KalamWhat is ALS?
ALS — amyotrophic lateral sclerosis — is a progressive neurological disease that affects the motor neurons: the nerve cells that let the brain and spinal cord control voluntary muscles.
As those cells stop working, the nervous system gradually loses its ability to control the muscles they serve. Over time this affects movement, using the hands, speech, swallowing, coughing and breathing.
ALS is a progressive disease, but its course varies a great deal from person to person.
Where the disease begins, the order in which different functions are affected, and how quickly it progresses can all differ considerably between people.
ALS, in simple terms
The brain sends its instructions to the muscles through nerve cells called motor neurons.
When you reach for a cup, take a step, speak, or draw a deep breath, these cells carry the signals that let the muscles move.
In ALS, the motor neurons gradually stop working. As fewer signals reach the muscles they control, those muscles lose strength and, over time, can lose the ability to perform movements they once could.
So although the effects of ALS show up in what the muscles can no longer do, the problem begins in the nerve cells that control them.
Where can ALS begin?
ALS can begin in different parts of the body. There are two main patterns of onset.
Limb onset
The first changes appear in an arm, a hand, a leg or a foot.
A person might begin to:
- trip, or catch a foot on the ground while walking
- find stairs harder to climb
- lose strength or precision in one hand
- drop things
Bulbar onset
The first changes appear in the muscles used for speaking and swallowing.
Speech may become slower or less clear. The voice may change, or swallowing and managing saliva may become more difficult.
Limb onset and bulbar onset describe where the disease begins. They do not allow anyone to predict precisely how it will progress.
Less commonly, ALS can begin in other ways, including early weakness in the breathing muscles.
What does it mean that ALS is “progressive”?
ALS continues to affect motor function over time.
But progressive does not mean predictable.
There is no fixed sequence that everyone goes through, such as:
legs → hands → speech → swallowing → breathing
One person may lose the ability to speak clearly while still being able to walk.
Another may lose the ability to walk while their speech stays clear.
And even within the same person, symptoms can progress at different speeds in different parts of the body.
The disease progresses, but the way it progresses differs from person to person.
What can change over time?
ALS affects voluntary motor function, but different abilities are not necessarily affected at the same time.
Movement and using the hands
Walking, keeping your balance, standing, transferring, holding your head up, reaching, gripping objects, writing, and using a phone or a computer can all become harder over time.
As motor function is lost, some of these movements may later become impossible without help or equipment.
Speech and communication
The muscles used for speech can weaken. Speech may become slower or quieter or harder to understand, and may eventually become unreliable.
Difficulty speaking does not mean losing the ability to communicate.
Communication can continue through writing, communication boards, speech-generating devices, switches, and eye-gaze systems.
Swallowing and nutrition
The muscles used for chewing and swallowing can also weaken.
Eating and drinking may become slower, more tiring or less safe. Getting enough nutrition and fluids can become harder, and a feeding tube can be used to supplement or replace eating by mouth.
Coughing, saliva and secretions
An effective cough depends on the strength of the breathing muscles.
As those muscles weaken, coughing may no longer be enough to clear saliva or secretions. Assisted-cough techniques, cough-assist machines, suction and certain treatments can then become an important part of care.
Breathing
ALS also affects the muscles used for breathing, including the diaphragm.
The beginning of respiratory weakness can show up indirectly — poor sleep, headaches on waking, tiredness during the day, breathlessness when lying down, or a weak cough.
This is why breathing function is usually monitored regularly, rather than waiting until breathing becomes visibly difficult.
How can breathing be supported?
The most widely used form of breathing support in ALS is non-invasive ventilation (NIV). The machine helps with breathing through a mask worn over the nose, or over the nose and mouth.
At first it may be needed mainly during sleep. As the breathing muscles weaken further, it may be used for longer periods during the day as well.
Ventilation supports weakened breathing muscles, but it does not stop ALS from progressing.
What about a tracheostomy?
Another form of breathing support is ventilation through a tracheostomy.
