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Charcot-Marie-Tooth Disease (Hereditary Motor and Sensory Neuropathy)

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Overview

Also known as hereditary motor and sensory neuropathy (HMSN), Charcot-Marie-Tooth disease (CMT) describes a group of inherited peripheral neuropathies. The most common types are autosomal dominant:

  • CMT type 1:
    • Abnormal myelin is produced which is unstable and spontaneously breaks down leading to demyelination
  • CMT type 2:
    • The axons themselves die, this is not demyelinating

Epidemiology

  • Most common inherited neurological disorder
  • Affects people of all ages, sexes, and ethnicities

Presentation

Features are mainly motor; some characteristic features are:

  • Clumsiness, difficulty with balance and ankle weakness since childhood
  • Patients may have a history of frequently sprained ankles
  • Lower motor neurone (LMN) signs
  • Hyporeflexia
  • Weakness of foot dorsiflexion and foot drop – typically bilaterally
  • Calf muscle atrophy and weakness – “stork leg appearance”
  • Pes cavus – high-arched feet
  • Disturbances in sensation – tingling/reduced pinprick and vibration sensation
  • In general, muscle weakness and sensory affect distal areas e.g. intrinsic foot muscles gradually including the lower leg and thigh

Differential Diagnoses

Motor neurone disease (MND)

  • There usually are no sensory signs/symptoms
  • In MND there are upper motor neurone (UMN) signs. Since peripheral neuropathies generally do not affect the central nervous system (CNS, where UMNs are found), UMN signs are not present in them.

Investigations

  • Investigations to rule out other causes:
  • Nerve conduction studies:
    • Performed in any patient with suspected neuropathy
    • Low or mildly-slowed/normal conduction velocities may be seen
  • Genetic testing may be considered 

Management

There is no cure, patients are given supportive management via a multidisciplinary approach.

Complications and Prognosis

Complications

  • Skin breakdowns/infections/burns of the feet due to reduced sensation
  • Ankle sprains
  • Osteoarthritis
  • Pain

Prognosis

  • CMT type 1 – most patients have a normal expectancy and remain ambulatory throughout life. In general, the disease progresses slowly and leads to little disability.
  • CMT type 2 – usually more severe than CMT type 1, most patients have motor weakness in school-age years and are non-ambulatory by 20 years 

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