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Terms from A to Z
ALS (amyotrophic lateral sclerosis)

Also known as Lou Gehrig's disease, ALS is a progressive neurodegenerative disease that affects the motor neurons in the brain (upper motor neurons) and spinal cord (lower motor neurons) which control the movement of muscles. The disorder causes muscle weakness, atrophy, and ultimately paralysis. Other symptoms could include fatigue, thick or slurred speech, and difficulty breathing and/or swallowing. Life expectancy is estimated at two to five years after diagnosis. There are two main forms of ALS, sporadic (sALS) and familial (fALS). Genetic testing can determine the presence of the genes currently known to cause fALS. There is no known cure.

ALS Research Collaborative (ARC)

Launched in 2023, ALS TDI’s ALS Research Collaborative (ARC) is an ambitious global initiative developed to better understand the underlying biology of ALS and significantly accelerate the discovery of treatments. The ARC study gathers extensive natural history data from people with ALS and then layers this with data that measures their underlying biological processes – providing a full picture of the various factors that can play a role in ALS onset and progression. 

ARC participants from around the world continue to contribute data on movement, lifestyle, medical history, genetics, biomarkers, voice recordings, and patient cell biology to the program. These data are utilized to inform research at ALS TDI and shared with the wider ALS research community through the ARC Data Commons.

ALS Research Collaborative (ARC) Data Commons

ARC Data Commons grants researchers access to over eight years of de-identified natural history data contributed by people with ALS – affording an unprecedented level of insight into this complex disease. Through the ARC Data Commons, researchers can begin to ask more targeted questions about the connections between ALS symptoms, genetics, and disease biology. By providing a large, ever-expanding dataset, and powerful tools to filter and visualize the data, the ARC Data Commons will enable scientists to answer these complex questions – that previously might have required months or years of research – in a matter of minutes. This database will continue to grow as people with ALS contribute more data to the ongoing ARC natural history study.


The Revised ALS Functional Rating Scale (ALSFRS-r) is a survey designed to be filled out by people with ALS, physicians and nurses caring for people with ALS, or ALS caretakers, at regular intervals. It asks the respondent about the person’s ability to complete 12 different tasks such as speaking, swallowing, handwriting, and walking. The ratings are done on a scale from zero to four – zero meaning they are incapable of accomplishing the task, and four meaning they can do it with no difficulty. These ratings are then totaled to make one overall score, from zero to 48.

Alzheimer's Disease

Alzheimer's Disease (AD) is the most common form of dementia in older people. This progressive and irreversible brain disease typically results in memory loss and confusion. Alzheimer's is a neurodegenerative disease, a group of neurological disorders which include ALS. 

amino acids
amino acids
Amino acids are the building blocks used by cells, including motor neurons, to create proteins. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked together to form a vast variety of proteins.

An antibody is a type of protein produced by the immune system to defend against harmful substances, called antigens. Antibodies can also be produced when the immune system mistakenly identifies healthy tissue as being harmful, as in the case of autoimmune disorders. These antibodies are called auto-antibodies.

An antigen is any foreign substance that triggers an immune response within the body. Antibodies are then produced, which help destroy these antigens. Examples of antigens include bacteria, viruses, and chemicals.

Antioxidants are substances that 'neutralize' toxic byproducts of respiration called free radicals, such as superoxide, which can damage healthy tissues. They can be found in fruits and vegetables, grains, nuts, and certain meats including beef, poultry, and fish. Antioxidants are suspected to be helpful in preventing a number of diseases.

An assay is a test carried out in the laboratory to determine the presence, quantity, or activity of a specific substance.
assay (bioassay)

See assay


Astrocytes are non-neuronal cells that nourish motor neurons by ensuring delivery of essential nutrients and protective factors. In people with ALS, these cells turn traitor and produce substances that kill motor neurons, fueling the progression of the disease. To learn more about the emerging role of astrocytes in ALS, click here.

Atrophy is the progressive wasting or loss of muscle tissue. There are two main types of atrophy; disuse atrophy, which occurs due to inactivity and/or a lack of exercise, and neurogenic atrophy, which is caused by an injury or disease of the nerves that connect to the muscle. Neurogenic atrophy occurs during the later stages of ALS.
autoimmune disease

An autoimmune disease is a condition in which the immune system mistakenly attacks and destroys the body's tissues. Autoimmune diseases include lupus and multiple sclerosis. The causes of autoimmune diseases are currently unknown.

