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.
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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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.
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.
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.
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