Physical Medicine and Rehabilitation for Charcot-Marie-Tooth Disease Workup

  • Author: Divakara Kedlaya, MBBS; Chief Editor: Robert H Meier III, MD   more...
 
Updated: May 1, 2012
 

Laboratory Studies

Results of all routine laboratory tests are within the reference range in Charcot-Marie-Tooth disease (CMT). Special genetic tests are available for some types of CMT.

  • CMT-1A - Pulsed-field gel electrophoresis or a specialized fluorescent in situ hybridization (FISH) assay is the most reliable genetic test, but it is not widely available. DNA-based testing for the PMP-22 duplication (CMT-1A) is widely available and detects more than 98% of patients with CMT-1A (see following image). Point mutations in the PMP-22 gene cause fewer than 2% of cases of CMT-1A and are identified by this technique. Approximately 70-80% of cases of CMT-1 are designated as CMT-1A, caused by alteration of the PMP-22 gene (chromosomal locus 17p11). Charcot-Marie-Tooth disease type 1A DNA test showiCharcot-Marie-Tooth disease type 1A DNA test showing duplication in the short arm of chromosome 17 (A) compared with normal (B).
  • CMT-1B - Genetic testing is performed primarily on a research basis, but it is available from a few commercial laboratories. Approximately 5-10% of CMT-1 is designated CMT-1B and is caused by a point mutation in the myelin P0 protein (MPZ) gene (chromosomal locus 1q22).
  • CMT-1C and CMT-1D - Very rarely, mutations occur in the EGR-2 (early growth response 2) gene or in the LITAF gene, causing CMT-1D and CMT-1C, respectively, for which molecular genetic testing also is clinically available.
  • CMT-2 - Clinically indistinguishable, the 4 subtypes of CMT-2 are distinguished solely from genetic linkage findings. The relative proportions of CMT-2A, CMT-2B, CMT-2C, and CMT-2D have not yet been determined. The chromosomal loci for CMT-2A, CMT-2B, CMT-2C, CMT-2D, CMT-2E, CMT-2F, CMT-2G, and CMT-2L have been mapped, but the genes have not been identified. Molecular genetic testing is clinically available only for CMT-2A, CMT-2B1, CMT-2E, and CMT-2F.
  • CMT-X - Molecular genetic testing of the GJB1 (Cx32) gene detects about 90% of cases. Such testing is clinically available.
  • Genetic testing is not currently available for other types of CMT.
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Imaging Studies

High-resolution ultrasonography of the median nerve and other peripheral nerves may serve as an adjunct to electrodiagnosis in Charcot-Marie-Tooth disease type 1A.[8, 9, 10, 11, 12, 13]

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Other Tests

Nerve biopsy rarely is indicated for the diagnosis of Charcot-Marie-Tooth disease (CMT), especially because genetic testing is available. Biopsies sometimes are performed in cases of diagnostic dilemmas. Findings vary in different types of CMT, as follows:

  • In CMT-1, peripheral nerves contain few myelinated fibers, and intramuscular nerves are surrounded by rich connective tissue and hyperplastic neurilemma. Lengths of myelin are atrophic along the fibers. Concentric hypertrophy of the lamellar sheaths is seen. Onion bulb formation, made up of circumferentially directed Schwann cells and their processes, frequently is observed.
  • In CMT-2, axon loss with wallerian degeneration generally is found.
  • In CMT-3, or Dejerine-Sottas disease, demyelination with thinning of the myelin sheath is observed.
  • Inflammatory infiltrate, indicating an autoimmune demyelinating process, should not be present.
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Procedures

Electromyography/nerve conduction study (EMG/NCS)[8, 9, 10, 11, 12, 13]

