Friedreich’s Ataxia (FRDA) is a rare inherited disease where the nerve fiber degeneration leads to impaired muscle coordination that worsens over time. Published data on cognition in Friedreich’s Ataxia in children only includes natural history data from three studies.
Given cerebellar involvement in the disorder, data from two boys ages 13 and 16 with genetically-confirmed FRDA are presented with particular attention to motor coordination and executive functions. In addition, social-emotional/behavioral difficulties are also discussed.
JCB is a 13-year-old boy with FRDA and 933 GAA repeats on both alleles. PS is a 16-year-old boy with two expanded FXN genes with repeat sizes of approximately 930 and 705 (+/- 50). Both boys completed comprehensive neuropsychological evaluations by this writer following referral from their care team.
Measured full scale IQ (FSIQ) for both PS and JCB fell in the impaired range (SS<80); however, intellectual functioning was negatively impacted by fine motor deficits, which likely affected timed measures in the visual-spatial and processing speed domains. Use of the General Ability Index, which does not include processing speed, likely more accurately estimates actual thinking skills, which for both boys instead fell in the Low Average range (SS>=80). Both PS and JCB also displayed neurocognitive deficits in aspects of non-motor thinking skills, including higher order aspects of executive functioning (i.e., cognitive inhibitory control, planning/organization). Social-emotional functioning was also affected. For PS, parent report indicated concern for depression. Self-report indicated concern for school/teacher problems, social stress, and weak interpersonal relations. For JCB, parent report indicated concern for hyperactivity, conduct problems, attention problems, and day-to-day executive functioning problems. Self-report indicated concern related to teachers and low self-esteem.
Comprehensive neuropsychological assessment is important natural history data for children with FRDA. Children display deficits in aspects of thinking and fine motor skills that are consistent with cerebellar involvement. Importantly, fine motor deficits artificially lower estimated IQ; however, even when limiting the inclusion of measures with high motor demands, intellectual functioning remains around 1 standard deviation below age-expectations. In addition to reduced intellectual functioning, children with FRDA are at risk for learning disabilities and ADHD. In the absence of ADHD, children with FRDA may still manifest with problems in aspects of executive functioning. School problems are common. Younger children may have difficulties with self-esteem while older youth report increased social struggles.