Introduction
  •  The most common form of spinocerebellar degenerative diseases
    • characterized by lesions in the 
      • dorsal root ganglia q
      • corticospinal tracts
      • dentate nuclei in the cerebellum
      • sensory peripheral nerves
  • Epidemiology
    • 1 in 50,000 births
    • onset usually between 7 and 25 years
      • age of onset related to number of GAA repeats
  • Genetics
    • autosomal recessive
    • repeat mutation leads to lack of frataxin gene 
      • frataxin is a mitochondrial protein involved in iron metabolism and oxidative stress
      • mutation is GAA repeat at 9q13
  • Associated conditions
    • pes cavovarus foot 
    • scoliosis
      • predictors of progression
        • onset of disease is less than 10 years of age
        • onset of scoliosis is before 15 years of age
    • cardiomyopathy
      • cardiology evaluation before surgery
      • antioxidants (Coenzyme Q) have been shown to decrease rate of cardiac deterioration but have no effect on ataxia
  • Prognosis
    • usually wheelchair bound by age 30
    • usually die by age 50 from cardiomyopathy
Presentation
  • Symptoms
    • ataxia
      • staggering wide based gait (spinocerebellar)
  • Physical exam
    • classic triad post
      • ataxia
      • areflexia
      • positive plantar response
    • weakness
    • nystagmus
    • cavovarus foot  
      • very high arch
      • rigid deformity
      • associated claw toes
    • scoliosis
Imaging
  • Radiographs
    • recommended views
      • standing scoliosis series
      • AP and lateral of foot if pes cavovarus present
Studies
  • EMG
    • shows defects in motor and sensory with an increase in polyphasic potentials
    • nerve conduction velocities are decreased in upper extremities
Treatment
  • Cavovarus foot 
    • nonoperative
      • observation
        • indications
          • only indicated in nonambulatory patient
          • deformity is rigid and progressive and resistant to bracing and stretching as treatment
    • operative
      • plantar release, transfers, +/- metatarsal and calcaneal osteotomy
        • indications
          • early disease in ambulatory patient
      • triple arthrodesis
        • indications
          • late disease in nonambulatory patients
  • Scoliosis
    • nonoperative
      • observation
        • indications
          • curves < 40 degree without predictors of progression (see above)
    • operative
      • PSF and instrumentation
        • indications
          • curve > 60 degrees
          • rapid progression with positive predictors of progression (see above)
          • usually does not need to be extended to pelvis