collect an extra tube of CSF for later analysis In any patient with signs of increased intracranial pressure, an LP should not be performed until head imaging can be done Electrolyte abnormalities may also cause seizures, with hyponatremia, hypocalcemia, and hypomagnesemia being the most common Unfortunately, seizures caused by electrolyte derangements are often refractory to anticonvulsant therapy and patients will continue to seize until the underlying abnormality is corrected In general, the routine screening for electrolyte abnormalities in a patient with brief seizure is of low value Serum electrolytes should be measured in all patients with seizure with significant vomiting or diarrhea; patients with underlying renal, hepatic, neoplastic, or endocrinologic disease; patients who are taking medications that may lead to electrolyte disturbances; or patients who have seizures that are refractory to typical anticonvulsant management Another clinical scenario involves hyponatremic seizures in infants, typically younger than months, after prolonged feedings of dilute formula (“infantile water intoxication”) Other patients may be evaluated on a case-by-case basis IV calcium, magnesium, and hypertonic (3%) sodium chloride should be used to treat the appropriate abnormal condition In the case of hyponatremia, 3% sodium chloride should be infused rapidly until the seizure activity has been stopped; subsequent to seizure resolution, a slower rate of sodium correction should be used to avoid possible central pontine myelinolysis Rarely, other chemistries can be helpful in identifying specific organ dysfunction, either as a cause of the seizure activity or as an assessment of systemic injury An elevated blood urea nitrogen or creatinine level suggests renal insufficiency (with associated findings such as hypertension and electrolyte disturbances) as a potential cause Elevated liver function tests (transaminases or coagulation times) can be a reflection of hepatic failure Metabolic acidosis or hyperammonemia can suggest an underlying metabolic disorder In patients with prolonged seizures, an arterial or venous blood gas level can help in assessing adequacy of ventilation and a creatine kinase level can identify possible rhabdomyolysis Toxicologic screening can also be helpful in the seizing patient because certain ingestions are managed with specific antidotes or treatments In general, the toxicologic screen should be directed at agents known to cause seizures (Table 72.1 ) or those suggested by a clinical toxidrome Radiologic imaging of the patient with seizure generally consists of a computed tomography (CT) scan for emergent imaging or, preferably, a magnetic