  • If Charcot-Marie-Tooth disease (CMT) is suggested, perform an EMG/NCS first. Findings vary depending on the type of CMT.
  • In demyelinating types of CMT, such as CMT-1, diffuse and uniform slowing of nerve conduction velocities is observed (see following image). Nerve conduction study showing decreased nerve conNerve conduction study showing decreased nerve conduction velocity in the median nerve in an 18-year-old woman with Charcot-Marie-Tooth disease type 1.
  • Harding and Thomas criteria for diagnosing CMT-1 include median motor nerve conduction velocity of less than 38 meters per second (m/s), with compound motor action potential (CMAP) and amplitude of at least 0.5 millivolts (mV). No focal conduction block or slowing should be present unless associated with other focal demyelinating processes.
  • All sensory and motor nerves that are tested show the same degree of marked slowing.
  • Absolute values vary, but they are approximately 20-25 m/s in CMT-1 and less than 10 in Dejerine-Sottas disease and congenital hypomyelination. Slowing of nerve conduction can also be found in asymptomatic individuals.
  • In neuronal (ie, axonal) types of CMT, nerve conduction velocity usually is normal, but markedly low amplitudes are noted in sensory (ie, sensory nerve action potential [SNAP]) and motor (ie, CMAP) nerve studies.
  • In neuronal (ie, axonal) types of CMT, increased insertional activity is evident, with fibrillation potentials and positive sharp waves seen. Motor unit potentials show decreased recruitment patterns and neuropathic changes in morphology.
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Histologic Findings

In Charcot-Marie-Tooth disease type 2 (CMT-1), peripheral nerves contain few myelinated fibers, intramuscular nerves are surrounded by a rich connective tissue and hyperplastic neurilemma, and lengths of myelin are atrophic along the fibers.

Concentric hypertrophy of the lamellar sheaths is seen. Formation of the typical onion bulb, made up of circumferentially directed Schwann cells and their processes, is noted.

In CMT-2, axonal degeneration is observed.

In CMT-3, Dejerine-Sottas disease, demyelination with thinning of the myelin sheath can be seen.

No inflammatory infiltrate should be present, indicating an autoimmune demyelinating process.

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Contributor Information and Disclosures
Author

Divakara Kedlaya, MBBS  Clinical Associate Professor, Department of Physical Medicine and Rehabilitation, Loma Linda University School of Medicine; Medical Director, Physical Medicine and Rehabilitation and Pain Management, St Mary Corwin Medical Center

Divakara Kedlaya, MBBS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Paraplegia Society, and Colorado Medical Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Milton J Klein, DO, MBA  Consulting Physiatrist, Heritage Valley Health System-Sewickley Hospital and Ohio Valley General Hospital

Milton J Klein, DO, MBA is a member of the following medical societies: American Academy of Disability Evaluating Physicians, American Academy of Medical Acupuncture, American Academy of Osteopathy, American Academy of Physical Medicine and Rehabilitation, American Medical Association, American Osteopathic Association, American Osteopathic College of Physical Medicine and Rehabilitation, American Pain Society, and Pennsylvania Medical Society

Disclosure: Nothing to disclose.

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

Disclosure: Medscape Salary Employment

Michael T Andary, MD, MS  Professor, Residency Program Director, Department of Physical Medicine and Rehabilitation, Michigan State University College of Osteopathic Medicine

Michael T Andary, MD, MS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, and Association of Academic Physiatrists

Disclosure: Allergan Honoraria Speaking and teaching

Kelly L Allen, MD  Medical Director, Medevals

Disclosure: Nothing to disclose.

Chief Editor

Robert H Meier III, MD  Director, Amputee Services of America; Active Medical Staff, Presbyterian/St Luke's Hospital, Spalding Rehabilitation Hospital, Select Specialty Hospital; Consulting Staff, Kindred Hospital

Robert H Meier III, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation and Association of Academic Physiatrists

Disclosure: Nothing to disclose.

