappearance of the hypoglossal MEP recorded from the tongue, could be considered a predictor of the postoperative hypoglossal nerve deficits.