Introduction
The nervous system in the body is divided into two components – the central nervous system, which describes the brain and the spinal cord, and the peripheral nervous system, which is – essentially – the rest of the nervous system.
The peripheral nervous system connects the brain to all the outlying parts of the body and incorporates three different types of nerves…
- Sensory nerves – these send signals relating to touch, pain and temperature, smell, sight back to the brain.
- Autonomic nerves – these control a range of functions of the body which are not consciously controlled (for example blood pressure, balance, digestion, sweating) .
- Motor nerves – these control muscle movements.
Where there is some form of pain that is generated by the peripheral nervous system (and it is not a 'normal' reaction to some form of external stimulus) this is referred to as 'peripheral neuropathy' or 'peripheral neuralgia' (these terms are interchangeable).
Most cases of peripheral neuralgia affect the hands, feet, arms or legs, although in some people it only affects one specific part of the body, for example a toe or a finger, or in the case of Bell's Palsy, one facial nerve.
The major risk of peripheral neuralgia is that the loss of feeling, in for example the legs and feet, can lead to the development of problems such as ulcers, and damage to the skin in the affected area/s.
Estimates vary, but it is believed that around 10% of the population over 55 are affected by peripheral neuralgia.
Causes
Peripheral neuralgia is caused by some type of damage to the nerves, which may be caused by some form of trauma (i.e. injury) or by another medical condition.
The most common cause of peripheral neuralgia is diabetes (see diabetic neuropathy). Other common causes of the condition are…
- Physical injury.
- Repetitive physical actions (for example in sport or at work).
- Plaster casts used to set broken bones – these may place continuous pressure on nerves.
- Viral infections (for example shingles) .
- Guillain-Barre Syndrome.
- Some autoimmune disorders (e.g. rheumatoid arthritis) .
- Excess alcohol consumption.
- Some medications (e.g. some chemotherapy and HIV treatments) .
- Disorders affecting the liver, kidneys and thyroid.
- Some cancers (e.g. lymphoma, multiple myeloma) .
- Some insecticides and solvents.
- Vitamin deficiency (especially B12 and folate deficiency) .
Peripheral neuralgia also runs in some families.
Symptoms
Symptoms depend on which type of nerves are affected…
Sensory nervous system
- Tingling or numbness in affected area.
- Inability to feel e.g. temperature changes or pain.
- Burning pain (especially in the affected foot / feet).
- Hypersensitivity, where a light touch is painful.
- Decrease in balance and/or coordination.
Motor nervous system
- Muscle cramping / twitching.
- Muscle weakness.
- Loss of muscle mass.
- 'Foot drop' – where the front of the foot droops a little while walking.
Autonomous nervous system
- Tachycardia (rapid heartbeat).
- Dizziness (caused by low blood pressure).
- Loss of bladder and/or bowel control.
- Erectile dysfunction.
- Problems with sweating – either no sweating or excessive sweating.
- Diarrhoea / constipation (often at night time).
- Generally feeling sick and / or bloated.
If only one specific nerve is affected, symptoms will be linked to the function of that nerve, for example Bell's Palsy, which causes weakness to one side of the face, or carpal tunnel syndrome, which causes pain and numbness in the hand and fingers.
Tests / Diagnosis
The first step in diagnosis is a full medical history to ascertain whether any of the risk factors listed above may be causing the problems, or whether neurological issues run in the family.
A physical examination may include initial tests of reflexes, muscle tone and strength and posture.
Blood tests may be recommended to check for diabetes or vitamin deficiencies, and various tests to check the function of the nerves may be recommended, for example, electromyography (EMG) which measures electrical activity in the muscles, and / or a nerve conduction study. In some cases, either a nerve biopsy (tissue sample) or skin biopsy may be recommended.