Below are brief explanations of the diagnostic tests performed by Drexel Neurology in Philadelphia, listed by condition being evaluated.
Cognition
Neuropsychological Evaluation
What is it?
A neuropsychological evaluation consists of paper-and-pencil or computerized tests that are used to determine brain function. Intelligence, memory, language function and executive function are usually evaluated.
Why should I do it?
To measure brain function when there might be a problem with intelligence, memory, language function and executive function due to dementia, stroke, multiple sclerosis, epilepsy, trauma, pain syndromes or ALS.
How is it performed?
Neuropsychological tests are typically administered to a single person working with an examiner in a quiet office environment, free from distractions. As such, it can be argued that neuropsychological tests at times offer an estimate of a person's peak level of cognitive performance. Neuropsychological tests are a core component of the process of conducting neuropsychological assessment, along with personal, interpersonal and contextual factors.
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Nerve and Muscle
Electromyography (EMG)
What is it?
An electromyogram (EMG) is a test that measures the electrical activity of a muscle. It detects any signs of blocking or slowing down of responses to nerve stimulation. The test provides information about the muscle itself and shows how well it receives stimulation from the nerve. A nerve conduction velocity (NCV) test is often done at the same time as an EMG.
Why should I do it?
An EMG is often used to evaluate unexplained muscle weakness, twitching or paralysis, and to find the causes of numbness, tingling and pain. EMG testing can differentiate between true weakness and reduced use because of pain or lack of motivation. It can also determine whether a muscle disorder begins in the muscle itself or is caused by a nerve disorder.
How is it performed?
In an EMG, a physician or technician inserts a very fine needle, which serves as an electrode, through the skin into the muscle. With the electrode in place, the patient is asked to slowly contract the muscle—for example, by bending the arm—with gradually increasing force, while the electrical activity is being recorded. The activity can be displayed visually on an oscilloscope or screen, or played audibly through a speaker. The results can provide information about the ability of the muscle to respond to nerve stimulation.
How will it feel?
You may feel some minor discomfort, similar to an injection, when the needle or needles are inserted. Afterward, the examined muscle may feel tender or sore for a few days, and there may be a small bruise.
Nerve Conduction Studies (EMG/NCS)
What is it?
A nerve conduction velocity test, also called a nerve conduction study, measures how quickly electrical impulses move along a nerve. It is often done at the same time as an electromyogram, in order to exclude or detect muscle disorders.
A healthy nerve conducts signals with greater speed and strength than a damaged nerve. The speed of nerve conduction is influenced by the myelin sheath—the insulating coating that surrounds the nerve.
Why should I do it?
This test is used to diagnose nerve damage or dysfunction and confirm a particular diagnosis. It can usually differentiate injury to the nerve fiber (axon) from injury to the myelin sheath surrounding the nerve, which is useful in diagnostic and therapeutic strategies.
How is it performed?
During the test, flat electrodes are placed on the skin at intervals over the nerve that is being examined. A low-intensity electric current is introduced to stimulate the nerves.
How will it feel?
There is generally minimal discomfort with the test because the electrical stimulus is small; usually it is barely felt by the patient.
Quantitative Sensory Testing (QST)
What is it?
Quantitative sensory testing (QST) is a method used to assess damage to the small nerve endings, which detect changes in temperature, and the large nerve endings, which detect vibration.
Why do it?
QST is used to diagnose and assess the severity of nerve damage, especially in the small nerve endings. It can also help determine if a neuropathy is responding to treatment. It is used to diagnose many different types of neuropathies, including peripheral neuropathies. It may also be used to identify where the nerves are damaged.
How is it performed?
QST uses a computer testing system to measure how the nerves involved react to vibration and changes in temperature. The test results are compared to a series of "normal" patients as well as to the patient's unaffected side.
How will it feel?
Depending on the specific test, the patient will feel mild vibrations and hot and cold sensations. The procedure is non-invasive—no needles are used. Overall, little or no discomfort should be felt during the test.
Laser Doppler Perfusion Imaging (LDPI)
What is it?
LDPI is based on the recording of Doppler shift caused by movements of red blood cells in the backscattered light of a laser beam that scans a tissue. It can estimate the blood flow to the overlying skin.
Why do it?
LDPI is done to measure changes in blood flow to skin that can occur with autonomic neuropathies such as CRPS.
How is it performed?
The instrument scans the hands and feet. It takes several minutes.
How will it feel?
Patients seldom feel anything abnormal when this test is performed.
Neuromuscular Ultrasound
What is it?
Ultrasound uses sound waves to provide real-time, high-resolution images of muscles and nerves throughout the body. Ultrasound is used to diagnose and treat a wide range of nerve and muscle disorders. Ultrasound can also be performed live, allowing dynamic evaluation of movement of nerves and muscles, as well as guiding needles to target areas throughout the body. Ultrasound does not use radiation. It can be used for diagnosis and treatment of carpal tunnel syndrome.
Why do it?
It is a painless way to evaluate swelling and entrapment of nerves and to get information about the health of muscles. This information can supplement other data about nerve and muscle function. It can also be used to guide diagnostic and therapeutic injections into tissues around nerves or into muscles in spasm. It can be used with BOTOX® injections.
How is it performed?
Conductive gel and a small ultrasound probe are placed on the skin. During ultrasound-guided injections, practitioners can directly visualize the needle passing to the target. Direct visualization ensures accuracy and a greater margin of safety. Smaller needles may also be used, improving patient comfort and potentially reducing risk.