Automatic Positive Airway Pressure (APAP)

A form of non-invasive mechanical ventilation which uses algorithms to sense changes in breathing and adjusts itself to provide the ideal pressure to the user.


Autophagy is the process by which cells dispose of protein aggregates and worn out cellular components. In people with ALS, these intracellular garbage disposals are thought to malfunction - enabling misfolded proteins to accumulate, contributing to the disease.

Average Volume Assured Pressure Support (AVAP)

A newer feature on a BiPAP machine. It measures the amount of air that a patient inhales (their tidal volume) over several breaths and then calculates and supplies the amount of pressure needed to reach optimum tidal volume.

The axon is the long, slender projection of a nerve cell, or neuron. Axons act as the primary transmission lines of the nervous system, conducting electrical impulses to nearby neurons or other cells. In people with ALS, the neuromuscular junctions crumble and motor neuronal axons degenerate, resulting in muscle weakness and paralysis.
Brain-Derived Neurotrophic Factor, or BDNF, is a type of growth factor produced in the brain. This substance supports the survival of existing neurons and encourages the growth and differentiation of new neurons.
Bilevel Positive Airway Pressure (BiPAP)

A BiPAP machine is similar to a CPAP machine in that it provides airflow to help a patient breathe. A BiPAP machine has two pressure settings: one is the pressure for inhalation (ipap) and the other a lower pressure for exhalation (epap). This dual setting allows a patient to get more air into and out of their lungs. It is usually provided through a nasal mask that seals around the nose to maintain the pressure level. 


A biomarker is a substance that can be used to diagnose or monitor disease. Currently, there is no biomarker available to diagnose or monitor ALS. To learn about efforts to identify biomarkers for ALS, click here.

blood brain barrier

The blood-brain barrier, or BBB, fortifies the walls of blood vessels to prevent the entry of certain toxic substances into the brain. The BBB can be a considerable challenge to ALS drug developers because these cellular walls have been shown to kick drugs, including riluzole, out of the brain.

bulbar onset

This refers to the type of ALS where initial symptoms appear in the face and neck, such as difficulty swallowing or forming words. 


About one of 10 cases of ALS appear to be linked to repeat sequences embedded in the C9orf72 gene, the most common form of ALS identified to date. How these repeat sequences contribute to ALS remains hotly debated and is the topic of intense research. An emerging therapy targeting these repeat sequences is currently at the preclinical stage. To learn more about C9orf72 and ALS, click here.

central nervous system (CNS)
The central nervous system (CNS) serves as the main information processing center of the body. The CNS consists of the brain and spinal cord.
The cerebellum is a region of the brain located at the back of the brain that is critical in adjusting, coordinating, and fine-tuning the movement of muscles.
cerebral cortex

The cerebral cortex is a thick layer of tissue covering the outer layer (cerebrum) of the brain. Referred to as "grey matter," much of the information processing of the brain takes place here. The cerebral cortex is critical in memory, attention, thought, language, awareness, and consciousness. Dementia occurs due to the degeneration of the cerebral cortex.

cerebral spinal fluid (CSF)

Cerebral spinal fluid, or CSF, is a clear, watery fluid which surrounds and shields the brain and spinal cord. CSF acts like a cushion protecting the brain and spine from injury.

clinical onset

Clinical onset refers to the time at which signs or symptoms of a disease first appear.

Clinical Trial

There are many different forms of clinical research, including clinical trials. In ALS, there is clinical research or trials occurring globally, including biomarker research efforts, treatment or “intervention” based clinical trials, and others. Intervention-based clinical trials evaluate the benefits and risks of experimental medicines for diseases. These studies involve testing potential treatments in people according to specifically designed experimental plans known as protocols. Clinical trials follow four basic phases; Phase I, Phase II, Phase III and Phase IV. Each phase provides more information about the safety, tolerability, and potential efficacy of the treatment being tested. You can find more information about clinical trials recruiting near you by visiting the Clinical Trial Database.

Clinical Trial, Phase I

A phase I clinical trial determines whether a treatment is safe and tolerable in people. Phase I studies are typically small in scale, several months in length, and used to understand how a treatment interacts with the human body. Preliminary information about how to administer the treatment, including dosing, is gathered and then used to inform the design of Phase II.

