Evaluation of the Effect of Body Mass Index on Epidural Fat Distance with Lumbar Magnetic Resonance Imaging

Objective: As it is known that the body mass index is associated with subcutaneous fat thickness, we aimed to investigate the effect of body mass index on epidural fat distance with lumbar magnetic resonance imaging. Methods: Lumbar MR images of the patients that performed for any reason were retrospectively reviewed and anterior, posterior epidural fat distances were measured at the level of L5-S1 vertebrae in sagittal T1 weighted images. Relation between epidural fat distances and body mass index obtained from height and weight values recorded before the examination, and also relation between epidural fat distances and subcutaneous adipose tissue thickness at the same level were investigated. Pearson correlation test was used in analysis of the data and p<0.05 value considered as statistically significant. Results: Total number of 542 patients, 342 female (63.1%) and 200 male (36.9%), were included in the study. The mean age± SD was calculated as 45.1 ± 14.5 years. According to body mass index patients showed a distribution as 14 (2.6%) underweight, 150 (27.7%) normal, 214 (39.3%) overweight, 118 (21.8% ) obese class 1 and 46 (8.5%) obese class 2. Subcutaneous adipose tissue thickness was measured 16.01±10.9 mm in underweight patients, 21.79±12.06 mm in normal patients, 28.46±13.34 mm in overweight patients, 39.16±15.78 mm in obese class 1 patients and 55.51±24.8 mm in obese class 2 patients. Anterior and posterior epidural spaces were found to be thicker in obese patients rather than in normal patients; respectively (4.46±1.65 mm vs 4.98±1.95 mm, p=0.014, 3.65±1.35 mm vs 4.06±1.48 mm, p=0.01). Conclusion: MRI is a very effective modality for the evaluation of epidural fat tissue and demonstration of other pathologies associated with epidural fat. Determination of hyperintense fat tissue around the hypointense dural sac can be easily performed on T1 MRI. Epidural fat tissue growth should also be considered next to degenerative diseases in the etiology in patients especially in obese who suffer pain, spinal cord and nerve root compression