OHSU

Diagnosing ALS and Neuromuscular Disorders

Neuromuscular (nerve and muscle) disorders such as ALS and other conditions can take time to diagnose. If you think you might have a neuromuscular disorder, you need to see a neurologist (doctor who specializes in the nervous system).

To diagnose a neuromuscular disorder, your doctor will do a variety of tests and examinations. These include:

  • Taking your complete medical history
  • Doing a complete physical examination, including a neurological examination (examination of your nerve responses and reflexes)

You might also have blood tests, imaging tests (CT, MRI or other scans) and other procedures, such as:   

Electromyography (EMG)

Electromyography (EMG) measures electrical activity inside your muscles. Your muscles produce electrical signals when they work (contract). To find out if your muscles are working correctly, you might have an EMG.

Your doctor does a brief history and physical exam to identify the muscles that need to be tested. Next, the doctor places very small needles in these muscles. The needles are very thin (like acupuncture needles). They are inserted just under your skin.

Your doctor asks you to relax and then gently contract (squeeze) the muscle being tested. The needles are connected to a nearby machine. When the needle picks up electrical activity in your muscles, it sends the signals to the machine, which produces graphs, sounds or numbers that tell the doctor how well your muscles are working.

This procedure causes little or no discomfort. You might feel a small sting when the needles are inserted.

It takes 25 to 30 minutes to test one arm or leg.

Muscle biopsy

A muscle biopsy takes a small piece of muscle tissue for examination. Looking at the tissue under a microscope gives your healthcare team information about your condition.

A nurse, technician or doctor injects a local anesthetic (numbing medicine) in the biopsy area. Next, a small incision (cut) is made through your skin into the muscle. A small piece of muscle tissue is removed.

This procedure usually causes little or no discomfort. The local anesthetic burns or stings when first injected. During the biopsy, you might feel pressure or a pulling sensation. The biopsy area might feel sore for a few days.

A muscle biopsy usually takes 20 or 30 minutes, but it may take longer depending on the area being biopsied.

Skin biopsy

A skin biopsy takes a small piece of skin for examination. Looking at the tissue under a microscope gives your healthcare team information about your condition.

A nurse, technician or doctor injects a local anesthetic (numbing medicine) in the biopsy area. Next, a small piece of skin is removed. This is done with a razor, scalpel or other small tool, depending on the type of skin biopsy.

This procedure usually causes minimal discomfort. The local anesthetic burns or stings when first injected. After that, you usually don't feel anything. Depending on the type of biopsy, you may have stitches to close the area. Otherwise, the area is covered with a bandage.

A skin biopsy usually takes about 15 minutes.

Nerve biopsy

A nerve biopsy takes a small piece of nerve tissue for examination, usually from your ankle or wrist. Looking at the tissue under a microscope gives your healthcare team information about your condition.

A technician or doctor injects a local anesthetic (numbing medicine) in the biopsy area. Next, a small incision is made and a sample of nerve tissue is removed.

This procedure causes different amounts of discomfort for different people. The local anesthetic burns or stings when first injected. When the tissue sample is taken, you feel a brief tingling sensation, and the biopsy area might feel sore for a few days.

A nerve biopsy takes about 30 minutes, but it may take longer depending on the nerve being biopsied.

Lumbar puncture

A lumbar puncture is done to take a sample of your cerebrospinal fluid (fluid around the brain and spinal cord). Testing this fluid gives your healthcare team information about your condition.  

For the test, you lie on your side with your knees pulled towards your chest. A doctor or technician cleans your back and injects a local anesthetic (numbing medicine) in your lower spine. Next, a needle is inserted to take a sample of fluid (like taking a blood sample). After the test, your back is bandaged and you lie flat for 20 minutes to an hour.

This test causes minimal to moderate discomfort. The local anesthetic stings or burns when first injected. You feel pressure when the spinal needle is placed in your back and some brief pain when the needle goes through the tissue around the spinal cord. This pain should stop in a few seconds.

A lumbar puncture usually takes 30 to 40 minutes, but it may take longer.

Autonomic testing (Qsart)

The quantitative sudomotor axon reflex test (QSART) tests the activity of nerve fibers that control your sweat glands. A technician cleans the skin on your leg and wrist with alcohol and wipes it dry. Four electrodes are placed on three areas of your leg and one on your wrist. The instrument is turned on and sweat responses are measured.

You should experience little or no discomfort. You might feel a warm sensation around the electrodes. This test takes 45 minutes to one hour.