Metabolic Workup for Seizure Patients

Core Laboratory Tests

The American College of Emergency Physicians recommends serum glucose and sodium tests for all adult patients presenting with seizures, as these are the most common metabolic abnormalities associated with seizures 1, 2
A pregnancy test is required for all women of childbearing age, as pregnancy can affect testing, disposition, and antiepileptic drug therapy 1, 3

For immunocompromised patients, a lumbar puncture is recommended after head CT, and for patients with fever or signs of meningeal irritation 1, 3
A drug of abuse screen should be considered in patients with first-time seizures, though evidence for routine use is limited 2, 3
An expanded electrolyte panel, including calcium, magnesium, and phosphate testing, should be considered in patients with known renal insufficiency, malnutrition, or those taking diuretics 1

The literature consistently shows that laboratory testing has a low yield in patients with new-onset seizures who have returned to baseline neurological status, with most abnormalities predictable by history and physical examination 1, 2
Glucose abnormalities, such as hypoglycemia and hyperglycemia, are among the most frequent findings, but are usually clinically apparent 1, 4
Hyponatremia is another common finding, typically predictable from clinical history 1
Studies have found very few cases of unsuspected metabolic abnormalities, with one prospective study finding only 1 unexpected case of hypoglycemia in 163 patients, and another study finding 2 cases of unpredicted hypoglycemia in 136 patients 1

Immunocompromised patients require more extensive evaluation, including lumbar puncture, due to higher rates of CNS infections presenting with seizures 1, 5
Alcohol withdrawal seizures should be a diagnosis of exclusion, especially in first-time seizures, and magnesium levels should be checked in patients with suspected alcohol-related seizures 2, 6

For all adult seizure patients, serum glucose and sodium tests, as well as a pregnancy test for women of childbearing age, are recommended 1
For patients with altered mental status, fever, or focal neurologic deficits, a complete metabolic panel, toxicology screen, head CT, and lumbar puncture should be considered as appropriate 1, 3
For immunocompromised patients, a complete metabolic panel, head CT, and lumbar puncture are recommended 1, 3
For patients with known medical disorders or taking diuretics, an extended electrolyte panel, including calcium, magnesium, and phosphate, should be considered 1

For patients with suspected alcohol-related seizures, checking magnesium levels is recommended, as hypomagnesemia is common in this population 7
MRI is the preferred imaging modality for new onset seizures if available, and emergent neuroimaging should be performed in patients with postictal focal deficits that do not quickly resolve 8
Additional testing, such as complete metabolic panel, head CT, and lumbar puncture, may be considered based on specific risk factors, including immunocompromised status, fever, meningeal signs, altered mental status, and suspected drug use 8