Clinical Trial, Phase II

A phase II clinical trial determines whether a treatment is safe, tolerable, and potentially effective in people with ALS. Phase II studies inform researchers (also called clinicians) about side effects, dosages, and initial indications about the efficacy of the treatment. Generally, Phase II studies can take up to 2 years to complete and often include several hundred participants. However, these trials aren’t large enough to determine definitively whether or not a treatment will be beneficial.

Clinical Trial, Phase III

A phase III clinical trial evaluates the potential efficacy of a treatment for people with ALS. Information is also gathered on long-term use and side effects. It is not uncommon for a phase III clinical trial in ALS to enroll upwards of 1000 participants and take several years to complete. The results from Phase III studies are used by the FDA to make a decision on the approval of a treatment for the public.

Clinical Trial, Phase IV

A phase IV clinical trial in ALS takes place after the treatment or intervention has been approved as safe for the general public by the FDA. Currently, the majority of clinical trials in ALS are in Phase II or Phase III. You can find more information about trials near you by visiting the Clinical Trial Database.


Ciliary Neurotrophic Factor, or CNTF, promotes the regeneration of neuronal axons and dendrites and the production of neurotransmitters. CNTF may also contribute to the reduction of tissue destruction during inflammatory attacks.

Continuous Positive Airway Pressure (CPAP)

A CPAP machine provides a constant airflow holding the airway open to allow uninterrupted breathing. It is usually provided through a nasal mask that seals around the nose to maintain the pressure level.


An excessive tightening (shortening) of muscles that results in reduced flexibility and immobility of the joints. In people with ALS, range-of-motion exercises are recommended to prevent the formation of contractures.

cord blood
Cord blood is the blood that remains in the umbilical cord after birth. Cord blood is rich in blood-forming stems cells, similar to those found in bone marrow. Cord blood stem cells are currently being explored as a treatment for a number of diseases including ALS.
definite ALS

If loss of upper and lower motor neurons is detected in three or more regions of the body, the disease is diagnosed as definite ALS.

The progressive decline in cognitive function due to damage or disease in the brain. Memory, attention, language, and problem solving ability may be impaired. Dementia can also result in confusion. Dementia occurs due to the degeneration of the cortex of the brain. Some people with ALS also experience dementia.
Dendrites are branched projections of a neuron that receive and transmit electrical impluses from other neurons.
diaphragm pacer
diaphragm pacer

A diaphragm or phrenic pacer is thought to boost the stamina of the respiratory muscles in people with ALS by electrically stimulating the phrenic nerve, the motor nerve that controls the movement of the diaphragm. FDA-approved in 2011, the NeuRX DPS diaphragm pacer is sometimes prescribed to patients which experience frequent trouble breathing (chronic hypoventilation). To learn more about the diaphragm pacer and how the device might help people with ALS, click here.

Drug Development Process

There are five stages involved in getting treatments to patients: (1) drug discovery or basic research, (2) preclinical research, (3) clinical research or clinical trials, (4) FDA approval, and (5) clinic. ALS TDI is predominantly a preclinical research institute, with the goal to discover and develop effective treatments for people with ALS today.

Dysphagia is defined as difficulty in swallowing. Dysphagia occurs due to the weakening of the throat muscles. In people with ALS, dysphagia often occurs in the late-stage of disease.
efficacy or efficacy study

If a drug or other treatment shows the potential to be of benefit in a preclinical study or clinical trial, it is referred to as effective. If this is a primary outcome of the study, it is often referred to as an efficacy study. At ALS TDI, we use efficacy studies in our preclinical research efforts to help determine if a potential treatment is a candidate for clinical development in ALS.

electrical impedance myography (EIM)

EIM is a non-invasive diagnostic tool used for muscle evaluation. By applying alternating low-intensity electrial currents to a muscle or group of muscles, doctors are able to detect abnormalities within the muscle fibers and membranes that indicate muscle health. 

electromyography (EMG)

An EMG checks whether muscles are healthy and functioning properly by measuring the electrical activity produced by them. Clinicians typically use EMG to help diagnose ALS and to monitor muscle function over the course of the disease.


