What is the work-up for seizures?

Workup for New-Onset Seizures

For new-onset seizures, obtain serum glucose and sodium levels immediately, perform emergent neuroimaging (CT or MRI depending on clinical context), and arrange EEG as part of the neurodiagnostic evaluation. 1

Initial Laboratory Testing

The laboratory workup should be targeted rather than comprehensive:

• Obtain serum glucose and sodium levels in all patients, as these are the only laboratory abnormalities that consistently alter acute management 1
• Obtain a pregnancy test if the patient has reached menarche 1
• Consider toxicology screening if there is any question of drug exposure or substance abuse 1
• Additional tests (CBC, comprehensive metabolic panel, calcium, magnesium) should only be obtained when suggested by specific clinical findings such as vomiting, diarrhea, dehydration, known cancer, or renal failure 1

Common pitfall: Routine comprehensive metabolic panels have extremely low yield—only hypoglycemia and hyponatremia consistently require immediate intervention 1, 2

Neuroimaging Decision Algorithm

Emergent CT Head Without Contrast is Indicated For:

• Age >40 years 1
• New focal neurological deficits 1
• Persistent altered mental status 1
• Fever or persistent headache 1
• Recent head trauma 1
• History of malignancy or immunocompromised state 1
• Patients on anticoagulation 1
• Partial-onset (focal) seizures 1
• Patient has not returned to baseline within several hours 1

CT identifies 100% of acutely treatable lesions, with 7% requiring urgent surgical intervention 3

MRI is Preferred for Non-Emergent Evaluation:

• MRI is the preferred imaging modality when not in an emergent situation, as it is more sensitive than CT for detecting epileptogenic lesions 1
• For low-risk patients (young, returned to baseline, normal neurologic exam, reliable follow-up), deferred outpatient MRI is acceptable 1
• For children with focal seizures, MRI with dedicated epilepsy protocol is indicated, as nearly 50% will have positive findings 1

Important caveat: 22% of patients with normal neurologic examinations still have abnormal imaging findings 1

Electroencephalography (EEG)

• EEG is recommended as part of the neurodiagnostic evaluation of a child with an apparent first unprovoked seizure 1
• Abnormal EEG findings predict increased risk of seizure recurrence 1

Lumbar Puncture Indications

Lumbar puncture should be performed selectively:

• Primary indication is concern for meningitis or encephalitis 1
• Consider in immunocompromised patients (perform after head CT) 1
• Fever with meningeal signs 1
• Routine lumbar puncture is NOT indicated for uncomplicated first-time seizures 1

Age-Specific Considerations

Neonates (0-29 days):

• MRI head is the preferred imaging modality to evaluate extent and characteristics of parenchymal brain abnormalities 4
• Ultrasound may be useful for unstable infants unable to have MRI, but has low sensitivity for hypoxic ischemic injury 4
• CT is helpful for identifying hemorrhagic lesions in encephalopathic infants with history of birth trauma, low hematocrit, or coagulopathy 4

Simple Febrile Seizures (6 months-5 years):

• Neuroimaging is NOT indicated for simple febrile seizures 4
• MRI abnormalities were found in 11.4% of children with simple febrile seizures, but none affected clinical management 4

Complex Febrile Seizures (6 months-5 years):

• Neuroimaging is generally unnecessary unless other neurological indications are present such as postictal focal deficits 4
• MRI may be indicated in children with febrile status epilepticus (seizure lasting >30 minutes) due to increased association with imaging findings 4

Post-Traumatic Seizures (Pediatric):

• CT head without contrast or MRI head without contrast should be performed urgently 3
• Post-traumatic seizure is an independent predictor for intracranial pathology regardless of current neurological status 3

Disposition Decisions

• Emergency physicians need not admit patients with a first unprovoked seizure who have returned to their clinical baseline in the ED 1
• Consider admission if: persistent abnormal neurologic examination, abnormal investigation results requiring inpatient management, or patient has not returned to baseline 1

Seizure Recurrence Risk

• The mean time to first seizure recurrence is 121 minutes (median 90 minutes), with >85% of early recurrences occurring within 6 hours 1
• Overall 24-hour recurrence rate is 19%, decreasing to 9% when alcohol-related events and focal CT lesions are excluded 1
• Nonalcoholic patients with new-onset seizures have the lowest recurrence rate (9.4%) 1

Critical pitfall: Approximately 28-48% of suspected first seizures have alternative diagnoses (syncope, nonepileptic seizures, panic attacks), highlighting the importance of careful history 1