Abstracts

Dizziness and ataxia are among the most common adverse events associated with antiepileptic medications. Despite this, few studies have attempted to quantitatively assess the effects of antiepileptic therapies on equilibrium. This study was undertaken to prospectively compare quantitative measures of balance in older people taking carbamazepine, gabapentin and lamotrigine. Thirty patients on monotherapy for idiopathic partial or generalized epilepsy were enrolled after giving informed consent. Patients had to be at least 50 years old and free of complaint of dizziness or imbalance, able to give consent, and on a stable dose of carbamazepine, gabapentin or lamotrigine for at least 30 days. Patients with a history of alcohol or drug abuse or any medical or neurological condition affecting equilibrium were excluded. Each patient underwent a history and examination, computerized dynamic posturography, the Activities-Specific Balance Confidence (ABC) Scale, Fregly Ataxia battery, and the Berg Balance scale. Serum drug levels of carbamazepine were obtained to eliminate patients with toxic levels upon enrollment. Two tailed paired t tests were used to determined statistical significance among those on each antiepileptic medication. Thirty patients were enrolled: 10 on gabapentin, 10 on lamotrigine and 10 on carbamazepine monotherapy for epilepsy. There were no differences in age or sex among those in each treatment group. The average dosages were 1120 mg per day for those on gabapentin, 335 mg for lamotrigine, and 640 mg for carbamazepine. There were no differences in the Activities-Specific Balance Confidence or the Berg balance scale scores. All patients had normal vestibular function by quantitative testing. Posturography showed no statistical differences. The Fregly ataxia battery includes the sum of timed trials in the sharpened Romberg (SR) position, standing on one leg with eyes closed (SOLEC), and when walking a line with eyes closed (WOLEC). The patients on lamotrigine exhibited ability to maintain balance in these positions significantly longer than did those on carbamazepine: SR (P [lt] .05), SOLEC (P [lt] .05) and WOLEC (P [lt] .05). The effects of antiepileptic medications on equilibrium in asymptomatic older people may require more dynamic and challenging measures of equilibrium than are commonly employed in physical therapy to monitor risk of falls. Although the sample size is small, this study suggests that lamotrigine may induce less disequilibrium than carbamazepine in older people on monotherapy for epilepsy. Further study in this area is needed particularly given the risks of imbalance and falling in the elderly. (Supported by Barrow Foundation, Glaxo Smith Kline.)