Electrophysiology is concerned with the electrical properties of cells and tissues. It includes measurements of the electrical activity of neurons and  action potential activity. An electrodiagnostic study in ALS involves both peripheral nerve conduction studies (NCS) and needle electromyography (EMG) to both exclude other diseases and to gather evidence for a definite ALS diagnosis. 


A collection of chemical tags that indicate which genes are turned on and off in the genome in our tissues. Changes in the epigenome are implicated in ALS. To learn about how scientists hope to restore the epigenome in people with ALS, click here.

executive dysfunction

About 1 out of 2 people with ALS have deficits in executive function. This is referred to as executive dysfunction. This includes difficulties planning, organizing, making decisions and time management.

familial ALS

Familial ALS is the inherited form of the disease. Approximately 15% of all cases of ALS are believed to be familial, triggered by mutations in ALS-associated genes. Genetic testing can determine if this gene is present and the likelihood of it triggering ALS.


A localized, uncontrolled, uncoordinated involuntary twitching of a single muscle group. Fasciculations could be benign or indicative of disease. Fasciculations are often described as one of the first symptoms of ALS.

forced vital capacity (FVC)

Forced vital capacity, abbreviated FVC, is a measurement of how much air a person can expel as fast as possible after deep inhalation. This test involves breathing into a mouthpiece of a spirometer. In ALS, the FVC helps doctors monitor breathing capacity.

frontotemporal dementia

Also called frontotemporal lobular degeneration (FTLD), frontotemporal dementia (FTD) is a term that refers to a number of disorders which occur due to shrinkage of the frontal and temporal lobes of the brain. Symptoms include executive dysfunction (difficulties in critical thinking and problem solving), language/speech deficits and behavioral problems. Certain people with ALS also have FTD. To learn more about ALS-FTD, click here.

A transcription factor that helps to appropriately produce thousands of proteins in tissues throughout the body. In most people with ALS, FUS accumulates in the cytoplasm of motor neurons in the brain and spinal cord, possibly contributing to the disease.
GDNF (Glial Derived Neurotrophic Factor)
GDNF (Glial Derived Neurotrophic Factor)

GDNF is a substance that promotes the survival of many types of neurons, including motor neurons. Researchers at Brainstorm Therapeutics are developing a treatment for ALS in which patient-derived adult stem cells obtained from the bone marrow are engineered to produce GDNF and re-introduced in hopes of preventing further deterioration of the motor nerves.

Gehrig, Lou
Gehrig, Lou

Henry Louis "Lou" Gehrig (1903-1941) was an American baseball player in the 1920s and 1930s who set several Major League records. He was popularly called "The Iron Horse" for his durability. His record for most career grand slam home runs (23) still stands today. Lou Gehrig was voted the greatest first baseman of all time by the Baseball Writers' Association. A native of New York City, Lou Gehrig played for the New York Yankees until his career was cut short by Amyotrophic Lateral Sclerosis (ALS), often referred to in the United States as Lou Gehrig's disease.

gene chip
gene chip

A gene chip (also called DNA microarray) is a glass slide encased in plastic which contains short sequences that can be used to identify the presence of genetic changes or dysregulated genes associated with disease. Gene chips can be used to monitor hundreds of thousands of genes simultaneously.

gene therapy

Gene therapy refers to the insertion of genes into an individual's cells and tissues to treat a disease. Gene therapy strategies being developed for ALS include the introduction of neurotrophins, substances which protect exisiting motor neurons and/or encourage axonal regeneration.


Glial cells (also known as glia or neuro glia) are non-neuronal cells in the central nervous system and the peripheral nervous system. They surround neurons and provide support for and insulation between them. Types of glial cells include astrocytes, oligodendrocytes and microglia.


Glutamate is an amino acid which plays an essential role in human metabolism. Glutamate is also a primary excitatory neurotransmitter in the central nervous system. High levels of glutamate are implicated in a wide variety of neurological diseases including ALS.

glutamate-induced excitotoxicity

High levels of the neurotransmitter glutamate can trigger the death of nerve cells in the brain and spinal cord. Called glutamate-induced excitotoxicity, this process has been implicated in a number of neurodegenerative diseases including ALS.

growth factor
A naturally occurring substance that stimulates the growth, proliferation and/or differentiation of cells.
Huntington's Disease

Huntington's Disease is an inherited disease that causes nerve cells in certain regions of the brain to waste away. The disease is inherently variable. Symptoms include cognitive deficits and difficulties in coordinating and controlling movement, speaking and swallowing. Genetic testing can determine whether the gene is present and is likely to result in the disease. Huntington's is a neurodegenerative disease, a group of neurological disorders which include ALS.

immune system

The immune system defends the body against germs and microorganisms. With a growing understanding that the immune system contributes to ALS, immunomodulation-based strategies may be promising therapeutic avenues to pursue in treating the disease.


