Clinical neurophysiology

Clinical neurophysiology uses measurement of electrical activity in the nervous system to diagnose and monitor disease. Electro-encephalography (EEG) and nerve conduction studies (NCS) with electromyography (EMG) are the tests most used in general medical patients. Specialized investigations for neurological diseases and operative or long-term monitoring are available, but are beyond the scope of this article.The EEG is a simple, non-invasive test of brain function used mostly to diagnose and classify epilepsy. Bilateral three per second spike and slow-wave complexes are seen in primary generalized epilepsy, and localized spike discharges in focal seizures. Prolonged recordings of seizures, allowing a clinical and electrographic correlation, are sometimes needed for precise diagnosis. Characteristic EEG waveforms (slow waves, triphasic or repetitive complexes) can help in the management and prognosis of other disorders such as encephalitis and encephalopathy. Nerve conduction and needle EMG studies investigate peripheral neuromuscular disorders, especially to confirm and assess the severity of peripheral nerve disease. Clinical neurophysiologists are often asked to investigate patients with undiagnosed neurological symptoms, and these tests can provide objective information as an extension of the clinical examination. Measurement of sensory nerve action potentials helps to locate lesions in sensory pathways. A combination of motor nerve conduction and needle EMG studies is particularly useful when investigating patients with weakness.