There are no specific tests to diagnose amyotrophic lateral sclerosis (ALS). To make a diagnosis, a doctor will perform tests to rule out other conditions with similar symptoms and indicate changes that are consistent with ALS.

ALS is a neurological condition that affects the nerves controlling voluntary muscles, which are the muscles that people consciously use.

This article discusses ALS testing, the types of tests doctors use, and how they make a diagnosis.

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According to the ALS Association, ALS is very challenging to diagnose. There is no specific test or procedure that can conclusively prove that someone has ALS.

One reason for this is that people with this condition can have very different early symptoms. The progression of ALS also varies, further complicating the diagnosis process.

To diagnose ALS, a doctor will perform a clinical examination, study a person’s individual and family medical history, and run a series of tests. The tests aim to look for changes that characterize ALS and rule out other conditions.

In most cases, the below diagnostic tests will help a doctor diagnose ALS.

Medical imaging tests

Medical imaging, such as MRI scans, can help diagnose or rule out:

An MRI uses radio waves from a computer and a powerful magnetic field within a large, cylindrical tube. It can create detailed images of bodily tissues, identify atypical mineral deposits, and assess blood flow.

Nerve or muscle biopsy

To determine if someone has a muscle or nerve condition other than ALS, a doctor may perform a muscle or nerve biopsy.

During these tests, a doctor will remove a small sample of nerve or muscle after numbing the skin with a local anesthetic. They will then send the sample to a lab, where pathologists will look for signs or markers associated with muscle or nerve conditions other than ALS.

In some cases, a biopsy can also show changes that occur due to ALS, such as shrinking.

Neurological exam

During a neurological exam, a doctor will assess a person’s:

  • sensory and motor skills
  • vision
  • coordination
  • mood
  • behavior
  • mental status
  • balance
  • speech
  • hearing
  • reflexes

To perform a neurological exam, a doctor may use tools such as a flashlight or reflex hammer.

Spinal tap

Also known as a lumbar puncture, a spinal tap is a procedure that doctors typically use to diagnose:

During a spinal tap, a doctor applies a local anesthetic to the skin before inserting a needle into the spinal canal. They remove a sample of the fluid called cerebral spinal fluid (CSF) then send it to a lab for analysis.

Electrodiagnostic tests

Electrodiagnostic tests assess the health of muscles, neuromuscular junctions, and the peripheral nervous system. They are a very important diagnostic tool in neurology.

One type of electrodiagnostic test is electromyography (EMG), which involves inserting needles attached to an EMG machine into a muscle. The wires monitor changes in electric signals in the muscles during rest and movement.

A surface EMG uses electrodes, which are less invasive and uncomfortable compared to fine needles or wires.

To help rule out other conditions, a doctor may also perform another type of electrodiagnostic test called a nerve conduction study (NCS). This test involves taping recording electrodes connected to an EMG machine over a muscle that sends a tiny electrical pulse to stimulate underlying nerves.

An NCS test helps assess how well nerves respond to electrical signals, the strength of the signal, and the speed the signals travel.

These tests often show certain abnormalities that occur due to ALS, and they can become more significant as the disease progresses.

Blood and urine tests

Laboratory screening tests, such as blood and urine tests, can help diagnose or rule out various conditions, including:

  • infections
  • clotting disorders
  • autoimmune diseases
  • hereditary disorders
  • muscle disorders
  • metabolic conditions
  • fat or protein-related disorders
  • some neurodegenerative conditions


Myelography can help diagnose spine or spinal cord tumors or compression from spinal fractures or herniated vertebral discs.

To perform a myelogram, a doctor injects anesthesia into a space between two spinal vertebrae within the lower back. They then insert a long needle into the spinal canal.

Next, they inject a contrast dye into the spinal canal and perform an X-ray or CT scan. In some cases, they may also remove a sample of CSF with the needle.

It is worth noting that healthcare professionals do not typically use this test when investigating possible cases of ALS.

The exact cause of ALS remains unknown. However, it may develop due to a mix of environmental and genetic factors.

