What is ALS?

Amyotrophic Lateral Sclerosis (more commonly referred to as Lou Gehrig’s disease or ALS) is a neuromuscular disease that causes damage to the nerve cells controlling voluntary muscle movement, also known as motor neurons. It belongs to a group of diseases, known as motor neuron diseases, which affect the motor system. The motor system is a tag team of nerve cells (neurons) that carries messages from the area that controls movement in the brain to the muscle. The first nerve cell in the tag team carries the signal from the brain to the lower part of the brain (brainstem) and the spinal cord. It is referred to as the upper motor neuron (UMN) or corticospinal tract. The upper motor neuron contacts a second motor neuron referred to as the lower motor neuron (LMN) or anterior horn cell. The LMN then carries the signal to the muscle
 
ALS is characterized by damage to both the UMN and the LMN. ALS generally affects people between 55 and 75 years of age although all ages can be involved. While it is usually sporadic (not inherited), about 5-10% are familial. The prevalence (how many people have the disease at one time) rate is about 4 per 100,000 while the incidence (how many new cases occur in a time period) is about 1 per 100,000 new cases each year. Males are more commonly affected by a ratio of about 2:1.
 
The symptoms of ALS vary from one person to the next. Symptoms reflect weakness and thinning of muscles due to the involvement of the LMN as well as stiffness from the UMN involvement. Onset can begin in the muscles that are innervated by the bulbar neurons (speaking, swallowing) or in muscles innervated by nerve cells in the spinal cord causing weakness in one arm or one leg. A person newly diagnosed with ALS may trip, drop things, slur their speech, twitch, and laugh or cry uncontrollably. The person may also experience abnormal fatigue of the arms or legs and muscle cramps. Walking and activities requiring the hands may prove more difficult for a person with the disease. In 20% of ALS cases, voice and swallowing begin to decline first. Another 40% have symptoms in the arm first while the rest of people experience problems due to leg involvement. Over time the disease spreads from one area to another and gradually the people living with ALS will lose movement in muscles throughout the body, including the muscles of breathing. The average lifespan is about 36 months.
 
How is the diagnosis of ALS made?
 
The diagnosis is made by identifying damage to only the motor system, with damage to both the upper and lower motor neurons. This is done using the clinical examination and an electomyogram (EMG test). All other possible causes of that damage must be excluded and there must be progression of the weakness over time with involvement of multiple areas in the nervous system. The areas that are evaluated include the bulbar region (speech and swallowing), cervical region (arms, diaphragm), thoracic region (muscles of breathing), and the lumbar region (legs).
 
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