Peripheral neuropathy refers to diseases affecting the peripheral nervous system, which consists of motor or sensory neurons, nerve roots, plexuses and peripheral nerves. Motor nerves control movements of all muscles under conscious control. Sensory inputs (e.g. heat, cold and touch) from skin receptors are conveyed to the brain via the sensory nerves. Autonomic nerves are found in vital organs (e.g. heart, lungs) and help to regulate body functions such as heart rate and breathing.
Clinical classification of peripheral neuropathy is based on:
The clinical presentation will depend on the type of nerve fibers affected.
Motor nerve damage causes weakness, painful cramps and muscle twitching.
Sensory nerve damage causes a decrease in the appreciation of pinprick, light touch or vibration sensations on the hands and feet. It may also cause unsteadiness when walking. Pain receptors can become oversensitised resulting in spontaneous burning pain, discomfort to light touch (Allodynia) and hypersensitivity to pain (Hyperalgesia).
Involvement of autonomic nerves results in a variety of symptoms, e.g. abnormal sweating, postural giddiness, irregular heart rate, urinary incontinence and erectile dysfunction in men.
There are many causes of peripheral neuropathy, inherited and acquired. Inherited neuropathies are due to inborn defects in the genetic code and are collectively known as Charcot-Marie-Tooth (CMT) disease.
Causes of acquired peripheral neuropathy include the following:
Your doctor will perform a thorough clinical evaluation to determine the part of the peripheral nervous system that is affected and the likely cause. The following investigations may be arranged:
Autonomic Function Test
Treatment will depend on the underlying cause and type of neuropathy. For example, in diabetic neuropathy, treatment will be directed at achieving good blood sugar control to prevent further nerve damage. Symptomatic relief for neuropathic pain can usually be achieved by medications, such as amitriptyline and gabapentin.
Immune-mediated neuropathies are treated with either intravenous immune globulin (IVIG) or steroids. IVIG is pooled donor plasma which contains normal antibodies that can temporarily counteract the abnormal ones in the body. Steroids will help to suppress an abnormal immune response that attacks the nerve.
Surgical decompression may benefit those with entrapment neuropathy, such as CTS.
Living with the condition
In most patients, symptoms and functional impairment can be managed effectively and normal life expectancy is expected unless there is a co-existent systemic disease.
One should adopt a healthy lifestyle so as to encourage nerve regeneration. Active and passive forms of exercise can improve muscle strength and prevent muscle wasting in paralysed limbs.
Meticulous foot care is also important, especially in diabetic polyneuropathy. Mechanical aids can help to reduce pain and improve function. Hand or foot braces can compensate for muscle weakness or alleviate nerve compression.
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