![]() ![]() (2) Not to be confused with posterior slow waves of youth. Comments: (1) often at a supra- or sub-harmonic of alpha frequency and may occur when no alpha rhythm is visible. Synonym: posterior dominant rhythm.Īlpha variant rhythms: An EEG rhythm recorded most prominently over the posterior regions of the head that differs in frequency, but resembles in reactivity, the alpha rhythm. Activities in the alpha band which differ from the alpha rhythm as regards their topography and/or reactivity, should either have specific appellations (for instance: the mu rhythm and alpha coma) or should be referred to as rhythms of alpha frequency or alpha activity. Comment: use of term rhythm must be restricted to those rhythms that fulfill these criteria. Blocked or attenuated by attention, especially visual, and mental effort. Best seen with the eyes closed, during physical relaxation and relative mental inactivity. Amplitude varies but is mostly below 50 µV in the adult, but often much higher in children. Greek letter: α.Īlpha rhythm: Rhythm at 8–13 Hz inclusive occurring during wakefulness over the posterior regions of the head, generally with maximum amplitudes over the occipital areas. Comment: Distortion and aliasing can occur at the Nyquist theorem frequency (see Nyquist theorem, sampling rate).Īlpha band: Frequency band of 8–13 Hz inclusive. The Nyquist theorem states that sampling rates should be at least twice the highest frequency, but accurate digitization of EEG signals requires even higher sampling rates. (2) Burst of rhythmic activity following a transient such as an evoked potential or a spike.Īliasing: Distortion of the EEG signal leading to misidentification of frequency, which occurs when the signal is sampled at less than twice the highest frequency present. (See active sleep).Īfter-discharge: (1) EEG seizure pattern following single or repetitive electrical stimulation of a discrete area of the brain via cortical or intracerebral electrodes. (See quiet sleep, activité moyenne, tracé discontinue, REM sleep).Īctivity, EEG: An EEG wave or sequence of waves of cerebral origin.Īctivité moyenne: Neonatal EEG pattern of wakefulness and active sleep in term and near term infants characterized by continuous, low to medium amplitude mixed frequency activity (25–50 µV) with a predominance of theta and delta and overriding beta activity. The EEG shows activité moyenne in term and near term infants, and tracé discontinue (discontinuous pattern) in preterm infants <34 weeks of post menstrual age (PMA) the inter-burst interval depends on the PMA. Examples include: eye closing, hyperventilation, photic stimulation, natural or drug-induced sleep, sensory stimulation (acoustic, somatosensory or pain).Īctive sleep: Normal sleep stage in neonates characterized by eye closure, intermittent periods of rapid eye movements, irregular respirations and scant body movements. Terms suggested, whenever appropriate: spike-and-slow-wave complex, 3 c/s spike-and-slow-wave complex, sharp-and-slow wave complex.Īctivation procedure: Any procedure designed to modulate EEG activity, for instance to enhance physiological waveforms or elicit abnormal paroxysmal activity. Use of term discouraged when describing EEG patterns. A proposal for the EEG report form is given in Appendix A.Ībsence: A generalized seizure type. The terminology of the EEG interpretation should follow common neurological and clinical practice and use terms understandable to other physicians not specialized in EEG. The EEG interpretation summarizes the results of the EEG and gives a clinical interpretation in light of the diagnosis and the questions posed by the referring physician. The interpretation of the EEG requires knowledge of the patient’s age, past medical and medication history, their clinical condition during the EEG, particularly level of consciousness/vigilance and ability to co-operate. The EEG report should follow a standard format that includes a factual description and a clinical interpretation of the EEG record. Biological and technical artifacts that interfere with an adequate EEG interpretation should either be eliminated or, if this is not possible, be noted in the description. The description should be independent of the recording parameters such as amplification, montages, and computer program/display. All EEG phenomena should be described as precisely as possible in terms of frequency, amplitude, phase relation, waveform, localization, quantity, and variability of these parameters ( Brazier et al., 1961). It is based on the previous proposals ( Chatrian et al., 1974, Noachtar et al., 1999, Noachtar et al., 1999) and includes terms necessary to describe the EEG and to generate the EEG report. ![]() This glossary includes the terms most commonly used in clinical EEG. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |