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Orthopedic Surgery for Friedreich Ataxia Workup

  • Author: Stephen Kishner, MD, MHA; Chief Editor: Harris Gellman, MD  more...
 
Updated: Jun 05, 2013
 

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.[10]

The polymerase chain reaction 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 varies from 7-22 units, whereas on disease chromosomes, the range varies from approximately 100-2000 repeats. A normal-sized repeat length on both chromosomes argues strongly against a diagnosis of FA.

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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.

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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
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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.

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Contributor Information and Disclosures
Author

Stephen Kishner, MD, MHA Professor of Clinical Medicine, Physical Medicine and Rehabilitation Residency Program Director, Louisiana State University School of Medicine in New Orleans

Stephen Kishner, MD, MHA is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Paul E Di Cesare, MD 

Paul E Di Cesare, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Surgeons

Disclosure: Nothing to disclose.

Chief Editor

Harris Gellman, MD Consulting Surgeon, Broward Hand Center; Voluntary Clinical Professor of Orthopedic Surgery and Plastic Surgery, Departments of Orthopedic Surgery and Surgery, University of Miami, Leonard M Miller School of Medicine, Clinical Professor, Surgery, Nova Southeastern School of Medicine

Harris Gellman, MD is a member of the following medical societies: American Academy of Medical Acupuncture, American Academy of Orthopaedic Surgeons, American Orthopaedic Association, American Society for Surgery of the Hand, Arkansas Medical Society

Disclosure: Nothing to disclose.

Additional Contributors

Jegan Krishnan, MBBS, FRACS, PhD Professor, Chair, Department of Orthopedic Surgery, Flinders University of South Australia; Senior Clinical Director of Orthopedic Surgery, Repatriation General Hospital; Private Practice, Orthopaedics SA, Flinders Private Hospital

Jegan Krishnan, MBBS, FRACS, PhD is a member of the following medical societies: Australian Medical Association, Australian Orthopaedic Association, Royal Australasian College of Surgeons

Disclosure: Nothing to disclose.

Acknowledgements

Natalya V Bulaeva, MD, PhD, and John Baker, MD, are gratefully acknowledged for their contributions to this article.

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