Abstracts

Rationale: Patients with epilepsy and taking anti-epileptic medication (AED) have an increased incidence of fractures. Potential causes for this association include bone disease and increased falls during seizure and at other times. We aimed to assess the effect of chronic AED use on muscle strength, gait and balance utilizing a matched twin and sibling AED-discordant pair approach.Methods: 27 same-sex pairs were studied: 5 monozygous and 5 dizygous twin pairs, and 17 sib pairs; 11 male, 16 female pairs; mean(SD) age 45.5(16.1), height 1.69(0.10)m, weight 77.3(16.2)kg and BMI 26.9(4.7)kg/m2 were assessed. For the AED users, mean(SD) duration of treatment was 22.7(16.6) years. Validated tests predictive of falls risk were performed: tests of static and dynamic balance - Chattecx Balance System [force platform tests of sway index(SI), measuring total sway, and left-right sway(LR), over 25 seconds, where increasing scores are correlated with falls risk, under different conditions - stable or moving platform, with or without distraction task (subtracting serial 3’s)] and Lord’s Balance Test(LBT) (a clinical balance test); muscle strength was measured using Kincom and Nicholas Manual Muscle tester; and gait measures, using Gaitrite® mat (velocity, cadence, stride length and double support duration – test available for 14 pairs). Human Activity Profile assessed activity scores, and relevant serum AED levels were measured. Results were adjusted for height and weight as appropriate: Kincom data (Nm) for weight; Lord’s Balance Test (LBT) sway data for height: mm/m; Chattecx Balance System data for height: sway index (SI)cm/m; left-right sway (LR) cm/m.Results: Indication for AED was epilepsy in 26 cases, and migraine in 1 case. There were no significant within-pair differences in age, height, weight, BMI, strength, measures of gait, Timed Up and Go test, and step test. AED users had significantly lower activity scores [maximal activity score -3.8 (p=0.05), adjusted activity score -9.0 (p=0.00)] and significantly poorer balance on a number of the static and dynamic Chattecx Balance System measures, with and without distraction (p=/<0.05) for bilateral and single leg stance tasks: Chattecx: stable platform + distraction: LR sway +0.38 (p=0.01); anteroposterior moving platform: SI +0.24 (p=0.01), LR sway +0.37 (p=0.02); mediolateral moving platform(MLMP): LR sway +0.63 (p=0.02); MLMP with distraction: SI +0.18 (p=0.05), LR sway +0.82 (p=0.01) and Single leg stance (SLS): stable platform SI +0.16 (p=0.04), LR sway +0.50 (p=0.04). For SLS tests: 1 pair both failed; 3 AED users failed where non-user passed; 2 pairs - test unavailable. One patient’s trough valproate level was above therapeutic range.Conclusions: Balance function is inferior in chronic AED users compared to their matched twin/sibling controls. This reduction in balance function may have important implications for AED users by increasing falls risk and contributing to the increased risk of fractures in this patient group.