Abstracts

Rationale: Little is known about the incidence and patterns of cognitive involvement in children with mitochondrial cytopathy.⁶ While preliminary studies have documented cognitive impairment, data are limited, with studies reporting on only a few children⁵ or older teenagers and adults.² Although studies have reported lower nonverbal versus verbal intelligence^2,3,5,8 and other effects such as cognitive slowing,⁴ the literature is limited. This retrospective chart review study was undertaken to define the clinical profiles of children with mitochondrial disorders. Methods: We retrospectively identified 32 patients with definitive mitochondrial diagnoses (based on the modified Walker criteria¹) who underwent neuropsychological evaluations at Seattle Children's Hospital. 16 had seizures (Group 1); 16 had none (Group 2). Each group had 11 males and 5 females. Mean ages were similar: Group 1 was 116 months; Group 2 106 months. Only 10 Group 1 patients had Wechsler IQ testing; all of Group 2 had Wechsler IQ testing. 6 Group 1 patients could not complete IQ testing, but the Vineland Adaptive Behavior Scale (Vineland) was administered. Because topiramate has been shown to have deleterious neuropsychological impact, 3 patients on topiramate were separated out although all of these patients only had Vineland interviews. Results: Group 2 (no seizures) obtained a mean Full Scale IQ of 93.1 (SD = 18.7) compared to Group 1 (seizures) FSIQ = 74.5 (SD = 27.6). Vineland mean summary scores were 52.3 (SD = 16.6) versus 40 (SD = 10.8) for the 3 patients on topiramate. Conclusions: Results suggest that seizures may represent a worse phenotype, as compared to no seizures, as suggested by consistently lower IQ means in conjunction with the finding that almost half of the patients with seizures were too low functioning to complete Wechsler IQ testing. Results were also consistent with previous smaller pilot studies that have identified a discrepancy between verbal and nonverbal abilities in patients with mitochondrial cytopathy.