What is the recommended diagnostic workup and treatment for a patient presenting with a seizure?

Diagnostic Workup for Seizures

For an adult patient presenting with a new-onset seizure who has returned to baseline neurologic status, obtain serum glucose and sodium levels immediately, as these are the only laboratory tests that consistently alter acute management and represent the most common metabolic abnormalities causing seizures. 1, 2, 3

Immediate Assessment and Core Laboratory Testing

Universal Laboratory Tests

• Serum glucose and sodium are the only universally recommended tests for all patients with seizures, as hypoglycemia and hyponatremia are the most frequent abnormalities identified and are the only ones that consistently require immediate intervention 4, 1, 2, 3
• Pregnancy test for all women of childbearing age, as this affects testing decisions, disposition, and antiepileptic drug selection 1, 2, 3

Risk-Stratified Additional Laboratory Testing

The history and physical examination will predict the majority of patients who will have laboratory abnormalities 4. Additional testing should be guided by clinical circumstances:

• Extended electrolyte panel (calcium, magnesium, phosphate) only for patients with renal insufficiency, malnutrition, diuretic use, or suspected alcohol-related seizures 1, 3
• Complete blood count only if infection is suspected 1, 3
• Toxicology screening if there is any question of drug exposure or substance abuse 4, 2, 3

Important caveat: In prospective studies, unsuspected metabolic abnormalities are extremely rare. One study of 163 patients found only 1 unexpected case of hypoglycemia, and another study of 247 patients found only 1 case of unsuspected hyponatremia 4, 3. Laboratory testing has very low yield in patients who have returned to baseline neurologic status 3.

Neuroimaging Decision Algorithm

Emergent Head CT (Without Contrast) Indications

Perform emergent CT in the ED for patients with any of the following high-risk features 1, 2:

• Age >40 years
• History of malignancy or immunocompromised status
• Anticoagulant use
• Fever or persistent headache
• Recent head trauma
• Postictal focal deficit that does not quickly resolve
• Persistent altered mental status
• Focal seizure onset before generalization
• Patient has not returned to baseline within several hours

Key finding: 41% of first-time seizure patients have abnormal CT findings, and 22% of patients with normal neurologic examinations still have abnormal imaging 2. In older adults, head CT is recommended for all patients with new-onset seizures to evaluate for structural lesions 1, 3.

Non-Emergent MRI

• MRI is the preferred imaging modality for new-onset seizures when not in an emergent situation, as it is more sensitive than CT for detecting epileptogenic lesions 1, 2, 3
• For low-risk patients (young, returned to baseline, normal neurologic exam, reliable follow-up), deferred outpatient MRI is acceptable 2

Electroencephalography (EEG)

• EEG is recommended as part of the neurodiagnostic evaluation for patients with an apparent first unprovoked seizure, as it is essential for proper classification of epileptic seizures and syndromes 1, 2
• Abnormal EEG findings predict increased risk of seizure recurrence 2
• EEG should be performed within 24 hours after a seizure, particularly in children 5

Lumbar Puncture Indications

Lumbar puncture should be performed only in specific circumstances 1, 2:

• Concern for meningitis or encephalitis (fever with meningeal signs)
• Immunocompromised patients (after head CT) 4, 2, 3
• When autoimmune encephalitis is suspected

Routine lumbar puncture is not indicated for uncomplicated first-time seizures 2.

Special Populations

Alcohol-Related Seizures

• Alcohol withdrawal seizures should be a diagnosis of exclusion, especially in first-time seizures 2, 3
• Check magnesium levels in patients with suspected alcohol-related seizures, as hypomagnesemia is common in this population 3
• Symptomatic causes should always be searched for before labeling as withdrawal seizures 2

Immunocompromised Patients

• Require complete metabolic panel, head CT, and lumbar puncture after imaging 1
• In HIV patients with new-onset seizures, 40% had acute lesions necessitating admission 4

Disposition 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 only if:

• Persistent abnormal neurologic examination results
• Abnormal investigation results requiring inpatient management
• Patient has not returned to baseline 2

Seizure Recurrence Risk

Understanding recurrence risk helps guide 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 seizure recurrence is 121 minutes (median 90 minutes), with >85% of early recurrences occurring within 6 hours of ED presentation 1, 2
• Nonalcoholic patients with new-onset seizures have the lowest recurrence rate (9.4%) 2
• Risk factors for higher recurrence include abnormal neurological examination, abnormal EEG, remote symptomatic seizures, or Todd's paralysis 2

Common Pitfalls to Avoid

• Misdiagnosis: Approximately 28-48% of suspected first seizures have alternative diagnoses (syncope, nonepileptic seizures, panic attacks) 2
• Over-testing: Avoid routine extensive laboratory panels in patients who have returned to baseline, as most abnormalities are predicted by history and physical examination 4, 3
• Missing structural lesions: Do not skip neuroimaging in high-risk patients based solely on normal physical examination 2
• Premature AED initiation: 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