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Foot deformities in a 16-year-old boy with Charcot-Marie-Tooth disease type 1A.
Charcot-Marie-Tooth disease type 1A DNA test showing duplication in the short arm of chromosome 17 (A) compared with normal (B).
Nerve conduction study showing decreased nerve conduction velocity in the median nerve in an 18-year-old woman with Charcot-Marie-Tooth disease type 1.
Table. Charcot-Marie-Tooth Disorders: Genetic and Clinical Feature Comparison
CMT TypeChromosome; Inheritance PatternAge of OnsetClinical FeaturesAverage NCVs§
CMT-1A (PMP-22 dupl.)17p11; AD*First decadeDistal weakness15-20 m/s
CMT-1B (P0 -MPZ)**1q22; ADFirst decadeDistal weakness< 20 m/s
CMT-1C (non-A, non-B)16p13;ADSecond decadeDistal weakness26-42 m/s
CMT-1D (EGR-2)#10q21; ADFirst decadeDistal weakness15-20 m/s
CMT-1E17p11; ADFirst decadeDistal weakness, deafness15-20 m/s
CMT-1F8p21; ADFirst decadeDistal weakness15-20 m/s
CMT-X (connexin-32)Xq13; XD‡Second decadeDistal weakness25-40 m/s
CMT-2A1p36; AD10 yDistal weakness>38 m/s
CMT-2B3q; ADSecond decadeDistal weakness,



sensory loss, skin ulcers



Axon loss; Normal
CMT-2C12q23-q24, ADFirst decadeVocal cord, diaphragm, and



distal weakness



>50 m/s
CMT-2D7p14; AD16-30 yDistal weakness, upper limb predominantlyAxon loss; N††
CMT-2E8p21; AD10-30 yDistal weakness, lower limb predominantlyAxon loss; N
CMT-2F7q11-q21; AD15-25 yDistal weaknessAxon loss; N
CMT-2G12q12-q13; ?AD9-76 yDistal weaknessAxon loss; N
CMT-2H?; AR†15-25 yDistal weakness, pyramidal featuresAxon loss; N
CMT-2I1q22; AD47-60 yDistal weaknessAxon loss; N
CMT-2J1q22; AD40-50 yDistal weakness, hearing lossAxon loss; N
CMT-2K8q13-q21; AR< 4 yDistal weaknessAxon loss; N
CMT-2L12q24; AD15-25 yDistal weaknessAxon loss; N
CMT – R-Ax (Ouvrier)ARFirst decadeDistal weaknessAxon loss; N
CMT – R-Ax (Moroccan)1q21; ARSecond decadeDistal weaknessAxon loss; N
Cowchock syndromeXq24-q26First decadeDistal weakness, deafness, mental retardationAxon loss; N
HNPP|| (PMP-22)



or tomaculous neuropathy



17p11; ADAll agesEpisodic weakness and numbnessConduction Blocks
Dejerine-Sottas-syndrome (DSS) or HMSN-3P0; AR



PMP-22; AD



8q23; AD



2 ySevere weakness< 10 m/s
Congenital



hypomyelination (CH)



P0, EGR-2 or PMP-22



AR



BirthSevere weakness< 10 m/s
CMT-4A8q13; ARChildhoodDistal weaknessSlow
CMT-4B



(myotubularin- related



protein 2)



11q23; AR2-4 yDistal and proximal



weakness



Slow
CMT-4C5q23; AR5-15 yDelayed walking14-32 m/s
CMT-4D (Lom)



(N-myc downstream-



regulated gene 1)



8q24; AR1-10 yDistal muscle wasting, foot and hand deformities10-20 m/s
CMT-4E (EGR-2)10q21; ARBirthInfant hypotonia9-20 m/s
CMT-4G10q23.2; AR8-16 yearsDistal weakness9-20 m/s
CMT-4H12p11.21-q13.11; AR0-2 yearsDelayed walking9-20 m/s
CMT-4F19q13; AR1-3 yMotor delayAbsent
*Autosomal dominant



†Autosomal recessive



‡X-linked dominant



§Nerve conduction velocities



||Hereditary neuropathy with liability to pressure palsy



¶Peripheral myelin protein



#Early growth response



**Myelin protein zero



††Normal



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