What are the current guidelines for rapid recognition, EEG confirmation, and treatment of non‑convulsive seizures (including non‑convulsive status epilepticus) in adults and children presenting with unexplained altered consciousness or subtle motor signs?

Non-Convulsive Seizure Management Guidelines

Immediate Recognition and EEG Confirmation

Order emergent EEG immediately for any patient who does not follow commands after a seizure or has unexplained altered mental status—this is a Class 1 recommendation with the highest level of evidence. 1

High-Risk Populations Requiring Urgent EEG

• Post-cardiac arrest patients who remain comatose after return of spontaneous circulation require urgent EEG within 24 hours, as 10-35% have seizures detectable only by EEG 1, 2
• Comatose ICU patients with unexplained impairment of mental status, particularly those with severe sepsis or renal/hepatic failure 1
• Patients with convulsive status epilepticus who do not return to functional baseline within 60 minutes after seizure medication 1
• Any patient with altered consciousness and unexplained neurological deficits 1

Clinical Signs to Observe

• Look for subtle motor manifestations: mouth twitching, digit movements, eyelid twitching 3
• Check for evidence of prior seizures: tongue biting, injuries, incontinence 3
• Non-convulsive status epilepticus cannot be diagnosed by clinical observation alone and requires EEG confirmation 3, 4
• Up to 8% of comatose patients without clinical seizure activity have non-convulsive status epilepticus 3

EEG Monitoring Strategy

Continuous EEG monitoring is superior to routine intermittent EEG for detecting non-convulsive seizures, as routine outpatient EEG misses approximately 50% of non-convulsive seizures compared to prolonged monitoring. 1

Duration and Timing

• Continue EEG for at least 24 hours if the patient does not return to baseline neurologic function 1
• Expect an average response time of approximately 3 hours from EEG request to preliminary reading, so order early 1
• Approximately 28% of electrographic seizures are detected only after prolonged monitoring 1
• For post-cardiac arrest patients, several days of continuous monitoring may be needed since epileptiform activity can emerge late 1

Technical Specifications

• Standard EEG should include 19 electrodes of the 10-20 International System for diagnostic purposes 1
• Recording duration should be 20-30 minutes minimum to capture variations in vigilance levels 1
• Simplified montages with 6-10 electrodes are acceptable alternatives in resource-limited settings, though they may miss some findings 1

Treatment Algorithm

First-Line Treatment

Treat non-convulsive seizures detected by EEG with standard antiseizure medications immediately—this is a Class 2a recommendation from the American Heart Association. 1

• Benzodiazepines are the mainstay of first-line therapy for non-convulsive status epilepticus 5, 4
• Lorazepam is significantly superior to phenytoin for overt status epilepticus in post-cardiac arrest patients 1

Second-Line Agents

When benzodiazepines fail or for ongoing management, use one of the following:

• Levetiracetam: 30 mg/kg IV at 5 mg/kg/min (efficacy rates 67-73%) 3
• Valproate: 30 mg/kg IV at 6 mg/kg/hour (efficacy rates 68-88%, no hypotension risk) 3
• Phenytoin/Fosphenytoin: 18-20 mg/kg IV at 50 mg/min or 150 mg/min PE respectively (efficacy 56-84%, but 12% hypotension risk) 3

Third-Line/Refractory Cases

• Propofol: 1-2 mg/kg IV bolus, followed by 2-10 mg/kg/hour infusion 3
• Phenobarbital: 20 mg/kg IV at 50-100 mg/min 3
• Midazolam infusion, pentobarbital infusion, or other anesthetic agents 1

Critical Pitfalls and Caveats

Avoid These Common Errors

• Do not use prophylactic antiseizure medications in adult survivors of cardiac arrest (Class 3: No Benefit recommendation from the American Heart Association) 2
• Do not rely on myoclonus alone to predict poor neurologic outcomes due to high false-positive rates of 5-11% 2
• Do not prognosticate early based solely on EEG findings; the earliest time to prognosticate poor neurologic outcome is 72 hours after cardiac arrest 2
• Do not wait for standard 30-minute definition of status epilepticus—treat after 5 minutes of continuous seizure activity or recurrent seizures without return to baseline 3, 5

Special Considerations for Treatment Aggressiveness

• For comatose patients with non-convulsive status epilepticus: Treatment is reasonable and may prevent secondary brain injury, though the optimal aggressiveness remains debated 1, 6
• For elderly patients: A more conservative approach may be warranted due to higher risk of systemic complications from hypotensive and sedative agents 7
• For post-cardiac arrest patients: Intractable and persistent status epilepticus lasting more than 72 hours in the absence of EEG reactivity to external stimuli may indicate poor outcome 2

Essential Diagnostic Workup

• Point-of-care glucose measurement is mandatory in all patients to identify hypoglycemia 3
• Order first-line laboratory studies: serum sodium, complete metabolic panel, antiepileptic drug levels, toxicology screen 3
• Obtain emergent neuroimaging for: first-time seizure, focal neurological deficits, persistent altered mental status, fever with concern for CNS infection, head trauma, known/suspected malignancy, or anticoagulation use 3

Pediatric Considerations

• Non-convulsive status epilepticus accounts for approximately one-quarter of all status epilepticus cases in children 8
• Suspect NCSE in children with epilepsy who have unexplainable behavior changes or recent onset changes in speech, memory, or school performance 8
• EEG testing for brain death in pediatric patients must be performed according to American Electroencephalographic Society standards 1
• The same treatment principles apply, though dosing adjustments are necessary 8