What investigations should be done in a case of seizures followed by post-ictal (after seizure) drowsiness for 30 minutes?

Investigations for Post-Ictal Drowsiness Following Seizure

Immediate Assessment

The investigation approach depends critically on whether this is a first-time seizure versus a known seizure disorder, with history and physical examination guiding the need for laboratory and imaging studies. 1

Clinical Context Determines Investigation Intensity

The 30-minute post-ictal drowsiness described is within the expected range for a typical post-seizure state, which normally resolves within 5-10 minutes but can extend to 20-30 seconds of confusion after syncope, or several minutes after generalized seizures. 1, 2 Post-ictal periods lasting 10-30 minutes suggest true seizure activity rather than syncope or other causes of transient loss of consciousness. 1

First-Time Seizure: Comprehensive Workup

Laboratory Testing

For an otherwise healthy adult with new-onset seizure who has returned to baseline neurologic status, laboratory testing should be guided by history and physical examination findings rather than performed routinely. 1 However, specific testing is indicated when:

• Electrolyte abnormalities are suspected (sodium, glucose, calcium, magnesium) as these represent life-threatening reversible causes 1
• Concurrent alcohol use or withdrawal is present - though this should remain a diagnosis of exclusion 1
• Metabolic derangements are suggested by history or examination 1

Neuroimaging

Brain imaging is essential for first-time seizures to identify structural causes:

• MRI is the preferred modality over CT for identifying potentially epileptogenic lesions 3
• Timing matters: If imaging is performed within 12 hours post-ictally, expect reversible findings including focal gyral swelling, decreased attenuation, and possible enhancement - these represent physiologic changes from seizure activity itself, not necessarily structural pathology 4
• Follow-up imaging may be needed if initial scan shows post-ictal changes, as these abnormalities typically resolve completely or near-completely 4
• CT perfusion patterns within 2 hours of seizure termination commonly show focal hypoperfusion in cortical ribbon patterns, multi-lobar or holo-hemispheric distribution, sparing basal ganglia - this should not be mistaken for stroke 5

Electroencephalography (EEG)

EEG is a necessary extension of the neurologic examination for seizure evaluation. 3 Key considerations:

• Normal interictal EEG does not rule out epilepsy - clinical diagnosis takes precedence 6
• EEG helps with confirmation, classification, and localization of seizure activity 3, 7
• For patients with impaired or fluctuating consciousness out of proportion to brain injury, continuous EEG monitoring for at least 24 hours is reasonable, as 28% of electrographic seizures are detected only after 24 hours 1

Known Seizure Disorder: Selective Approach

When to Investigate Further

For patients with established epilepsy, extensive investigation is generally not needed unless:

• The seizure pattern has changed significantly
• Post-ictal period is prolonged beyond the patient's typical recovery time 2
• New focal neurologic deficits emerge
• Concern exists for status epilepticus (traditionally defined as ≥30 minutes of seizure activity or recurrent seizures without return to consciousness) 1

Risk Stratification

Monitor for early seizure recurrence risk factors during the post-ictal period: 2

• Age ≥40 years
• Alcoholism
• Hyperglycemia
• Glasgow Coma Scale score <15

Critical Timing Considerations

Imaging Timing

Optimal timing for interictal functional imaging:

• Wait at least 24 hours after focal aware seizures 1
• Wait at least 48 hours after focal impaired awareness or focal-to-bilateral tonic-clonic seizures before performing interictal SPECT or FDG-PET 1

Post-Ictal Management

• Keep patient NPO until swallowing screening is completed to prevent aspiration 2
• Swallowing assessment should ideally occur within 24 hours of hospital arrival 2
• Monitor neurological status for changes during the post-ictal period 2

Common Pitfalls to Avoid

Do not mistake post-ictal imaging changes for acute stroke - focal hypoperfusion on CT perfusion within 2 hours of seizure, especially in non-vascular distributions with normal CT angiography, likely represents post-ictal changes rather than ischemia. 5

Do not assume all post-ictal confusion is benign - if impaired consciousness persists or fluctuates out of proportion to the degree of brain injury, consider subclinical seizures and obtain continuous EEG monitoring. 1

Do not routinely start prophylactic antiseizure medications - prophylaxis after spontaneous seizures has not been shown to prevent early or long-term seizures and may negatively affect cognitive function. 1 Treatment is indicated only for documented seizure activity contributing to clinical impairment.