Abstracts

RATIONALE: The introduction of a new antiepileptic drug (AED) necessitates careful evaluation of its effect on cognition. However, since its introduction there have been few empirical studies published that investigate cognitive effects of zonisamide (ZNS) therapy, although cognitive complaints are not uncommon in clinical practice. Reported here are the preliminary findings from a group of 16 epilepsy patients who were administered neuropsychological measures prior to and during treatment with ZNS. The objective is to investigate the effects of ZNS on cognitive functioning.
METHODS: Sixteen epilepsy patients (mean age = 37.8 years, 31% male) were selected from clinic files who had been administered a battery of neuropsychological tests prior to and during ZNS therapy for partial onset seizures. Patients were included in the study if they had a baseline Full-Scale IQ greater than 70. Length of time from initiation of ZNS ranged from three to 429 days, with the majority of participants being on ZNS for a minimum of 58 days at the time of testing. ZNS dosage ranged from 100 to 800 mg (mean dosage at the time of testing = 406 mg). The majority of patients were on polytherapy, which may have fluctuated during the course of ZNS treatment. The cognitive battery included measures of sustained attention, working memory, verbal fluency, and psychomotor speed. Paired t-tests were calculated to compare mean performances at baseline and during ZNS therapy. Spearman rho correlations were also calculated to investigate the relationship between cognitive change and ZNS dose.
RESULTS: Mean scores on cognitive tests declined for all tests relative to baseline with the exception of one measure of motor speed and dexterity (Grooved Pegboard). Statistically significant decline was observed on measures of verbal fluency (Controlled Oral Word Association) and working memory (Digit Span). There was a trend toward lower scores on measures of visuomotor processing speed (Digit Symbol-Coding) and verbal fluency (Animal Naming), although these comparisons did not reach statistical significance. Individual change scores were calculated for each measure and correlated with ZNS dose. None of the comparisons reached statistical significance with the exception of a negative correlation observed between dosage and reaction time on a computerized continuous performance test (Vigil CPT).
CONCLUSIONS: These preliminary results suggest ZNS may be associated with cognitive decline in some patients. Performance may be more affected on tasks requiring cognitive processing as opposed to psychomotor speed. Additional research is needed to further investigate the possible effects of dose, titration, and duration of ZNS therapy on cognitive test performance and to determine the incidence of patients[scquote] subjective complaints of cognitive change.