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Please note: This is a basic revision aid, not a comprehensive and reliable statement of medical fact. These notes should not be used to guide treatment. For reliable information and advice, consult a qualified practitioner.
[Last updated: 7th April 2004]
CMT is now referred to as Hereditary Motor and Sensory Neuropathy (HMSN), sometimes also described as Peroneal Muscular Atrophy
There are thought to be many different types of HMSN but primary classifications are:
See table below for further details.
Epedimiological studies quote rates of 1.8:10,000 in Japan (Kurihara et.al., 2002); 17.5:100,100 in Central-southern Italy (Morocutti et.al., 2002) and 1:2500 in Norway (cited by Aarskog & Vedeler, 2002). HMSN 1a is the most common form.
Variable. Some forms are symptomatic by 5 years of age. HMSN 1 is usually evident before 30 years of age, while HMSN 2 tends to appear later.
| Type | Inheritance | Pathology |
|---|---|---|
| HMSN 1a | Autosomal Dominant | Demyelinating |
| HMSN 1b | Autosomal Dominant | Demyelinating |
| HMSN 1 | Autosomal Dominant/Recessive? | Demyelinating |
| HMSN 2 | Autosomal Dominant/Recessive? | Axonal |
The above is only a broad categorisation: there are many types of HMSN. See our separate guide to genetic conditions for a fuller explanation of autosomal dominant and autosomal recessive inheritance.
Diffuse degeneration of myelin or of the axon -- see above for specific forms. There is a slowing of nerve conduction speeds in Type 1 (due to demyelination), but not in Type 2. There is now a DNA test available.
Both forms tend to produce atrophy of peroneal muscles, amongst other distal atrophy, giving an appearance sometimes characterised as "inverted champagne bottle legs". Mild sensory loss is common, as is pes cavus (high arched feet). Sore feet and aching limbs can be a problem, as can back pain due to poor posture. Wasting of the muscles of the hand may appear later. Likely problems include claw and hammer toes, impaired mobility and balance, foot drop (bilateral) and possibly scoliosis. Occasionally, respiratory problems may appear.
Very variable -- some may have severe mobility problems by middle age while others remain relatively asymptomatic. No reduction in life expectancy.
Medical treatment is symptomatic only at present. Orthoses may be required, or surgical correction of deformities of the foot. Physiotherapy may help maintain muscle strength.
Mobility problems are common, but vary greatly in severity. Wheelchairs may be needed in some cases. There may be problems with transfers, or an increased risk of falls (in which case some form of community alarm may be needed). Isolation, emotional problems and frustration may need to be addressed, particularly if mobility is affected. Bathing may be difficult, necessitating provision of equipment such as bath lifts or shower seats. Dressing may be problematic due to wasting of the hand muscles, causing problems with buttons, zips and laces.
The relative rarity of the condition often causes frustration due to a lack of knowledge among professionals and lack of understanding of the condition generally.
Genetic counselling is strongly advisable if there are already children or if children are a future possibility.
Hand splinting may be necessary due to wasting of the hand muscles. Sometimes the fingers can tend to be slightly clawed, and there can be wasting of the muscles in the snuff box area. Therapists may feel the need for advice from specialist sources such as the National Hospital for Neurology and Neurosurgery or other specialist centres.
Driving can be problematic -- the person with HMSN should notify the DVLA. Disqualification is by no means automatic, and adaptation of the vehicle may help.
Because of the age of onset, there may be difficulties with work, and Occupational Therapists may be involved in assessing work practices and environment. The psychological implication of loss of roles if work becomes impossible should, of course, be considered.
Kurihara S, Adachi Y, Wada K, Awaki E, Harada H, Nakashima K. (2002) An epidemiological genetic study of Charcot-Marie-Tooth disease in Western Japan. Neuroepidemiology 2002 Sep-Oct;21(5):246-50
Morocutti C, Colazza GB, Soldati G, D'Alessio C, Damiano M, Casali C, Pierelli F. (2002) Charcot-Marie-Tooth disease in Molise, a central-southern region of Italy: an epidemiological study. Neuroepidemiology 2002 Sep-Oct;21(5):241-5
Aarskog NK, Vedeler CA (2002) [Molecular genetic diagnosis of Charcot-Marie-Tooth disease and hereditary neuropathy with liability to pressure palsies] Tidsskr Nor Laegeforen 2002 Feb 10;122(4):382-5 [Article in Norwegian]
Author: Mike Griffin, PGDipOT
The author works as a community occupational therapist with a London social services department.
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