Hereditary sensory and motor neuropathy (HSMN) is the term used to describe a range of genetic conditions affecting the peripheral nerves (nerves which exit from the spinal cord). It is caused by a chromosome abnormality which affects the protective coating surrounding the nerves. This is known as the myelin sheath and its function is to protect the nerve fibre (also known as the axon) and speed up transmission of messages. When the myelin is damaged nerve transmission is affected and the axon is vulnerable to damage leading to weakness and impaired sensation.
There are different types of hereditary sensory and motor neuropathy including:
- HSMN 1A: affects the myelin sheath (demyelinating neuropathy)
- HSMN type 2 or axonal HSMN: affects the nerve fibres or axons
- Spinal HSMN or Distal Spinal Muscular Atrophy: affects the motor nerves only
Onset may vary according to the type of HSMN, however symptoms usually appear gradually and appear in childhood or adolescence. Diagnosis is usually made by a neurologist after a thorough neurological examination. Tests such as electromyography and nerve conduction studies may be used to assess the nerves and confirm diagnosis. MRI or CT scans may be used to exclude other conditions.
Physiotherapy treatment for HSMN can help to maximise independence and function by advising on appropriate exercises and equipment to help keep you as active as possible.
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