Orthopedic Surgery for Friedreich Ataxia Workup

Updated: Nov 22, 2022
  • Author: Stephen Kishner, MD, MHA; Chief Editor: Vinod K Panchbhavi, MD, FACS, FAOA, FABOS, FAAOS  more...
  • Print

Laboratory Studies

The diagnosis of Friedreich ataxia (FA) essentially is a clinical one. Confirmation of the diagnosis by DNA testing is recommended for all patients in whom FA is clinically suspected. [13]

Polymerase chain reaction (PCR) with nucleotide primers spanning the repeated region is used to amplify the DNA in intron 1. The products then are fractionated on an agarose or polyacrylamide gel. On normal chromosomes, the number of GAA repeats ranges from 7 to 22 units, whereas on disease chromosomes, the number ranges from approximately 100 to 2000 repeats. A normal-sized repeat length on both chromosomes argues strongly against a diagnosis of FA.


Imaging Studies

Findings from computed tomography (CT) and magnetic resonance imaging (MRI) are normal or show mild cerebellar atrophy (usually observed late in the disease). The cervical spinal cord often is atrophied.

Echocardiography reveals evidence of hypertrophic cardiomyopathy in approximately 40% of patients. The severity of left ventricular hypertrophy is related to the number of GAA repeats.


Other Tests

Electrocardiography (ECG) yields abnormal results in approximately two thirds of patients, most distinctively with widespread T-wave inversion. If this is present in this context, it is virtually diagnostic of FA.

Electromyography (EMG) and nerve conduction study (NCS) may be helpful. Electrodiagnostic findings that support the diagnosis of FA include the following:

  • Median motor conduction velocity higher than 40 ms; absent or reduced amplitude of sensory nerve action potential
  • Absent H-reflex
  • Abnormal central motor conduction time after transcranial magnetic stimulation

Histologic Findings

The spinal cord exhibits loss of axons and gliosis in the posterior columns, the distal portions of corticospinal tracts, and the spinocerebellar tracts. Degeneration of neurons is present in the spinal cord (Clarke column), brain stem (cranial nerve nuclei VIII, X, and XII), cerebellum (dentate nucleus and the Purkinje cells of the superior vermis), and, to some extent, the Betz cells of the motor cortex.

Large dorsal root ganglion neurons also are decreased in number, their large myelinated axons traveling first in the dorsal root ganglion and then in dorsal columns, thereby undergoing secondary degeneration. The heart is enlarged and may have pericardial adhesions. Multifocal destruction of myocardial fibers with inflammation and fibrosis is detectable in about one half of the patients who come to autopsy examination.