Generalized EEG Abnormality
Electroencephalography (EEG) is performed by placing electrodes on the scalp to record the electrical activity of the brain. The test is painless and takes about 90 minutes.
If a physician wants to study brains patterns that occur during sleep, patients are asked to come for the test without sleeping the night before.
Digital ambulatory electroencephalography records brain activity for 24 hours. The test is performed while patients go about their everyday activities. They wear a small digital recorder on their waist and electrodes are applied to their scalp with a glue-like substance. The patient is given a diary and asked to monitor and record symptoms that might occur throughout the day.
EEGs are sometimes used during certain types of brain or spinal cord surgery to provide the surgeon with information about how the brain is functioning.
EEGs are performed to help diagnose different neurological conditions, the most common of which are seizure disorders, headaches, and dizziness. EEGs are also used in cases of stroke, degenerative brain disease, irreversible brain death, psychiatric illness, and even some disabilities that occur in children.
Evoked potential (EP) tests record the electrical activity of the brain, spinal nerves, or sensory receptors through electrodes placed on the scalp and other places on the body. These electrodes record the patient's response to specific types of external stimulation. A series of stimuli are produced through the electrodes, and hundreds of responses are recorded and graphed.
Evoked potential studies help evaluate neurological conditions such as spinal cord injuries, optic neuritis, acoustic neuroma, neuropathies, degenerative neuromuscular diseases, multiple sclerosis, and other neuromuscular and neurological diseases.
There are different types of evoked potential testing. Each tests a different neurological pathway and may be performed as an outpatient procedure for diagnostic purposes or during surgery to monitor nerve, brain, and spinal cord function. The most common types of evoked potentials are as follows:
Brainstem Auditory Evoked Response (BAER). In a brainstem auditory evoked response (BAER) test, earphones deliver a series of clicks or tones to each ear. Brainstem auditory evoked responses are recorded to evaluate the auditory (hearing) nerve pathways from the ears through the brainstem. Brainstem auditory evoked responses are evoked potentials used to detect, localize, and monitor auditory and neurological deficits in difficult-to-test populations such as patients unable or unwilling to participate in a traditional behavioral test protocol. Brainstem auditory evoked responses are also used in the evaluation and identification of neurological abnormalities.
Somatosensory Evoked Potentials. Somatosensory evoked potentials (SSEPs) testing is performed by applying a small, painless electrical current to the skin over nerves on the arms or legs. SSEPs are used to assess the neural pathways from the arms or legs to the spinal cord to the brainstem or cerebral cortex.
Visual Evoked Potentials. Visual evoked potential (VEP) testing is used to evaluate the visual nerve pathways from the eyes to the occipital cortex (visual center) of the brain. Patients stare at a pattern on a video screen while visual evoked potentials are recorded. Patients concentrate on a checkerboard pattern on a video screen while visual evoked potentials are recorded.
All Evoked Potential testing takes roughly 1 to 1.5 hours to complete.
Nerve Conduction Studies
Nerve conduction studies are performed by placing electrodes on the skin over particular nerves or a muscle that is innervated by a nerve. Electrical stimulation is applied to activate the nerve. The test is not painful, but a tingling sensation is felt. Nerve conduction studies are used to evaluate conditions that produce numbness, tingling, pain, loss of sensation or other neurological diseases affecting the peripheral nervous system.
Nerve conduction studies are performed by a technologist. Testing usually takes 1 to 1.5 hours but can vary depending on the diagnosis and findings.
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