Sections View Full Chapter Figures Tables Videos Annotate 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 ... Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Download the Access App: iOS | Android Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.