Clinical features

The onset of symptoms and signs in motor neurone disease is often insidious. The person reports clumsy or stiff movements with cramps and pain in the affected limb. As the disease progresses muscles become weak and wasted, and movement of the limb or part of the limb is impaired. Affected muscles display fasciculation (fine involuntary twitching of the muscle fibres that is visible to the naked eye). The reflexes are usually brisk at the beginning of the disease, but later are lost.

Motor neurone disease does not affect sensation or the neuromuscular control of urination and defaecation.

Characteristically amyotrophic lateral sclerosis (65% cases)affects the hands first, when the person reports cramps and weakness of one hand, and then the other. Fine movements and grip become weakened and muscle wasting and fasciculation is seen on examination. In some people the disease affects the feet before the hands causing foot drop and difficulty in walking. The disease then progresses to the rest of the limbs with increasing stiffness, pain, fasciculation, wasting of the muscles and paralysis of movement. With increasing immobility pain becomes a prominent symptom. The person becomes progressively unable to lift, carry or reach and unable to stand, walk, rise from a chair, move around in the house, climb stairs, bend down and turn in bed. Weakness of the muscles of the chest wall and diaphragm leads to difficulty in breathing.

In people with bulbar symptoms the condition affects the muscles controlling facial expression, the tongue, the palate, the throat and the voice. The person develops increasing difficulty in chewing, eating and swallowing, and they tend to choke and regurgitate food through the nose. The ability to speak diminishes and the speech becomes slurred and weak, as the muscles controlling the vocal cords become paralysed. The ability to cough effectively and clear secretions is lost. Saliva and food may be aspirated into the chest causing pneumonia. There is often substantial weight loss due to inability to eat properly and general loss of muscle bulk.

Death is usually due to respiratory failure or aspiration pneumonia complicated by malnutrition

In a small number of cases the degenerative changes affect the brain leading to symptoms of dementia. Some people with bulbar symptoms experience inappropriate episodes of laughing or crying due to the condition affecting the brain stem; this is known as emotional lability.

Amended June 2008