Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content ++ General principle ++ ▪ The EEG is unable to distinguish between different etiologies. The major usage of the EEG is to determine the severity of encephalopathy, prognosis, and response of treatment. ▪ Common etiology: ▸ Metabolic, toxic, inflammation, anoxic, and degenerative diseases ▪ Few EEG patterns associated with more specific etiologies for the encephalopathy: ▸ Periodic pattern: Anoxic encephalopathy Certain encephalitis ▸ Triphasic waves (TWs) or 14- and 6-Hz positive spike bursts: Metabolic encephalopathy Lithium and ifosphamide toxicity ▸ High-voltage beta activity: Benzodiazepine or barbiturate intoxication ▸ Low-voltage fast patterns: Alcohol withdrawal ▸ Bursts of high-voltage delta activity interspersed with mixed frequencies: PCP (angel dust) intoxication ▪ Prognosis in most EEG patterns is usually correlated with underlying diseases and reactivity of EEG to external stimuli. ▸ Ischemic strokes and anoxic ischemia after cardiorespiratory arrest are almost completely irreversible. ▸ Brain injury produced by head trauma, subdural hemorrhages, and some intracranial hemorrhages, in the absence of raised intracranial pressure, may be partially, moderately, or occasionally wholly reversible. ▸ Electrical disturbances with seizures and status epilepticus (SE), metabolic, and some toxic encephalopathies may be completely reversible. ▪ Some particular patterns have been identified that may have some prognostic significance: ▸ Poor prognosis Triphasic waves (TWs). Alpha coma (AC) patterns in patients with anoxic encephalopathy nonreactive to noxious stimuli. Continuously diffuse polymorphic delta activity (unless due to a toxic/metabolic disturbance) typically bodes poorly for the patient, when these patterns are low voltage. Marked bilateral suppression coma. Burst-suppression (B-S) patterns. ▸ Better prognosis: Spindle coma (SC) patterns Beta coma ▪ Severity: ▸ Milder encephalopathy: Spontaneous variability Evidence of EEG reactivity to painful stimulation ◊ Reduction of amplitude, increase in frequency, and reduction in the slow activity ◊ Paradoxical activation, which is a period of more severe delta slowing following painful stimuli ▸ Severe encephalopathy: Invariant EEG—no spontaneous variability or reactivity to external stimuli ▪ Combination of diffuse and focal EEG abnormalities: ▸ Associated focal process such as old infarction or tumor ▸ Nonketotic hyperosmolar coma ▸ Focal seizure ▸ Herpes simplex encephalitis and Creutzfeldt-Jakob disease (CJD) ++ Selected specific conditions ++ Drug intoxication ++ ▪ Generalized theta-delta activity with superimposed beta frequency activity is highly characteristic of sedative drug intoxication. ▪ With more severe intoxication, the fast activity shows a slower frequency (10–13 Hz), widespread distribution, but anterior predominance. ▪ In the absence of prominent slow activity, the anterior-dominant generalized fast activity caused by sedative drug intoxication produces an alpha and SC pattern in the EEG that is indistinguishable from that seen with severe anoxic encephalopathy. ▪ Phencyclidine (PCP) or ketamine is associated with a distinctive EEG pattern similar to that of subacute sclerosing panencephalitis (SSPE). ++ Anoxic encephalopathy ++ ▪ EEG should be done at least 5–6 hours after resuscitation. ▪ B-S pattern or electrocerebral silence (ECS) does not carry as ominous prognosis as when they occur in the setting ... GET ACCESS TO THIS RESOURCE Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth Get Free Access Through Your Institution Contact your institution's library to ask if they subscribe to McGraw-Hill Medical Products. What is MyAccess? Create a FREE MyAccess profile to: Use this site remotely Bookmark your favorite content Track your self-assessment progress and more!