An opening is made in the neck into the windpipe, and a tube is placed in it that provides a direct airway and can be connected to a ventilator.
For some people with ALS, tracheostomy ventilation becomes part of long-term breathing support. It may be planned in advance, or in some cases it happens during a respiratory emergency.
Not everyone with ALS will need or choose it. The decision depends on the person’s wishes, their respiratory condition, the care that is actually available, and what invasive ventilation means in daily life.
When a tracheostomy is used, there is often a clear before and after in day-to-day care.
Ventilation may become necessary for long periods or continuously. Secretions may need to be suctioned through the tube. The airway and the tube need regular care, caregivers usually need training, and the amount of support required at home can increase considerably.
The way a person speaks and communicates may also need to be reassessed.
For these reasons, it is better to understand what tracheostomy ventilation involves before it becomes an urgent question.
How is ALS diagnosed?
ALS can be difficult to diagnose in its early stages.
No single symptom and no single test proves the diagnosis on its own. The first symptoms may be limited to one part of the body and resemble other neurological or muscular conditions, or problems in the spine.
So a neurologist looks at the whole picture:
- the symptoms that have appeared
- how they have progressed
- the findings of a neurological examination
- tests such as electromyography (EMG)
- the tests used to rule out other causes
EMG can detect signs that muscles are losing their nerve supply, including in muscles where weakness is not yet obvious.
Sometimes the diagnosis is clear from the first specialist assessment. In other cases the picture becomes clearer over time, and the examination or the EMG may be repeated.
This is why diagnosing ALS can take time, and why another explanation for the symptoms may be considered at first.
Muscle twitching, cramps or weakness on their own do not mean that someone has ALS.
After an ALS diagnosis, genetic testing may also be discussed. Identifying certain genetic changes associated with the disease can now affect treatment options for some people.
Why does ALS happen?
We still do not know exactly why ALS happens.
Research has identified genetic changes that can cause or contribute to some forms of the disease, as well as biological mechanisms linked to motor neuron damage.
Research has also found associations between ALS and a number of other factors. But an association does not necessarily mean a direct cause.
And to this day, no one can explain precisely why a particular person develops ALS.
Thinking and awareness
ALS primarily affects motor function.
Losing the ability to speak or to move does not, in itself, mean losing awareness, understanding, or the ability to think. A person can become severely limited physically while remaining entirely aware of what is happening around them.
Some people do experience changes in thinking or behaviour, and in some cases there is a recognised biological overlap between ALS and frontotemporal disorders. So it would not be accurate to say that thinking is never affected.
But these changes are not what defines the disease.
Losing motor function and losing cognitive function are not the same thing.
ALS has been diagnosed. Where do you start?
Understanding the disease is one thing. Living with it raises more practical questions.
Which treatments should be discussed? How are breathing, swallowing and nutrition monitored? When should alternative ways to communicate be prepared? What equipment can help? And what is worth planning before it becomes urgent?
Our practical ALS guide brings these questions together in one place.
Sources and further reading
- ALS Association — What is ALS?motor neuron damage, and the progressive loss of voluntary motor control.
- ALS Association — Symptoms and diagnosishow onset, symptoms and the speed of progression differ between people.
- MND Association — How is MND diagnosed?why there is no single test, the role of EMG, and why a diagnosis can take time.
- NICE guideline NG42 — motor neurone disease (UK)clinical guidance on respiratory signs, monitoring breathing, and ventilation.
- MND Association — Breathing and ventilationnon-invasive ventilation, tracheostomy ventilation, and what each involves day to day.
- ALS Association — Genetic testing for ALSgenetic testing after a diagnosis, and how a result can affect treatment options.
- ALS Association — Who gets ALS?what is currently known, and not known, about genetic and other associated factors.
- ALS Association — ALS, cognitive impairment and dementiathe overlap with frontotemporal disorders, and how varied cognitive changes are.
This page provides general information about ALS. It does not replace individual medical care.