What is the recommended treatment plan for a patient with a history of seizure-like activity, who had a negative electroencephalogram (EEG) for the first event and Right parietal slowing (P8–O2) on the EEG for the second event, and is currently on levetiracetam (Keppra)?

Management of Seizure-Like Activity with Evolving EEG Findings

Continue levetiracetam and obtain urgent continuous EEG monitoring to definitively characterize the right parietal slowing and determine if this represents focal seizures requiring escalation of therapy. 1

Interpretation of EEG Findings

The evolution from a negative EEG to right parietal slowing (P8-O2) is clinically significant and requires aggressive diagnostic clarification:

• Right parietal slowing does not definitively establish epileptic seizures but represents a concerning focal abnormality that may indicate an ictal-interictal continuum pattern or evolving focal epilepsy. 1

• Continuous EEG monitoring for at least 24-48 hours is essential because 28% of electrographic seizures are detected only after 24 hours, and 94% by 48 hours—intermittent EEG may miss critical seizure activity. 2

• The right parietal location is particularly relevant as focal cortical involvement represents a high-risk feature for seizures, and focal slowing may represent subclinical seizure activity that requires video-EEG correlation. 2, 3

Immediate Management Algorithm

Step 1: Diagnostic Clarification

• Obtain continuous video-EEG monitoring immediately to determine if the right parietal slowing represents:

  • Electrographic seizures (epileptiform discharges >2.5 Hz for ≥10 seconds with evolution) 1
  • Ictal-interictal continuum patterns (periodic discharges 0.5-2.5 Hz) 1
  • Post-ictal slowing without ongoing seizure activity 4

• Skilled interpretation by a neurophysiologist is mandatory as correct categorization of these EEG patterns requires expert analysis and directly determines treatment decisions. 1

Step 2: Medication Management During Diagnostic Phase

• Continue current levetiracetam dose while awaiting continuous EEG results—do not discontinue or taper until the nature of events is definitively established. 5, 6

• Levetiracetam remains the optimal first-line agent for focal seizures with proven efficacy in partial onset seizures, including those of parietal origin. 7, 6, 3

Step 3: Treatment Based on EEG Results

If continuous EEG confirms electrographic seizures:

• Escalate levetiracetam dosing from current dose toward target of 3000 mg/day in divided doses, as this dose demonstrated superior seizure control in clinical trials. 6, 8
• Levetiracetam 3000 mg/day achieved 23% greater reduction in seizure frequency compared to placebo in refractory partial onset seizures. 6
• High-dose levetiracetam (1500 mg/day) demonstrated faster symptom control and lower recurrence rates compared to lower doses. 8

If EEG shows ictal-interictal continuum without definite seizures:

• A therapeutic trial of levetiracetam dose escalation may be reasonable given the focal parietal abnormality and clinical seizure-like events, though evidence is limited. 1
• The TELSTAR trial showed no overall benefit for treating periodic discharges, but post-hoc analysis suggested possible benefit in the small subgroup with true electrographic seizures. 1

If EEG shows only post-ictal slowing without ongoing seizure activity:

• Maintain current levetiracetam dose and schedule repeat EEG in 3-6 months to monitor for evolution. 5
• Consider gradual tapering only if prolonged seizure-free period is documented and repeat EEG remains normal. 5

Critical Pitfalls to Avoid

• Never rely on single intermittent EEG to rule out seizures—the evolution from negative to abnormal EEG in this patient demonstrates the limitation of snapshot testing. 1, 2

• Do not assume right parietal slowing is benign—focal cortical abnormalities carry high seizure risk and may represent subclinical seizure activity requiring treatment. 2, 3

• Avoid phenytoin or fosphenytoin if additional antiseizure medication is needed—these agents have inferior efficacy and higher adverse effect profiles compared to levetiracetam. 2, 7

• Do not prematurely discontinue levetiracetam based on a single normal EEG when clinical events continue—the second EEG's focal abnormality validates the decision to continue treatment. 5, 6

Additional Diagnostic Considerations

• Obtain brain MRI if not already performed to evaluate for structural lesions in the right parietal region that could explain both the focal slowing and seizure-like events. 9, 10

• Exclude metabolic or toxic precipitants including electrolyte abnormalities, hypoglycemia, or medication effects that could cause focal slowing. 2

• Consider paroxysmal slow wave event (PSWE) quantification using automated algorithms, as increased PSWEs in the first 72 hours after a seizure predict epilepsy with 82% accuracy. 4

Prognosis and Follow-Up

• Schedule regular neurological follow-up every 3-6 months during the diagnostic and treatment optimization phase to monitor for breakthrough seizures and medication tolerability. 5

• Levetiracetam has excellent safety profile with minimal drug interactions and low risk of serious adverse events, making it suitable for long-term use if epilepsy is confirmed. 6, 8

• Focal parietal seizures typically respond well to levetiracetam monotherapy, with one case report documenting complete seizure control with levetiracetam 500 mg prophylaxis for right parietal-onset seizures. 3