Which motor signs are characteristic of Charcot-Marie-Tooth (CMT) disease?

Updated: May 22, 2018
  • Author: Timothy C Parsons, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Motor signs tend to develop before sensory signs. Due to length dependent axonal degeneration, weakness and atrophy is first seen in intrinsic foot muscles, followed by ankle and toe dorsiflexors. This mismatch between strength in the affected peroneal-innervated muscles and the less affected tibial-innervated muscles leads to the typical high arched feet, hammer toes, and difficulty with heel walking seen early on physical examination. [4, 73]

Muscle atrophy and weakness progress proximally over time, and as distal leg muscle bulk is lost, the legs assume a characteristic “inverted champagne bottle” appearance. The distal thighs and hands can become involved, and weakness of intrinsic hand muscles gives rise to the typical “claw hand” deformity seen in CMT. Areflexia is frequent, especially distally. Proximal weakness only affects a small minority of patients. [71, 66] Gait is impaired by muscle weakness, foot deformities that result from weakness, and proprioceptive loss. Despite these obstacles, most patients remain ambulatory. [63]

Bienfait and colleagues found that CMT2 had later disease onset and had a lower incidence of areflexia, foot deformities, and weakness of foot dorsiflexors, but concluded that there were no robust clinical signs to differentiate CMT1 from CMT2. [74] Men affected by CMTX are more likely to show hand weakness with early thenar atrophy and relative preservation of tendon reflexes. [47]


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