Immunosuppressants are substances that act to reduce the activation or efficacy of the immune system. Immunosuppressants are often prescribed to people who undergo whole organ transplants. ALS researchers are evaluating immunosuppressants (in part) to prevent rejection of transplanted stem cells, as a potential therapy for the disease.

in vitro

This method uses proteins or living cells to confirm and/or assess the benefit of potential ALS drugs. Scientists in ALS will often conduct these types of studies before testing them in more costly in vivo or animal studies.

in vivo

This preclinical method uses animal models of disease to discover, develop, and evaluate the safety of potential medicines. This is also referred to as animal studies. ALS TDI is internationally recognized for our work in creating and using new animal models of neurodegeneration to validate whether or not a potential treatment should go to clinical trial in humans.


Incidence refers to the occurrence of new cases of a condition. Incidence is commonly measured in new cases per 1,000 (or 100,000) of population at risk, per year. The incidence of ALS typically varies between 1 and 4 diagnoses per 100,000 per year in the U.S.


Inclusions refer to clumps of misfolded proteins. Scientists suspect that the buildup of inclusions, particularly in motor neurons, contributes to ALS.

induced pluripotent stem (iPS) cells

Created typically in the laboratory by turning back the clock in skin cells, iPS cells can be used to generate many cell types including motor neurons and astrocytes. To learn more about how scientists hope to use iPS cells to discover underlying causes of ALS and new drugs for the disease, click here.


Inflammation is a protective response which occurs due to injury or damage of tissues. In people with ALS, microglia and astrocytes become activated producing inflammatory substances which further deteriorate the motor nerves, fueling the progression of the disease.


Intramuscular injection (IM), is the injection of a substance into muscle. 


Intrathecal delivery refers to the route of administration in which the drug is directly introduced into the brain or spinal cord. Certain emerging ALS medicines are being developed intrathecally due to their inability to otherwise penetrate the blood brain barrier.

Refers to the type of ALS where initial symptoms appear in the limbs. It is the most common form of ALS, the other type being bulbar-onset.
lower motor neuron

The motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles. In ALS, the motor neurons degenerate or die, ceasing to send messages to muscles. Unable to function, the muscles gradually weaken resulting in paralysis.

lumbar puncture
See spinal tap.

A type of white blood cell that ingests (takes in) foreign material in a process called phagocytosis. Macrophages are key players in the immune response to foreign invaders such as infectious microorganisms and viruses.

magnetic resonance imaging (MRI)

MRI is a medical imaging technique used to visualize the integrity of specific structures and tissues in the body. It has much greater soft tissue contrast than computed tomography (CT) making it especially useful in neurological, musculoskeletal, cardiovascular, and oncological imaging. Scientists hope to use MRI to diagnose ALS more quickly. To learn more, click here.

magnetic resonance spectroscopy (MRS)

An MRI-based technique that neurologists use to quantitate chemical changes that occur in specific tissues due to injury or disease. Neurologists are currently evaluating this non-invasive technique as a means to diagnose and monitor ALS. To learn more, click here.

maximum voluntary ventilation (MVV)

A measure of respiratory function. Maximum voluntary ventilation (MVV) is a measurement of how much air a person can expel during 12-15 seconds of deep and rapid breathing. This test involves breathing into a mouthpiece of a spirometer. In ALS, the MVV helps doctors monitor disease progression in patients.

Mesenchymal stem cells (MSCs)

Mesenchymal stem cells (MSCs) are multipotent bone marrow derived cells that can terminally differentiate into osteocytes (bone), myocytes (muscle), adipocytes (fat), and chondrocytes (cartilage). 


Microglia are the watchdogs of the brain and spinal cord which keep the central nervous system free from infection. But in people with ALS, these cells enter "neurotoxic mode" and become key instigators of inflammation. To learn more about microglia and how to combat them in ALS, click here.


