ALS Glossary of Terms

A

• ALS (amyotrophic lateral sclerosis) A chronic and progressive motor neuron disease characterized by the degeneration of nerve cells that control voluntary muscle movement within the central nervous system. Also known as Lou Gehrig’s disease.

• Assay A laboratory test used to determine the presence, and/or measure the quantity or activity of a specific substance.

• Atrophy The progressive loss of muscle mass, or wasting of the muscle tissue. In ALS, muscle atrophy occurs due to the degeneration of the nerves connecting to the muscle.

• Axon The projection of a nerve cell, or neuron, that acts as the main communication lines of the nervous system by conducting electrical impulses to other neurons or different cells. 

B

• Biomarkers Biomarkers are biological characteristics that can be used to predict or measure the progression of disease or response to treatment. An example is “serum cholesterol,” which is a biomarker for risk of cardiovascular disease and cerebrovascular disease. Biomarkers can be classified into several types: diagnostic, therapeutic, and prognostic. A diagnostic biomarker is a biological measure that is useful in diagnosing a specific condition. A therapeutic biomarker predicts response to a treatment. Prognostic biomarkers provide insight into the future outlook of one’s conditions with a particular disease.

• Bulbar muscles The muscles of the face and neck that control speech, chewing and swallowing.

• Bulbar onset Bulbar onset refers to when the first symptoms of ALS appear in the face and neck region, affecting speech and swallowing.

C

• C9ORF72 The Chromosome 9 Open Reading Frame 72 (C9ORF72) gene accounts for a significant proportion of ALS, frontotemporal dementia (FTD), and ALS-FTD cases when mutated. Discovered in 2011, it accounts for 5-7% of apparently sporadic cases of ALS, 15-20% of familial FTD, and 6% of apparently sporadic FTD.

• Cerebral spinal fluid (CSF) A clear fluid that surrounds and protects the brain and spinal cord.

• Central Nervous System (CNS) The central nervous system is composed of the brain and spinal cord, and is the main information processing center of the body.

• Chromosome Chromosomes are composed of tightly packed DNA, which contain the information for the proper building and functioning in the body. Humans have 23 pairs of chromosomes.

• Clinical Trial A research study where study participants or groups of participants are assigned to one or more health-related interventions (or no intervention) to evaluate the effects on health outcomes.

• CMT Hereditary Neuropathy Charcot-Marie-Tooth (CMT) hereditary neuropathy is a group of disorders characterized by chronic motor and sensory polyneuropathy due to damage to the axons and myelin sheaths of nerves running from the arms and legs to spinal cord and brain. Symptoms include weakness and atrophy in distal muscle groups, sensory loss in hands and feet, depressed tendon reflexes, and foot deformity.

• Cutometer A device used to measure the elastic properties of skin. A small probe is lightly pressed against the skin and suction is applied, creating a vacuum that lifts and stretches the skin before releasing it. Skin displacement is then measured and recorded.

D

• Dementia A condition characterized by progressive decline in mental functioning which interferes with the ability to perform routine activities.

• Dendrite The branched projections of a neuron that receive and transmit electrical impulses from other neurons.

• Diagnosis The determination of the disease or condition that is the cause of a person’s signs and symptoms.

• Diffusion Tensor Imaging (DTI) DTI is an imaging tool that uses radio frequency waves and magnetic field-gradient pulses to track the movement of water molecules through the brain. As water molecules tend to move along the length of axons due to the myelin surrounding them, allowing for the creation of pictures of axons within the brain.

• DNA DNA (deoxyribonucleic acid) is what stores our genetic information.

• Dysarthria Impaired speech due to the weakness or stiffness in muscles used for speaking.

• Dysphagia Difficulty swallowing.

E

• Electrical Impedance Myography (EIM) EIM is a procedure used to collect information about the physical properties of muscle. The non-invasive and painless procedure involves the placement of sticky electrodes over muscles of interest, and then passing a high-frequency, low intensity current through the muscles.

• Electromyography (EMG) An EMG is used to record and measure the electrical activity of a muscle. A thin needle is inserted into the muscle, which then acts as a microphone to amplify the sound made by the muscle when it is contracted and when it is relaxed. These sounds are recorded and can be interpreted by a neurologist to learn something about the health of muscles and nerves.

• Exome Term used to describe the all the protein-encoding genes within a genome.

F

• Familial ALS Familial ALS (also known as fALS) is a term used to describe ALS that runs in a family. ALS can be defined as familial when at least two blood relatives have been affected. This form of ALS is rare, and found in only about 10% of ALS cases.

• Fasciculation Irregular and involuntary twitching of individual muscle fibers of a muscle group. Fasciculations can be benign or indicative of disease, such as ALS.

