Ataxia, Friedreich

Key Features

• Most common of the autosomal recessive ataxias

• Incidence is about 1 in 30,000–50,000 and a carrier rate is 1 in 85

• Does not exhibit other neurologic symptoms, such as seizures, but does tend to involve systems outside of the nervous system

Clinical Findings

• Symptoms present between the ages of 5–25 years

  • Progressive gait and limb ataxia

  • Dysarthria

  • Loss of proprioception and vibration

  • Areflexia

  • Abnormal eye movements

  • Pyramidal weakness of the feet with upgoing toes

  • In addition, systemic symptoms develop; patients may have associated pes cavus, cardiomyopathy, diabetes, and scoliosis

• Spinocerebellar ataxia, poor balance with falls, difficulty with hand coordination, dysarthria, vertigo, and diplopia may be seen

• Peripheral neuropathy, with loss of proprioception and vibratory sense, may also be seen

Diagnosis

• Genetic testing confirms diagnosis

  • 98% of patients have a triplet GAA expansion in the frataxin gene on chromosome 9q13

  • In general, a greater number of repeats predicts an earlier onset of disease, more severe systemic manifestations, and more severe ataxia

• Neuroimaging does not show progressive cerebellar degeneration

• Mild atrophy of the cervical spinal cord may be seen

Treatment

• Yearly screening needs to be performed with a radiograph to monitor scoliosis; serum glucose and hemoglobin A_1C to monitor for the onset of diabetes, and echocardiogram to monitor cardiomyopathy

• Trials have demonstrated that coenzyme Q10 and vitamin E can result in improvement in cardiac symptoms, and low-dose idebenone can reduce cardiac hypertrophy

• However, none of these have resulted in improvement in neurologic symptoms, and therefore treatment of the progressive neurologic symptoms remains symptomatic