Peripheral nerves refer to all the nerves in the body outside the brain and spinal cord. Strictly speaking, a neuropathy is any disease process affecting peripheral nerves, which includes pathology affecting only a single nerve (mononeuropathy), or the nerve roots (radiculopathy), or the nerve plexuses (plexopathy). However, the term ‘peripheral neuropathy’ is usually used for what is technically called polyneuropathy. Polyneuropathy is a generalized or widespread process affecting the peripheral nerves, often in a symmetrical fashion and causing symptoms that are more pronounced distally.

HOW COMMON IS PERIPHERAL NEUROPATHY?

Peripheral neuropathy is a diverse condition incorporating many different diseases, and we do not have very good statistical information on how common it is as a single entity. One study estimated that the prevalence of peripheral neuropathy in the general practice setting is 8 percent in persons 55 years and older. The prevalence in the general population may be as high as 2.4 percent. In patients with diabetes, a large study serially evaluated patients over 25 years and showed that by 25 years, 50 percent of patients had neuropathy.

WHAT ARE THE MAIN TYPES OF PERIPHERAL NEUROPATHY?

Peripheral neuropathy encompasses a wide range of diseases and can manifest in different patterns. It can be classified in several ways, such as whether it is inherited or acquired, whether it is rapid or insidious in onset, which part of the peripheral nervous system it affects (motor, sensory, autonomic), whether it has an axonal or demyelinating pattern on electrodiagnostic testing, or what it is caused by, e.g. metabolic, drugs and other toxins, infective, inflammatory/immune, paraneoplastic (cancer related).

Some possible patterns of peripheral neuropathy are:

1. Distal symmetric length-dependent neuropathies – examples are neuropathies associated with diabetes, B12 deficiency, hypothyroidism, alcohol, kidney failure
2. Demyelinating polyneuropathies – e.g. Charcot-Marie-Tooth disease (type 1), Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN)
3. Predominantly autonomic neuropathies – e.g. diabetic neuropathy, Guillain-Barre syndrome, Sjogren’s syndrome, amyloidosis
4. Multifocal mononeuropathies – e.g. vasculitis causing mononeuritis multiplex, multifocal acquired demyelinating sensory and motor neuropathy (MADSAM), hereditary neuropathy with liability to pressure palsies (HNPP)
5. Axonal polyradiculo(neuro)pathy – some variants of Guillain-Barre syndrome, sarcoidosis, Lyme disease
6. Sensory neuronopathy – e.g. Sjogren’s syndrome, paraneoplastic cause
7. Small fibre neuropathy – e.g. diabetes, impaired glucose tolerance, alcohol
8. Someone else in my family had Peripheral Neuropathy- am I at risk of getting it too?

Peripheral neuropathy is a common disorder that can be caused by other medical conditions such as diabetes, renal failure, alcoholism, adverse effects of drugs, and certain immune disorders, to name a few. Having a close relative with peripheral neuropathy caused by another condition does not affect your risk of getting peripheral neuropathy, unless of course, you have the same predisposing disease.

Some peripheral neuropathies, however, have a hereditary cause. The most common hereditary neuropathy is called Charcot-Marie-Tooth (CMT) disease. There are various forms of CMT caused by different genetic mutations. Generally speaking, CMT causes neuropathy onset at a young age, usually below the age of 20. Its onset is gradual and it slowly progresses over decades. It usually presents with weakness and muscle wasting beginning in the feet, and over time progressing more proximally to the legs, then the thighs, hands and forearms. As well as muscle weakness and wasting, the feet usually develop high arches and hammer toes. Patients usually report difficulty in running from an early age, as well as tripping, difficulty in walking, and foot drop. In addition to the motor symptoms, CMT also causes sensory loss with decreased sensation of touch, pain and vibration beginning in the feet and hands. Depending on the form of CMT, patients usually have an affected first-degree relative such as a parent. If your symptoms fit with this description, you should be checked by a neurologist.

WHAT ARE THE COMMON SYMPTOMS OF PERIPHERAL NEUROPATHY?

Symptoms of peripheral neuropathy can be classified into motor, sensory and autonomic symptoms. Motor symptoms include muscle weakness and wasting. Most commonly, the weakness begins distally, involving most severely the muscles of the feet and legs before the hands and forearms are involved. If weakness begins in childhood, there will often be deformities of the feet, hands and spine such as claw feet, high arches or hammer toes.

Sensory symptoms consist of both negative symptoms (loss of sensation) as well as positive symptoms (abnormal sensation). Negative sensory symptoms are impairment or loss of sensory modalities such as touch-pressure, pain, temperature, vibration and joint position sense. Positive sensory symptoms include pins and needles (paraesthesia), pain, and abnormal, uncomfortable sensation (dysaesthesia).

Autonomic symptoms are caused by damage to nerves which control autonomic functions such as maintenance of blood pressure, pupillary reflexes, sweating, tear secretion, salivation, and control of the bladder, bowels and erectile function. Autonomic dysfunction results in lack of sweating, dizziness on standing caused by a drop in blood pressure, delayed gastric emptying, abdominal distension, urinary retention or incontinence, constipation, and erectile dysfunction.

CAN PERIPHERAL NEUROPATHY BE PREVENTED?

This depends on the cause of the neuropathy. Some of the most common causes of peripheral neuropathy are preventable or treatable to some degree. For example, diabetic neuropathy can be prevented or have its onset or progression delayed with intensive glucose control. Alcoholic neuropathy can be prevented by abstaining from alcohol. Neuropathy due to vitamin B12 deficiency can be reversed with vitamin B12 supplementation. Many other neuropathies are not preventable, however, such as the hereditary neuropathies.

HOW IS A DIAGNOSIS OF PERIPHERAL NEUROPATHY MADE?

Peripheral neuropathy is diagnosed on the basis of a clinical assessment conducted by a neurologist, which includes taking the history of the patient’s symptoms, and a physical examination. Often, nerve conduction studies will also be performed to confirm the diagnosis.

HOW IS PERIPHERAL NEUROPATHY TREATED?

Treatment can be divided into treatment which targets the underlying disease process and treatment for the relief of symptoms. Treatment targeting the underlying disease process depends on the underlying cause, for example improving glucose control in a diabetic patient, giving vitamin B12 supplementation in the case of vitamin B12 deficiency, or giving immune suppressing drugs and intravenous immunoglobulin in neuropathies due to immune causes. Treatment for symptomatic relief, particularly for the pain associated with neuropathy, is also available.

WHAT IS THE PROGNOSIS FOR PERIPHERAL NEUROPATHY?

The prognosis for peripheral neuropathy very much depends on the cause and severity of the neuropathy. You would need to speak to your neurologist about your individual case.

WHAT ARE NERVE CONDUCTION STUDIES AND EMG?

Nerve conduction studies are tests of nerve function which use electrical stimulation of nerves and the resultant responses measured. EMG stands for electromyography, which is another test of nerve function. In EMG, fine needle electrodes are inserted into muscles and the electrical activity within these muscles measured both at rest and with contraction.