• Forced Vital Capacity (FVC) FVC is a measure of the total volume of air that is able to be expired after a deep inhalation; important information for determining breathing capacity. This measure is obtained using a spirometer, where the individual breathes in and out through a mouthpiece, finally exhaling out as much as possible as fast as possible, following a full breath in.
• Frontotemporal dementia (FTD) FTD includes a group of disorders caused by the atrophy of the frontal and temporal lobes of the brain, affecting the critical thinking, language/speech, and behavioral regions of the brain. FTD has been linked with some subtypes of ALS.

• Frontotemporal lobar degeneration (FTLD) The severe atrophy of the frontal and temporal lobes of the brain due to the accumulation of one of the following proteins: tau, TDP-43, or FUS.

• FUS Mutations in the FUS genes have been established as one of the genetic causes of ALS.

G

• Genome All the genetic material, or genes, of an organism. It includes all the information that is needed to build and maintain an organism. A copy of the entire genome lies within the nucleus of every cell in the human body.

• Genotype The genetic make-up of a cell or organism.

• Glutamate An excitatory neurotransmitter (chemical) in the central nervous system.

H

• Hereditary Spastic Paraplegia (HSP) HSP is a group of inherited disorders which are characterized by progressive weakness and spasticity, typically affecting the legs.

• Huntington’s Disease Huntington’s Disease is an inherited fatal neurodegenerative disease caused by the degeneration of nerve cells within regions of the brain. HD results in cognitive deficits, difficulties in coordinated movement, speaking and swallowing.

I

• IBMPFD IBMPFD, or Inclusion Body Myopathy with early-onset Paget disease and frontotemporal dementia, is a condition that affects the muscles, bones and brain.

• Incidence The occurrence of new cases of a condition or disease.

• Inclusion Body Myopathy IBM is a genetic degenerative disorder that is characterized by the formation of inclusions (clumps of misfolded proteins) resulting in progressive weakness of the skeletal muscles.

• Induced Pluripotent Stem (iPS) cells iPS cells are cells that are created in the lab by turning a cell samples, such as skin cells, back into stem cells. The resulting iPS cells can then be used to create other types of cells within the human body, including those related to ALS, such as motor neurons.

• Inflammation Inflammation is nonspecific response of the immune system to injury or damage of tissues in the body.

L

• Lower Motor Neurons Lower Motor Neurons are the motor neurons which connect the spinal cord to muscle fibers, transmitting the nerve impulses from the upper motor neurons out to the muscles. The result is contraction, or movement. With the loss of lower motor neuron function, the lack of transmission to the muscles causes them to weaken and eventually results in paralysis, as is seen with ALS.

• Lumbar Puncture A lumbar puncture, also known as a spinal tap, is a procedure used to collect cerebral spinal fluid (CSF) surrounding the spinal cord and brain. It is performed with the individual underdoing the procedure sitting upright and leaning forward to round their back, or lying on their side curled up in the fetal position. The area of the lower back, including skin and underlying tissues is numbed by injection of numbing medication. Under surgical sterile conditions, a needle is inserted into the lower back into the fluid-containing sac surrounding the spinal cord. This procedure is performed below the level of the spinal cord, so there is no risk for spinal cord damage.

• Lou Gehrig Lou Gehrig is a National Hall of Fame baseball player, well known for leading the New York Yankees to six World Series titles in the 1930s. He earned the name “Iron Horse of Baseball” for his strength and endurance on and off the field. Gehrig’s baseball career was cut short, after he was diagnosed with the disease in 1939. His diagnosis and “luckiest man” speech at his farewell address at Yankee Stadium brought national attention to the disease, and is why ALS is often referred to as Lou Gehrig’s Disease to this day.

M

• Magnetic Resonance Imaging (MRI) An MRI is an imaging tool used to view the inside of living things using radiofrequency waves. These radiofrequency waves create a magnetic field that ‘excites’ atoms in the living tissue being imaged. The excitation and relaxation of atoms is what is used to create a three-dimensional picture of body organs, such as the brain and spinal cord.

• Magnetic Resonance Spectroscopy (MRS) MRS is an imaging technique that is able to measure chemical signatures of specific tissues.

• Motor Neuron Motor neurons are the nerves of the central nervous system that innervate muscles to control their activity.

• Motor Neuron Disease (MND) MNDs are a group of neurodegenerative diseases that lead to muscle weakness and paralysis, as well as other symptoms including difficulty breathing, speaking, and swallowing. ALS is the most common motor neuron disease.

• Motor Unit Number Estimation (MUNE) MUNE is a procedure used to quantitate the approximate number of motor neurons within a muscle or group of muscles. It is also able to measure motor unit size, thus allowing for the monitoring of motor unit loss and the compensatory mechanism of motor unit reinnervation.

