This glossary defines key terms used in the context of ALS/MND. It is intended as a general reference for people living with ALS/MND, their families, and caregivers. For a broader glossary of ALS-related terms, the Roon ALS Glossary is a free resource available online.
A
ALS (Amyotrophic Lateral Sclerosis)
The medical term most commonly used in North America and South America for the disease also known as Motor Neurone Disease (MND). “Amyotrophic” refers to muscle wasting; “lateral” refers to the areas of the spinal cord affected; “sclerosis” refers to the hardening or scarring of those areas. See also: Motor Neurone Disease (MND).
Augmentative and Alternative Communication (AAC)
A range of tools and strategies that support or replace speech when a person’s ability to communicate verbally has been affected. AAC includes low-tech options such as letter boards, and high-tech options such as speech-generating devices and eye-tracking technology.
B
Biomarker
A measurable indicator — such as a protein, gene, or imaging result — that can signal the presence, progression, or severity of a disease. Researchers are working to identify reliable biomarkers for ALS/MND that could support earlier diagnosis and the development of new treatments.
Bulbar onset
A form of ALS/MND in which the first symptoms affect the muscles used for speaking, swallowing, and breathing, rather than the limbs. Bulbar onset accounts for approximately 25% of ALS/MND cases.
C
CALS (Caregivers of people living with ALS/MND)
The term used by the Alliance to refer to family members, friends, and others who provide care and support to people living with ALS/MND.
Clinical trial
A research study that tests whether a new treatment, drug, or intervention is safe and effective in people. Clinical trials for ALS/MND may be interventional (testing a treatment) or observational (studying how the disease progresses without intervention).
Cognitive and behavioural changes
Changes in thinking, memory, language, or behaviour that can occur in some people living with ALS/MND. These changes are more common in people who also have frontotemporal dementia (FTD), which overlaps with ALS/MND in a proportion of cases.
D
Diagnostic testing (genetic)
A type of genetic test offered to a person who already has an ALS/MND diagnosis. It looks for a known genetic change that may be linked to their ALS/MND. See also: Predictive testing.
Dysarthria
Slurred, slow, or difficult speech caused by weakness or loss of control of the muscles used for speaking. Dysarthria is a common symptom as ALS/MND progresses.
Dysphagia
Difficulty swallowing, caused by weakness in the muscles of the mouth, throat, or oesophagus. Dysphagia is a common symptom in ALS/MND and can affect nutrition and hydration.
E
El Escorial criteria
A set of diagnostic criteria developed to standardize the diagnosis of ALS/MND for clinical and research purposes. The criteria assess the presence and spread of upper and lower motor neuron signs across different regions of the body.
EMG (Electromyography)
A diagnostic test that measures the electrical activity of muscles and the nerves that control them. EMG is one of the key tests used in the diagnosis of ALS/MND.
F
Familial ALS/MND
ALS/MND in which more than one person in the same family has been diagnosed with the disease. Familial ALS/MND accounts for approximately 10% of cases and is often associated with an identifiable genetic change. See also: Sporadic ALS/MND.
Fasciculations
Involuntary, small muscle twitches visible under the skin. Fasciculations are a common symptom of ALS/MND, resulting from the abnormal firing of motor neurons. They are also common in the general population and can occur for many reasons unrelated to ALS/MND, such as fatigue, stress, or caffeine intake.
FTD (Frontotemporal Dementia)
A form of dementia caused by damage to the frontal and temporal lobes of the brain, which affects behaviour, personality, and language. FTD overlaps with ALS/MND in a proportion of people, and the two conditions share some genetic and biological features.
G
Gene
A segment of DNA that carries the instructions for making a specific protein. Changes in certain genes — such as C9orf72, SOD1, TARDBP, and FUS — are associated with ALS/MND.
Genetic counselling
A conversation with a trained specialist who reviews personal and family medical history, explains what genetic testing may or may not show, and helps a person decide whether genetic testing is right for them. See the Genetic Counselling and Testing page for more information.
