by Dr. John Rees
Helping us to understand Peripheral Neuropathy – a nerve disorder – Dr Rees highlights the causes, symptoms and treatments
Peripheral Neuropathies are disorders of those nerves that are outside the brain and spinal cord and supply us with all the sensory information and motor power to carry out normal activities. They all have the protective myelin layer which is made by different cells from the brain myelin. The many causes of disorders of the Peripheral Nerves all attack and damage either the myelin or the peripheral nerve cell itself (the axon), which runs the whole length of the nerve. Peripheral nerves have sensory and motor components and either one or both can be affected depending on the disorder.
Toxins of various sorts can cause nerve damage for example: heavy metals such as lead and arsenic, organophosphates as we have seen recently in the press and many drugs especially anti-cancer drugs. They usually damage the axon itself. Nutritional deficiencies e.g. vitamins B1, B5, B12 and vitamin E. Metabolic disorders e.g. diabetes, low thyroid, kidney failure and porphyria.
Hereditary disorders, of which there are legion, one of the best known being Charcot Marie Tooth disease, originally described by two French and one English neurologist in the 1880’s. As a result of recent advances in genetics, the causes of these hereditary neuropathies are becoming much better understood and treatments developed. There is a hereditary condition which makes the sufferer liable to so called ‘pressure palsies’ such as carpal tunnel syndrome and foot drop.
Trauma can cause damage to peripheral nerves especially where they are close to the skin and underlying bone and are more likely if the nerve is already compromised e.g. by diabetes, other metabolic illnesses or a liability to pressure palsies as just mentioned. Major trauma can obviously also cause serious damage, either directly or because the blood supply to the nerve has been compromised.
Inflammatory and/or auto immune neuropathies are a very large, possibly the largest group. We have become more aware over the last 20-30 years of numerous conditions occasionally associated with a distant cancer, where the body’s immune (defence) system attacks the body itself. Often this is manifest as an inflammation blocking the small blood vessels of the nerves or it may damage the protective myelin layer, so-called demyelination. Unusual reactions to common, often viral infections, can cross react and cause widespread damage to large nerves e.g. Guillain Barre syndrome, which may require intensive care treatment.
Autonomic neuropathies are less common but very important since these nerves are involved with control of blood pressure, heart rate, breathing and bladder control. Metabolic and autoimmune diseases, toxins, distant cancers and degenerative conditions can all damage the autonomic nerves.
Patients usually present with gradual and progressive symptoms of disordered sensation and/or weakness in the extremities, depending on the cause and which nerves are involved. The symptoms can be local or generalised, can remain slight or become very severe with considerable disability.
The diagnosis is made by carefully discovering from the patient exactly how and where the symptoms began and how they evolved. Clinical examination helps to delineate the extent of the problem and nerve conduction studies which examine the nerve electrically will usually confirm the diagnosis. Blood tests are invariably required and rarely a small biopsy of the nerve is taken for analysis. Treatment, which may be long term, depends entirely on the cause and may involve medication, dietary supplements, rarely surgery and even complex procedures such as filtering antibodies from the blood. There are many conditions for which no treatment is currently available but they are diminishing.
Neurology departments have experts in these conditions, physio and occupational therapy are often essential and help can be found from The Brain and Spine Foundation.