Charcot-Marie-Tooth (CMT) disease, also known as hereditary motor and sensory neuropathy (HMSN), is the most commonly inherited neuropathy of lower motor (to a lesser degree sensory) neurons.
Signs and symptoms usually become first evident in childhood. Typically this starts in the lower limbs with weakness, atrophy and deformity, and later affects the upper limbs. It rarely involves the more proximal musculature and rarely involves the cranial nerves. Sensory changes are present but usually to a lesser degree.
It is not a single condition, but a cluster of heterogeneous mutations with many subtypes, classified by which gene is affected. As expected the number and classification is in flux. Most frequently it is autosomal dominant in inheritance (although this is variable).
CMT type 1
- this form of CMT disease is a disorder of peripheral myelination
- repeated cycles of demyelination and remyelination result in a thick layer of abnormal myelin around the peripheral axons
- these changes cause what is referred to as an onion bulb appearance
CMT type 2
- this primarily is a neuronal (i.e. axonal) disorder, not a demyelinating disorder. CMT type 2 results in peripheral neuropathy through direct axonal death and Wallerian degeneration
CMT type 3 (also known as Dejerine-Sottas disease)
- characterized by infantile onset, this condition results in severe demyelination with delayed motor skills; it is much more severe than type 1
- CMT X (X-linked CMT) and CMT 4: these are also demyelinating neuropathies
Some enhancement may be seen on MRI, but it is not usually a prominent feature.
History and etymology
It is named after Jean-Martin Charcot, Pierre Marie and Howard Henry Tooth.
- 1. Morano JU, Russell WF. Nerve root enlargement in Charcot-Marie-Tooth disease: CT appearance. Radiology. 1986; 161(3): 784. Radiology [pubmed citation]
- 2. Castillo M. Neuroradiology. Philadelphia : Lippincott Williams & Wilkins, c2002. (2002) ISBN:0781736641. Read it at Google Books - Find it at Amazon
- 3. Miura T, Hirabuki N, Imakita S et-al. Radiological findings in a case of Charcot-Marie-Tooth disease. Br J Radiol. 1985;58 (694): 1017-20. doi:10.1259/0007-1285-58-694-1017 - Pubmed citation