Friedreich's ataxia

Key Points:

  • Progressive neuromuscular disorder mainly affecting the heart and nervous system
  • Clinical features include ataxia, loss of deep tendon reflexes at the knee and ankle, and an upgoing Babinski sign
  • Orthopaedic concerns include scoliosis and pes cavovarus
  • Medical comorbidities include cardiomyopathy and diabetes mellitus 

Description:

Friedreich’s Ataxia was first described in 1863 by Nikolaus Friedreich, a professor of medicine in Germany. It is an autosomal recessive disease caused by mutation in the FXN gene, which affects the creation of the frataxin protein.  Clinically, there is acute onset with progressive nervous system damage.  The onset typically occurs between 10 and 15 years of age.  The sequence and severity of symptoms is highly variable (Pandolfo, 2009).

Epidemiology:

About 1/50,000 children are affected (Pandolfo, 2009). This is the most common form of a spinal cerebellar degenerative disease.

Clinical Findings:

Patients with Friedreich’s Ataxia present initially with poor coordination, muscle weakness, or ataxia.  Upon further examination there is often a loss of reflexes.  These children may also have a sensory impairment, including decreased sensation and, occasionally, hearing or vision loss.

Pes cavus may initially be flexible but may become fixed and require surgical intervention.  Diminished proprioception may also be noted on foot examination.

Scoliosis occurs in 63% of patients (Milbrandt, 2008). It often is associated with hyperkyphosis and the curves are variable in both type and magnitude (Milbrandt, 2008; Tsirikos, 2012).

From a medical standpoint, hypertrophic cardiomyopathy should be monitored (Pandolfo, 2009).  Heart failure may lead to a decrease in life expectancy.   About 10% of patients present with diabetes (Pandolfo, 2009).

Imaging Studies:

Initial imaging should be based on clinical findings.  Spine radiographs are frequently obtained based on the high rate of scoliosis.  If there is foot deformity, an AP and lateral of the foot or feet are obtained accordingly.

Etiology:

Friedreich’s Ataxia is an autosomal recessive disorder that occurs as a result of a mutation of the FXN gene on chromosome 9, leading to reduced expression of the frataxin protein (Pandolfo, 2009).

Treatment:

There are various medical treatments, which are not typically managed by orthopaedic surgeons.

With regards to orthopaedic interventions, occasionally correction is recommended for symptomatic pes cavus.  This may entail a plantar release, tendon transfers, and/or metatarsal and calcaneus osteotomies.  If the patient presents late in the disease process, or if they are nonambulatory, a triple arthrodesis may be the best surgical intervention.

Scoliosis braces are rarely effective in preventing curve progression (Milbrandt, 2008; Tsirikos, 2012).  Spinal fusion is recommended if there is a greater than 50 to 60 degree curve (Milbrandt, 2008; Tsirikos, 2012).  Of note, SSEP monitoring is often ineffective in these patients (Milbrandt, 2008).  The operating surgeon may need to rely on a wake up test.

Complications:

Cardiac dysfunction is a frequent cause of premature death in Friedreich’s Ataxia patients (Tsirikos, 2012; Pandolfo, 2009).  Progressive ataxia and muscle weakness often require use of a wheelchair for mobility and the need for assistance in activities of daily living. Dysarthria is common (Pandolfo, 2009).

References:

  1. Milbrandt TA, Kunes JR, Karol LA. Friedreich’s ataxia and scoliosis: the experience at two institutions. JPO, 2008. 28 (2): p. 234-8.
  2. Pandolfo M. Friedreich ataxia: the clinical picture. Journal of Neurology, 2009. March; 256 suppl 1: p. 3-8.
  3. Tsirikos AI, Smith G. Scoliosis in patients with Friedreich’s Ataxia. JBJS Br, 2012. 94 (5): p. 684-9.

Top Contributors:

Dana Olszewski MD