EEG: Medication and Drug Effects

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Questions and Answers

What is a primary challenge in interpreting EEG changes related to medications?

  • The lack of experienced EEG technicians.
  • The limited availability of EEG technology.
  • EEG recordings are not sensitive enough to detect medication effects.
  • Changes in EEG recordings are typically not specific to a particular drug. (correct)

What is a characteristic EEG finding associated with barbiturates and benzodiazepines?

  • Suppression of all brain activity
  • Excess fast frequencies (beta) (correct)
  • Focal slowing
  • Increased alpha activity

When analyzing the effects of medication on an EEG, what information is MOST critical for the reader to know?

  • The patient's age and sex
  • What medications the patient was taking (correct)
  • The patient's blood pressure and heart rate
  • The patient's past medical history

Which of the following EEG patterns is LEAST likely to be specific to medication effects?

<p>Focal slowing (A)</p>
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What is the typical frequency range associated with excess fast activity (beta) on EEG due to medication effects?

<p>15-25 Hz (B)</p>
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How do medications generally affect epileptiform patterns on EEG?

<p>Medications have been described as both creating and suppressing epileptiform patterns. (C)</p>
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What is a key consideration when interpreting periodic patterns observed on an EEG in relation to medication effects?

<p>Whether the discharges are a result of underlying cerebral dysfunction or related to the medication effect (B)</p>
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What is the initial effect of most anesthetic medications on EEG?

<p>A pattern of creating excitation with increased amplitudes (D)</p>
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What is the effect of halogenated inhalational anesthetics on EEG?

<p>Dose-related reduction in amplitude and frequency (A)</p>
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What is a common effect of antiseizure medications (ASMs) on EEG, especially in quantitative studies?

<p>Increase in theta and delta frequencies diffusely (A)</p>
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In which frequency range do benzodiazepines typically create faster rhythmic activity on EEG?

<p>18-25 Hz (D)</p>
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What effect does phenytoin have on EEG at therapeutic doses?

<p>It produces slowing, especially with clinical toxicity. (B)</p>
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How does lamotrigine typically affect the background activity of the EEG?

<p>Does not appear to have a significant impact (A)</p>
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Which of the following intravenous barbiturates has a briefer duration of action and less sedation, leading to a quicker return to EEG baseline?

<p>Methohexital (C)</p>
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Which of the following is LEAST likely to cause excess slow activity on an EEG?

<p>Lamotrigine (A)</p>
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A patient on an EEG shows generalized periodic discharges (GPDs) after being administered an anesthetic. What should be considered?

<p>The GPDs could be distinct from prior seizure activity and may resolve upon withdrawal of the anesthetic. (C)</p>
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A patient is administered benzodiazepines during an EEG. The recording shows rhythmic fast activity in the 10 to 16 Hz range. What might this suggest?

<p>The patient may have been administered benzodiazepines in sedative doses or is experiencing intoxication. (C)</p>
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A researcher aims to study the effect of a novel antiseizure medication (ASM) on EEG using quantitative methods. Given the information, what would be the MOST challenging aspect of this study?

<p>The paucity of literature on the qualitative analysis of newer ASMs, with the focus shifted to quantitative assessments. (D)</p>
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Which medication effect on EEG would be MOST difficult to differentiate from nonconvulsive status epilepticus (NCSE)?

<p>Generalized periodic discharges (A)</p>
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What is a significant consideration when evaluating EEG changes in patients on multiple medications?

<p>EEG changes are typically nonspecific, and patients often take multiple medications. (A)</p>
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What is the primary focus of the chapter regarding the effects of medications on EEG?

<p>Effects of medications on EEG in persons with epilepsy or those undergoing neurologic evaluation for clinical purposes. (A)</p>
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When analyzing EEG results, what historical context regarding the patient is MOST important?

<p>The patient's age, state, and administered medications. (D)</p>
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What is a significant challenge in interpreting EEG findings related to medications?

<p>The lack of specificity in EEG findings can make it difficult to distinguish medication effects from other etiologies. (C)</p>
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Which of the following is commonly observed on EEG as a result of medication effects?

<p>Excess fast frequencies (beta) and/or an increase of slowing frequencies (theta or delta). (B)</p>
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What is a critical piece of information needed when analyzing the effects of medication on an EEG?

<p>What medications the patient was taking and when the doses were administered. (D)</p>
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How do anesthetics generally affect EEG patterns as dosages are increased?

<p>They follow a pattern of excitation, progressive slowing, burst-suppression, and potentially complete suppression. (B)</p>
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What effect do benzodiazepines typically have on EEG at therapeutic doses?

<p>Rhythmic fast activity, often in the 18 to 25 Hz range. (A)</p>
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What is a key consideration when observing generalized periodic discharges (GPDs) on an EEG in relation to medication?

<p>It is important to distinguish whether the discharges are due to underlying cerebral dysfunction or medication effects. (C)</p>
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Which of the following best describes how antiseizure medications (ASMs) can affect epileptiform patterns on EEG?

<p>ASMs can both create and suppress epileptiform patterns. (D)</p>
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Which of the following must be known to accurately interpret the effects of medications on an EEG?

