Amyotrophic Lateral Sclerosis (ALS), commonly known as Lou Gehrig's disease, is a progressive neuromuscular disease. ALS is characterized by a progressive degeneration of motor nerve cells in the brain (upper motor neurons) and spinal cord (lower motor neurons). When the motor neurons can no longer send impulses to the muscles, the muscles begin to waste away (atrophy), causing increased muscle weakness. ALS does not impair a person's intellectual reasoning, vision, hearing or sense of taste, smell and touch. In most cases, ALS does not affect a person's sexual, bowel or bladder functions.
ALS is often referred to as a syndrome because the disease becomes apparent in various patterns. ALS occurs rarely and spontaneously. Currently, there is no cure for amyotrophic lateral sclerosis.
- Most people who develop ALS are between the ages of 40 and 70, although the disease can occur at a younger age.
- It occurs throughout the world with no racial, ethnic or socioeconomic boundaries.
- It affects as many as 30,000 in the United States, with 5,000 new cases diagnosed each year.
- Estimates suggest that ALS is responsible for as many as five of every 100,000 deaths in people aged 20 or older.
- ALS is most common among persons over age 60.
- The incidence of ALS is five times higher than Huntington's disease and about equal to multiple sclerosis.
Many ALS patients can live longer and more productive lives because of current research into the cause, prevention and cure for the disease. Improvements in medical management, including nutrition and breathing, regularly increase patient survival. Fifty percent of affected patients live at least three or more years after diagnosis; 20 percent live five years or more; and up to 10 percent will survive more than ten years.
Causes of ALS
ALS is a somewhat diverse and decidedly mystifying disease. In more than nine out of every 10 cases diagnosed, no clear identifying cause of the disease is apparent, that is, patients lack an obvious genetic history, complete with affected family members. Also, nothing about the way patients live their lives gives scientists and clinicians clues as to what causes ALS. Nothing in patients’ diet, where they’ve lived, how they’ve lived or what they’ve done with their lives can easily explain why they’ve developed this late onset, fully developed and progressive disease.
However, in about 5 percent of cases, a clear genetic history exists. The disease is classed as autosomal dominant in these patients; that is, that almost half of all family members show a clear history of ALS. Studies in the early 1990s on the genetic form of the disease, including work by one of our scientific advisors, Dr. Robert Brown, revealed that a single gene defect could account for a portion of these familial cases.
Mutations in the gene for the enzymes superoxide dismutase 1 (SOD1) or copper zinc superoxide dismutase have been found in approximately 15-20 percent of the familial cases of ALS. Some quick math shows, then, that approximately 1 to 2 percent of all cases of ALS involve this particular gene mutation.
Still, for the majority of ALS cases, we do not know what causes the disease. Researchers haven’t been idle, however, and several attractive theories exist on what could cause or contribute to the death of motor neurons in ALS. Center scientists are focusing on these pathogenic theories.
What are the Symptoms of ALS?
The following are the most common symptoms of ALS. Each individual, however, may experience symptoms differently. Symptoms may include:
- twitching and cramping of muscles, especially those in the hands and feet
- loss of motor control in the hands and arms
- impaired use of the arms and legs
- weakness and fatigue
- tripping and falling
- dropping things
- uncontrollable periods of laughing or crying
- slurred or thick speech and difficulty in projecting the voice
As the disease progresses, symptoms may include:
- shortness of breath
- difficulty breathing
- difficulty swallowing
The symptoms of ALS may resemble other conditions or medical problems. Consult a physician for diagnosis.
How is ALS Diagnosed?
In addition to a complete medical history and physical examination, diagnostic procedures for ALS may include:
- laboratory tests - including blood and urine studies and thyroid functioning tests
- muscle and/or nerve biopsy
- cerebral spinal fluid analysis (spinal tap) - a procedure used to make an evaluation or diagnosis by examining the fluid withdrawn from the spinal column.
- magnetic resonance imaging (MRI) - a way to image soft tissues that's noninvasive and that doesn't involve X-rays. MRI produces a sharp, two-dimensional view of the brain and spinal cord.
- electrodiagnostic tests (i.e., electromyography (EMG) and nerve conduction velocity, or NCV) - studies that evaluate and diagnose disorders of the muscles and motor neurons. Electrodes are inserted into the muscle, or placed on the skin overlying a muscle or muscle group, and electrical activity and muscle response are recorded.
How is ALS Medically Classified?
Making a proper diagnosis in ALS is complicated because symptoms can vary in each patient. For greater accuracy, physicians have classified every known form:
Classical ALS - a progressive neurological disease characterized by a deterioration of upper and lower motor neurons (nerve cells). This type of ALS affects more than two-thirds of those with the disease.
Primary Lateral Sclerosis (PLS) - a progressive neurological disease in which the upper motor neurons (nerve cells) deteriorate. If the lower motor neurons are not affected within two years, the disease usually remains a pure upper motor neuron disease. This is the rarest form of ALS.
Progressive Bulbar Palsy (PBP) - a condition that starts with difficulties in speaking, chewing and swallowing due to lower motor neuron (nerve cell) deterioration. This disorder affects about 25% of those with ALS.
Progressive Muscular Atrophy (PMA) - a progressive neurological disease in which the lower motor neurons (nerve cells) deteriorate. If the upper motor neurons are unaffected within two years, the disease usually remains a pure lower motor neuron disease.
Familial - a progressive neurological disease that affects more than one member of the same family. This type of ALS accounts for a very small number of people with ALS in the United States (between five and ten percent).