Electroencephalography (EEG) is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain’s spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus on thespectral content of EEG, that is, the type of neural oscillations that can be observed in EEG signals. 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.A secondary clinical use of EEG is in the diagnosis ofcoma, encephalopathies and brain death. A third clinical use of EEG is for studies of sleep and sleep disorders where recordings are typically done for one full night, sometimes more. EEG used to be a first-line method for the diagnosis of tumrs, stroke and other focal brain disorders, but this use has decreased with the advent of anatomical imaging techniques with high (
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 of the human body.Nerve conduction velocity (NCV) is a common measurement made during this test.
Nerve conduction studies are used mainly for evaluation of paresthesias (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 thorough history also help to direct the investigation. Some of the common disorders that can be diagnosed by nerve conduction studies are:
• Peripheral neuropathy
• Carpal tunnel syndrome
• Ulnar neuropathy
• Guillain-Barre syndrome
• Facioscapulohumeral muscular dystrophy
• Spinal disc herniation
• Cubital Tunnel Syndrome
• Tarsal Tunnel Syndrome
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. It is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, recruitment order or to analyze the biomechanics of human or animal movement.