<p>The type, timing, and dosage of medications that the patient is taking. (C)</p>
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Which medication is known for having a briefer duration of action and quicker return to EEG baseline compared to amobarbital?

<p>Methohexital (B)</p>
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A patient on an EEG is administered a medication, and the recording shows diffuse slowing in the delta range. What should the interpreter consider?

<p>The slowing could also be due to etiologies other than medication, such as metabolic or structural abnormalities. (A)</p>
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Which of the following is LEAST likely to be a direct effect of medication on EEG?

<p>Localized focal slowing (D)</p>
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What is a significant challenge when trying to correlate specific ASMs with their qualitative effects on EEG?

<p>There is limited qualitative literature with a shift towards quantitative assessments of newer ASMs impact on EEG. (D)</p>
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What EEG change is most commonly associated with excess beta activity on the EEG?

<p>Frontal predominance during drowsiness (D)</p>
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In a scenario where an awake patient on therapeutic medications presents with beta frequencies in the 20 to 25 Hz range, how should the EEG be interpreted?

<p>Consistent with therapeutic medication use (A)</p>
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A patient is on lamotrigine and shows a reduction in interictal epileptiform discharges. What are the implications for clinical seizure frequency?

<p>There may not be a clinical effect on seizure frequency. (D)</p>
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Why is considering the pharmacologic profile of a patient crucial in EEG interpretation?

<p>To avoid misinterpreting medication effects as pathological changes. (C)</p>
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What is the MOST important reason to interpret EEG changes in clinical context?

<p>To account for factors like age, medication timing, and comorbidities. (D)</p>
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Why is differentiating between diffuse and focal EEG effects important?

<p>Because focal findings usually suggest underlying pathology. (C)</p>
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Excess slow activity (Theta/Delta) on an EEG is MOST likely associated with which condition?

<p>Toxic levels of antiseizure medications or metabolic encephalopathies. (C)</p>
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Excess fast activity (Beta) on an EEG is commonly associated with which class of medications?

<p>Benzodiazepines and barbiturates. (C)</p>
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What should be strongly considered when periodic patterns are observed on an EEG?

<p>Nonconvulsive status epilepticus (NCSE). (D)</p>
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Benzodiazepines typically have what effect on frontal beta activity on EEG?

<p>Increase frontal beta activity. (D)</p>
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What EEG changes are associated with barbiturates?

<p>Beta slowing, burst suppression, and ultimately ECI. (C)</p>
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How does phenytoin toxicity typically manifest on EEG?

<p>Mild slowing. (B)</p>
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Which of the following is a noted effect of carbamazepine on EEG?

<p>Inconsistent slowing; may initially increase spikes. (D)</p>
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What effect does valproate toxicity have on EEG?

<p>Toxic slowing. (B)</p>
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Which medication is associated with a minimal effect on EEG but may suppress spikes?

<p>Lamotrigine. (D)</p>
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Which of the following is associated with a shorter-acting effect and faster EEG recovery?

<p>Methohexital. (B)</p>
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What should be considered when an alert patient displays diffuse delta activity on EEG?

<p>Drug toxicity. (C)</p>
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Why should focal findings observed on EEG prompt further investigation?

<p>They usually indicate underlying pathology. (B)</p>
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What is most likely the cause of the enhanced paroxysmal fast activity?

<p>Generalized paroxysmal fast activity is easily confused with beta. (D)</p>
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EEG changes as a result of taking Levetiracetam can be expected to show:

<p>Suppressed interictals. (D)</p>
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After sedative withdrawal, what activity can return on an EEG?

<p>Epileptiforms. (D)</p>
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What EEG changes are associated with Propofol?

<p>Beta slowing, burst suppression, and ultimately ECI. (D)</p>
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What EEG changes are associated with Etomidate?

<p>Enhanced amplitude/spikes. (D)</p>
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Flashcards

Electroencephalograph (EEG)

A recording of brain electrical activity using electrodes on the scalp or in the brain.

Quantitative EEG (qEEG)

Advanced techniques used to evaluate medication effects on EEG recordings.

Excess Fast Activity on EEG

Excess fast activity (15-25 Hz) often indicating a medication effect.

Epileptiform Activity on EEG

Medications can both create and suppress these patterns, requiring careful history correlation.

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Periodic Patterns on EEG

Patterns that have been linked to certain medications, requiring differentiation from underlying cerebral dysfunction.

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Anesthetics and EEG

Dose-related reduction in amplitude and frequency on EEG, caused by halogenated inhalational anesthetics.

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Antiseizure Medications (ASMs) on EEG

Medications that can alter background activity and interictal epileptiform discharges on EEG.

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Benzodiazepines on EEG

These medications typically cause rhythmic fast activity (18-25 Hz) on EEG, frontally predominant.

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Barbiturates on EEG

Similar to benzodiazepines, these medications can create fast frequencies and, with increasing doses, burst-suppression patterns

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Phenytoin on EEG

Medication, has been shown to produce slowing at toxic levels

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Carbamazepine on EEG

Medication, implicated in creating excess slow activity on EEG; inconsistent data.

