Peripheral nervous system disorders

Published on 03/03/2015 by admin

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10 Peripheral nervous system disorders

Part 1: Guillain–Barré syndrome (GBS)

GBS is classified as a disease of the peripheral nervous system, those nerves controlling movement and senses, and is quite rare, with a prevalence of approximately 1 in 100 000 in European countries. It affects about 1500 people in the UK every year. It is slightly more common in men than women and can affect people of any age, including children. It is also sometimes referred to as acute inflammatory polyradicular neuritis.

The exact cause of GBS is unclear and there is no way to pinpoint who is most at risk from the condition. However, in most cases of GBS, the person affected will have had a viral or bacterial infection a few weeks before getting the condition. It is likely that the infection causes the immune system to attack the body’s own nerves.

In GBS, the body’s immune system attacks these nerves, causing them to become inflamed (swollen). Although axonal demyelination is an established pathophysiological process in GBS, the rapid improvement of clinical deficits with treatment is consistent with Na+ channel blockade by antibodies or other circulating factors, such as cytokines [1]. Most people with GBS make a full recovery within a few weeks or months and do not have any further problems. Some people may take longer to recover and there is a possibility of permanent nerve damage.

Symptoms

Symptoms usually appear after a preceding infection. They increase in intensity over a period of time, varying from a few hours in serious cases to around 4 weeks in most patients. The symptoms also vary with regard to the pattern in which they appear. Their distribution is usually symmetrical and double-sided. This means that the symptoms appear on both the left and right side of the body, but they may also appear randomly, especially in the beginning. They may also appear and disappear quite randomly. Inflammation of the peripheral nerves leads to a tingly, numbing sensation in the arms and legs. This can eventually result in a short-term loss of feeling and movement (temporary paralysis).

Fever is not a symptom of GBS, but may be caused by the preceding infection that triggered the syndrome. GBS symptoms vary, depending on whether the syndrome has affected the sensory nerve fibres or the motor nerve fibres. When both motor and sensory nerves are affected, the patient experiences a mixture of symptoms. The patient may also experience disruption in the working of the autonomous nervous system.

Damage to sensory nerves

Symptoms generally begin in the patient’s feet, hands or face, spread to the legs or arms, and increase in intensity as they move towards the centre of the body. They generally appear on both left and right sides of the body. However, GBS is unpredictable, and cases have been reported in which this ‘glove and stocking’ pattern is not followed. Instead, motor symptoms or disruptions in the autonomous system may be observed. GBS may also affect an arm or a leg alone, without spreading to the rest of the body.

Gradually muscle pain is experienced in the large muscles, such as the thighs, back and shoulders. Pain in the lower back, buttocks or thighs is common, and is often the earliest symptom. Stiffness and cramping pain or deep, aching muscle pain is common. The sensory symptoms then make themselves felt, as the sensory nerves are attacked. The patient experiences loss or reduction of the sense of touch, or abnormal sensations such as burning, tingling, pins and needles, ‘ants under the skin’, vibrations and numbness.

In some patients, the skin develops hyperalgesia, or tenderness to touch, made worse by bed covering, socks and tight-fitting shoes; in some cases, pain may limit walking. Patients with symptoms at first limited to the feet and ankles may observe similar symptoms in the fingertips; as the symptoms extend to the knees, they may also extend to the wrists. The symptoms usually remain peripheral, i.e. beyond the knee and the elbow. The patient loses the ability to tell the difference between hot and cold, and may feel cold or may sweat for no apparent reason. Minor injuries may occur without being noticed. The patient’s sense of taste can be affected too.

Damage to motor nerves

The motor nerves control movement, and damage to them results in partially or completely blocked signals, causing reduced movement or coordination. The patient’s muscles weaken and atrophy. Tendon reflexes are reduced or lost. Progressive weakening or paralysis may occur, typically beginning in the feet, hands or face. The paralysis characteristically involves more than one limb, most commonly both legs. The paralysis is progressive and usually ascending, spreading to the rest of the limb, and from there may spread to the legs, arms and the rest of the body.

It will be difficult to stand up or climb stairs, to walk or stand and the patient will often say that the legs feel heavy. The patient may have difficulty holding and manipulating small objects, and because the arms feel weak they can no longer lift heavy objects. The weakness is often accompanied by pain and muscle spasms. Constipation can sometimes be a problem, due to the reduced activity of the intestines, change of diet and weakened stomach muscles that resist efforts by the patient to empty the bowel.

Damage to the cranial nerves can affect the face, producing a form of facial palsy. The speech muscles and vocal cords may also be affected, causing unintelligible speech. If swallowing and breathing are involved then the disease becomes life-threatening. Admission to hospital may be necessary if the GBS develops very quickly. Patients showing signs of weakness are carefully observed for signs such as paralysis of the throat, which signals a potential respiratory failure. In this case a ventilator will be necessary and if the heart rhythm becomes unstable a heart monitor may also be used.

Physiotherapy treatment

Recovery generally begins within a month of the height of the illness and has the potential to be complete. Unfortunately approximately 30% of patients will retain a residual paralysis or paresis, most usually in the lower limbs. Statistically significant correlations have been found between the degree of residual motor deficit and the severity of the weakness in the acute phase, the duration of the plateau phase or the duration of artificial ventilation [2].

Complications such as contractures, particularly those around joints, will delay or prevent full recovery and physiotherapy often concentrates treatment on these. Gentle stretching is undertaken to prevent the patient remaining for long periods in a bent or contracted posture and positioning in bed or when seated needs to be carefully controlled to ensure a good position. Splints may be used and active-assisted exercises slowly introduced.

Another complication to recovery is fatigue, so any exercises need to be carefully graduated in order to strengthen without overtiring the muscles. Temporary use of mobility aids such as wheelchairs and orthoses may be desirable to prevent overstrain. Patients with GBS do seem to have a reduced quality of life and functioning with persistent levels of distress even after the recovery period [3].

Pain can also be a problem, mostly caused by the affected muscles. Correct positioning and comfortable support will assist with this but often analgesia is required, especially at night. Anxiety is undoubtedly a factor in such a sudden and serious illness and is associated with perceived slowness in recovery.