Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is a serious neurological disease that attacks the nerve cells that control voluntary muscles. It may begin with muscle twitching or weakness in an arm or leg, or with slurring of speech. Eventually, amyotrophic lateral sclerosis affects your ability to control the muscles needed to move, speak, eat and breathe.
In the United States, amyotrophic lateral sclerosis is often called Lou Gehrig's disease, after Hall of Fame baseball player Lou Gehrig of the New York Yankees, who died of the disease in 1941.
The cause of amyotrophic lateral sclerosis remains elusive, as does any treatment that can reverse the relentless progression of the disease. Treatment of amyotrophic lateral sclerosis typically focuses on efforts to relieve symptoms and maintain quality of life in the years after diagnosis.
The basic units of your central nervous system — which includes your brain and spinal cord — are nerve cells (neurons). Each neuron consists of a cell body, a major branching fiber (axon) and numerous smaller branching fibers (dendrites). Nerve cells communicate with adjacent nerve cells at contact points called synapses. They also send and receive signals throughout your body.
Nerve signals provide information to your brain through your senses. They communicate with your involuntary muscles — the ones that control activities such as digestion, sexual function and heartbeat. Nerve signals also activate your voluntary muscles.
Amyotrophic lateral sclerosis is a disease that involves death of motor neurons — the nerve cells that control voluntary muscles. These are the muscles you use to move your limbs, face, neck and torso and to talk, chew, swallow and breathe. In ALS, both upper motor neurons, located in your brain, and lower motor neurons, located in your spinal cord, gradually die. As a result, your voluntary muscles no longer receive messages. These muscles become weak and begin to waste away (atrophy).
Researchers aren't sure what causes motor neuron deterioration, but amyotrophic lateral sclerosis appears to fall into two categories :
- Inherited (familial) ALS. Up to one in 10 cases of ALS appear to be inherited. About 20 percent of these cases result from a specific gene mutation in an enzyme known as superoxide dismutase 1 (SOD1). Scientists and researchers are still trying to identify other ALS gene mutations that may be inherited.
- Sporadic ALS. More than 90 percent of cases of ALS appear to occur randomly, with no identifiable cause and no obvious risk factors.
One possible cause of amyotrophic lateral sclerosis is excess glutamate — one of the many chemicals (neurotransmitters) that neurons use to send signals to one another. People with ALS appear to have too much glutamate in their nervous systems, which can cause neurons to die.
Researchers are studying other factors that may contribute to amyotrophic lateral sclerosis, including viruses, immune system abnormalities, environmental toxins, cell suicide (apoptosis), defects in the energy-producing parts of a cell (mitochondria) and the buildup of certain proteins known as neurofilaments. Some researchers believe that a combination of more than one factor may trigger ALS.
Risk Factor :
Although most cases of amyotrophic lateral sclerosis have no apparent cause, a small percentage of people who have ALS inherit it. Inherited ALS may strike at a younger age and will affect consecutive generations. If you're the first person in your family to have amyotrophic lateral sclerosis, you likely don't have an inherited form, and your children aren't at a greater risk.
Noninherited ALS often develops between ages 40 and 60, although the disease affects people of all ages. ALS affects more men than women.
When to seek medical advice :
If you've noticed weakness in one of your limbs or twitching and cramping in your muscles, see your doctor to determine if there may be a neurological cause such as amyotrophic lateral sclerosis. Although there's no treatment to reverse the course of ALS, other neurological conditions that may mimic some of the signs and symptoms of ALS are treatable.
It's easy to ignore the early, sometimes subtle signs of amyotrophic lateral sclerosis. In fact, it takes about a year before most people are diagnosed with ALS. But the sooner you see your doctor, the sooner a diagnosis and treatment decisions can be made.
