Tests
1st tests to order
blood glucose
Test
An important initial test. Hypoglycemia and hyperglycemia should be excluded in patients presenting with a first seizure episode.[36]
Result
extreme hypoglycemia or hyperglycemia can cause provoked focal seizures
CBC
Test
Helpful in establishing an underlying systemic or central nervous system infection.[36]
Result
elevated WBC can indicate a central nervous system infection
electrolyte panel
Test
Electrolyte disturbances (including uremia, decreased/elevated sodium, and magnesium or calcium abnormalities) should be excluded in patients presenting with a first seizure episode.[36]
Result
possible electrolyte disturbances
toxicology screen
Test
Indicated if use of illicit substances is suspected.[36]
Result
variable
lumbar puncture and cerebrospinal fluid analysis
Test
Indicated when a central nervous system infection is suspected (fever present) as the underlying cause of the seizure episode.[36]
Contraindicated without prior neuroimaging if the patient has a depressed level of consciousness.
Result
evidence of excessive WBCs; elevated protein and/or low glucose may be present if central nervous system infection
CT head
Test
Usually ordered when a patient presents in the emergency department with a first seizure episode.[39] It is useful for identifying acute causes of seizures, but is less sensitive for smaller abnormalities often seen on MRI.
Result
intracranial hemorrhage; skull fracture; presence of structural lesion
MRI brain
Test
Regarded as the test of choice in the workup of focal seizures.[40][41] It can be ordered initially (usually first test ordered when patient presents in the office), or obtained after head CT (usually first test ordered when patient presents in the emergency room).
Sensitivity of the MRI may be increased by using gadolinium enhancement or thin coronal sections without skips through the temporal lobes, with fluid-attenuated inversion recovery (FLAIR) sequences.
Developmental lesions include focal cortical dysplasia, nodular heterotopia, schizencephaly, polymicrogyria, and hemimegalencephaly.
Result
anatomic temporal lobe abnormalities (mesial temporal sclerosis, neoplastic lesions, vascular malformations, and developmental lesions)
electroencephalogram (EEG)
Test
Useful in the initial workup of focal seizures. Overall, the sensitivity of the first routine EEG is about 50%; this increases to 90% after 4 EEGs or following a 24- to 48-hour continuous EEG study.[38] However, a normal EEG does not exclude a diagnosis of epilepsy.
Result
focal spikes or sharp waves with associated slowing of the electrical activity in the area of the spikes
Tests to consider
video/electroencephalogram (EEG) long-term monitoring (LTM)
Test
Not required in the initial investigation, but may be useful in a number of clinical situations; for example, to confirm the diagnosis when there is uncertainty (and when there is no response to usual therapy), as well as in the surgical workup for treatment-resistant focal epilepsy.
Result
capturing seizure activity simultaneously on video recording and EEG; increased EEG sampling may reveal evidence of interictal abnormalities (spikes and sharp waves), which may make the diagnosis of focal seizures more likely
PET scan
Test
Performed as part of the surgical evaluation of treatment-resistant focal epilepsy.[49]
Result
ictal: hypermetabolic; interictal: hypometabolic
single photon emission computed tomography (SPECT) scan
Test
Performed as part of the surgical evaluation of treatment-resistant epilepsy. For an ictal SPECT scan, a radioactive tracer such as 99m-Tc-HMPAO is injected at the onset of the seizure, and the patient is scanned. This is compared with a scan taken when the patient is seizure-free (interictal scan).
Result
ictal SPECT shows increased vascular perfusion in the region of seizure onset compared with interictal SPECT
functional MRI scan
magnetoencephalography (MEG) scan
Test
Not required in the initial workup of seizures.
May provide important complementary information toward the identification of the epileptogenic zone and possible functional localization of language and motor cortex, so used mainly in detailed planning for epilepsy surgery.
Result
epileptic focus localized
neuropsychological testing
Test
A comprehensive evaluation of memory, language, and intellectual function. Deficits in all these spheres are common in patients with treatment-resistant epilepsy. Patterns of deficits may emerge, which may support the results of the other tests, and help to localize the epileptogenic focus.
Result
deficits in language or memory, localized to an area of the brain
Wada test
Test
The Wada test (intracarotid amobarbital test), which is used to confirm the lateralization of language and to discern memory dominance prior to epilepsy surgery, has increasingly been replaced by functional MRI.[46][47]
The Wada test may, however, be indicated when there is a high risk of postsurgical global amnesia (despite its reliability for this purpose being questioned) or when functional MRI fails to show clear left-lateralization.[44][45][48]
The test involves inactivating one hemisphere of the brain at a time for a 3- to 5-minute period with an intracarotid administered barbiturate agent (e.g., methohexital), and testing the "awake" side using cards with images and words. It is important to demonstrate that memory is supported by the side of the brain opposite the suspected seizure focus. The presence of a poor memory function on the side presumed to be the epileptogenic focus suggests that additional memory deficit post surgery is less likely.
Result
language localized to the left hemisphere; memory intact on the right, but reduced on the left, in a patient with presumed left mesial temporal sclerosis
Emerging tests
7T MRI scan
Test
Studies have demonstrated the added value of 7T MRI (compared with 1.5 and/or 3T MRI) in patients with and without known epileptogenic lesions.[50]
Currently used mostly as a research tool; not commonly available in clinical practice.
Result
identifies structural brain lesions
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