Amyotrophic lateral sclerosis (ALS): an animated, cited guide
This page needs JavaScript for its animations. The outline and key answers are below, and every claim in the full version carries a numbered citation.
Not medical advice. ALS Companion is an educational synthesis of published literature. It does not replace a clinician.
What is in it
- What ALS is Who gets it, the numbers, and the ways it starts.
- Upper and lower motor neurons Two neurons, two sets of signs, animated.
- TDP-43 and what goes wrong A protein leaves the nucleus and clumps.
- Genes: C9orf72, SOD1 and more Familial ALS, repeat expansions and genetic testing.
- Diagnosis and criteria The Gold Coast, revised El Escorial and Awaji criteria, as a calculator.
- The differential Conditions that can look like ALS, and how they differ.
- ALSFRS-R and the course The 12-item scale, the progression rate and the stages.
- Riluzole, edaravone and others What each drug targets and what the trials found.
- Tofersen An antisense drug that lowers SOD1, for SOD1-ALS.
- Breathing and NIV Weak breathing muscles, the tests, and when ventilation is offered.
- Swallowing and feeding tubes Why weight matters and when a gastrostomy is discussed.
- Living with ALS Communication, cognition, symptoms, planning and end of life.
- Nursing care Assessment, giving the medicines, teaching and documentation.
- Toward a cure Every route under study, with the evidence for each.
- History and people From Charcot to tofersen.
- Flashcards, quiz and glossary Revision for students.
- Sources Every reference behind the guide.
Common questions
What is ALS?
Amyotrophic lateral sclerosis is a disease of the motor neurons, the nerve cells that carry movement signals from the brain to the muscles. Upper motor neurons in the brain and lower motor neurons in the brainstem and spinal cord both degenerate, so muscles weaken and waste, and speaking, swallowing and breathing are affected as it progresses. Motor neurons for eye movements and bladder control are relatively spared.
How long do people live with ALS?
It varies widely. A systematic review found median survival of 20 to 48 months from symptom onset, with 10 to 20 percent of people living more than 10 years; population registers report 7 to 12 percent alive at 10 years. Respiratory failure is the most common cause of death. Older age, bulbar onset and faster early decline predict shorter survival.
Is ALS inherited?
Most ALS is not inherited. Population registers find a family history in about 5 percent of people with ALS, while reviews that count relatives with frontotemporal dementia give 10 to 15 percent. In Europe, C9orf72 repeat expansions are found in about a third of familial and 5 percent of sporadic cases, and SOD1 variants in about 15 percent of familial cases. A 2023 US consensus recommends offering genetic testing to everyone with ALS.
How is ALS diagnosed?
There is no single test. Diagnosis rests on progressive upper and lower motor neuron signs found on examination and electromyography (EMG), and on excluding conditions that mimic ALS, using MRI and blood tests. The Gold Coast criteria of 2020 simplified the older El Escorial categories; in a 2026 pooled analysis they were more sensitive (96 percent against 87 percent) but less specific.
What treatments are approved for ALS?
Riluzole, approved in 1995, probably extends median survival by about two to three months. Edaravone slowed decline in one trial in a selected group and is approved in the US and Japan but not in the EU. Tofersen, an antisense drug for people with SOD1 variants, received FDA accelerated approval in 2023 and EU approval in 2024. Breathing support with non-invasive ventilation also prolongs survival.
What is the ALSFRS-R?
The revised ALS Functional Rating Scale scores 12 everyday functions in four areas (bulbar, fine motor, gross motor and breathing) from 0 to 4 each, for a total of 48. In pooled trial data it fell by about 1 point a month on average, and the rate of fall early in the disease predicts survival. Decline is often not a straight line, and some people have plateaus.
When is non-invasive ventilation used in ALS?
Guidelines list results that should prompt a discussion about breathing support, such as forced vital capacity below 50 percent of predicted, a sniff nasal pressure below about 40 cmH2O, or lower values with symptoms such as breathlessness lying flat. In a randomised trial, non-invasive ventilation improved survival by a median of 205 days in people with better bulbar function, with quality of life maintained.
When is a feeding tube considered in ALS?
When swallowing becomes difficult or weight keeps falling. Guidelines advise placing a gastrostomy before breathing becomes too weak, because the procedure carries more risk when forced vital capacity is below 50 percent. In the ProGas study, losing more than 10 percent of body weight before the tube was placed was linked to shorter survival.