INTRODUCTION: Diffusion‐weighted imaging (DWI) can provide valuable information regarding the microstructure of tissues and quantitative diffusion values. The purpose of this study was to measure apparent diffusion coefficient (ADC) of the lumbar nerve roots in patients with lumbar foraminal stenosis and to investigate the nerve root course using neurography.
METHODS: 14 patients (8 male, 6 female, median age 62.0 years) who had unilateral radicular symptoms with lumbar foraminal stenosis were studied. 14 healthy volunteers (7 male, 7 female, median age 55 years) served as controls.
DWI was performed using a 1.5‐T MRI and diffusion‐weighted whole body imaging with a background body signal suppression (DWIBS). Circular regions of interest (ROIs) were placed in the fourth and fifth lumbar nerve roots and sacral nerve root in axial ADC maps and mean ADC values were calculated. The neurography was also used for evaluation of nerve root course. Statistical analyses were performed with Stat View software and a post hoc test was used. A p‐value < 0.05 was considered significant.
RESULTS: In patients, neurography frequently showed abnormalities such as nerve swelling (100 %) and running transversely (71.5 %). The mean ADC (× 10–3 mm2/s) of proximal nerve roots on the side of entrapment was 1.387 higher than the 1.206 on the intact side and distal spinal nerve ADC on the side of entrapment was 1.507 higher than the 1.154 seen on the intact side (P
DISCUSSION: Lumbar foraminal stenosis is a condition in which a nerve root or spinal nerve is entrapped in the narrowed lumbar foramen.
In this study, ADC values in entrapped nerve roots were higher than they were in intact nerve roots, suggesting demyelination and edema by slow compression caused by an increased degree of diffusion. Our study also demonstrated that neurography can accurate localization of nerve compression in the foramen.