How will it feel?
Patients seldom feel anything abnormal when this test is performed.
Cutaneous (Skin) Nerve Biopsy
What is it?
Cutaneous nerve biopsy is a sample of skin that will be analyzed microscopically to determine the health of the small nerves in skin. It is used to diagnose and monitor small fiber neuropathies.
Why do it?
This is a way to visualize the small nerves in skin that cannot be studied electrically. A diagnosis of small fiber neuropathy can be made based upon these results. This commonly occurs in patients with diabetes. Cutaneous nerve and skin biopsies can also be useful to diagnose patchy numbness.
How is it performed?
After anesthetizing the skin, a small (3 mm) circular needle is used to core a piece of skin. There can be mild bleeding afterward. This is usually done at two sites near the ankle.
How will it feel?
There should be little or no pain after the injection of anesthesia. There could be tenderness for a week after the biopsy.
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Epilepsy
Electroencephalogram (EEG)
What is it?
An EEG measures and records the electrical activity of the neurons in the brain. It is used in the diagnosis and follow-up of epilepsy. It can also be used to evaluate alterations to the patient's level of consciousness.
Why do it?
EEGs are done to determine if a patient is having seizures. The test can be done to evaluate problems with memory and level of consciousness.
How is it done?
The head is measured and 21 electrodes are placed on the brain with a conductive gel. These electrodes are connected to the EEG equipment which amplifies the brain's activity. Usually, you will be asked to breathe heavily for up to three minutes. A strobe light will be flashed at you at different rates. Brain activity is recorded for 20 minutes. The entire procedure takes about an hour.
How will it feel?
You are lying in a bed during the procedure. Many patients fall asleep during the test. There is no pain involved. You will have to wash your hair afterwards.
Ambulatory EEG (AEEG)
What is it?
AEEG is a continuous recording of your brain activity for up to 72 hours or more. You are able to go about normal activities at home.
Why do it?
AEEG is done when conventional EEG testing has been inconclusive.
How is it done?
The same 20 electrodes are place on the brain with a more durable adhesive. The electrodes are connected to a portable recorder that you carry around with you.
How will it feel?
There is no pain or discomfort with this test.
Inpatient Video EEG Monitoring
What is it?
When routine or ambulatory EEGs have been inconclusive, a patient can be admitted to our inpatient epilepsy monitoring unit. Video and EEG recording is collected for 72 hours or more, if needed.
Why do it?
Inpatient video EEG monitoring is done to "catch" seizure activity and to correlate it with the outwardly observed behaviors.
How will it feel?
There is no pain or discomfort with this test.
Evoked Potential (EP)
What is it?
EPs are a way to measure electrical conduction through the central nervous system. We can measure conduction through the optical system (visual evoked potential-VEP), sensory system (somato-sensory evoked potential-SSEP) and hearing system (brainstem auditory evoked potential-BAEP).
Why do it?
EP testing is a useful adjunct to the diagnosis of MS. It can also be used to study abnormal conduction through the spinal cord in compression and tumors. Auditory testing is helpful with tumors of the auditory nerve.
How is it performed?
Electrodes are place on the head. For VEP, you look at a monitor with changing patterns. For SSEP, electrodes are also placed of the limbs and spinal cord. You will feel mild electrical shocks during the test. For BAEP, ear buds play clicks.
How will it feel?
The only test that has some discomfort is the SSEP test.
Balance Testing (BESTest)
What is it?
BESTest is a means to differentiate balance into 6 underlying systems that may constrain balance: Biomechanical, Stability Limits, Postural Responses, Anticipatory Postural Adjustments, Sensory Orientation, and Dynamic Balance During Gait and Cognitive Effects.
Why do it?
This unique evaluation tool is appropriate for patients of any age with any severity of balance problems. In addition to patients with MS, it can also be useful in Parkinson's disease, cerebellar ataxia, vestibular disorders, neuropathy, head injury, stroke, and cerebral palsy. The BESTest is a sensitive, quantitative balance assessment that can identify subtle deficits and suggest changes with therapy.
How is it performed?
A physical therapist asks you to do certain balance tasks while taking measurements.
How will it feel?
It will feel like your balance is being tested.
Lumbar Puncture (spinal tap or LP)
What is it?
It is the way to collect cerebrospinal fluid (CSF) for testing. CSF is normally clear and colorless. It surrounds the brain and spinal cord and acts as a buffer. Any changes in the fluid's color, consistency or quantity may indicate a neurological disease or disorder.
Why do it?
To identify autoimmune disorders, such as Guillain-Barré Syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP), multiple sclerosis or infection and to guide proper treatment. White blood cells may be present during infection. High protein levels are often a sign of peripheral nerve disorder such as GBS or CIDP. Abnormal antibodies may suggest multiple sclerosis.
How is it performed?
The patient is positioned lying on his/her side. A small anesthetic is injected into the skin in the middle of the lower back. A long, thin needle is inserted into this region and in the spinal canal. The CSF pressure is measured and fluid is collected for testing. After the sample is collected, the needle is removed and the patient remains flat for an hour after the test.
How it will feel?
Overall, discomfort from the procedure is minimal. The entire procedure usually takes about 30 minutes. The actual pressure measurement and fluid collection take only a few minutes. Some patients experience headaches, hours or days after the test. These headaches almost always disappear spontaneously over time.
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