Some normal variants, such as mu or lambda, can be made to appear and disappear through the manipulation of the mental state of a conscious individual and as such, can provide. Seyed m mirsattari, md, phd, frcpc departments of clinical. Single epileptiform waves posterior occipital sharp transients of sleep. May 11, 2018 epileptiform normal variants are electroencephalographic eeg patterns that resemble epileptogenic abnormalities. Some eeg patterns look spiky and rhythmic and are commonly interpreted as abnormal findings. Statemodulation of corticocortical connections underlying normal eeg alpha variants jose.
The phrases electroencephalogram eeg variant waves or normal eeg variants refer to waves that are rare or unusual but not generally abnormal. Eeg manual for residents and fellows crossroads academy. These variant waveforms include waveforms and patterns that are rare or unusual but are known to be generally benign. Recognition of normal eeg patterns and normal variants is necessary to appropriately interpret the study. Eeg artifacts and benign variants linkedin slideshare. Recognizing variations of a normal tracing can be challenging. It should also identify and describe normal variants in addition to abnormal findings. Electroencephalogram an overview sciencedirect topics. The tragedy of overread eegs and wrong diagnoses of epilepsy. The human electroencephalogram eeg was discovered by the german psychiatrist, hans berger, in 1929. Eeg is an important tool used to assess patients with central nervous system symptoms.
Statemodulation of corticocortical connections underlying normal eeg alpha variants. The neurologist has just informed you that your eeg is normal even though you recently experienced your first tonicclonic seizure. Scroll down to view images of normal anatomical variants. This chapter describes normal eeg features and variants, characteristic patterns of development, and some patterns that are unusual for age, from the neonatal period to adolescence. Husain a clear understanding of a normal eeg is mandatory before studying abnormalities. The range of benign variants includes wicket waves, rhythmic midtemporal theta of drowsiness rmtd or rttd, benign small sharp spikes bsss, sometimes denoted bsst for benign small sleep transients, 14. Pathological epileptiform discharges have a high specificity for seizures but may be mimicked by variations and variants of normal and by artifact. Posts are a normal eeg variant, occurring in less than 10% of unselected eeg recordings, mostly in younger adults, without gender predominance.
Doctor of philosophy clinical psychology, august 2008, 86 pp. A common normal variant finding, often mistaken for pathological activity during drowsiness, is rmtd. Its potential applications in epilepsy rapidly became clear, when gibbs and colleagues in boston demonstrated 3 per second spike wave discharge in what was then termed petit mal epilepsy. Eeg and can be considered one of the normal elements of sleep. Oct 09, 2019 the phrases electroencephalogram eeg variant waves or normal eeg variants refer to waves that are rare or unusual but not generally abnormal. Benign variants in the eeg electroencephalography eeg. The objective of this eeg primer is to provide neurologists, epileptologists, residents, and fellows in training in the field of neurology and neurophysiology and eeg technologists with a. Therefore understanding the boundaries of normal eeg waveforms and their variants is paramount in avoiding. The eeg patterns that can be overread include wellknown normal variants, but in reality these are relatively rare and the vast majority of overread patterns are either wicket rhythms or nameless variants, that is, simple fluctuations of sharply contoured background rhythms or. Epileptiform normal variants are electroencephalographic eeg patterns that resemble epileptogenic abnormalities. Although the mu rhythm is traditionally defined as a normal eeg variant, recent.
Normal variants and normal physiologic activities seen in the posterior head. In addition, alpha rhythms usually are sharper in morphology because the scalp and skull act as a highfrequency filter and pass lower frequencies more efficiently than higher frequencies. These variations and fluctuations, along with benign variants, can be misinterpreted as abnormal. Recognition of normal eeg variants and artifacts is crucial for accurate eeg interpretation. In healthy adults with no declared history of seizures, the incidence of epileptiform discharge in routine eeg was 0. Eeg measures voltage fluctuations resulting from ionic current within the neurons of the brain. Rapid eye movement rem sleep can be roughly described as a period when the brain is active and the body is paralyzed. Normal variants the term normal variants refers to eeg waveforms that are considered to be normal findings, but whose presence is not required for an eeg to be normal. While some normal patients lack wellformed alpha activity, the frequency, symmetry, and reactivity of alpha merits special attention and comment in any eeg report. Apart from the above described rhythms there are normal variants that have no pathologic significance and can be difficult to distinguish from abnormal rhythms table 2westmoreland 1996.
A normal variant is an atypical finding that is seen in a percentage of the population, which generally has no clinical significance, and is considered within the spectrum of normal findings. Most of these patterns initially were thought to be associated with epilepsy or other neurologic conditions but subsequently were demonstrated to have no such significance. Goidstein, md nine girls with rett syndrome had 22 electroen cephalographic studies performed over 5 years. There are six main types of rhythmic variant eeg patterns. Handbook of eeg interpretation download ebook pdf, epub. If read conservatively being careful not to overinterpret normals, the speci. Nine teen waking tracings demonstrated moderate back ground slowing. Normal variants are commonly overread as interictal. Click on an image to see a full larger version with arrows. Abnormalities may be characterized by altered developmental characteristics as well as specific patterns or waveforms. The morphology of the segments is concave curving upward and thus reassuring.
In the normal adult there are two main stages of sleep that alternate at about 90minute intervals. Normal eeg variants and artifacts often present with distinctive electrographic features that may include morphology, distribution, and occurrence in specific stages wakefulness, drowsiness, or sleep. The slow alpha variant has a frequency of 4 to 5 hz and can have a notched appearance figure 11. Recording eeg during these periods also requires adapting the recording techniques to the specific age in order to obtain interpretable records. American clinical neurophysiology society guideline 7. There are several variants of the alpha rhythm, and they include temporal alpha, characterized by independent alpha activity over the temporal regions seen in older patients.
The overinterpretation of eeg is a common and underreported problem 9, 14 and a major cause for the misdiagnosis of epilepsy. Electroencephalography 2 the electric potentials generated by single neurons are far too small to be picked by eeg or meg. All have the same distribution and reactivity as normal alpha rhythm and often occur admixed with it. The brain has a limited repertoire of normal frequencies, durations, and amplitudes that may vary and fluctuate throughout the course of eeg recording westmoreland and klass, 1990.
The fast alpha variant occurs at a harmonic of the underlying alpha rhythm, usually 16 to 20 hz figure 11. Some normal variants, such as mu or lambda, can be made to appear and disappear through the manipulation of the mental state of a conscious individual and as such, can provide additional reassurance of a healthy functioning brain. Pdf electroencephalographic normal variants or with. Rhythmic temporal theta burst of drowsiness psychomotor variant. Quizlet flashcards, activities and games help you improve your grades. Pdf statemodulation of corticocortical connections. They now are considered normal variants of no clinical significance. Eeg continues to play a central role in diagnosis and management of patients with seizure disordersin.
Berger 1929 the slow variant is subharmonic of alpha rhythm which is likely due to fusion of adjacent waves blume 2002 it is usually 45 hz seen in around 1% of normal eeg. Click download or read online button to get handbook of eeg interpretation book now. Normal eeg variants and artifacts often present with distinctive electrographic features that may include morphology, distribution, and occurrence in. The normal neonatal eeg undergoes rapid and predictable changes as a consequence of brain growth and development. Eeg abnormalities aid diagnosis of rett syndrome elizabeth a.
Abnormal eeg patterns correlation with underlying cerebral lesions and neurological diseases suthida yenjun definition of the abnormal eeg an eeg is abnormal if it contains epileptiform activity slow waves amplitude abnormalities or deviations from normal patterns in most abnormal eegs, the abnormal patterns appear only. Does a normal eeg mean that you didnt have a seizure and the headache and muscle aches you felt were related to some other illness. Ndt 101 lecture notes fundamentals of eeg technology, volume 1 chapter 14 normal variants study guide by kmhouser includes 91 questions covering vocabulary, terms and more. It is typically noninvasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used, as in electrocorticography. This activity was previously known as psychomotor variant. In one study of 324 patients at an epilepsy center, eeg was one of the two most important factors leading to a clinical misdiagnosis smith et al. The importance of understanding normal eeg lies in appreciating the wide range of normal signals that can beguile the interpreter. Electroencephalography eeg is an electrophysiological monitoring method to record electrical activity of the brain. Interpreting rhythmic or sharply contoured normal discharges as abnormal and epileptiform can lead to the erroneous diagnosis of epilepsy and years of unnecessary treatment 1,2. Patterns that are normal at one development stage may be abnormal at another. Introduction the term normal variant pattern refers to thoserhythms or waveforms that have features reminiscentof either interictal or ictal eeg abnormalities. Technologists must be knowledgeable of the normal eeg patterns, normal variants, and unique abnormalities seen in the elderly population. Atlas of eeg patterns is a wellwritten, comprehensive, and succinct guide with appropriate figures to depict various eeg patterns.
Before learning abnormal eeg patterns, it is absolutely important to master the normal eeg range and normal variants for specific age groups. Eeg in the diagnosis, classification, and management of. Incorrect interpretation may result in patient anxiety, over treatment or mistreatment. Posterior occipital sharp transients of sleep posts are one of the most common normal variants seen in the. Normal electroencephalography variants in sleep request pdf. Benign epileptiform variants seyed m mirsattari, md, phd, frcpc departments of clinical neurological sciences, medical biophysics, diagnostic imaging, psychology university of western ontario london, ontario eeg course, cnsf, quebec city, qe friday june 11, 2010. The stsegment elevations seen in the precordial leads are benign early repolarization with elevated j points purple arrows, which are normal variants in the pediatric population. Eeg continues to play a central role in diagnosis and management of patients with seizure. It is critical that any person interpreting eegs be. Paradoxical alpha occurs when alertness results in the presence of alpha, and drowsiness does not. The eeg patterns that can be overread include wellknown normal variants, but in reality these are relatively rare and the vast majority of overread patterns are either wicket rhythms or nameless variants, that is, simple fluctuations of sharply contoured background rhythms or fragmented a activity that do not fit into. Chapter 11 normal variants in the electroencephalogram. Neuropsychologic correlates of a normal eeg variant.
Accurate recognition and distinction of benign variants in the eeg are essential to avoid over interpretation of such findings as epileptiform, and subsequent errant diagnosis of epilepsy. The term normal variants refers to eeg waveforms that are considered to be normal findings, but whose presence is not required for an eeg to be normal. When an abnormality is identified, the degree of abnormality should be stated. Harmonic of the alpha rhythm is frequently seen in an intracranial eeg. Ndt 101 lecture notes fundamentals of eeg technology, volume 1 chapter 14 learn with flashcards, games, and more for free. The range of benign variants includes wicket waves, rhythmic midtemporal theta of drowsiness rmtd or rttd, benign small sharp spikes bsss, sometimes denoted bsst for benign small sleep transients, 14 and 6 positive spikes, 6hz phantom spike and wave, subclinical rhythmic eeg discharge of adults sreda. Epilepsy and eeg in clinical practice mayo clinic school. Rapid eye movement rem sleep can be roughly described as a period when the brain is active and the body is paralyzed except for eye movements, middle ear ossicles, and respiration. Alpha rhythm was the first recognized eeg pattern in eeg. An introductory text and atlas of normal and abnormal. Benign epileptiform variants canadian neurological sciences.
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