Abstracts

Rationale: Persons with epilepsy have a 2-6 fold increased risk of fracture. Both low bone mineral density (BMD) and abnormal bone microarchitecture are associated with fracture. We aimed to evaluate areal BMD (aBMD) and indices of bone structural integrity and quality using dual energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) in persons with epilepsy treated with antiepileptic drugs (AEDs). Methods: We studied 111 persons with epilepsy on various AEDs: 39 older men (58 7), 50 premenopausal women (37 7) and 22 postmenopausal women (61 5). Excluded were subjects with bone disease or with illnesses or on medications that affect the skeleton. Areal BMD was measured by DXA (Hologic QDR 4500) at the spine (LS), total hip (TH), femoral neck (FN), and 1/3 radius (1/3R). Volumetric BMD (vBMD) and trabecular (Tb) and cortical (Ct) microarchitecture were measured at the nondominant distal radius and tibia by HR-pQCT (XtremeCT; SCANCO Medical AG; voxel size ~82 microns). DXA sex-specific Z-scores were compared to reference population normative values provided by Hologic Corp. HR-pQCT sex-specific Z-scores were compared to normative values provided by Boutroy for premenopausal women and postmenopausal women and by Chaitou et al. (JBMR, 2010) for older men. Results: DXA Z-scores did not differ from normative values at any site for men with epilepsy (Table). For postmenopausal women with epilepsy, DXA Z-scores did not differ at LS, TH or FN, but were significantly higher at the 1/3R. For premenopausal women with epilepsy, the FN Z-score was below and the 1/3R Z-score was above normative values, while Z-scores at the LS and TH were normal. At the radius, cross-sectional area (CSA), a measure of bone size, was low in men and postmenopausal women. Total vBMD was normal in all groups. Cortical vBMD was high in men and normal in premenopausal women and postmenopausal women. Cortical thickness (CtTh) was normal in all groups. Trabecular vBMD was low in premenopausal women and men, but not postmenopausal women. There were consistent increases in trabecular number (TbN) and decreases in trabecular thickness (TbTh) in all groups. At the tibia, CSA was normal in men and postmenopausal women and high in premenopausal women. Total vBMD was low in premenopausal women and men, but not postmenopausal women. All groups had low cortical vBMD and thickness and normal trabecular vBMD. As at the radius, TbN was higher and TbTh was lower in all groups.Conclusions: In summary, compared to age-matched and gender norms, aBMD by DXA was low only at the FN and only in premenopausal women. HR-pQCT differences were most marked and consistent at the tibia where persons with epilepsy had thinner, less dense cortices. Trabecular vBMD was normal, likely because higher TbN compensated for lower TbTh. These differences in bone quality, namely thinner, less dense cortices and thinner trabeculae, could contribute to increased fracture risk in persons with epilepsy.