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Lamotrigine on EEG

Rarely impacts background EEG; may suppress interictal epileptiform discharges.

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Levetiracetam on EEG

Reduces interictal epileptiform discharges, especially in generalized epilepsies.

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Anesthetic Medications on EEG

Often used with EEG to induce anesthesia or for critical care; create excitation then suppression.

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Amobarbital and Methohexital on EEG

Drugs commonly used for language/memory testing (Wada test); cause behavioral/neurological effects.

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Valproate on EEG

Can cause excess slow activity at toxic levels, may reduce generalized spike-wave discharges.

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Methohexital

Anesthetic that has a briefer duration of action.

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Medication Effects on EEG

A comprehensive assessment of how medications can modify EEG recordings.

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Excess Beta Activity

A common finding associated with medication effects, especially with barbiturates and benzodiazepines.

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Excess Slow Activity

Slow frequencies of EEG activity which can also be related to metabolic or toxic conditions; they may also be related to medications.

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Drug-Induced Seizures

May be triggered by medications; requires careful history and correlation with medication timing.

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Sedative-Hypnotics on EEG

Can dose-dependently reduce brain activity on EEG, potentially leading to burst suppression or ECI.

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Dose-Related EEG Suppression

A pattern of diffuse slowing, intermittent suppression, or burst suppression ultimately resembling electrocerebral inactivity (ECI).

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Teasing Out Medication Effects

The process of distinguishing between medication effects, underlying conditions, or network dysfunction in EEG interpretation.

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EEG Interpretation

Consider the patient's pharmacologic profile during EEG interpretation.

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Clinical Approach to EEG

Know medications, assess state, differentiate effects, correlate changes, and use qEEG when available.

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Excess Slow Activity (Theta/Delta)

Diffuse slowing often seen with toxic anti-seizure medication (ASM) levels or metabolic issues.

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Propofol on EEG

Dose-dependent beta slowing, progressing to burst suppression and ECI.

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Etomidate on EEG

Increases amplitude and is often used in Neurophysiologic Intraoperative Monitoring (NIOM).

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Pentobarbital on EEG

Typically produces Generalized Periodic Discharges (GPDs) during withdrawal and may cause suppression patterns.

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Medication Effects vs. Underlying Conditions

Distinguish medication effects from underlying conditions or network dysfunction.

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Study Notes

Why This Matters

  • EEG interpretation should consider the patient's pharmacologic profile.
  • Many CNS-active medications affect the EEG.
  • These effects are often nonspecific, and recognizing them prevents misinterpretation.
  • Changes in EEG must be interpreted in clinical context, including age, medication timing, and comorbidities.

Clinical Approach: EEG with Medications in Mind

  • Know the patient's medications, including route and timing.
  • Assess state-dependent patterns (awake/drowsy/sleep).
  • Differentiate diffuse vs focal effects; focal findings usually indicate pathology.
  • Correlate changes with known medication profiles.
  • Use qEEG for spectral analysis when available.

Core EEG Changes by Pattern

  • Excess Slow Activity (Theta/Delta): Diffuse slowing, seen with toxic ASM levels or metabolic encephalopathies.
  • Excess Fast Activity (Beta): Associated with benzodiazepines, barbiturates, propofol; frontally predominant.
  • Epileptiform Activity: May be suppressed or mimicked by drugs. Correlate with timing and response to withdrawal.
  • Periodic Patterns: May resemble NCSE; differentiate by response to benzodiazepine challenge.
  • Burst Suppression: Seen with anesthetic titration; may lead to ECI.

Specific Medication Effects

  • Benzodiazepines: Increase frontal beta, suppress interictals.
  • Barbiturates: Beta slowing, burst suppression, ECI.
  • Phenytoin: Mild slowing in toxicity; no beta increase.
  • Carbamazepine: Inconsistent slowing; may initially increase spikes.
  • Valproate: Toxic slowing; Reduces generalized discharges.
  • Primidone: Slowing, reduces spikes.
  • Lamotrigine: Minimal effect, may suppress spikes.
  • Levetiracetam: Reduces interictals in generalized epilepsy.

Anesthetics & Sedatives

  • Propofol: Dose-dependent pattern: beta slowing, burst suppression, ECI.
  • Etomidate: Increases amplitude, used in NIOM.
  • Pentobarbital: GPDs on withdrawal; suppression pattern.
  • Amobarbital: Used in Wada test; longer recovery.
  • Methohexital: Shorter-acting; faster EEG recovery.

Clinical Pearls

  • Don't confuse beta with generalized paroxysmal fast activity.
  • Diffuse delta in alert patients suggests toxicity.
  • Focal findings should prompt investigation.
  • Epileptiforms may rebound after sedative withdrawal.

Summary Table

  • Benzodiazepines: Frontal beta, suppress spikes.
  • Barbiturates: Beta slowing, burst suppression.
  • Valproate: Slows at toxic levels, suppresses generalized spikes.
  • Carbamazepine: Diffuse slowing, possibly increases spikes.
  • Phenytoin: Mild slowing in toxicity.
  • Propofol: Beta ECI.
  • Etomidate: Enhances amplitude/spikes.
  • Levetiracetam: Suppresses interictals.

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