Spinal epidural lipomatosis – an easily ignored secondary intraspinal disorder in spinal kyphotic deformities

BACKGROUND A previous study reported a high prevalence of spinal epidural lipomatosis (SEL) in patients with Scheuermann kyphosis (SK) and suggested that it may play a role in the pathogenesis of this disease. According to our observation, however, SEL occurs in other spinal kyphotic deformities as well. The aim of this study was to test the hypothesis that SEL commonly occurs in patients with different types of kyphotic deformities as a secondary intraspinal disorder. METHODS MR images of 16 patients with congenital kyphosis (CK), 40 patients with SK, 13 patients with tuberculotic kyphosis (TK), and 69 age- and sex-matched controls were retrospectively evaluated. The body mass index (BMI), kyphosis Cobb angle, and sagittal diameters of spinal epidural fat (EF) and the dural sac (DS) in the apical region (EFA, DSA) and non-kyphotic region (EFN, DSN) were measured. The EF ratios at the apical vertebral level (EFRA) and in the non-kyphotic region (EFRN) were calculated as EF / (EF + DS). RESULTS EFA and EFRA were significantly higher among patients with CK, SK, and TK than among controls (P < 0.05). Seven CK patients (43.8%), 8 SK patients (20.0%), and 11 TK patients (84.6%) fulfilled the diagnostic criteria for SEL, while only 6.3, 2.5, and 0% of patients in the control groups did (P = 0.019, 0.014, and < 0.001, respectively). Spearman's correlation analysis showed statistically significant correlations between the kyphosis Cobb angle and the amount of EF in all three patient groups. CONCLUSIONS SEL is a common secondary intraspinal disorder in different types of kyphotic deformities, and surgeons should pay increased attention to this intraspinal anomaly because excessive EF may compress the spinal cord and cause neurological deficits.