Initial Workup Investigations for Seizure Patients
All adult patients presenting with seizures should receive serum glucose and sodium testing, and all women of childbearing age require a pregnancy test—these are the only universally recommended laboratory tests for otherwise healthy patients who have returned to baseline neurological status. 1, 2
Core Laboratory Tests for All Seizure Patients
Serum glucose is essential as hypoglycemia and hyperglycemia are among the most frequent metabolic causes of seizures, though most cases are clinically apparent from history and physical examination 3, 1
Serum sodium testing is mandatory as hyponatremia is the second most common metabolic abnormality, typically predictable from clinical history 3, 1
Pregnancy test is required for all women of childbearing age because pregnancy affects testing decisions, disposition, and antiepileptic drug selection 1, 2
Risk-Stratified Additional Testing
The decision to pursue additional laboratory testing depends entirely on clinical presentation and risk factors identified through history and physical examination 3, 4:
For Patients with High-Risk Features
Obtain expanded testing if any of the following are present:
Altered mental status, fever, or focal neurologic deficits warrant complete metabolic panel, head CT, and consideration of lumbar puncture 3, 1
Immunocompromised status requires complete metabolic panel, head CT, and lumbar puncture after imaging 1, 2
Known renal insufficiency, malnutrition, or diuretic use necessitates extended electrolyte panel including calcium, magnesium, and phosphate 1, 2
Suspected alcohol-related seizures require magnesium level testing, as hypomagnesemia is common in this population 1, 2
For Otherwise Healthy Patients at Baseline
Routine serum chemistries have extremely low yield in patients who have returned to baseline neurological status, with prospective studies finding only 1 unexpected hypoglycemia case in 163 patients 3, 4
Drug screening may be considered in first-time seizures with suspected substance use, though evidence for routine use is limited 1, 2
Neuroimaging Recommendations
MRI is the preferred imaging modality for new-onset seizures when available 1, 5
Emergent head CT should be performed for patients with postictal focal deficits that do not quickly resolve, first-time seizures in older adults, or when acute intracranial bleeding is suspected 1, 2, 6
CT scanning identified abnormalities in 25% of selected patients (5 of 19) in prospective studies, making it useful when clinically indicated 4
Critical Pitfalls to Avoid
Alcohol withdrawal seizures must be a diagnosis of exclusion, especially in first-time presentations—do not assume this diagnosis without ruling out other causes 3, 2
History and physical examination successfully predict laboratory abnormalities in the vast majority of cases—avoid reflexive ordering of comprehensive metabolic panels in low-risk patients who have returned to baseline 3, 4
Anticonvulsant levels are only useful in patients with known epilepsy on medications—they were the most common "significant" finding in one study (96 of 104 abnormalities), but this is irrelevant for new-onset seizures 4
Algorithm for Clinical Decision-Making
Step 1: Check glucose, sodium, and pregnancy test (if applicable) in all patients 1, 2
Step 2: Assess for high-risk features (altered mental status, fever, focal deficits, immunocompromised status) 3, 1
Step 3: If high-risk features present, obtain complete metabolic panel, neuroimaging, and consider lumbar puncture 1, 2
Step 4: If patient has returned to baseline with normal examination and no risk factors, additional laboratory testing beyond glucose and sodium is not indicated 3, 4
Step 5: Consider extended electrolyte panel only for patients with specific risk factors (renal disease, malnutrition, diuretics, suspected alcohol withdrawal) 1, 2