Diagnosis

Diagnosing ALS is a very long and complicated process because ALS is a “diagnosis of exclusion.” There is not any one test that can determine someone has ALS. Therefore, several criteria must be met to arrive at a diagnosis of ALS. First, all other potential causes of the patient’s symptoms must be ruled out through extensive diagnostic testing. There are many diseases with symptoms similar to ALS and there are several diseases that are known ALS-mimic diseases that must be carefully considered and tested to exclude them from the differential diagnosis (a list of diseases that could be causing the symptoms). Tests that should be performed include: - Brain and full spine (cervical, thoracic, and lumbar) MRI with and without contrast - Lumbar puncture - Muscle Biopsy - blood and urine tests - other tests based on the patient’s particular symptoms (such as CT and PET scans, all three kinds of Evoked Potentials, genetic tests, etc.) Second, the doctor must perform a physical neurological exam, looking for evidence of muscle weakness, muscle atrophy, and brisk/hyperactive reflexes in the head, arms, trunk, and legs. The doctor also looks for special reflexes such as the Jaw Jerk, Babinski, and Hoffman's Sign to be positive. It is also important for the doctor to examine the patient repeatedly over time to establish the progressive spread of these symptoms. Progressive muscle weakness and atrophy and hyperactive reflexes are indicative of UPPER MOTOR NEURON DEGENERATION and a requirement for the diagnosis of ALS. Third, the doctor will consider the results of the NCV/EMG test (see more information below). In ALS, the NCV results are usually normal, but the EMG will show evidence of neurogenic changes, such as increased insertional activity, fasciculations, increased amplitude, decreased recruitment, spontaneous bursts of activity, etc., which are indicative of LOWER MOTOR NEURON DEGENERATION and a requirement for the diagnosis of ALS. The two widely used systems of diagnostic criteria for ALS are called the "El Escorial Criteria for ALS" and the "Awaji Criteria for ALS." Both systems assign a degree of certainty of an ALS diagnosis based on how many signs of UMN and LMN degeneration are found in the four regions of the body: - the bulbar region (muscles for speaking, chewing, and swallowing), - the upper extremities (arms), - the paraspinals (trunk muscles), and - the lower extremities (legs). To diagnose DEFINITE ALS, there must be evidence of UMN and LMN DEGENERATION present in at least 3 of those areas. If evidence is found in fewer areas, it reduces the degree of confidence in the ALS diagnosis, which is indicated by use of the terms Suspected ALS, Possible ALS, or Probable ALS. You can perform a Google search for “El Escorial Criteria” and “Awaji Criteria” for more specific information and consult the graph below:

NCV/EMG

When we talk about having an EMG, that is a bit of a misnomer, as it is not a stand- alone test. What we really mean is the NCV/EMG, which is a two- or three-part test.

The NCV (Nerve Conduction Velocity test) is a test to see how fast electrical signals move through a nerve. It is done first and is noninvasive. Surface electrodes are placed on the skin and apply small electric charges to nerves. The resulting electrical activity of the nerve is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to measure the speed of the nerve signals. Usually, either both arms and at least one leg or both legs and at least one arm are tested for comparison, based on your symptoms. In ALS, the results of the NCV are usually "within normal limits" or "normal." The EMG (ElectroMyoGraphy) is the second and most important part. This is the test where a thin needle electrode is inserted into various muscles. As you relax and contract the muscle and the doctor moves and turns the needle, the electrical impulses are shown on an oscilloscope (screen) and heard through a speaker as static sounds. When considering ALS as a possible diagnosis, the doctor is looking to see and hear if neurogenic changes, such as increased insertional activity, fasciculations, increased amplitude, decreased recruitment, spontaneous bursts of activity, etc. are present, all of which are indicative of lower motor neuron degeneration. The doctor will test (insert the needle into) a variety of muscles all over the body. If you look at a chart that is filled out during an EMG, there is a horizontal line across the page for each muscle tested, and the vertical columns contain items such as insertional activity, amplitude, recruitment, fasciculations, etc. In each intersecting box, the doctor will notate the findings in that muscle for that item. “Norm” or “Normal” indicates findings within normal expectations; while “Abnormal,” +1, +2, +3, or other notations indicate findings outside the normal expectations. The doctor will test several muscles in at least three of the four regions of the body: - the bulbar region (usually the tongue), - the upper extremities (arms), - the paraspinals (trunk muscles), and - the lower extremities (legs). The RNS (Repetitive Nerve Stimulation) is the third part of the test. The doctor may or may not order this part to be completed based on their differential diagnosis and/or your presenting symptoms. It is similar to the NCV but follows a different procedure. A surface electrode is placed on a nerve, the nerve is stimulated, and the response is recorded by the electrodes. Then the technician will have you "exercise" that muscle for a prescribed amount of time, and then repeat the nerve stimulation at certain time intervals. Decrease in responses between stimulations in this test would be indicative of one of several potential conditions, including Myasthenia Gravis. It is important to note that EMG results are dependent on the talent and interpretation of the doctor performing the test... which is also true of the physical exam. That is why second (and even third) opinions are common and a good idea when dealing with a catastrophic diagnosis like ALS.

Other conditions that mimic ALS

Many conditions might mimic ALS so it is important that you know for sure whether or not you have ALS. Covid is a virus that mimics many of the symptoms of ALS, getting a covid test is important to help rule out that condition. If symptoms continue after testing negative for covid then you might have ALS. Another condition that mimics ALS is lyme disease, getting a blood test can help rule that condition out. For additional information reference these articles: https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC6137639/ https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/neuromuscular-disorders-affecting-the-thorax-amyotrophic-lateral-sclerosis/

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