ALS Diagnosis
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Confirming a diagnosis of amyotrophic lateral sclerosis (ALS) is typically a complex process that involves testing for signs indicative of the progressive neurodegenerative disease, and ruling out other potential disorders that could cause similar symptoms.
Because it shares common symptoms and signs with other neurological diseases, there is no definitive test for ALS, which usually begins in patients between ages 55 and 75.
Instead, the diagnosis is based on a period of observation to track the progression of symptoms, combined with a series of clinical tests to exclude other conditions. It generally takes about 10-16 months from the onset of symptoms before a diagnosis of ALS is confirmed.
El Escorial criteria
ALS, also known as Lou Gehrig’s disease, is caused by motor neurons becoming progressively damaged and dying. Motor neurons are the nerve cells that control movement, and such damage leads to the early signs of ALS.
The disease affects motor neurons in both the brain and spinal cord, called upper and lower motor neurons. Damage to upper motor neurons typically causes symptoms such as muscle stiffness and overactive reflexes, while the degeneration of lower motor neurons results in weakness, muscle atrophy, and muscle twitches.
The main parameters used to diagnose ALS are called the El Escorial criteria, named after a conference center in Spain where the diagnostic guidelines were first developed by the World Federation of Neurology. These guidelines were initially published in 1994, but have since been updated to account for advances in the scientific understanding of ALS.
Under the most recent update, published in 2015, three criteria must be met for a diagnosis of ALS to be confirmed. These consist of:
- signs of progressive degeneration in both upper and motor neurons affecting one body region, or lower motor neuron impairments impacting more than one body region
- evidence of disease progression (i.e., symptoms worsening over time and spreading to affect multiple parts of the body)
- clinical evaluations that exclude any other condition which might explain a patient’s symptoms.
What tests are used to diagnose ALS?
For a full ALS diagnosis, a doctor will thoroughly examine a person’s medical and family history and perform a complete neurological assessment.
Physicians also will require a number of clinical tests to make an accurate diagnosis and rule out other conditions that can cause similar symptoms. Among such other disorders are:
- autoimmune diseases like myasthenia gravis, multiple sclerosis, and Guillain-Barre syndrome
- genetic conditions like bulbospinal muscular atrophy and oculopharyngeal muscular dystrophy
- infection-related problems such as HIV or post-polio syndrome
- nutritional problems like vitamin B12 or copper deficiency
- hormonal issues like elevated thyroid hormone or parathyroid hormone (hyperparathyroidism)
- other neurological problems like Parkinson’s disease, stroke, or damage in the spinal cord.
Nerve conduction study
A nerve conduction study — also called a nerve conduction velocity test — measures the speed at which neurons transmit electrical impulses to muscles in different areas of the body. This test can help identify ALS-associated abnormalities in motor neuron signaling and exclude disorders that affect the peripheral nerves (the nerves outside the brain and spinal cord).
To diagnose ALS, at least two sites are tested during the exam. These include one upper limb and one lower limb, usually starting with the site that shows the most severe symptoms. During the test, one metal disc electrode stimulates the nerve by delivering a small electrical shock, while another is placed over the muscle directly controlled by that nerve to record the electrical signal.
Patients with ALS tend to show abnormally low compound muscle action potential amplitudes, meaning the signal from the nerve doesn’t trigger as much muscle activity as would be expected. Such a result is indicative of issues with motor neuron function.
Nerve conduction studies of sensory nerves — the nerves responsible for detecting sensations like pressure, temperature, and pain — are usually normal in ALS patients.
Electromyography
In electromyography (EMG), a small needle electrode is inserted into a muscle and used to record its electrical activity, both at rest and during muscle contractions. This can be used to help confirm ALS-related damage to lower motor neurons, and can exclude other potential causes of muscle weakness such as primary lateral sclerosis, which affects only upper motor neurons but not lower motor neurons.
Due to lower motor neuron damage, muscle cells in people with ALS do not receive the signals that normally regulate their activity. As a consequence, EMG results for ALS usually show spontaneous electrical activity when the muscle is at rest.
Abnormalities on EMG for ALS may be detectable even before there are overt symptoms in the affected muscle. EMG is commonly performed at the same time as nerve conduction studies.
MRI
MRI is a noninvasive method that uses a magnetic field along with radio waves to produce detailed images of structures inside the body. In ALS, it may be used to evaluate the brain and spinal cord, or to visualize changes in muscle tissue.
People with ALS generally have normal MRI scans of the brain and spine, so these imaging tests can help rule out other conditions that may result in similar symptoms. MRI imaging of muscle may be useful for tracking disease progression and for differentiating between ALS and other similar diseases.
Muscle and nerve biopsies
A biopsy involves collecting a small sample of a patient’s tissue for analysis in a laboratory. Biopsies of muscle and/or nerve tissue may be performed during the diagnostic workup for ALS.
