Cognitive evaluation of neurologically asymptomatic boys with X-linked adrenoleukodystrophy

Background: Various studies have demonstrated abnormal neuropsychological function in boys with the childhood cerebral phenotype of X-linked adrenoleukodystrophy. Not much is known about the cognitive function of neurologically asymptomatic boys with X-linked adrenoleukodystrophy who have normal brain magnetic resonance imaging results. Objective: To describe the cognitive profile of 52 neurologically asymptomatic boys with X-linked adrenoleukodystrophy (mean±SD age, 6.7±3.6 years). Methods: Neuropsychological tests included evaluation of IQ (full-scale IQ, verbal IQ, and performance IQ), 5 major cognitive domains (language, visuospatial skills, perception, visuomotor or graphomotor skills, memory, and attention or executive function), adaptive skills, and academic achievement. Standardized z scores relative to age-appropriate published norms were generated. Association between age and cognitive performance was evaluated using nonparametric Spearman rank correlation and robust median regression adjusting for full-scale IQ and socioeconomic status. Results: All but 4 patients had normal cognitive function. There was a negative correlation between age and visual perception as well as age and visuomotor skills after adjustment for full-scale IQ and socioeconomic status. Conclusions: This study provides, to our knowledge, the first evidence of overall normal cognitive function in neurologically and radiologically normal boys with X-linked adrenoleukodystrophy, indicating no evidence of neurodevelopmental abnormalities despite the inherent ABCD1 mutation. Subtle deterioration with age was observed in some functional domains. This suggests that prevention and timely institution of therapy can potentially preserve cognitive function seen in patients with the cerebral X-linked adrenoleukodystrophy phenotype. X-linked adrenoleukodystrophy should be considered a candidate disorder for neonatal screening.