By Dr Ananya Mandal, MD
Motor neurone disease is a progressive neurodegenerative disorder that leads to loss of muscle control and eventually disability and paralysis.
Symptoms of the condition are often mild at first and begin with a tendency to drop things or difficulty picking objects up. However, the disease rapidly progresses over a period of months and eventually leads to a complete loss of muscle function.
In most cases of motor neurone disease, the severity of symptoms varies according to whether a patient is in the initial, advanced or end stage of disease.
Initially, symptoms may be mild or go unnoticed. The symptoms of motor neurone disease may also be mistaken for symptoms caused by other disorders. In around two thirds of patients, there is limb involvement in the initial stages, which is typically characterized by the following:
Weakness of grip and inability to pick up or hold objects. The person may drop things frequently.
Shoulder weakness making it difficult to raise the arms over the head. The patient may complain that they are unable to comb their hair, for example.
Weakness of the ankle joints causing an increased tendency to trip or fall.
Initial symptoms may be accompanied by twitching of the muscles and muscle cramps, which are termed muscle fasciculations.
In around one third of cases, patients develop a form of motor neurone disease called progressive bulbar palsy. In this form of the condition, the muscles that control speech, swallowing and chewing are the first affected, leading to slurred speech (dysarthria) and difficulty swallowing (dysphagia).
In rare cases, the initial onset of symptoms involves the respiratory system, which is referred to as respiratory-onset disease. In these cases, there may be obvious symptoms such as breathing difficulty or more subtle symptoms such as headache felt on awakening or fatigue during the day.
Symptoms of advanced stage
After the initial phase, motor neurone disease progresses to an advanced stage. At this stage, the different forms of the condition are harder to distinguish as the disease starts to cause a more generalized loss of muscle function.
As the muscles become more weak and start to waste away, there is an increasing loss of ability to move the limbs, which may also become stiff (called spacticity). The muscles wastage and stiffness may also cause pain in the joints.
In around two thirds of cases, it will become increasingly difficult to speak and swallow and a reduced ability to swallow can lead to excessive drooling of saliva. Sometimes, sufferers find they cannot stop yawning, which can cause pain in the jaws. Motor neurone disease can also cause emotional changes with sufferers experiencing episodes of uncontrollable crying or laughing which is referred to as emotional lability. Cognitive changes can also occur and affect the patients ability to plan, judge and concentrate. As the muscles involved in respiration become affected, breathing difficulties may also become more prominent.
End stage symptoms
In the final stages of motor neurone disease, the patient becomes increasingly disabled and may need help performing simple tasks and daily activities such as cleaning or feeding themselves. Breathing may become particularly difficult at night, requiring the use of a breathing mask to enhance sleep quality and decrease day time drowsiness. Eventually breathing assistance can no longer make up for the loss of lung function, which often leads to death in these individuals.
Reviewed by Sally Robertson, BSc