ALS, also known as Lou Gehrig’s disease, is a progressive neurological disorder that damages nerve cells, weakens muscles and causes disability. It leads to paralysis and death within an average of two to five years of diagnosis. ALS affects about one in 300 individuals. Without an official surveillance program anywhere in the world, it’s impossible to say if the prevalence is rising with the overall tide of neurodegenerative disease.
As with other forms of neurodegenerative disease, there is no cure for ALS, although treatments are available to help manage the condition.
Lou Gehrig, the Hall of Famer from New York Yankees, became the poster child for the disease when it forced his retirement from baseball in 1939. It took his life shortly thereafter.
Since Lou Gehrig’s death, hundreds of thousands of lives have been lost due to ALS.
The buildup of proteins in the brain and spinal cord is a hallmark of ALS. Now, researchers from the University of Cambridge in England report that familial ALS type 1-associated superoxide dismutase 1 (SOD1) can spread from neuron to neuron. Once inside these neurons, these renegade proteins can multiply and mutate, which suggests that ALS may be a prion disease, such as Creutzfeldt-Jakob disease.
The onset of ALS can be so subtle that the symptoms are overlooked but gradually these symptoms develop into more obvious weakness or atrophy. Early symptoms include:
- Muscle twitches in the arm, leg, shoulder, or tongue;
- Muscle cramps;
- Tight and stiff muscles (spasticity);
- Muscle weakness affecting an arm, a leg, the neck, or diaphragm;
- Slurred and nasal speech; and
- Difficulty chewing or swallowing.
The first sign of ALS usually appears in the hand or arm and can show as difficulty with simple tasks such as buttoning a shirt, writing, or turning a key. In other cases, symptoms initially affect one leg. People experience awkwardness when walking or running, or they may trip or stumble more often. When symptoms begin in the arms or legs, it is referred to as “limb onset” ALS, and when individuals first notice speech or swallowing problems, it is termed “bulbar onset” ALS.
As the disease progresses, muscle weakness and atrophy spread to other parts of the body. Individuals may develop problems with moving, swallowing (called dysphagia), speaking or forming words (dysarthria), and breathing (dyspnea). Although the sequence of emerging symptoms and the rate of disease progression can vary from person to person, eventually individuals will not be able to stand or walk, get in or out of bed on their own, or use their hands and arms.
Individuals with ALS usually have difficulty swallowing and chewing food, which makes it hard to eat. They also burn calories at a faster rate than most people without ALS. Due to these factors, people with ALS tend to lose weight rapidly and can become malnourished.
Because people with ALS usually can perform higher mental processes such as reasoning, remembering, understanding, and problem solving, they are aware of their progressive loss of function and may become anxious and depressed. A small percentage of individuals may experience problems with language or decision-making, and there is growing evidence that some may even develop a form of dementia over time.
Individuals with ALS eventually lose the ability to breathe on their own and must depend on a ventilator. Affected individuals also face an increased risk of pneumonia during later stages of the disease. Besides muscle cramps that may cause discomfort, some individuals with ALS may develop painful neuropathy (nerve disease or damage).
What causes ALS?
The cause of ALS is not known, and scientists do not yet know why ALS strikes some people and not others. However, scientific evidence suggests that both genetics and environment play a role in motor neuron degeneration and the development of ALS.
Gene mutations indicate there may be defects in protein recycling—a naturally occurring process in which malfunctioning proteins are broken down and used to build new working ones. Still others point to possible defects in the structure and shape of motor neurons, as well as increased susceptibility to environmental toxins. Researchers are studying the impact of environmental factors, such as exposure to toxic or infectious agents, viruses, physical trauma, diet, and behavioral and occupational factors. For example, exposure to neurotoxins, head trauma, or both could explain why some veterans and athletes appear to be at increased risk of developing ALS. Ongoing research may show that some factors are involved in the development or progression of the disease.
There is no single test that provides a definitive diagnosis of ALS. It is primarily diagnosed based on a detailed history of the symptoms observed by a physician during physical examination, along with a review of the individual’s full medical history and a series of tests to rule out other diseases. A neurologic examination at regular intervals can assess whether symptoms such as muscle weakness, muscle wasting, and spasticity are progressively getting worse.
Muscle and imaging tests:
- Electromyography (EMG) is a recording technique that detects electrical activity of muscle fibers and can help diagnose ALS.
- A nerve conduction study (NCS) measures the electrical activity of the nerves and muscles by assessing the nerve’s ability to send a signal along the nerve or to the muscle.
- Magnetic resonance imaging (MRI) is a noninvasive procedure that uses a magnetic field and radio waves to produce detailed images of the brain and spinal cord.
- Blood and urine tests may be performed based on the person’s symptoms, test results, and findings from the examination. A physician may order these tests to eliminate the possibility of other diseases.
- A muscle biopsy may be performed to determine whether a physician believes an individual has a muscle disease other than ALS. Under local anesthesia, a small sample of muscle is removed and sent to the lab for analysis.