Muscle biopsies in ALS characteristically show a loss of muscle fibers due to muscle atrophy, or shrinkage. There also may be changes in muscle morphology, or the appearance and shape of the muscle cells. Loss of nerve supply and abnormalities in mitochondria, which supply energy to cells, also can be detected during a muscle biopsy. Such biopsies can be useful for tracking the progression of ALS, as more pronounced abnormalities tend to accumulate over time.
Nerve biopsy in ALS is mainly useful for excluding disorders that affect peripheral nerves, or those outside the brain and spinal cord. ALS nerve biopsy also may reveal damage to axons, the long wire-like fibers that nerve cells use to send electrical signals.
Spinal tap
A spinal tap, also called a lumbar puncture, is used to collect a sample of cerebrospinal fluid (CSF) — the liquid that surrounds the brain and spinal cord — to be examined for abnormal cells and proteins.
This approach can be helpful for excluding certain conditions that may cause ALS-like symptoms, particularly inflammatory diseases of the nervous system. It’s most commonly performed when a person has unusual symptoms of ALS, such as spinal nerve abnormalities, or no sign of the abnormal reflexes or spasticity that typically characterize the disease.
Use of a spinal tap also can detect certain biomarkers of nerve damage, such as levels of structural nerve proteins called neurofilaments. These neurofilaments may be helpful for tracking ALS disease progression.
Genetic tests
When someone has a family history of ALS, even if they show no symptoms of the disorder, a genetic test can identify disease-causing mutations. There are many genetic tests available to identify ALS-associated mutations, ranging from those that scan for a few specific mutations to analyses of a person’s entire genetic code. Such tests are typically done on a blood sample.
While many genetic mutations have been linked to ALS, these associations are complex — not everyone with ALS-related changes in genetics will develop the disease, and most people who develop ALS don’t have known disease-causing mutations.
Given these complexities, genetic testing usually is only performed if an individual is known to have a family history of the disease. Identifying a disease-associated mutation may aid in making the diagnosis, but is not sufficient to confirm a diagnosis of ALS.
Other tests
A number of other tests may be involved in the diagnostic workup of ALS. These assessments can check for the presence of other conditions that can cause similar symptoms. They include blood and/or urine tests to detect specific antibodies or proteins, and other, more advanced brain imaging techniques, such as magnetic resonance spectroscopy.
Next steps and support after receiving ALS diagnosis
After a person is diagnosed with ALS, the patient and their clinical team should work together to determine the next steps. This will generally include discussions about treatment, including both medications that may slow ALS progression as well as therapies aiming to address particular disease symptoms.
Many patients also benefit from other interventions and lifestyle changes that aim to improve life quality, such as physical or occupational therapy and the use of adaptive equipment. Emotional support, such as therapy or ALS support groups, also is available for people diagnosed with the disease — and for their family members. Healthcare providers can usually offer guidance about accessing these resources, which typically are available both in person and online.
As ALS is a severe disease that usually causes substantial physical disability and death within a few years of symptom onset, next steps after diagnosis also will usually include discussions about the patient’s desires regarding life support and end-of-life care. These conversations can be emotionally taxing, but they are critical for ensuring the patient’s wishes are carried out even if communication becomes difficult or impossible.
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 other 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.
FAQs about ALS diagnosis
Amyotrophic lateral sclerosis (ALS) can develop at any age, although it is more common with increasing age. The majority of patients are diagnosed between the ages 55 and 75, but there are reports of the disease being diagnosed in young children.
Symptoms of muscle weakness that get progressively worse over time characterize amyotrophic lateral sclerosis (ALS). In most patients, this weakness starts in the hands and/or feet on one side of the body before spreading elsewhere, though more rarely it can begin affecting the muscles around the mouth and throat. Signs such as unexplained difficulty with writing or carrying things, problems walking, or unexplained speech abnormalities may prompt a diagnostic workup for potential ALS.
There is no single test that can diagnose amyotrophic lateral sclerosis (ALS). Instead, a diagnosis is made based on the combination of signs and symptoms indicative of the disease, together with tests to exclude other potential explanations for the symptoms. It’s common for a diagnostic evaluation for ALS to take several months; most people are diagnosed between 10 and 16 months after symptoms first appear.
Amyotrophic lateral sclerosis (ALS) is a progressive disorder, meaning it will get increasingly worse over time. Without a proper diagnosis, people with ALS cannot receive appropriate care, including treatments that may slow the progression of the disease.
Amyotrophic lateral sclerosis (ALS) is diagnosed via a combination of assessments that aim to identify disease-related damage to motor neurons that gets progressively worse over time. Diagnosis also involves tests to exclude other conditions that may cause similar symptoms.
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