Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School



Your doctor will ask about your medical history, and do a physical exam to look for the following signs:

  • A loss of muscle bulk, and muscle weakness, particularly in the arms and legs

  • Muscle twitching

  • Spasticity. The arms or legs resist being moved by someone else.

  • Abnormal tendon reflexes

  • The Babinski sign. The toe moves upward when the sole of the foot is stroked.

  • Difficulty taking a deep breath in and out

  • Facial weakness

  • Slurred speech

Your doctor will also check to see whether the following have been affected:

  • Your sense of pain, touch, heat

  • Eye movement

  • Higher thought processes, such as:

    • Perception

    • Reasoning

    • Judgment

    • Imagination

There is no single test result that confirms an ALS diagnosis. Your doctor will diagnose ALS based on the examination, and by excluding other causes of your symptoms.

Electromyography (EMG) tests how electrical signals travel down your nerves to your muscles. This test can be abnormal in ALS.

Because other neurological conditions besides ALS can cause similar symptoms, other types of studies sometimes are done to try to diagnose these other neurological conditions:

  • Blood tests

  • Spinal fluid analysis

  • Magnetic resonance imaging (MRI) scans

A neurologist is usually the physician who diagnoses ALS. A neurologist is an expert in diseases of the nervous system. If your doctor suspects ALS, he or she should refer you to a neurologist for evaluation.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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