ABPN Clinical Neurophysiology key terms

An international method for placing scalp electrodes at measured proportional distances between landmarks like the nasion and inion, so that electrode positions are reproducible across patients and laboratories.

A bipolar longitudinal EEG layout that chains electrodes along each temporal and parasagittal line from front to back, allowing side-to-side comparison of activity across the hemispheres.

An EEG display in which each active scalp electrode is compared against a single common reference, making it useful for judging the true amplitude and field of a discharge.

A pattern in bipolar recordings where two adjacent channels deflect in opposite directions, localizing the source to the electrode shared by those channels.

An EEG channel created by subtracting the voltage at one electrode from another nearby electrode, emphasizing focal differences in activity between the two sites.

A posterior-dominant sinusoidal rhythm near 8 to 13 Hz that appears with relaxed wakefulness and eye closure and attenuates with visual attention or eye opening.

The background rhythm seen over the occipital regions of a normal awake adult, typically in the alpha frequency range and symmetric between hemispheres.

An arch-shaped 7 to 11 Hz rhythm over the central scalp that attenuates with contralateral movement or the thought of movement, an normal variant easily mistaken for a focal discharge.

Faster, higher-amplitude activity over a skull defect caused by loss of the filtering effect of bone, which can mimic an epileptiform focus.

A sharply contoured EEG transient such as a spike or sharp wave that stands out from background and suggests cortical hyperexcitability, though it does not by itself prove epilepsy.

A discharge consisting of a spike followed by a slow wave, classically seen in generalized absence epilepsy at about 3 Hz.

A chaotic, high-amplitude, disorganized EEG pattern with multifocal spikes and slow waves seen in infantile spasms and other severe early encephalopathies.

An EEG pattern of high-amplitude bursts alternating with nearly flat suppression, indicating severe cortical depression from anesthesia, hypoxia, or deep coma.

Absence of detectable cortical electrical activity on EEG at maximal sensitivity, used as an ancillary test supporting the diagnosis of brain death when appropriate conditions are met.

The ongoing EEG rhythms present between transients, whose frequency, amplitude, symmetry, and reactivity provide information about overall cerebral function.

The earliest EEG change marking a focal seizure, such as rhythmic activity, a sudden frequency shift, or low-voltage fast activity, used to localize the epileptogenic zone.

The evolving rhythmic EEG activity during a clinical seizure, typically changing in frequency, amplitude, and field as the event progresses.

The summed electrical response recorded from a muscle after its motor nerve is stimulated, reflecting the number of excitable motor axons and their conduction.

The small electrical response recorded from a sensory nerve after stimulation, used to assess sensory axonal integrity and conduction velocity.

The speed at which an action potential travels along a nerve, calculated from the distance between stimulation sites divided by the difference in response latencies.

A late motor response produced by backfiring of anterior horn cells after antidromic travel of an impulse, useful for assessing proximal nerve segments.

A monosynaptic reflex response recorded from muscle after submaximal nerve stimulation, analogous to the ankle jerk and helpful for evaluating proximal sensory pathways.

A technique using a needle electrode inserted into muscle to record spontaneous and voluntary electrical activity at rest and during contraction.

A spontaneous, brief, regular discharge of a single muscle fiber seen at rest after nerve injury, indicating active denervation.

A spontaneous needle EMG waveform with an initial positive deflection followed by a slow negative return, another sign of active denervation.

The waveform recorded from a motor unit during voluntary contraction, whose duration, amplitude, and number of phases help distinguish neuropathic from myopathic disease.

The orderly addition of motor units as contraction effort increases, normally beginning with smaller units firing faster before larger units are added.

Nerve disease that slows conduction or blocks impulses, producing markedly prolonged latencies and reduced velocities with relative preservation of response amplitude.

Nerve disease that reduces the number of functioning axons, typically lowering response amplitudes with only mild slowing of conduction.

A cortical response recorded over the occipital scalp after a patterned visual stimulus, used to detect demyelination or compression along the visual pathways.

A series of short-latency waves recorded after click stimulation that reflect conduction through the auditory nerve and brainstem, useful for detecting acoustic neuroma or brainstem lesions.

Cortical and subcortical responses recorded after electrical stimulation of a peripheral nerve, used to assess the dorsal column pathway and for intraoperative monitoring.

The number of apneas and hypopneas per hour of sleep, the standard measure used to grade the severity of sleep-disordered breathing.

A multichannel overnight recording of brain waves, eye movements, muscle tone, breathing, oxygen saturation, and heart rhythm used to stage sleep and diagnose sleep disorders.

A sleep stage with low-voltage mixed-frequency EEG, rapid eye movements, and very low chin muscle tone, during which most vivid dreaming occurs.

A pause in breathing during sleep caused by absent respiratory effort rather than airway obstruction, distinguished from obstructive events by respiratory monitoring channels.

A test that measures sweat output after iontophoretic acetylcholine stimulation to assess postganglionic sudomotor nerve function and diagnose small-fiber autonomic neuropathy.

A procedure that monitors heart rate and blood pressure as the patient is moved upright to reproduce syncope and identify neurally mediated or orthostatic causes.

The beat-to-beat variation in heart rate, reflecting the balance of sympathetic and parasympathetic control and used to assess autonomic function.