A short RNA that reduces the production of substances by either blocking its expression or synthesis.

misfolded protein

A protein that is improperly assembled when produced. Internal quality control mechanisms usually remove them but in people with ALS these misfolded proteins accumulate, contributing to the disease.


Mitochondria are the power plants of cells supplying the energy to meet the body's needs. In people with ALS, these power plants malfunction in motor neurons, contributing to neurodegeneration and disease. To learn more about the role of mitochondria in ALS, click here.

motor endplate

The region of the motor neuron that transmits electrical signals to the muscle fiber. 

motor nerves

A nerve is an enclosed, cable-like bundle of fibers that use electrical and chemical signals to transmit sensory and motor information from one body part to another.

motor neuron

Motor neurons are located in the central nervous system (CNS) and project their axons outside the central nervous system to control muscles. In ALS, motor neurons degenerate or die, ceasing to send messages to muscles. Unable to function, the muscles gradually weaken, resulting in paralysis.

motor neuron disease (MND)

Motor neuron diseases (MNDs) are a group of progressive neurological disorders that result in muscle weakness and paralysis. Other symptoms include difficulty breathing, speaking and swallowing. ALS is the most common motor neuron disease and is often referred to as MND outside of the U.S.

multiple sclerosis (MS)

A chronic degenerative disease of the central nervous system in which the body "eats away" myelin, the protective sheath that surrounds and insulates the nerves in the brain and spinal cord. Symptoms include muscular numbness or weakness, fatigue and visual deficits or loss. People with MS are often diagnosed at 20 to 40 years of age. MS is thought to be an auto-immune disease.


A permanent change in the sequence of a gene. Mutations in nearly 20 genes have been linked to ALS.


Of, relating to, or affecting both nerves and muscles.

neuromuscular junction (NMJ)

Specialized connections between the motor nerves and skeletal muscles. In people with ALS, these connections deteriorate leading to muscle weakness and paralysis. To learn more about how scientists hope to strengthen neuromuscular junctions in people with ALS, click here.


This term refers to mechanisms within the nervous system which protect neurons from degeneration following a brain or spinal cord injury or as the result of neurodegenerative disease. Scientists are developing treatment strategies to boost these mechanisms either by introducing specific neuroprotective substances or cells that produce them. To learn more click here.


Astrocytes and microglia that produce susbtances that kill motor neurons are referred to as being in the "neurotoxic" mode. In people with ALS, neurotoxic astrocytes and microglia are key instigators of inflammation that fuel the progression of the disease. To learn more about neuroprotective strategies scientists are developing to shield motor neurons from this neurotoxic onslaught in people with ALS, click here.


Neurotransmitters are substances used by the brain and spinal cord to communicate. These chemicals relay, amplify, and modulate signals between neurons or a neuron and another cell. These chemicals are released by the transmitting neuron into the synapse and actually bind receptors onto the receiving neuron's nerve terminal.


See diaphragm pacer

noninvasive ventilation (NIV)

A machine that supports breathing by delivering oxygen through the nose through a face mask. NIV is routinely recommended for people with ALS that have trouble breathing and/or sleeping. See also: CPAPBiPAPAPAP, AVAP


These myelin-producing cells might help ensure/maintain energy flow in motor neurons by supplying key energy-rich metabolites to mitochondria located in axons. Reductions in metabolite-delivering oligodendrocyte populations are implicated in ALS. To learn more about the emerging role of oligodendrocytes in ALS, click here.

oxidative stress

Oxidative stress occurs due to an imbalance between the production of reactive oxygen species (ROS) and the ability to detoxify them, resulting in damage. ROS damage components of the cells' membranes, proteins or genetic material by "oxidizing" them. Numerous studies have found evidence of increased oxidative stress in ALS pathogenesis.

Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative brain disease that results in shaking (tremors) and muscle stiffness. Other symptoms include trouble walking or maintaining balance. The disease is thought to occur due to loss of dopamine-producing neurons in the brain.

pharmacokinetics/pharmacodynamics (PK/PD)

Pharmacokinetics (PK) is a branch of pharmacology which studies the fate of substances administered to a living organism. These substances include drugs, hormones, nutrients, and toxins. Pharmacokinetics includes the study of the mechanisms of absorption, distribution metabolism, and the excretion of these substances.


A phenotype refers to everything observable about a living organism. ALS is often a described as a disease with variable phenotypes because the symptoms of the disease can differ between individual patients.

phrenic pacer

See diaphragm pacer

possible ALS

If loss of both upper and lower motor neurons is detected in one region of the body, the disease is often diagnosed as possible ALS.

Post hoc analysis

 A post hoc analysis involves taking an additional look at the data from a study after that study has been completed. 

Precision Medicine Program (PMP)

The PMP was an ALS natural history study that was created by ALS TDI and began collecting data from people with ALS in 2014. Through the PMP, researchers at ALS TDI have partnered with people with ALS to gather data to learn more about this disease. Participants from around the world have contributed data on movement, lifestyle, medical history, genetics, biomarkers, voice recordings, and patient cell biology to the program. In 2023, ALS TDI launched the ALS Research Collaborative (ARC), an evolution of the PMP that allows researchers across the ALS space to access the wealth of data collected by the program. All of the PMP's data collection activities now continue as part of ARC.

preclinical research

A drug is often first identified, discovered, and developed in models of disease. This is referred to as preclinical research. These studies help researchers decide whether an experimental compound is safe and promising enough to be tested in people. This is done through in vitro cell culture studies and in vivo animal studies. ALS TDI is the world’s largest preclinical research institute for ALS, with over 10 years of experience rigorously validating drugs and other potential treatments.

Primary Lateral Sclerosis (PLS)

PLS is a rare neuromuscular disease characterized by progressive muscle weakness in the voluntary muscles. It belongs to a group of disorders known as motor neuron diseases. Onset of PLS usually occurs between 40 and 60. Symptoms include muscle stiffness, weakness and spasticity (sudden involuntary muscle spasms) and difficulties speaking and maintaining balance. The disease progresses gradually over a number of years, or even decades and is not typically fatal.

probable ALS

If loss of both upper and lower motor neurons is detected in two regions of the body, the disease is often diagnosed as probable ALS.


A forecasting of the probable course and outcome of a disease, especially of the chances of recovery.


The study of proteome, the proteins present in a given tissue. A number of ALS researchers are using proteomics in hopes of identifying biomarkers that can be used to diagnose and monitor the disease.


A protocol is a precise and detailed plan for a study. In a clinical trial, a protocol describes the therapeutic procedure, including the frequency and duration given, and how the treatment will be subsequently evaluated for safety, tolerability and efficacy.

Pseudobulbar Affect (PBA)

Uncontrollable laughing and crying. PBA occurs in about 20-50% of people with ALS. It is thought to occur due to structural damage in certain regions of the brain that control emotions.


The process of turning cells from one type to another. Skin cells from ALS patients are often "reprogrammed" or transformed into motor neurons that can be studied to uncover the underlying mechanism of the disease. To learn more about how scientists hope to use reprogramming technologies to help people with ALS, click here.

RNA interference (RNAi)

RNA interference is a naturally occurring mechanism that turns off the expression of specific genes. Many organisms utilize RNAi to target and destroy invading viruses, to regulate development, and to maintain the integrity of their genomes. Scientists hope to develop RNAi-based therapeutics to treat many diseases including ALS. ALS RNAi-based treatment strategies currently being developed include medicines that inhibit production of mutant superoxide dismutase 1 (SOD1) to lower toxic accumulation of this protein in motor neurons.

routes of administration

A route of administration is the path by which a substance such as a drug is brought into contact with the body. Such routes typically used for emerging medicines for ALS include oral (pill by mouth), intrathecal (into the centrospinal fluid in the spinal cord) and intramuscular (into the muscle) injections.

slow vital capacity (SVC)

SVC is the measurement of how much air a person can exhale slowly with minimum effort. Used in conjunction with the forced vital capacity (FVC) measurement, doctors can monitor the breathing capacity of ALS patients.

sniff nasal inspiratory pressure (SNIP)
sniff nasal inspiratory pressure (SNIP)

A measure of diaphragm strength. During the test, a person with ALS is asked to sniff 10-15 times. 30 second rest periods between measurements reduce fatigue. A probe inserted in one nostril enables the strength of the respiratory muscles to be assessed. The strongest sniff (nasal inspiratory pressure) is recorded.

spinal cord
spinal cord

The spinal cord is the part of the central nervous system that extends from the base of the skull through the lower back. It is continuous with the brain stem and encased in a triple sheath of membranes. The spinal cord is typically 15 to 17 inches long and contains 33 vertebrae and 31 pairs of nerves. The spinal cord enables the brain to communicate with the rest of the body.

spinal tap
A spinal tap is a diagnostic procedure in which a needle is inserted in the lower back (lumbar) region of the spine in order to collect a sample of cerebrospinal fluid for analysis. The procedure is also known as a lumbar puncture.

A machine often used to measure breathing abilities. The progression of ALS is often monitored in part, using this device.

stem cells
Stem cells are cells that have the ability to self renew (create new stem cells) and transform into many cell types. Stem cells can come from a variety of sources including embryos, bone marrow and umbilical cord blood. Some scientists hope to introduce neural stem cells into people with ALS to create populations of cells that in some way help to protect the motor nerves from further deterioration. To learn more about how scientists hope to use stem cells to treat ALS, click here.
superoxide dismutase 1 (SOD1)
superoxide dismutase 1 (SOD1)

Superoxide dismutase (SOD) is an antioxidant enzyme that destroys DNA-damaging superoxide, a highly reactive form of oxygen. About 20% of familial cases are linked to mutations in one of three superoxide dismutases, superoxidase dismutase 1 (SOD1).


Information spreads in the brain and spinal cord through synpases, connections between neurons or a neuron and another cell. These tiny spaces span the ends of a neuron (nerve terminals) or in the case of connections between the motor nerves and muscle, the motor end plate. In people with ALS, the muscle-nerve connections called neuromuscular junctions deteriorate leading to muscle weakness and paralysis.


A transcription factor that helps to appropriately produce thousands of proteins in tissues throughout the body. In most people with ALS, TDP-43 accumulates in the cytoplasm of motor neurons in the brain and spinal cord, possibly contributing to the disease. To learn more about TDP-43 and its possible role in ALS, click here.

therapeutic index
The therapeutic index is the ratio of the dosage of a therapeutic agent required for efficacy to that which results in toxicity. Drug developers strive to create medicines which have a high therapeutic index to maximize therapeutic benefits while minimizing risks.

A therapy is the treatment of a disease or disorder that alleviates symptoms or reduces the severity of a disease. The terms therapy and treatment are used interchangeably. Currently, there is no cure for ALS. The mission of ALS TDI is to discover and develop effective treatments for ALS as soon as possible.


Transcriptome refers to the entire collection of genes expressed (mRNAs) in a group of cells or tissues at a given moment. The analysis of the transcriptome (also known as molecular profiling) using gene chips can provide insight into underlying molecular mechanisms including diseases. In ALS, researchers are using transcriptomics to identify pathways that can be targeted to treat the disease.


A mouse in which genetic information from another species has been inserted into its genome. Scientists frequently use transgenic mice containing human ALS associated mutant genes to investigate the underlying cause and develop new treatments for the disease.

translational medicine

Translational medicine is a branch of medical research that brings benchtop scientific discoveries to the bedside.


A tremor is an unintentional shaking or trembling in one of more parts of the body. A tremor can affect the hands, arms, head, face, vocal cords, trunk and legs. Tremors occur most often in middle-aged or older people. In some people, tremors are a symptom of neurological disorders such as Parkison's Disease.

upper motor neuron
upper motor neuron

Upper motor neurons (UMNs) originate in the motor cortex of the brain. Upper motor neurons enable certain movements including walking and chewing food.


This is the process of establishing that a potential treatment is capable of producing a consistent, reproducible benefit in preclinical studies. Validation of a potential treatment gives it credibility to be considered for clinical development. In its history, ALS TDI has screened more than 400 compounds, with many in validation studies in an attempt to reproduce the results of another study.


A vector is a delivery vehicle used in gene therapy-based treatment strategies to introduce therapeutic genes into diseased tissues. In ALS, these therapeutic genes encode typically neuroprotective substances such as VEGF. Vectors are typically disabled non-infectious adenoviruses or retroviruses.

ALS Therapy Development Institute compiled this glossary from the following sources:
ALS TDI thanks the above sources for the use of their terms.