With no specific test to confirm ALS, diagnosis is a process that involves lab tests, neurological tests and observation. For patients, it can be a frustrating journey: On average, it takes about a year to get a confirmed ALS diagnosis.1
With familial (inherited) ALS, genetic testing may be able to determine whether a person has a gene mutation linked to the disease. But more than 90% of people with the disease have no family history of ALS. Moreover, the mere presence of the mutation does not mean the individual will develop ALS. Genetic testing can establish only that a person has one of the mutated genes associated with the disease.2
An ALS diagnosis requires the following: 3,4
- Signs of lower motor neuron degeneration
- Signs of upper motor neuron degeneration
- Progression of symptoms from to other regions, and
- An absence of evidence of other diseases that could explain the symptoms
The journey begins with a referral to a neurologist.
How is ALS diagnosed?
It typically requires a neurologist to diagnose ALS. So the first step is for your primary care provider to refer you to a neurologist.
During that first neurology visit, you’ll be asked about your symptoms and medical history, as well as your family health history and even about where you’ve lived and worked.
Next, the neurologist will conduct a physical exam. Finally, you’ll undergo tests to eliminate other possible causes of the symptoms.5
Understanding the physical exam
This part of the exam focuses on muscle strength, reflexes, coordination and sensation. Among the things the neurologist will be looking for are:6,7
- Muscle weakness in the limbs (often on just one side of the body)
- Muscle weakness in the mouth and tongue; this would show up as slurred or slow speech
- Muscle twitches — called fasciculations
- Hyperactive reflexes and muscle spasticity
- Emotional and cognitive changes
The tests for ALS come next.
Blood and urine: A starting point
An analysis of blood and urine samples can eliminate other possible diagnoses, including thyroid disorders, HIV, vitamin B12 deficiency, hepatitis, autoimmune diseases and certain types of cancer.
Blood tests can also measure creatine kinase, an enzyme that’s released when muscles are injured or die. Recent research suggests that it is significantly elevated in people with ALS and that higher levels appear to correlate with better survival rates in patients. That means they can help with prognosis as well as diagnosis.8
Depending on your work or environmental history, the doctor may also test your urine for heavy metals.
Scans, biopsies and other diagnostic tests for ALS
The next step is to conduct tests to help rule out other possible conditions. These tests include:9,10,11,12
- An electromyogram (EMG) assesses the health of muscles and the nerve cells that control them (motor neurons). It does this by evaluating electrical activity in response to a nerve’s stimulation of the muscle. The doctor inserts a thin needle electrode through the skin into various muscles.
- A nerve conduction study is usually done along with an EMG. It stimulates specific nerves and records how fast — and how well — they send the impulse to the muscle. Typically, the nerve is stimulated with electrode patches attached to your skin. (This is also called a nerve conduction velocity test.)
- An MRI can reveal other causes for your symptoms, such as spinal cord tumors or herniated disks.
- Lumbar puncture (spinal tap) involves taking a sample of cerebrospinal fluid via a small needle inserted in the lower back. For many patients, this test may not be necessary.
- Muscle biopsies are rarely performed as part of an ALS diagnostic workup. However, they are sometimes needed to look for muscle-specific diseases. During a muscle biopsy, a small bit of muscle is removed for analysis while you’re under local anesthetic.
ALS is a progressive disease, which means that it gets worse over time. As a result, your diagnosis journey may pause here. That’s because the neurologist will likely recommend repeating all the tests in about six months to confirm the diagnosis.13
How to tell if you have ALS: You can’t
ALS symptoms vary, but its onset typically manifests in one of two ways: either as weakness in the limbs, called limb (or spinal) onset, or difficulty in speaking or swallowing, termed bulbar onset.14 But merely having these symptoms doesn’t mean you have ALS.
As we discussed before, ALS mimics other diseases, and other diseases mimic ALS. That’s why it’s so important to get a referral to an experienced neurologist if you and your primary care provider think you may have ALS.
The sooner you can get a definitive diagnosis, the better. Even though ALS is incurable, treatments alleviate symptoms. The sooner you have that diagnosis, the sooner you can begin treatments that can improve your prognosis and quality of life.
2 Fanos, J., Gronka, S., Wuu, J. et al. Impact of presymptomatic genetic testing for familial amyotrophic lateral sclerosis. Genet Med 13, 342–348 (2011). https://doi.org/10.1097/GIM.0b013e318204d004
5 National Institute of Neurological Disorders and Stroke op. cit.
8 Chen, X.-P. et al.: Creatine kinase in the diagnosis and prognostic prediction of amyotrophic lateral sclerosis: a retrospective case-control study. Neural Regeneration Research 16 (2021)
14 Amyotrophic Lateral Sclerosis (ALS) Fact Sheet National Institute of Neurological Disorders and Stroke