Investigations
1st investigations to order
electroencephalogram (EEG)
Test
An EEG is indicated after any unprovoked seizure event. It can be used to support the diagnosis of generalised-onset or focal-onset epilepsy. A normal test does not prove that a patient does not have a potential for seizures; multiple or extended (>45 minutes) EEG studies may be warranted to increase the sensitivity.[40][41]
Long-term video-EEG monitoring (telemetry) may occasionally be required to distinguish epileptic seizures from conditions associated with intermittent symptoms attributable to non-epileptic mechanisms.[42][43]
Result
generalised epileptiform activity or focal, localising abnormality
blood glucose
Test
An important initial test to check for a provoking metabolic disturbance.
Result
extreme hypoglycaemia or hyperglycaemia can cause provoked generalised tonic-clonic seizures
FBC
Test
Evaluate for evidence of systemic or central nervous system (CNS) infection.
Result
elevated WBC can indicate a systemic or CNS infection, which can lead to a provoked generalised tonic-clonic seizure
electrolyte panel
Test
Evaluate for sodium imbalance, uraemia, or other metabolic abnormalities.
Result
electrolyte imbalance, particularly hyponatraemia, hypernatraemia, or uraemia, can lead to a provoked generalised tonic-clonic seizure
toxicology screen
Test
Useful if use of illicit substances is suspected. Cocaine, amfetamines, heroin, phencyclidine, and gamma-hydroxybutyric acid have been implicated in generalised tonic-clonic seizures (GTCSs).[23]
Result
a variety of illicit substances may cause a provoked GTCS
head CT
Test
Should be performed urgently if there are focal neurological deficits or a patient is not recovering to baseline following a seizure.[44]
More readily available than MRI in an emergency setting.
In a patient who has returned to baseline and has a normal neurological examination, the utility of a head CT is limited.
Result
may reveal evidence of a structural lesion or other process that has caused the seizure
Investigations to consider
MRI brain
Test
Standard imaging test for a patient who has returned to baseline and has a normal neurological examination.[44] Unless contraindicated, all patients with an unprovoked seizure event should have an MRI scan with and without gadolinium contrast within 1 month of the event. A 3 Tesla MRI (if available) is a more sensitive measure than head CT for detecting abnormalities such as cortical dysplasia, migrational defects, or small neoplasms, and can be used to better characterise other larger lesions.[44][45][46] Dedicated seizure- or epilepsy-specific MRI protocol should be requested.
Result
structural lesion (neoplasm, infarct, demyelination, cortical dysplasia, neuronal migrational defect, or other congenital or acquired abnormality) may be present as a cause for a focal-onset seizure; there are no pathognomonic imaging features of generalised-onset epilepsy.
lumbar puncture
Test
May be performed if a primary CNS infection is suspected, if the patient is not returning to baseline, or if there is persistent neurological deficit.
How to perform a diagnostic lumbar puncture in adults. Includes a discussion of patient positioning, choice of needle, and measurement of opening and closing pressure.
Result
normal or elevated WBC in infection
serum creatine kinase (CK)
Test
This test may be used when differentiating a seizure event from either syncope or another non-epileptic event. When drawn several hours after the event or followed sequentially until the next day, an elevated serum CK can provide evidence that a generalised tonic-clonic seizure has occurred.[38] However, serum CK has low specificity and sensitivity; it may be elevated in a number of other clinical conditions, and normal postictal CK levels do not exclude epilepsy.[38][39]
Result
levels >200 mU/mL (>200 units/L) or sequential increase in levels after 24 hours
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