Screening and diagnosis

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.