The EEG is performed by placing electrodes on the scalp. Generally, these are superficial stickers which are attached to wires which carry information to the monitor which displays the results. In some cases where a continuous EEG is to be taken for a prolonged period of time, such as in a comatose head trauma victim, the electrodes can be implanted in the scalp as tiny needles. The electrodes record electrical activity from the surface of the brain which is converted to a trace on the electroencephalogram output, traditionally wiggly lines on a sheet of paper although nowadays they are often simply displayed on a computer screen. The shape, frequency, amplitude and other characteristics of the trace from various regions of the brain are interpreted by a physician, usually a neurologist, and can reveal changes in the electrical activity of the brain. Evaluation with an EEG varies depending on the clinical situation. In some patients a short EEG will be taken while in others a prolonged EEG overnight or even longer may be required. Patients with epilepsy will often undergo prolonged EEG monitoring in the attempt to catch a seizure on the EEG so that physicians can determine the location it originated from and other characteristics which may help in treatment. The EEG is also used to evaluate other general changes in the activity of the brain. For example, patients in coma are sometimes followed with EEG both to rule out subclinical seizures but also to evaluate for signs of recovery or brain death. In fact, determination of brain death sometimes utilizes EEG to determine if there is any normal brain activity. While the diagnosis of brain death does not require an EEG, it sometimes helps physicians feel confident that their is no normal brain activity. An EMG is often performed along with a nerve conduction study as part of a neurological assessmentfor various diseases that affect the muscles and/or nervous system. The nerve conduction study is performed by placing surface electrodes over nerves, usually in the arms and/or legs. The electrodes are used to stimulate the nerves and then record the conduction of the signal down the nerve to some other point. This can be done in several positions to help determine the site of nerve injury or disease which may be causing the patient's symptoms. The information supplied by the test can aid in the diagnosis of these disorders and in some cases can help direct treatment as well. For example, it may direct a surgeon to the likely site of injury of the nerve so that their treatment can be focused on the correct area.What Is It?
An electroencephalogram (EEG) is a neurological test which records the electrical activity at the surface of the brain by way of electrodes placed on or in the scalp.What Is It Used For?
Because the EEG reveals changes in the electrical activity of the neurons in the brain, it can aid in the diagnosis of various pathologies. Traditionally, besides general nervous system research, the EEG has been used to evaluate patients with epilepsy. Seizures, either generalized to the whole brain or focal, can often be seen as a characteristic rhythmic activity on the EEG which is quite different from the normal, seemingly random activity. Therefore, the electroencephalogram is often used to diagnose and work-up patients who present with seizures or activity which is suspicious for epilepsy.Electromyogram (EMG)
What Is It?
An electromyogram (EMG) is a neurological test, usually performed by a neurologist, which evaluates the responses of muscles and the nerves that supply them. It is performed by inserting small needles into various muscles that act as stimulating and recording electrodes. Through these electrodes the muscle is stimulated and the EMG can record the responses that occur in the muscle.What Is It Used For?
The EMG provides the physician with information about the functioning of both the muscle and the nerves that supply that muscle. This can be used to help diagnose various diseases that affect these structures. For example, EMG may be used as part of the work-up for diseases of the muscle such as muscular dystrophies. Additionally, along with a nerve conduction study, it may be used to evaluate disease of the peripheral nerves such as peripheral nerve tumors, neuropathies, traumatic nerve injuries, nerve entrapments (such as carpal tunnel syndrome) and various diseases of the spine which involve the nerves as the enter or leave the spinal cord.Nerve Conduction Study
What Is It?
A nerve conduction study is a neurological test, usually performed by a neurologist and often along with anelectromyogram, which evaluates the conduction of electrical impulses down peripheral nerves. Because nerves conduct signals at a standard speed and amplitude, diseases of the nerves which may alter these impulses can be detected by measurement of these signals.What Is It Used For?
The nerve conduction test provides physicians with information about the functioning of the peripheral nerves including both the type of dysfunction and the likely location of its cause. This can be used to help diagnose various diseases that impact the nerves. Some pathologies of the peripheral nerves for which work-up can include a nerve conduction test include peripheral nerve tumors, neuropathies, traumatic nerve injuries, nerve entrapments (such as carpal tunnel syndrome) and various diseases of the spine which involve the nerves as the enter or leave the spinal cord.
Wednesday, March 31, 2010
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