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Amyotrophic Lateral Sclerosis (ALS)


Recommended guidelines have been published for the diagnosis of ALS. The revised El Escorial criteria1,2 and Awaji criteria3 are the most commonly used diagnostic criteria for ALS, and consensus diagnostic classifications based on these two criteria are also available. These criteria may include:

  • Signs of degeneration of lower motor neurons, which are in the spinal cord and brainstem, by clinical examination or specialized testing
  • Signs of degeneration of upper motor neurons, which are in the brain, by clinical examination
  • Progressive spread of signs within a region to other regions
  • The absence of electrophysiological, pathological, and neuroimaging evidence of other disease processes that might explain the observed clinical signs.

A thorough medical and family history and physical examination are the starting points of a neurologic work-up, which includes simple, in-office tests of muscle and nerve function.

If ALS is suspected, the next step is usually an electromyography, or EMG. This test measures the signals that run between nerves and muscles and the electrical activity inside muscles to see if there is a pattern consistent with ALS. If there is, more tests likely will be ordered. EMG patterns in ALS are due to the acute and chronic denervation and reinnervation of the affected muscles.

Additional tests may include imaging of the spinal cord and brain, usually by MRI (magnetic resonance imaging), and sometimes a test of the fluid surrounding the spinal cord (spinal tap or lumbar puncture), which involves inserting a needle into the back between two lower vertebrae.

Some evidence suggest that ultrasound of the muscles can detect fasciculations that can aid in the diagnosis of ALS.

Blood tests to exclude disorders that mimic ALS are also performed. In some instances, a muscle biopsy, which involves taking a small sample of muscle under local anesthesia, is performed.

In some cases, genetic tests (performed on a blood sample) can confirm the diagnosis (see Causes/Inheritance).

However, the diagnosis of ALS is often a “rule-out” procedure. This means ALS is diagnosed after all other possibilities have been ruled out by specific tests.

Among the conditions that resemble ALS are some forms of muscular dystrophy, the neurologic conditions known as spinal-bulbar muscular atrophy, intraspinal tumor, the nerve-to-muscle transmission disorder known as myasthenia gravis, and more.

If your condition has been diagnosed as ALS outside a major medical center or without extensive testing, it may be worth getting a second opinion.

MDA Care Centers are staffed by professionals who are highly skilled at diagnosing ALS and the conditions that resemble it.


  1. Brooks, B. R. El escorial World Federation of Neurology criteria for the diagnosis of amyotrophic lateral sclerosis. in Journal of the Neurological Sciences (1994). doi:10.1016/0022-510X(94)90191-0
  2. Brooks, B. R., Miller, R. G., Swash, M. & Munsat, T. L. El Escorial revisited: Revised criteria for the diagnosis of amyotrophic lateral sclerosis. Amyotroph. Lateral Scler. (2000). doi:10.1080/146608200300079536
  3. Costa J, Swash M, de Carvalho M. Awaji criteria for the diagnosis of amyotrophic lateral sclerosis: A systematic review. Archives of Neurology. 2012;69(11):1410-1416. doi:10.1001/ARCHNEUROL.2012.254

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