Abstracts

Rationale: Despite proven efficacy for the treatment of infantile spasms (IS) and partial-onset seizures in adults, vigabatrin use has been limited by concerns of drug-associated retinal toxicity resulting in peripheral vision loss. The purpose of the current study was to assess the incidence of acquired visual field constriction and retinal toxicity for pediatric patients with IS or refractory complex-partial epilepsy treated with vigabatrin. Methods: We conducted a retrospective chart review of data for patients followed in the child neurology clinics at Cincinnati Children s Hospital between 1998-2010 who were treated with vigabatrin. Data collected included age; seizure etiology, frequency, and description; and vigabatrin dosing regimen. Ophthalmologic specialist evaluation reports were reviewed for methodology of assessment and any abnormalities detected. Only patients under the age of 21 who were evaluated by a pediatric ophthalmologic specialist subsequent to initiating treatment with vigabatrin were included. Results: Of 146 patients treated with vigabatrin during the analysis period, 53 were able to be included in the present analysis. Patients ages ranged from 0-12 years (mean age was 3.0 years) when vigabatrin was initiated. Patients were treated an average of 23.9 months, with an average daily dosage at steady state of 88 mg/kg/day. Ophthalmologic assessments were performed, on average, after 19.1 months of therapy (range 0-68 months). Pre-existing, chronic non-refractive vision or fundoscopic abnormalities were noted for 14 of 43 patients with tuberous sclerosis complex (TSC), which manifested most commonly as retinal astrocytic hamartomas. Non-refractive abnormalities (most commonly optic nerve hypoplasia or cortical blindness) were noted at baseline for 6 of 10 patients without TSC. In addition to age- and cognitive-related difficulties, several ophthalmologists cited these findings as reasons limiting detailed functional visual field assessment or formalized testing with electroretinography (ERG). Nonetheless, no evidence of visual field impairment or retinal toxicity was observed for 52 of 53 patients (98%). Vigabatrin-associated toxicity could neither be confirmed nor excluded for 1 patient noted to have decreased scotopic but normal photopic function in both eyes, as determined upon ERG. Moreover, 34 of 53 patients (64%) have continued on current therapy because of favorable seizure control via vigabatrin therapy and the absence of identifiable treatment-related retinal toxicity or peripheral vision loss. Conclusions: Although concern for retinal changes and visual field constriction is widespread among parents and practitioners alike, actual incidence of vigabatrin-associated toxicity is extremely low in pediatric patients with epilepsy.