More than 12 genetic mutations seem to influence the development of ALS. According to research, 10% of people without a family history of the condition have genetic mutations linked to ALS.

Researchers believe some genetic mutations with links to ALS influence the development and progression of the condition. They may do this by causing changes in the processing of RNA. Molecules of RNA help produce molecules within cells and contribute to gene activity.

Other genetic mutations that have associations with ALS appear to cause abnormalities in protein recycling in the body. In this process, the body breaks down nonfunctioning or atypical proteins and rebuilds them.

Some gene mutations with links to ALS may also increase how susceptible a person is to environmental factors with correlations to ALS.

A genetic test may help identify why someone develops ALS, how the condition may progress, or whether someone’s children may be at an increased risk of developing ALS in their lifetime.

If individuals have specific gene mutations linked with ALS, they may be eligible to enroll in clinical drug trials. This knowledge may also help other family members access targeted gene therapy in the future.

A person with a family member with both ALS and one of the disease-causing genes may decide to undergo a predictive genetic test for the condition to see whether they are at an increased risk of developing it.

To undergo a genetic test for ALS, a healthcare professional will collect a blood or saliva sample from a person.

They send these samples to a lab where technicians will isolate the DNA and examine them for mutations associated with ALS.

A person may also undergo a genetic test for ALS by using a special testing kit to collect a sample of cells inside their cheek, saliva, or blood and send it to a laboratory testing company in a prepaid envelope.

Cost of genetic testing

If a healthcare professional orders a genetic test for ALS, most health insurance plans will cover the cost. In some cases, a person must pay for the cost of genetic testing out of pocket.

The ALS Identified program offers genetic testing for ALS free of charge to people with ALS and their families.

There is no cure for ALS, but the medications edaravone and riluzole may help reduce or slow the progression of its symptoms. People with the condition may also benefit from the below.

Communications support

People with ALS who have trouble speaking may work with a speech therapist to learn ways to adapt.

Those with the condition may also use devices, such as a computer-based speech synthesizer with eye-tracking technology, to allow people to answer questions using eye movement or other nonverbal methods.

Individuals with ALS may also decide to store recordings of their own voice while they can still speak to use when they cannot, in a process called voice banking.

A brain-computer interface system can also help those with the condition communicate or control items, such as a wheelchair, using brain activity alone.

Occupation and physical therapy

A physical or occupational therapist may help someone with ALS learn to manage their symptoms better using exercises or special equipment.

Physical therapists can teach people exercises that help strengthen healthy muscles and improve their range of motion using stretching exercises to help reduce painful stiffness or muscle changes without overworking the muscles.

Occupational therapists may advise and teach someone ways to conserve their energy and remain mobile as long as possible using supportive devices, such as wheelchairs, walkers, braces, and ramps.

Breathing support

Someone with ALS who has trouble breathing may use a mask to help them breathe. People with the condition may also use mechanical cough assistive devices and other techniques to help them generate a stronger cough.

As symptoms of ALS progress and become more severe, a person may need to rely on mechanical ventilation devices that mechanically deflate and inflate the lungs to facilitate breathing.

Nutritional support

A nutritionist can help teach people with ALS and their caregivers how to prepare small, healthy meals that contain enough fiber, fluid, and calories and avoid foods that are hard to swallow or may cause choking.

As ALS symptoms progress, individuals may also need to use suction devices to remove excess saliva or fluids and help prevent them from choking. When someone with ALS can no longer eat, they may need a feeding tube.

There is no specific test to diagnose ALS. Doctors typically diagnose it by performing a series of tests to find changes consistent with ALS and rule out all other conditions that could explain someone’s symptoms.

People should consider speaking with a doctor as soon as possible if early signs of ALS develop, including unexplained:

  • muscle stiffness or tightness
  • muscle twitches in the legs, arm, shoulder, or tongue
  • muscle cramps
  • muscle weakness in the leg, neck, arm, or chest
  • speech changes
  • trouble swallowing and chewing