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University of Pittsburgh

What Is ALS?

Amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s Disease, is a type of motor neuron disease that affects 20,000 to 30,000 Americans (both adult men and women). It is a degenerative disease that affects so-called “lower” and “upper” motor neurons (see figures below). The lower motor neurons are nerve cells that reside in the spinal cord and base of the brain. They start the circuit that powers the muscles in your arms, legs, face, mouth, voice box, and diaphragm (breathing muscle). They are like the circuit breakers in your house. If there is a problem at the circuit breaker, there won’t be power to your wires (nerves) or to what you plug into the outlet (muscles). Because of this problem, the muscles get weak, lose bulk (amyotrophy), may twitch (fasciculate), and sometimes cramp. There may also be involvement of upper motor neurons in the brain. These neurons send their signals through the spinal cord. If they are damaged, the outer or lateral spinal cord becomes scarred or sclerotic and there can be stiffness in the limbs and increased reflex activity when we tap on your tendons. There is usually no major impact on thinking, but a small percentage of patients have dementia, and a moderate number of patients will have some changes in their thinking. These changes could include loss of interest in various activites, heightened anxiety and problems with decision-making. ALS does not affect vision, hearing, bowel, or sexual functions. The internal organs are also not affected. We now think there may be mild urination problems in some ALS patients and sometimes there may be mild abnormalities in sensation. There may also be difficulty in controlling emotions (pseudobulbar affect) in a moderate number of patients.

The cause of ALS is unknown. In 5-10% of patients, the disease is inherited. In all others, it is not. We think that a toxic build-up of some substances (glutamate - an amino acid, or oxygen free radicals) might be important, but other causes are possible.

The diagnosis is made on the basis of history, neurologic examination, EMG and by ruling out other causes which may require an MRI of the neck or brain, chest X-ray, mammogram, blood work, and occasionally a muscle biopsy and spinal tap. Depending on the clinical findings and test results, we can diagnose possible, probable, and definite ALS. There are more slowly progressive forms of ALS and rarely patients with ALS plateau and improve within the first year. Yes, there is hope! There are also more slowly progressive “relatives” of ALS called progressive muscular atrophy, primary lateral sclerosis, and progressive bulbar palsy. Therefore, the prognosis is variable.

Although ALS is typically progressive, 10% of patients are still alive at ten years, and many patients maintain a good quality of life. Treatments are advancing; function can be maximized; complications can be managed; and support from various sources is crucial.