What is the recommended management for a patient with abnormal EEG findings, including mild diffuse slowing of the background and rare left temporal interictal epileptiform discharges, but no electrographic seizures?

Management of Abnormal EEG with Interictal Epileptiform Discharges

Do not initiate antiseizure medications for this patient, as prophylactic treatment is not indicated for interictal epileptiform discharges without clinical or electrographic seizures. 1, 2

EEG Interpretation

Your EEG shows two key findings that require different management approaches:

Mild Diffuse Slowing

• This represents nonspecific cerebral dysfunction and does not require antiseizure medication 1
• Focus on identifying and treating the underlying etiology (metabolic derangements, medications, systemic illness, structural brain injury)

Rare Left Temporal Interictal Epileptiform Discharges

• These are epileptiform abnormalities detected between seizures that indicate cortical irritability 3, 4
• Critical distinction: Interictal discharges are NOT seizures and do not meet criteria for treatment 1
• The presence of interictal epileptiform discharges approximately doubles the risk of future seizure recurrence compared to normal EEG, but this alone does not justify starting antiseizure medications 3, 4

When to Treat vs. When to Monitor

DO NOT treat with antiseizure medications if:

• Only interictal epileptiform discharges are present without clinical or electrographic seizures 1, 2
• Patient is neurologically intact and following commands 1
• No history of clinical seizures has been documented 1, 2

Prophylactic antiseizure medications are not recommended because they do not prevent seizures and are associated with worse functional outcomes, increased adverse events, and no demonstrated benefit 1, 2

DO treat with antiseizure medications if:

• Clinical seizures occur (convulsive activity observed) 1, 2
• Electrographic seizures are documented on EEG (epileptiform discharges >2.5 Hz for ≥10 seconds or any pattern with definite evolution lasting ≥10 seconds) 1
• Patient has impaired consciousness with seizures contributing to altered mental status 1, 2

Monitoring Strategy

When to Perform Continuous EEG Monitoring:

• If the patient develops impaired or fluctuating consciousness out of proportion to the degree of brain injury or metabolic abnormalities 1, 2
• If clinical seizures are suspected but not clearly observed 1, 5
• Duration: At least 24-48 hours of continuous monitoring is reasonable, as 28% of electrographic seizures are detected after 24 hours and 94% by 48 hours 1, 2

When Repeated EEG is Reasonable:

• If patient does not follow commands after any acute neurological event 1, 5
• To reassess if clinical status changes 1

Medication Selection IF Treatment Becomes Necessary

If seizures develop and treatment is indicated:

First-line agent: Levetiracetam

• Preferred due to better tolerability and fewer adverse effects 2
• No specific dosing provided in stroke guidelines, but standard epilepsy dosing applies

Avoid: Phenytoin/Fosphenytoin

• Associated with worse outcomes, particularly in intracerebral hemorrhage patients 1, 2
• Should not be used as first-line therapy 2

Alternative: Valproate

• Can be considered for complex partial seizures 6
• Initial dosing: 10-15 mg/kg/day, increased by 5-10 mg/kg/week 6
• Therapeutic range: 50-100 μg/mL 6

Common Pitfalls to Avoid

• Do not treat interictal discharges as if they were seizures - this is the most common error and leads to unnecessary medication exposure 1, 2
• Do not use risk scores or presence of epileptiform discharges to justify prophylactic antiseizure drugs - there is no evidence they prevent seizures 2
• Do not assume interictal discharges worsen outcomes - prospective studies show they are not independently associated with worse neurological outcomes or mortality 1, 2
• Do not continue prophylactic medications beyond 7 days if they were started inappropriately, as there is no evidence they prevent late seizures 2

Clinical Context Considerations

If this EEG was obtained in the setting of:

Intracerebral hemorrhage:

• Cortical involvement increases seizure risk, but still does not justify prophylaxis 1, 2
• Only treat documented clinical or electrographic seizures 2

Post-cardiac arrest:

• Interictal patterns on the ictal-interictal continuum may warrant a therapeutic trial of nonsedating antiseizure medication 1
• However, your patient's "rare" left temporal discharges do not meet criteria for ictal-interictal continuum patterns (which require >1.0 Hz periodic discharges with plus modifiers or fluctuation) 1

Stroke or other acute brain injury:

• Monitor clinically for seizure development 1
• Repeat EEG if consciousness becomes impaired 1, 5