What it is: This test measures how well a muscle responds to stimulation. We use it to identify problems in how nerves and muscles interact. To see if symptoms come from a muscle or nerve disorder, we often combine EMG with nerve conduction studies.

How it works: We place tiny needles called electrodes into the muscle, then stimulate it with a mild electrical current. A tool called an oscilloscope records the electrical activity as waves on a screen. The wave size and shape tell us how well the muscle responds to nerve stimulation. We measure your muscle:

• At rest, when it shouldn’t produce waves.
• When you contract it mildly, such as with bending or lifting.
• When you contract it more forcefully, such as with lifting a heavy weight.

What it is: A nerve conduction study, or nerve conduction velocity test, measures how well and how fast electrical impulses pass through a nerve. We use this test to see if the nerve is damaged.

How it works: We attach two electrodes to your skin with a patch. The first electrode sends mild electrical stimulation. The other records the nerve’s response. A computer measures the signal’s speed. A delayed signal could indicate a problem with nerve function.

What it is: Changes to nerves that control sweating can be an early sign of nerve damage. This test, known as QSART, measures the function of these nerves. Results can tell us how much nerve damage you may have, if any. We may use this test to follow up after a nerve conduction study.

How it works: We do QSART in three phases on the arm or leg to measure how much sweat you produce. We measure:

• Your normal skin temperature when you’re resting.
• Sweat output when you rest.
• Sweat output after we stimulate your body to produce sweat.

We stimulate sweat by placing a safe chemical, acetylcholine, on the skin. The chemical activates the sweat gland by sending a painless electrical signal. A small cup placed on the skin measures your skin temperature and the amount of sweat. We analyze results to see how well the nerves are working.

What it is: An evoked potential study uses electrodes to measure the brain’s electrical response to sight, sound and touch. We use this test to:

• Assess hearing or sight, particularly in infants or young children
• Find problems with an eye (optic) nerve
• Check the brain function of people in a coma
• Detect brain or spinal cord tumors
• Diagnose or confirm multiple sclerosis

How it works: We attach electrodes to the skin with a paste. The location depends on what we’re studying:

• Visual evoked potentials, or VEPs, measure visual stimulation by having you look at a pattern on a screen. You wear electrodes on your scalp.
• Auditory brainstem evoked potentials, or ABEPs, send a test sound through headphones to stimulate hearing. We place the patches on top of the scalp and on both earlobes.
• Somatosensory evoked potentials, or SEPs, stimulate other nerves. You’ll most likely wear an electrode on your scalp and anywhere else we need to measure, such as the back of the knee.

We pass painless electrical signals through one electrode. The signal travels to the second electrode, where we measure it with a recorder. To make a diagnosis, your doctor interprets the electrical activity and the time it takes signals to travel.

What it is: This test tracks your sleep cycles to identify sleep patterns and disorders. You may get this test to look for a connection between neuropathy and sleep problems.

While you sleep, we record and analyze your:

• Brainwaves
• Oxygen levels in the blood
• Heart rate
• Eye and leg movements

How it works: You arrive at our sleep center in the evening and get ready for bed. A technologist connects sensors to a computer and to your:

• Scalp and temples
• Chest
• Legs

We clip oxygen sensors to your finger and earlobe, and monitor you through the night. We may suggest you use a positive airway pressure (PAP) machine to help your breathing. You go home in the morning. Your doctor evaluates results over the following days and shares the findings.

What it is: This painless imaging test uses high-frequency sound waves to create pictures of structures inside the body. It enables your doctor to check for problems with organs or muscles. Because sound waves can’t travel through air-filled body parts or bone, your doctor may also use other imaging tests.

How it works: We place gel on the skin to eliminate air pockets that could block sound waves. Your doctor or technician puts a handheld device called a transducer against the skin. The transducer sends sound waves into your body and collects them when they bounce back. The computer turns the sound waves into pictures.

We may also use transducers designed to go inside the body through the throat, rectum or vagina for a better picture.

What it is: Magnetic resonance imaging, or MRI, uses radio waves and magnets. It creates 3D pictures of your body’s internal structures. We use it to diagnose a disease or injury and to monitor the effectiveness of treatments.

How it works: You’ll come to one of our imaging centers. The scan takes about an hour, depending on where we ask the center to look. Once you arrive, you need to remove all external metal, such as jewelry. (Because it uses strong magnets, MRI isn’t appropriate for people with internal metal, such as pins or screws.) Sometimes dye is injected into one of your veins to help us see certain structures more clearly.

• Open MRI is open on all sides, so you feel less confined.
• Traditional MRI has you lying on a padded bench inside a tube with a hole at each end.
• Short-bore MRI machines enclose just the part of the body being scanned.

All types do the same thing — create a magnetic field inside your body. A computer uses signals from the magnets to make pictures that a radiologist reads.

What it is: This test uses small metal discs (electrodes) to detect the brain’s electrical activity. Your neurologist reads the resulting brain wave patterns to make a diagnosis.

How it works: We attach up to 25 electrodes to your scalp with a sticky paste. You stay still while sensors record your brain’s electrical activity. To produce different waves, we may ask you to do things such as track a bright light with your eyes or change your breathing. Your neurologist will review findings and discuss them with you.

What it is: This test collects fluid from around the brain stem (the trunk of the brain that connects to the spinal cord) or within the spinal canal (the space around the spinal cord). We test the fluid to diagnose infection, bleeding or disorders of the nervous system.

How it works: We clean your back and use a solution to numb your skin. We insert a hollow needle between two vertebrae into the spinal canal. We measure the pressure in the canal. Higher-than-normal pressure can indicate infection, swelling or bleeding.

We remove a fluid sample to check for:

• Abnormal protein levels
• Bacteria, fungi or viruses
• Sugar (glucose) levels
• White blood cell counts
• Cancer cells

Your doctor will receive findings, typically within days, and share them with you.

What they are: These biopsies collect a small sample of muscle or nerve tissue. We examine the sample under a microscope to help diagnose disorders. For example:

• A nerve biopsy can show damage to the nerve covering or fiber.
• A muscle biopsy can show damage from a hereditary neuropathy.

How it works: Your doctor will numb the area and make a small incision to remove a bit of nerve or muscle. Your doctor will contact you with results.

Blood or urine samples can show:

• Blood vessel damage
• Bone marrow disease
• Infection or inflammation
• Protein levels and disorders
• Toxin levels that could affect the nervous system
• Levels of medication used as treatment

What it is: Genes are parts of your cells that tell the body how to make proteins or perform a function. Changes to genes may affect many bodily processes.

We use genetic testing to identify or confirm a hereditary (passed down from parents) neurologic condition or disease. For example, parents who have a condition may want to know if their child will have it, too. Testing can:

• Rule out that a genetic change (mutation) caused a condition.
• Help doctors develop a treatment plan.
• Understand a condition’s severity.

How it works: We collect a blood, another fluid or a tissue sample and send it to a laboratory. The laboratory looks for changes in genes. Your doctor or medical geneticist receives a report and talks with you about what the results reveal about the condition and risks.