Diagnostic Testing at the Drexel Neurosciences Institute
Below are brief explanations of the diagnostic tests performed by the Drexel Neurosciences Institute in Philadelphia, listed by the condition being evaluated.
- Neuropsychological evaluation
Nerve and Muscle
- Electromyography (EMG)
- Nerve conduction studies (NCS)
- Quantitative sensory testing (QST)
- Laser doppler perfusion imaging (LDPI)
- Neuromuscular ultrasound
- Cutaneous nerve biopsy
Epilepsy and Multiple Sclerosis
- Electroencephalogram (EEG)
- Ambulatory EEG (AEEG)
- Inpatient video EEG monitoring
- Evoked potential
- Balance testing
- Lumbar puncture (spinal tap or LP)
Cognitive Diagnostic Testing
A neuropsychological evaluation consists of paper-and-pencil or computerized tests that are used to determine brain function. Intelligence, memory, language function, and overall function are usually evaluated to see if there is an indication of loss of ability due to dementia, stroke, multiple sclerosis, epilepsy, trauma or pain syndromes.
Neuropsychological tests are administered privately with an examiner in a quiet office environment, free from distractions. This allows for an evaluation of a person at their highest level of concentration.
Nerve and Muscle
An electromyography (EMG) test measures the electrical activity of a muscle. It detects any signs of blocking or slowing down of responses to nerve stimulation. An EMG provides information about the muscle itself and shows how well the muscle receives stimulation from the nerve. A nerve conduction velocity test (see below) is often done at the same time as an EMG.
An EMG is often used to evaluate unexplained muscle weakness, twitching or paralysis, and to find the causes of numbness, tingling and pain. During 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. Patients may feel some discomfort after the test.
Nerve Conduction Studies (EMG/NCS)
A nerve conduction velocity test, also called a nerve conduction study, measures how quickly electrical impulses move along a nerve. A healthy nerve conducts signals with greater speed and strength than a damaged nerve. A nerve velocity test is often done at the same time as an electromyography test (see above), in order to exclude or detect muscle disorders. 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.
Quantitative Sensory Testing (QST)
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. QST is used to diagnose and assess the severity of nerve damage and to determine if a neuropathy is responding to treatment. Quantitative sensory testing uses a computer testing system to measure how the nerves involved react to vibration and changes in temperature.
Laser Doppler Perfusion Imaging (LDPI)
Laser doppler perfusion imaging (LDPI) records the movements of red blood cells and can estimate the blood flow to the overlying skin of the area in focus. LDPI is done to measure changes in blood flow to skin that can occur with autonomic neuropathies such as CRPS.
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 including carpal tunnel syndrome. Because ultrasound is performed live, doctors can effectively and painlessly evaluate the movement of nerves and muscles.
Ultrasound is also used to guide needles to target areas throughout the body for steroid and BOTOX® injections.
Cutaneous (Skin) Nerve Biopsy
Cutaneous nerve biopsy is when a small sample of skin is taken to be analyzed microscopically to determine the health of the small nerves in skin. It is used to diagnose and monitor small fiber neuropathies. Cutaneous nerve biopsy allows doctors to visualize the small nerves in skin that cannot be studied electrically.
During cutaneous nerve biopsy the skin is anesthetized and a small circular needle is used to collect a piece of skin. There should be little or no pain after the injection of anesthesia. Some tenderness may occur after the biopsy.
Epilepsy and Multiple Sclerosis
An electroencephalogram measures and records the electrical activity of the neurons in the brain. It is used in the diagnosis and follow-up of epilepsy to determine if a patient is having seizures and to evaluate problems with memory and level of consciousness.
During an EEG, 21 electrodes are placed on the brain with a conductive gel. The electrodes are connected to the EEG equipment which amplifies the brain's activity. Brain activity is recorded for 20 minutes.
Ambulatory EEG (AEEG)
Ambulatory EEG (AEEG) is a continuous recording of brain activity for 72 hours or more. The test is similar to EEG, but patients are given a portable device to record activity and they can go about their normal activities at home. AEEG is done when conventional EEG testing has been inconclusive.
Inpatient Video EEG Monitoring
When routine EEGs have been inconclusive, a patient can be admitted to our inpatient epilepsy monitoring unit. Video and EEG data are collected for 72 hours or more, if needed. Drexel neurologists use this close monitoring to "catch" seizure activity and to correlate it with outwardly observed behaviors.
Evoked potential tests are a way to measure electrical conduction through the central nervous system. We can measure conduction through the optical system (visual evoked potential or VEP), sensory system (somato-sensory evoked potential or SSEP), and hearing system (brainstem auditory evoked potential or BAEP). Evoked potential testing is used to diagnose multiple sclerosis. 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.
Balance testing analyzes six different aspects of balance. This unique evaluation tool is appropriate for patients of any age with any severity of balance problems. In addition to patients with multiple sclerosis, it can also be useful in Parkinson's disease, cerebellar ataxia, vestibular disorders, neuropathy, head injury, stroke, and cerebral palsy.
Lumbar Puncture (spinal tap or LP)
A lumbar puncture, or spinal tap, is the collection of 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. A spinal tap is used to identify autoimmune disorders, such as Guillain-Barré Syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), multiple sclerosis, or infection. During a spinal tap, anesthetic is injected into the skin of the lower back, followed by a long, thin needle that will measure the CSF pressure and collect fluid for testing. After the sample is collected, the needle is removed. The patient remains flat for an hour after the test.
The information on these pages is provided for general information only and should not be used for diagnosis or treatment, or as a substitute for consultation with a physician or health care professional. If you have specific questions or concerns about your health, you should consult your health care professional.