A set of recording electrodes is taped to the skin over the muscles or skin. Wires connect the electrodes to an EMG machine. A small electrical pulse similar to the sensation of static electricity is given on the skin a short distance away to stimulate the nerve to the muscle or skin.
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The electrical signal is viewed on the EMG machine. The physician then reviews the response to verify any nerve damage or muscle disease. There is minimal discomfort and no risk associated with this test. Electronystagmography ENG describes a group of tests used to diagnose involuntary eye movement, dizziness, and balance disorders. The test is performed at a clinic or imaging center. Small electrodes are taped on the skin around the eyes to record eye movements.
If infrared photography is used in place of electrodes, the person being tested wears special goggles that help record the information. Both versions of the test are painless and risk-free. Evoked potentials , also called evoked response, measure the electrical signals to the brain generated by hearing, touch, or sight. Evoked potentials are used to test sight and hearing especially in infants and young children and can help diagnose such neurological conditions as multiple sclerosis, spinal cord injury, and acoustic neuroma small tumors of the acoustic nerve.
Evoked potentials are also used to monitor brain activity among coma patients, and confirm brain death. A machine records the amount of time it takes for impulses generated by stimuli to reach the brain. Myelography involves the injection of contrast dye into the spinal canal to enhance imaging of the spine, by CT or by X-ray. Myelograms have mostly been replaced by MRI, but may be used in special situations.
For example, myelograms may be used to diagnose tumors of the spine or spinal cord or spinal cord compression from herniated discs or fractures. The procedure takes about 60 minutes and can be performed as an outpatient procedure.
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Following an injection of anesthesia to a site between two vertebrae in the lower back, a small amount of the cerebrospinal fluid is removed by spinal tap see cerebrospinal fluid analysis, above. Contrast dye is injected into the spinal canal and a CT scan or a series of x-rays is taken. People may experience some pain during the spinal tap as well as headache following the spinal tap. There is a slight risk of fluid leakage or allergic reaction to the dye. It is performed over one or more nights at a sleep center. The person may be videotaped to note any movement during sleep.
Results are then used to identify any characteristic patterns of sleep disorders, including restless legs syndrome, periodic limb movement disorder, insomnia, and breathing disorders such as sleep apnea. Polysomnograms are noninvasive, painless, and risk-free. Thermography also known as digital infrared thermal imaging uses infrared sensing devices to measure small temperature changes and thermal abnormalities between the two sides of the body or within a specific organ.
Some scientists question its use in diagnosing neurological disorders. It may be used to evaluate complex regional pain syndromes and certain peripheral nerve disorders, and nerve root compression. It is performed at a specialized imaging center, using infrared light recorders to take pictures of the body.
The information is converted into a computer-generated two-dimensional picture of abnormally cold or hot areas indicated by color or shades of black and white.
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Thermography does not use radiation and is safe, risk-free, and noninvasive. Ultrasound imaging , also called ultrasonography, uses high-frequency sound waves to obtain images inside the body. During an ultrasound examination, the person lies on a table or reclines in an examination chair. A jelly-like lubricant is applied to the bare skin and a transducer, which both sends and receives high-frequency sound waves, is passed over the body.
The sound wave echoes are recorded and displayed as a computer-generated real-time visual image of the structure or tissue being examined. Ultrasound is painless, noninvasive, and risk-free. The test is performed on an outpatient basis and takes between 15 and 30 minutes to complete.
Ultrasound can be used to assess changes in the anatomy of soft tissues, including muscle and nerve. It is more effective than an x-ray in displaying soft tissue changes, such as tears in ligaments or soft tissue masses. In pregnant women, ultrasound can suggest the diagnosis of conditions such as chromosomal disorders in the fetus. The ultrasound creates a picture of the fetus and the placenta. Ultrasound also may be used in newborns to diagnose hydrocephalus build-up of cerebrospinal fluid in the brain or hemorrhage.
X-rays can be used to view any part of the body, such as a joint or major organ system. In a conventional x-ray, a concentrated burst of low-dose ionized radiation passes through the body and onto a photographic plate. Since calcium in bones absorbs x-rays more easily than soft tissue or muscle, the bony structure appears white on the film.
Any vertebral misalignment or fractures can be seen within minutes. Tissue masses such as injured ligaments or a bulging disc are not visible on conventional x-rays. Fluoroscopy is a type of x-ray that uses a continuous or pulsed beam of low-dose radiation to produce continuous images of a body part in motion.
The fluoroscope x-ray tube is focused on the area of interest and pictures are either videotaped or sent to a monitor for viewing. Fluoroscopy is used to evaluate swallowing and can be used for other procedures, such as a lumbar puncture, angiogram for clot removal, or myelogram. Scientists funded by the National Institute of Neurological Disorders and Stroke seek to develop additional and improved screening methods to more accurately and quickly confirm a specific diagnosis and investigate other factors that might contribute to disease.
Technological advances in imaging will allow researchers to better see inside the body, at less risk to the person. These diagnostics and procedures will continue to be important clinical research tools for confirming a neurological disorder, charting disease progression, and monitoring therapeutic effect. Box Bethesda, MD NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency.
Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history. Skip to main content. Submit Search.
Where can I get more information Diagnostic tests and procedures are vital tools that help physicians confirm or rule out a neurological disorder or other medical condition. Doctors may also use a type of blood test called a triple screen in order to identify some genetic disorders, including trisomies disorders such as Down syndrome in which the fetus has an extra chromosome in an unborn baby. A blood sample is taken from a pregnant woman and tested for three substances: alpha-fetoprotein, human chorionic gonadotropin, and estriol.
The test is performed between the 15th and 20th week of pregnancy. It usually takes several days to receive results from a triple screen. However, the test has many false positive results, so additional testing is needed to confirm if there is a problem. Amniocentesis is usually done at weeks of pregnancy. It tests a sample of the amniotic fluid in the womb for genetic defects the cells found in the fluid and the fetus have the same DNA. About 20 milliliters of fluid roughly 4 teaspoons is withdrawn and sent to a lab for evaluation.
Test results often take weeks. Chorionic villus sampling is performed by removing and testing a very small sample of the placenta during early pregnancy. The sample, which contains the same DNA as the fetus, is removed by catheter or fine needle inserted through the cervix or by a fine needle inserted through the abdomen.
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Results are usually available within 2 weeks. Computed tomography CT scan uses X-rays to produce two-dimensional images of organs, bones, and tissues. A CT scan can aid in proper diagnosis by showing the area of the brain that is affected.