While there’s no single test to diagnose ALS, a neurologist will run a series of tests that can rule out other conditions to arrive at an ALS diagnosis.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative condition. About 5,000 Americans receive an ALS diagnosis every year.

In its early stages, ALS may cause symptoms such as muscle weakness, muscle stiffness, and slurred speech. Sometimes the early effects of ALS can seem similar to some effects of other disorders such as myopathy or neuropathy.

The process of diagnosing ALS can sometimes be stressful and take weeks or longer. Multiple tests might be needed to rule out other conditions before a diagnosis can be confirmed.

The diagnosis of ALS is based on a combination of symptom history, physical examination, and diagnostic tests. There’s no single test that can be used on its own to rule in or rule out ALS.

Instead, ALS is diagnosed through neurological testing and through tests that help rule out other conditions that cause similar symptoms. Testing that helps diagnose ALS includes:

  • Medical history review: A doctor may want to review your medical history and any medications you’re taking.
  • Neurological exam: Neurological exams test reflexes and muscle strength. These tests can be repeated often to look for changes in symptoms. Sensation isn’t affected in ALS, and reflexes can be diminished beginning in the early stages, while weakness becomes apparent as the disease progresses.
  • Nerve conduction study (NCS): An NCS is a test that measures how well your nerves are able to communicate with your muscles.
  • Electromyography (EMG): An EMG is a test that records the electrical activity of your muscle fibers.
  • Lumbar puncture: This test is also known as a spinal tap. It’s done by inserting a needle into your spine and removing a sample of spinal fluid to check for inflammation. A spinal tap might be done during the diagnostic process to see if other spinal conditions are causing your symptoms.
  • MRI scan: An MRI scan is an imaging test that can help doctors get a detailed look at your brain and spine.
  • Muscle biopsy: A muscle biopsy can help rule out conditions that aren’t ALS but could cause similar symptoms. During this test, a sample of muscle tissue is removed and sent to a laboratory for testing.
  • Laboratory tests: You might have blood work drawn or be asked for a urine sample. These tests can help look for infections, check how well your organs are functioning, look for markers of certain diseases, and provide an overall picture of your health. They’re a good way to help rule out other conditions.

Many people with ALS have a team of medical professionals who help provide care.

During the diagnostic process, a neurologist is the best person to oversee testing and confirm results. Neurologists are experts in conditions such as ALS and are the professionals best able to identify, diagnose, and treat this condition.

At what age is an ALS diagnosis usually made?

Although ALS can develop at any time, the average age at diagnosis is 55 years. ALS is usually diagnosed when people are between 40 and 70 years of age.

People with “familial ALS,” a type of ALS that runs in families, often develop ALS earlier than people who have what’s called “sporadic ALS,” which develops without a known family connection.

It’s common for familial ALS to be diagnosed when people are in their late 40s or early 50s, but sporadic ALS typically isn’t diagnosed until people are in their late 50s or early 60s.

Learn more about the average age of ALS diagnosis here.

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ALS is progressive and degenerative, which means that symptoms will get worse as the disease continues.

ALS damages motor neurons, and symptoms will increase as more neurons are affected. In the beginning, symptoms can be vague and similar to the symptoms of other conditions.

Early symptoms of ALS include:

There are multiple conditions that can look like ALS, especially in the early stages. These conditions share some symptoms with ALS, and most of them are more common than ALS.

Usually a few conditions are considered during the initial diagnostic workup, and a diagnosis is narrowed within the first few weeks.

Conditions with symptoms similar to ALS include:

  • Multiple sclerosis: Multiple sclerosis is a chronic condition that can cause ALS-like symptoms, such as muscle stiffness and muscle spasms. Multiple sclerosis causes a wide range of additional symptoms and progresses slowly.
  • Parkinson’s disease: Similar to ALS, Parkinson’s disease can cause difficulties with movement, speech, and swallowing. However, the conditions progress in very different ways. The progression of Parkinson’s disease affects the brain’s ability to control specific movements and body actions.
  • Benign fasciculation syndrome: The word “fasciculation” means muscle twitching. Sometimes muscle twitches similar to the ones observed in ALS have easily remedied causes, such as excess alcohol or overexercising a muscle. This muscle twitching is called “benign fasciculation syndrome.” If the condition happens often, for instance as it might in a high-level athlete, it could resemble ALS at first.
  • Myasthenia gravis (MG): MG is a condition that causes difficulty swallowing, like ALS. However, MG has biomarkers that can be tested for. Additionally, ALS may cause tongue weakness and atrophy, while MG doesn’t.
  • Spinobulbar muscular atrophy: Spinobulbar muscular atrophy is a condition that causes weakness in the muscles that control speech, neck movement, and the limbs. It can resemble ALS at first, but it doesn’t progress in a similar way and doesn’t have any additional overlapping symptoms.
  • Peripheral neuropathy: Peripheral neuropathy is a disease of the peripheral nerves. Peripheral neuropathy can occur due to underlying conditions, such as diabetes or chronic alcohol toxicity, and it can cause muscle atrophy and weakness.
  • Myopathy: Myopathy is a muscle disease that can cause weakness and muscle atrophy. It may be caused by chronic disease or a medication side effect.

Next steps if you suspect ALS

It’s a good idea to make a medical appointment if you suspect ALS. The diagnosis process may be long, so it helps to start as soon as possible.

If you’re able, you can directly contact a neurologist in your area. You can use this guide from the American ALS Association to find experts in your area.

Keep in mind that it’s important to check your insurance information before you make an appointment. Depending on your plan, you might need to see a primary care doctor for a referral before you see a neurologist. Either way, it’s best to get in contact with a medical professional as soon as you can.

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ALS can be a difficult condition to diagnose. There isn’t a test that can confirm the diagnosis with information such as biomarkers, images, or chemical levels in your body.

Instead, you’ll need a variety of tests to help assess your symptoms and to rule out other conditions that could be causing them. These tests can help rule out conditions that resemble ALS, especially in the early days before symptoms progress, including multiple sclerosis and Parkinson’s disease.

The diagnosis process could include tests such as neurological tests, nerve response tests, imaging tests, lumbar punctures, and biopsies. Schedule a visit with a doctor if you’re displaying symptoms of ALS, and they’ll be able to refer you to a neurologist.