Laboratory Tests for Post-Ictal Seizure Patients
All adult patients presenting with post-ictal seizures should receive serum glucose and sodium testing, with a pregnancy test for all women of childbearing age, as these are the core recommended tests by the American College of Emergency Physicians. 1, 2, 3
Essential Laboratory Tests for All Patients
Serum glucose is mandatory for all seizure patients, as hypoglycemia is one of the most common metabolic causes of seizures, though most cases are clinically apparent 1, 2, 3
Serum sodium is mandatory for all seizure patients, as hyponatremia can both cause and result from seizure activity 1, 2, 3
Pregnancy test is required for all women of childbearing age, as pregnancy affects testing decisions, disposition, and antiepileptic drug selection 1, 2, 3
Additional Testing Based on Clinical Context
For Patients with Specific Risk Factors:
Complete metabolic panel (including BUN, creatinine, electrolytes) should be ordered for patients with altered mental status, fever, focal neurologic deficits, or suspected metabolic abnormalities 1, 2
Calcium and magnesium levels should be checked in patients with known renal insufficiency, malnutrition, those taking diuretics, or suspected alcohol-related seizures 1, 2
Creatine kinase (CK) should be measured at least once to identify patients at risk for rhabdomyolysis and acute renal failure, particularly after generalized tonic-clonic seizures where CK elevations are common 4
Complete blood count (CBC) is recommended to evaluate for infection or hematologic abnormalities 2
For Specific Clinical Scenarios:
Drug/toxicology screen should be considered in first-time seizures with suspected substance use, though routine screening has limited evidence for benefit 1, 2, 3
Magnesium levels are specifically indicated for suspected alcohol-related seizures, as hypomagnesemia is common in this population 1, 2
Lumbar puncture (after head CT) is recommended for immunocompromised patients, those with fever, or signs of meningeal irritation 1, 2
Important Clinical Considerations
Laboratory testing has low yield in patients who have returned to baseline neurological status, with most abnormalities predictable from history and physical examination—one study found only 1 unexpected hypoglycemia case in 163 patients 1, 2
Prolactin testing (drawn 10-20 minutes post-ictally) can help differentiate epileptic seizures from psychogenic non-epileptic seizures with high specificity and moderate sensitivity 4, 5
Liver and renal function tests should be measured on at least one occasion to quickly identify metabolic and toxic encephalopathies as potential causes 4
Common Pitfalls to Avoid
Do not order extensive laboratory panels routinely in patients who have returned to baseline without specific clinical indicators 1, 2
Alcohol withdrawal seizures should be a diagnosis of exclusion, especially in first-time seizures 1, 2
Phenytoin is ineffective for seizures secondary to alcohol withdrawal, theophylline toxicity, or isoniazid toxicity 6
Most patients with secondary seizures do not have epilepsy and should be counseled accordingly 6