4 Tests That Help Diagnose ALS

There isn’t one test that doctors can use to determine if a person has amyotrophic lateral sclerosis (ALS). Instead, doctors need to perform a series of tests to eliminate other similar neurological diseases and to arrive at an ALS diagnosis. The process can be slow, taking an average of 12 to 14 months in the U.S. The patient will be told that they have suspected, possible or probable ALS which will depend on the parts of the body affected. It’s only as the disease progresses that doctors will know more.

According to the ALS Therapy Development Institute, doctors assess a patient’s physical symptoms, along with taking simple blood and urine tests and a spinal tap.

To rule out other neurological disorders, they may also run the following tests:

Electromyography (EMG) and nerve conduction studies (NCS)
These two tests will allow doctors to see if the motor nerves  are still working correctly or if they’ve degenerated. NCS tests the strength of the signals that motor nerves can send to the muscles and EMG measures how the muscles respond to signals from the motor nerves. The tests help to eliminate other disorders, particularly ones affecting the peripheral nerves.

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Muscle biopsy
A muscle biopsy will allow a doctor to investigate specific muscles the patient is experiencing difficulties with. The tissue will then be studied under a microscope to rule out other neuromuscular diseases.

MORE: An overview of the signs and symptoms of ALS

MRI scan
Magnetic resonance imaging (or MRI) can look at the tissue in the spinal cord and brain, helping to rule out conditions such as multiple sclerosis and brain tumors as well as diseases of the spinal cord.

Genetic testing
Around 10 percent of ALS cases are genetic. If there is a family history of the disease, doctors may order genetic tests to see if the patient has one of the nine identified mutated genes associated with ALS.

MORE: Explaining the progression of ALS

ALS News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.


  1. Larry Berg says:

    Explain to me what the purpose of this article is considering that those of us with ALS already know this.

    • Ashley says:

      I don’t have ALS, and specifically googled how they test for ALS. This was the first site that came up.

  2. Laurie Taylor says:

    Other websites include a lumbar punch test. What tests are carried out with the spinal fluid and what mimics or conditions does it rule out.

  3. Susan Alley says:

    I have almost every symptom as if I were on the meds, and have not even been diagnosed yet everyone, including myself, knows I have ALS.The problem is I have been waiting for 6 months to get diagnosed! I am on a so called “emergency” wait list in Nebraska. My appointment is Sept.5,2018, which I scheduled 4 mos. ago, have called the office twice now and tried to move it up with no luck and have a pre-diagnosis from my M.D. which means nothing, because as we all know, it has to come from the neurologist.

  4. Cecil Marble says:

    I have burning muslces spasms cramping inside right leg numb feels like nerve damage down to my ankle had two knee replacement surgery on my right knee and several surgeries after have to go get this implant taking out because it bad but I burn so bad and nerve pain very bad

  5. Peter Ferguson says:

    I was diagnosed relatively quickley. At a special multi disciplinary ALS clinic at Toronto’s Sunnybrook Hospital. They used several of the tests outlined.

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