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Sean M. Healey & AMG Center for ALS
Learn more about how ALS diagnosed, including the clinicians and specialists involved, the neurological exam and diagnostic testing.
How Is ALS Diagnosed?
Although individuals experience symptoms differently, a common first response to feelings of muscular weakness, slurred speech or a change in ability to perform tasks such as buttoning clothes or tying shoes is to attribute these changes to “getting older.”
Over time, however, an individual or a family member may realize that frequent tripping or falling, an inability to hold a full cup of coffee or slowed speech might be something more than a sign of aging. Occasionally, a coworker or boss may notice that the person’s ability to perform at their normal capacity at work has changed. Rarely, a person may realize that he or she is having difficulty catching his or her breath while performing various tasks.
Clinicians Involved in the Diagnostic Process
An appointment with a primary care physician (PCP) is often the first step to understanding symptoms and changes. The time that elapses between first noticing symptoms to visiting the doctor varies widely among patients and often depends on how rapidly symptoms worsen.
A PCP typically refers an individual to a neurologist for further evaluation but this referral can be delayed if symptoms are minor or are developing and changing slowly. Consulting with other types of doctors is a common experience that many patients have. Once the symptoms are recognized as a neurological problem, a neurologist will be consulted.
A neurologist will perform a detailed physical examination that focuses on muscle strength, reflexes, coordination, and sensation. Typically, a neurologist will perform tests to rule out many of the other possible causes of a patient’s symptoms. The type of symptoms, how fast or how slow they progress and change, and what other disease have to be excluded will affect the time it takes to determine the diagnosis.
Even after the tests rule out other disorders, a diagnosis of ALS may still be unclear. As a next step, individuals are often referred to a neuromuscular specialist, who specializes in nerves and muscles. The neuromuscular specialist will either assist in making a diagnosis or offer a second opinion to help confirm the possible diagnosis of ALS.
A neuromuscular specialist will review the results of the tests that have already been performed and may repeat some of them to see if there have been any changes over time. Meeting with a neuromuscular specialist will help ensure that the medical evaluation has been thorough and complete.
The Diagnostic Process
The first important step in the diagnostic process is an examination by a neurologist. This will include detailed family, work, and environmental histories. During the exam, the neurologist will look for typical features of ALS that may include:
The neurologist will also look for signs such as pain, loss of sensation, or extra-pyramidal rigidity, which is a different type of muscle rigidity that is frequently seen in Parkinson’s type disorders.
The next step in the diagnostic process often involves a series of test. These typically include an MRI (magnetic resonance imaging) of the neck, and sometimes of the head and lower spine, an EMG (electromyography) which tests nerve conduction, and a series of blood tests.
Sometimes urine tests, genetic tests, or a lumbar puncture (also called a spinal tap) are also necessary.
The EMG is a very important part of the diagnostic procedure. Although this test can sometimes be uncomfortable, it is very important to have it done.
In the first part of the EMG, small electric shocks are sent through the nerves to measure how fast they conduct electricity and to find out whether there is any nerve damage. The shocks tend to feel like the kind you get from static electricity but may sometimes feel a bit stronger.
This first part of the EMG determines whether the individual has “nerve block,” which is a feature of a different disease called multifocal motor neuropathy. There is a chart at the end of this section which explains this disease a bit more. The first portion of the EMG also tests whether the nerves that communicate sensation are affected, which may also indicate a disease other than ALS.
The second part of the EMG tests the electrical activity of selected muscles. This is done by inserting a very fine needle into the selected muscles and using it to “listen” to the pattern of electrical activity in these muscles. No electric shocks are involved in this part of the test and the needle does not inject anything into, or take anything out of, your muscles.
Learn more about EMGs
An MRI is a painless, non-invasive procedure that offers a very detailed picture of the spinal cord, the nerves that come out of the spinal cord, and the bones and connective tissues that surround and protect the spinal cord. It shows more detail than a CAT (computed axial tomography) scan or X-rays. The MRI will help rule out pressure on the spinal cord or major nerves (such as from a herniated vertebral disk), Multiple Sclerosis, and tumors or bony abnormalities that compress the nerves. It can help detect vascular changes and strokes that sometimes affect the spinal cord or brain.
The MRI takes about 30 minutes. The individual having the MRI lies down inside a machine that is basically a large, rotating magnet. The test is noisy but it is painless. Some people have trouble being in a small, confined spaces and it is important to tell the doctor about this before the MRI begins so that medication can be given to help the person relax.
Blood tests are used to look for evidence of other diseases whose symptoms are similar to early signs of ALS. These include tests for thyroid and parathyroid disease, vitamin B12 deficiency, HIV, hepatitis, auto-immune diseases, and some types of cancer. Creatine kinase (CK), a muscle enzyme released when muscles are injured or die, is also measured.
Specialized blood tests, such as autoimmune antibody tests, anti-GM1 antibody tests, and tests looking for high levels of protein in the blood and urine that may be related to some types of cancers, are also performed. Depending on the individual’s work and environmental history, the doctor may also test his or her urine for heavy metals.
In some rare cases, genetic tests and tests of hexosaminidase A levels, which can be related to juvenile spinal muscle atrophy, may also be performed. Genetic testing for ALS is usually only done when someone else in the family has ALS.
Occasionally, a lumbar puncture (also called a spinal tap) may be required. For this test, a small needle is inserted into the lowest part of the spine (below the spinal cord) to remove fluid which will be examined for abnormal cells. A lumbar puncture is usually done only if the individual has unusual features of ALS, such as spinal nerve abnormalities, or has no sign of abnormal reflexes or spasticity. Similarly, some people who have uncommon patterns of weakness, pain, or very high creatine kinase (CK) levels may need a muscle biopsy to look for muscle-specific diseases. However, this is rarely necessary.
Once these tests have been completed, the neurologist may be able to tell whether an individual has ALS. Sometimes, not all of the symptoms and findings that are required to make the diagnosis are present, especially in the early phase of the disease. In this case, the neurologist will repeat the physical and neurological exams and the EMG at a later date to look for changes over time.
The symptoms and disorders chart below explains some of the alternative diseases that neurologists look for when trying to determine whether an individual has ALS. These disorders share some symptoms that resemble those seen in ALS.
Modified from Layzer, RB. Chapter 415. Heredity and acquired intrinsic motor neuron diseases. In: Bennett and Plum (Eds), Cecil Textbook of medicine, W.B. Saunders, Philadelphia 1999.
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