Signs of amyotrophic lateral sclerosis are typically subtle at first. The disease commonly begins in one part of the body and progresses to other areas. Gradual death of nerve cells saps muscles of their control. Early signs and symptoms of ALS include :
- Difficulty lifting the front part of your foot (footdrop)
- Weakness in your leg, feet or ankles
- Hand weakness or clumsiness
- Slurring of speech or trouble swallowing
- Muscle cramps and twitching in your arms, shoulders and tongue
- Fatigue in combination with the above signs and symptoms
The disease frequently begins in your hands, feet or limbs, and then spreads to other parts of your body. It eventually affects chewing, swallowing, speaking and breathing — which are known as bulbar functions after the bulb-shaped part of the brainstem that houses nerve cells controlling these functions. Less commonly, ALS begins with these bulbar symptoms. As the disease advances, your muscles become progressively weaker until they're paralyzed.
Eventually, amyotrophic lateral sclerosis paralyzes the muscles needed to breathe. Most people with ALS die of respiratory failure, usually within three to five years after symptoms begin. Sometimes, people with amyotrophic lateral sclerosis develop pneumonia because they can't swallow and they inhale (aspirate) food and oral secretions into their lungs.
ALS usually leaves intellect intact and spares the senses of sight, hearing, smell, taste and touch. It doesn't affect involuntary muscles, such as the muscles that control heartbeat and bladder and bowel function.
Amyotrophic lateral sclerosis is difficult to diagnose early because it may appear similar to other neurological diseases. Your doctor may refer you to a doctor who specializes in brain and nervous system disorders (neurologist).
Diagnosing amyotrophic lateral sclerosis first involves reviewing your family's medical history and your signs and symptoms. You'll then have a physical examination that may include some basic in-office testing of your nerves and muscles. Additionally, you'll undergo a variety of tests, including tests to rule out other conditions. These diagnostic tests may include :
- Electromyogram (EMG). Electromyography measures the tiny electrical discharges produced in muscles. A thin-needle electrode is inserted into the muscles that your doctor wants to study. An instrument records the electrical activity in your muscle as you rest and contract the muscle.
- Nerve conduction study (NCS). As a part of an electromyography study, two electrodes are taped to your skin above a nerve or muscle to be studied. A small shock is passed through the nerve to measure the size and speed of nerve signals.
- Imaging. Your doctor may suggest magnetic resonance imaging (MRI) or a computerized tomography (CT) scan to produce images of your brain and spinal cord. These tests can help your doctor determine if something other than ALS may be causing your signs and symptoms.
- Spinal tap (lumbar puncture). This test analyzes the fluid surrounding your brain and spinal cord (cerebrospinal fluid). You typically lie on your side with your knees drawn up to your chest. A local anesthetic is injected in an area over your lower spine to reduce any discomfort from the procedure. Then a needle is inserted into your spinal canal, and fluid is collected. Tests on this fluid indicate the number and types of white blood cells, the level of sugar, and the levels and types of proteins. Additional tests on this fluid can indicate evidence of bleeding, infection and abnormal cells.
- Blood and urine tests. Analyzing samples of your blood and urine in the laboratory may help your doctor eliminate other possible causes of your signs and symptoms.
- Muscle biopsy. If your doctor believes you may have a muscle disease rather than ALS, you may undergo a muscle biopsy. In this procedure, a small portion of tissue is removed while you're under local anesthesia and is sent to a lab for analysis.
Because there's no reversing the course of amyotrophic lateral sclerosis, treatments mainly involve efforts to make you more comfortable and independent and to slow the progression of symptoms. Treatments may involve many professionals, including doctors, therapists, dietitians, social workers and hospice nurses, and may include :
Researchers are investigating many other medications for their usefulness in treating amyotrophic lateral sclerosis. Examples include the antibiotic minocycline (Minocin), the breast cancer drug tamoxifen, the antioxidant coenzyme Q10 and a nerve-nourishing drug called insulin-like growth factor (IGF-I). Increasingly, researchers are studying drug "cocktails" — which are combinations of medications. Stem cell therapy is another avenue of research. Early studies show that stem cells may have the ability to repair or replace the motor neurons damaged by ALS, but clinical use or clinical trials with stem cell therapy is still a long way off. Only time will tell if these new treatments will be useful.
It's important to work closely with a doctor who specializes in amyotrophic lateral sclerosis, who will be informed as new discoveries and treatments may become available. Some health care centers offer ALS clinics where people with ALS can work with physical therapists, occupational therapists, speech therapists, nurses, social workers and other people with ALS — all in the same place.