L
Limb onset
A form of ALS/MND in which the first symptoms appear in the arms or legs, such as weakness, tripping, or difficulty with fine motor tasks. Limb onset is the most common presentation of ALS/MND. Some limb-onset cases are classified as “flail arm” or “flail leg” syndrome, where weakness is more localized and tends to progress more slowly than typical limb onset.
Lower motor neurons
Nerve cells that carry signals from the spinal cord and brainstem directly to the muscles. Damage to lower motor neurons in ALS/MND causes muscle weakness, wasting, and fasciculations. See also: Upper motor neurons.
M
MND (Motor Neurone Disease)
The term most commonly used in the United Kingdom, Australia, and parts of Europe for the group of diseases that includes Amyotrophic Lateral Sclerosis (ALS), Progressive Muscular Atrophy (PMA), Progressive Bulbar Palsy (PBP), and Primary Lateral Sclerosis (PLS). The Alliance uses “ALS/MND” to reflect both terms. See also: Amyotrophic Lateral Sclerosis (ALS), Progressive Muscular Atrophy (PMA), Progressive Bulbar Palsy (PBP), and Primary Lateral Sclerosis (PLS).
Multidisciplinary care
An approach to care in which a team of specialists from different fields — such as neurology, physiotherapy, occupational therapy, speech therapy, respiratory medicine, and nutrition — work together to support a person living with ALS/MND. Multidisciplinary care is considered the standard of care for ALS/MND.
Mutation
A change in the sequence of DNA. In the context of ALS/MND, certain genetic mutations are known to increase the risk of developing the disease or to cause it directly. The terms “mutation” and “variant” are often used interchangeably in clinical and research contexts.
P
PALS (People living with ALS/MND)
The term used by the Alliance to refer to individuals who have been diagnosed with ALS/MND.
Palliative care
Specialized care focused on relieving symptoms, managing pain, and improving quality of life for people with serious illness. Palliative care in ALS/MND can begin at any stage of the disease and is provided alongside other treatments.
PBP (Progressive Bulbar Palsy)
A subtype of motor neuron disease that primarily affects the muscles used for speaking, swallowing, and breathing. PBP is considered part of the ALS/MND spectrum.
Penetrance
The likelihood that a person who carries a genetic change associated with ALS/MND will actually develop the disease. Some genetic changes have high penetrance, meaning most carriers will develop ALS/MND; others have lower penetrance, meaning only some carriers will be affected.
PLS (Primary Lateral Sclerosis)
A subtype of motor neuron disease that affects only the upper motor neurons. PLS progresses more slowly than ALS and does not always shorten life expectancy, though it can cause significant disability.
PMA (Progressive Muscular Atrophy)
A subtype of motor neuron disease that affects only the lower motor neurons, causing muscle wasting and weakness. PMA is considered part of the ALS/MND spectrum.
Predictive testing (genetic)
A type of genetic test offered to a family member who does not have ALS/MND but who may be at risk because a known genetic change has been identified in their family. Predictive testing cannot determine if or when a person will develop ALS/MND. See also: Diagnostic testing.
R
Respiratory support
Interventions used to assist breathing when the muscles involved in respiration are weakened. Options include non-invasive ventilation (NIV), which delivers air through a mask, and invasive ventilation, which requires a tracheostomy. The timing and type of respiratory support is discussed with the care team based on individual needs and preferences. See also: Tracheostomy.
S
Sporadic ALS/MND
ALS/MND in which only one person in a family is affected and there is no known family history of the disease. Sporadic ALS/MND accounts for approximately 90% of cases. A genetic change may still be present in sporadic cases, even without a family history. See also: Familial ALS/MND.
T
Tracheostomy
A surgical procedure in which an opening is made in the neck to allow a breathing tube to be inserted directly into the windpipe. Tracheostomy ventilation is an option for people with ALS/MND who require long-term breathing support.
U
Upper motor neurons
Nerve cells in the brain that send signals down to the spinal cord and brainstem. Damage to upper motor neurons in ALS/MND causes stiffness, spasticity, and exaggerated reflexes. See also: Lower motor neurons.