Neuropsychological findings from older premutation carrier males and their noncarrier siblings from families with fragile X syndrome.

Objective: Carriers of the FMR1 premutation allele are at a significantly increased risk for a late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). The primary features of FXTAS are late-onset intention tremor and gait ataxia. Previous reports have shown global deficits in neuropsychological measures among males with FXTAS, particularly those related to executive functioning. The purpose of this study was to investigate the neuropsychological profile among older males with the premutation who are at risk for FXTAS.

Method: Premutation carriers, 66 with motor symptoms and 23 without, and 18 noncarrier siblings were recruited from pedigrees diagnosed with fragile X syndrome, all over age 50. Subjects were examined with a neurological test battery to identify symptoms of FXTAS and a neuropsychological test battery to investigate cognitive and behavioral profiles. Linear regression and ANCOVA were used to determine the effect of the premutation on outcome measures adjusting for age and education.

Results: We identified a significant decrease in scores of general intelligence and a marginally significant decrease in scores of logical memory among premutation carrier males with motor symptoms compared to the noncarrier male siblings. We did not identify deficits in executive functioning in our sample of premutation carrier males with motor symptoms.

Conclusions: Similar to other reports, we found that the FMR1 premutation is associated with deficits in general intelligence and memory among older males with symptoms of FXTAS. However, our results differed in that we found no evidence of premutation-associated executive dysfunction. We provide possible explanations for this difference.