The symptoms of motor neurone disease can be varied to begin with before getting progressively more widespread.
The symptoms usually follow a pattern that falls into three stages:
- the initial stage
- the advanced stage
- the end stage
The initial symptoms of motor neurone disease usually develop slowly and subtly over time. It can be easy to mistake early symptoms for those of several unrelated conditions that affect the nervous system.
In about two-thirds of people with motor neurone disease, the first symptoms occur in the arm or leg. This is sometimes called limb-onset disease. These symptoms include:
- a weakened grip, which can cause difficulties picking up or holding objects
- weakness at the shoulder, making lifting the arm above the head difficult
- tripping up over a foot because of weakness at the ankle or hip
These symptoms are usually painless and may be accompanied by widespread twitching of the muscles (fasciculations) or muscle cramps.
In the other one-third of cases, problems initially affect the muscles used for speech and swallowing. Increasingly slurred speech (dysarthria) is usually the first sign of this type of motor neurone disease.
As the condition progresses, it may become increasingly difficult to swallow. The medical term for swallowing difficulties is dysphagia.
In very rare cases, motor neurone disease starts by affecting the lungs. This is called respiratory-onset disease. In some cases the initial symptoms are obvious, such as breathing difficulties and shortness of breath.
In other cases the symptoms are less noticeable, such as waking up frequently during the night because the brain is temporarily starved of oxygen when lying down.
This in turn can make you feel very tired the next morning. You may also wake up early in the morning with a headache.
As motor neurone disease progresses to an advanced stage, the differences between the various types of disease are less noticeable as more parts and functions of the body are affected.
The limbs become progressively weaker and the muscles in your limbs begin to waste away. As a result, you'll find it increasingly difficult to move your affected limbs.
Certain muscles in your limbs may become unusually stiff. This type of muscle stiffness is known as spasticity.
Muscle wasting and stiffness can cause joint aches and pains.
Difficulties speaking and swallowing
About two-thirds of people with motor neurone disease eventually find the ability to speak and swallow increasingly difficult as the disease progresses. However, this is rarely fatal.
Reduced swallowing can cause excessive or constant drooling of watery saliva. Sometimes, thicker saliva may be harder to clear from the chest or throat because of weakened cough muscles.
Some people with motor neurone disease have episodes of uncontrollable, excessive yawning, even when they're not tired. This can sometimes cause jaw pain.
Motor neurone disease doesn't usually affect a person's intelligence, but it can lead to changes in their ability to control their emotions.
One of the most common signs is when a person has episodes of sudden uncontrollable crying or, more rarely, laughter. Doctors may call this emotional lability.
Changes to mental abilities
Occasionally, people with motor neurone disease may have difficulties with planning, language and concentration. This is known as cognitive change and overlaps with a condition called frontotemporal dementia.
Typically the changes are quite subtle, making it difficult to tell them apart from the normal ageing process, and do not usually affect a person's capacity to make their own decisions.
About 10% of people with motor neurone disease develop more profound frontotemporal dementia, typically soon after their first muscle symptoms.
As the nerves and muscles that help control the lungs become progressively more damaged, your breathing will become increasingly difficult.
This usually starts as a feeling of being very short of breath after doing everyday tasks, such as walking up the stairs. Over time, you may become very short of breath even when you're resting.
This shortness of breath may be particularly troublesome at night. Some people find it difficult to breathe when they're lying down. Others may wake up suddenly in the night because of breathlessness.
As motor neurone disease progresses, a non-invasive breathing mask may be recommended at night to improve sleep quality and help reduce drowsiness during the day.
As motor neurone disease progresses to its final phase, a person with the condition will probably experience:
- increasing body paralysis, meaning they need help with most normal daily activities
- significant shortness of breath
Eventually, non-invasive breathing assistance won't be enough to compensate for the loss of normal lung function. At this stage, most people with motor neurone disease become increasingly drowsy before falling into a deep sleep. They usually die peacefully in their sleep.