What is the initial evaluation and treatment approach for a patient with new onset seizure?

Initial Evaluation and Treatment of New-Onset Seizure

For an adult patient with new-onset seizure who has returned to baseline neurologic status, obtain serum glucose and sodium levels, perform a pregnancy test if applicable, and arrange for neuroimaging—preferably emergent head CT in the ED for high-risk patients or deferred outpatient MRI for low-risk patients with reliable follow-up. 1, 2

Immediate Laboratory Testing

Core tests required for all patients:

• Serum glucose and sodium are the only universally indicated laboratory tests, as these represent the most common metabolic abnormalities that alter acute management 1, 2, 3
• Pregnancy test for all women of childbearing age (post-menarche), as this affects imaging decisions, disposition, and antiepileptic drug selection 1, 2, 4

Risk-stratified additional testing:

• Extended electrolyte panel (calcium, magnesium, phosphate) only for patients with renal insufficiency, malnutrition, diuretic use, or suspected alcohol-related seizures 2, 4
• Complete blood count only if infection is suspected 3
• Toxicology screening if drug exposure or substance abuse is suspected 2
• Lumbar puncture (after head CT) for immunocompromised patients or those with fever and meningeal signs 1, 2, 3

The evidence consistently shows that routine laboratory panels have low yield in patients who have returned to baseline, with most abnormalities predictable by history and physical examination. 2, 4 Only 3 cases out of 247 patients in one study had unpredicted metabolic abnormalities (1 hypoglycemia, 1 hyponatremia, 1 hypocalcemia). 1

Neuroimaging Decision Algorithm

High-risk patients requiring emergent head CT without contrast in the ED: 1, 2

• Age >40 years
• History of malignancy or immunocompromised state
• Recent head trauma
• Anticoagulation use
• Fever or persistent headache
• Focal neurologic examination findings
• Focal seizure onset before generalization
• Persistent altered mental status or failure to return to baseline

Low-risk patients (young, returned to baseline, normal neurologic exam):

• Deferred outpatient MRI is acceptable when reliable follow-up is available 1, 2
• MRI is the preferred imaging modality for non-emergent evaluation as it is more sensitive than CT for detecting epileptogenic lesions 1, 2

The evidence shows 22-34% of first-time seizure patients have abnormal head CT findings, and 17% of patients with normal neurologic examinations still have focal CT lesions. 1 However, the multidisciplinary consensus allows for deferred imaging in low-risk patients based on the absence of studies demonstrating outcome benefit from ED imaging. 1

Electroencephalography

EEG is recommended as part of the neurodiagnostic evaluation, particularly for children with apparent first unprovoked seizure 1, 2 Abnormal EEG findings predict increased risk of seizure recurrence. 2

Disposition and Admission Decisions

Emergency physicians need not admit patients with a first unprovoked seizure who have returned to their clinical baseline in the ED. 2

Consider admission if any of the following are present: 2

• Persistent abnormal neurologic examination
• Abnormal investigation results requiring inpatient management
• Patient has not returned to baseline
• Unreliable follow-up or social concerns

Seizure Recurrence Risk

Understanding recurrence risk informs disposition decisions:

• Overall 24-hour recurrence rate is 19%, decreasing to 9% when alcohol-related events and focal CT lesions are excluded 2
• Mean time to first recurrence is 121 minutes (median 90 minutes), with >85% of early recurrences occurring within 6 hours of ED presentation 2
• Nonalcoholic patients with new-onset seizures have the lowest recurrence rate (9.4%), while alcoholic patients with seizure history have the highest (25.2%) 2

Antiepileptic Drug Initiation

Do not routinely initiate antiepileptic drugs for a single, self-limited seizure in the ED. 2 The evidence shows that antiepileptic drug treatment reduces 1-2 year recurrence risk but does not affect long-term recurrence rates or remission rates, and exposes patients to medication adverse effects without proven mortality or morbidity benefit. 2

Consider antiepileptic drug initiation for patients at high risk for recurrence: 5

• History of brain insult
• EEG demonstrates epileptiform abnormalities
• MRI demonstrates structural lesion
• Second unprovoked seizure (meets criteria for epilepsy diagnosis)

Critical Pitfalls to Avoid

• 28-48% of suspected first seizures have alternative diagnoses (syncope, nonepileptic seizures, panic attacks), highlighting the importance of detailed history focusing on: 2

  • Tonic-clonic movements that are prolonged and begin simultaneously with loss of consciousness (strongly suggests seizure) 4
  • Presence of postictal confusion
  • Tongue biting, incontinence, or witnessed seizure activity

• Alcohol withdrawal seizures should be a diagnosis of exclusion, especially in first-time seizures—always search for symptomatic causes before labeling as withdrawal seizures 2

• Do not miss structural lesions by failing to perform appropriate neuroimaging in high-risk patients 2

• Do not overlook CNS infections in immunocompromised patients—these require lumbar puncture after head CT 1, 2