Electroencephalography (EEG) is the recording of electrical activity along the scalp. An electroencephalogram (EEG) is a noninvasive test that records electrical patterns in the brain. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. An EEG measures electricity that your brain makes; it does not measure thoughts or feelings, and it does not send any electricity into your brain. In a clinical context, EEG refers to the recording of the brain spontaneous electrical activity over a short period of time, usually 40 minutes, as recorded from multiple electrodes placed on the scalp. In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study. Secondary clinical use of EEG is in the diagnosis of coma, encephalopathies, and brain death. EEG is also used for studies of sleep and sleep disorders where recordings are typically done for one full night, sometimes more.
Nerve Conduction and EMG
A nerve conduction study (NCS) is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves in the human body. Nerve conduction velocity (NCV) is a common measurement made during this test. Nerve conduction studies are used mainly for evaluation of paresthesia (numbness, tingling, burning) and/or weakness of the arms and legs. The type of study required is dependent in part by the symptoms presented. A physical exam and a thorough history also help to direct the investigation. Some of the common disorders that can be diagnosed by nerve conduction studies are: