Basic Concepts, Organizing, and Displaying Data
This chapter introducesbiostatistics as a discipline that deals with designing studies, analyzingdata, and developing new statistical techniques to address the problems in the fields of life sciences. This includes collection, organization, summarization,
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Drug Effects on EEG Warren T. Blume
Abstract: Although excess beta activity and a mild theta increase may be the most common EEG alterations associated with medication, more remarkable changes may also appear. Although changes such as diffuse delta, triphasic waves, bisynchronous spikes or polyspikes, burst suppression or electrocerebral inactivity may indicate a dismal prognosis under many circumstances; these patterns may fully resolve to a normal EEG if drug administration is the unique or principal cause. Key Words: Drug effects, EEG, Prognosis. (J Clin Neurophysiol 2006;23: 306–311)
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s a substantial proportion of patients undergoing electroencephalography (EEG) take one or more medications of various kinds, the electroencephalographer must bear their effects in mind when reading the EEG and phrasing its clinical interpretation. Moreover, an asymmetry of drug effects may reflect a focal or hemispheric lesion whose EEG effects may not have been otherwise recognized.
PRINCIPLES OF DRUG EFFECTS Factors Quantity of medication in the patient influences the EEG. This quantity varies according to dose, volume of distribution, and rate of metabolism. Systemic effects of medication, e.g., hyponatremia from Carbamazepine, may diffusely perturb the EEG. Any preexisting systemic disorder may augment this effect. Additionally, anecdotal experience suggests that prominence of drug-related EEG alterations vary among patients beyond the aforementioned factors. Anomalous target or multidrug transporter mechanisms may apply (Loscher et al., 2006).
Principal Modifications Table 1 lists features discussed in the following sections. Typically, these should appear symmetrically and possibly diffusely. Less effect in one hemisphere or region may indicate a lesion there (Blume et al., 2002a). A greater effect, usually as beta activity, may relate to a skull defect, i.e., a breach rhythm (Blume et al., 2002b). Professor Emeritus of Neurology, University of Western Ontario, London, Ontario, Canada Address correspondence and reprint requests to Warren T. Blume, MDCM, FRCPC, Professor Emeritus of Neurology, University of Western Ontario, London, Ontario, Canada N6A 5A5; e-mail: [email protected] Copyright © 2006 by the American Clinical Neurophysiology Society ISSN: 0736-0258/06/2304-0306
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SPECIFIC MODIFICATIONS Beta An augmentation of voltage, field distribution, and persistence of normally appearing 15 to 25 Hz Beta activity most commonly indicates the presence of a medication effect on the EEG (Figs. 1–3). Barbiturates and benzodiazepines most prominently produce this effect ( G. Bauer and R. Bauer, 2005; Van Cott and Brenner, 2003). Greater than usual theta activity may accompany such beta excess (Blume et al., 2002). Central nervous system stimulants such as cocaine, amphetamines, and methylphenidate as well as tricyclic antidepressants may evoke greater beta activity at low voltage (G. Bauer and R. Bauer, 2005; Van Cott and Brenner, 2003). Withdrawal from alcohol and barbiturates may produce a similar low voltage EE
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