How is Charcot-Marie-Tooth (CMT) disease diagnosed?

Updated: Feb 19, 2019
  • Author: Francisco de Assis Aquino Gondim, MD, PhD, MSc, FAAN; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Answer

The first challenge for the clinician is to demonstrate that a patient's weakness and sensory loss result from peripheral nerve disease and not from abnormalities elsewhere in the nervous system.

This can usually be accomplished by a clinical examination revealing distal weakness and muscle wasting, stocking-glove type sensory loss, and hyporeflexia.

Pes cavus and hammertoes are nonneurologic stigmata of the disease, and although not specific (can occasionally be observed in other forms of chronic acquired neuropathies), should raise the suspicion of CMT if clinical context is appropriate.

If the patient has a neuropathy and a positive family history, CMT becomes likely.

Pedigree analysis can clarify inheritance patterns.

Slow nerve conduction velocities distinguish CMT1 from CMT2, although significant variation may exist within families.

Although exceptions exist, uniform conduction slowing distinguishes most type 1 cases from acquired disorders such as chronic inflammatory demyelinating polyneuropathies, in which conduction slowing typically varies along the same nerve and between nerves. The Guillain-Barré syndrome also has asymmetric slowing and a more rapid onset. Dispersion and conduction block are rarely described in CMT and are more compatible with acquired neuropathies.

Finally, acquired disorders may cause neuropathy, including diabetes mellitus; alcohol abuse; monoclonal gammopathy; infections such as HIV, hepatitis C, leprosy, and Lyme disease; and renal disease. Medications should be evaluated when considering the possibility of inherited neuropathies in patients.


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