• Multiple Sclerosis (MS) MS is a degenerative disease where the myelin of the axons in the central nervous system is destroyed. Myelin surrounds axons and serves to protect and insulate nerves. Its destructions results in muscle weakness or numbness, decreased coordination, and speech and visual decline.

• Multisystem Proteinopathy (MSP) MSP is an inherited degenerative disorder that affects the muscles, bone and/or the central nervous system.

• Muscle Weakness The loss of muscle strength associated with increased fatigue, loss of coordination, and decreased motor skills.

• Mutation A permanent change in the DNA or RNA sequence due to a random event or environmental factors, such as radiation. The resulting change may be silent (have no effect) or result in disease.

N

• Nerve Conduction Studies (NCS) A test used to measure the conduction of an electrical impulse through a nerve. Electrodes are placed on the skin over a nerve, to both stimulate the nerve and record the result. Impulses are recorded by the electrodes and can help detect the presence of nerve damage or destruction.

• Neuron Neurons are nerve cells that comprise the central nervous system. They are made up of dendrites (receive incoming electrical signals), the soma (cell body), a single axon (conveys the electrical signal to other neurons).

• Neuromuscular Of or relating to, the nerves and muscles.

• Neuromuscular Junction (NMJ) The neuromuscular junction is the point of connection, or innervation, between motor neurons and skeletal muscles.

O

• Observational study Studies where participants are observed or designated outcomes are measured. No treatment or intervention is used to affect the outcomes.

• Onset The time at which a disease or condition begins, typically before symptoms are first noticed, and occurring prior to diagnosis.

P

• Parkinson’s Disease A neurodegenerative disease caused by the loss of gray matter (dopamine-producing nerve cells) within the nervous system. Symptoms include uncontrolled muscle tremors and stiffness, ambulatory and balance problems.

• Phenotype The physical characteristics of an organism.

• Primary Lateral Sclerosis (PLS) A neurodegenerative disease affecting the upper motor neurons, causing muscle spasticity and weakness, as well as speech and balance deficits.

• Progressive Muscular Atrophy (PMA) A neurodegenerative disease affecting the lower motor neurons, causing muscle wasting, fasciculations and muscle cramping, as well as potential respiratory decline.

• Pseudobulbar affect (PBA) Uncontrollable laughing or crying that is thought to be due to damage to the emotion control regions of the brain. PBA is seen in 20-50% of ALS affected individuals.

R

• Rilutek ® [Generic Name: Riluzole] Rilutek is currently the only FDA-approved drug available for the treatment of ALS. It works by inhibiting the release of glutamate, and has been found to increase the life expectancy of patients of an average of 3 months.

S

• Slow Vital Capacity (SVC) SVC is the measure of the total amount of air an individual can exhale slowly with minimum effort, following a deep inhalation. This information is used to monitor breathing capacity.

• Sniff Nasal Inspiratory Pressure (SNIP) The SNIP test measures diaphragm strength. A small probe is inserted into the entrance of one nostril, and the individual is asked to sniff 10 to 15 times.

• Spasticity The feeling of stiffness or tightness of the muscles due to involuntary muscle spasms or sustained muscle contraction.

• Spinal cord Part of the central nervous system that runs from the brain stem at the base of the skull and down the spinal column in the vertebrae. The spinal cord carries signals from the brain to the body, and relays information from the body back to the brain.

• Spirometer A machine use to perform respiratory function tests, such as vital capacity.

• Sporadic ALS A diagnosis of ALS where there is no history of other family members having had ALS (or frontotemporal dementia).

• Stem Cells Unspecialized cells that are able to differentiate into the many different types of specialized cells found within the body, such as a nerve cell or liver cell. They usually differentiate when subjected to appropriate conditions, or biochemical stimulus.

• Superoxide dismutase 1 (SOD1) Superoxide dismutase is an enzyme that destroys superoxide, a highly reactive form of oxygen. Mutations in the SOD1 gene have been found to be responsible for over 20% of familial ALS cases.

• Synapse The small connective spaces between neurons, or a neuron and another type of cell, through which information travels in the form of electrical impulses.

T

• TDP-43 Mutations in the TDP-43 gene have been established as one of the genetic causes of ALS.

• Tremor An involuntary shaking or trembling of one or more parts of the body, such as the hands, arms, head, trunk, and legs. Tremors are usually seen in middle-aged or elderly populations; however they can be a symptom of some neurological disorders including Parkinson’s Disease.

U

• Upper Motor Neurons Neurons originating from the motor cortex of the brain and running through the spinal cord.

V

• Valosin-containing protein (VCP) Mutations in the VCP gene have been established as one of the genetic causes of ALS.

W

• Whole Exome Sequencing (WEG) A new technique used to rapidly identify rare variants in the protein-coding portion of the genome.

• Whole Genome Sequencing (WGS) Complete sequencing of the entire DNA make-up of an organism.