Pediatric Status Epilepticus Workup

Every patient who presents with SE requires electroencephalography (EEG); however, treatment should not be delayed to wait for EEG results. When a seizure persists longer than 30-60 minutes, making immediate arrangements for an EEG is advisable.

Likewise, laboratory testing should proceed concurrently with stabilization. Although routine laboratory studies are not always useful in assessing patients with brief seizures who present to the emergency department (ED), children with generalized tonic-clonic status epilepticus (GTCSE) require a more aggressive workup. Lumbar puncture with opening pressure measurement is performed for prolonged SE of unknown etiology. It is also indicated in immunocompromised patients.

Stabilize all children before CT scanning or other imaging studies are performed. Obtain imaging studies based on likely etiologies

The choice of laboratory studies is based on age and likely etiologies. They may include the following:

• Blood glucose level
• Complete blood count (CBC)
• Electrolyte levels
• Calcium and magnesium levels, particularly in neonates
• Arterial blood gases
• Toxicology screen
• Anticonvulsant levels (if indicated by history of ingestion or known therapy^[13] )

Stabilization phase studies

While attending to the patient’s airway, breathing, and circulation (ABCs) and inserting an intravenous (IV) line, obtain a CBC and tests for levels of anticonvulsant medication, electrolytes, blood urea nitrogen (BUN) and creatinine, calcium, and magnesium.

Serum glucose measurement is particularly important if the child or another household member uses insulin or other hypoglycemic agents; hypoglycemia may be a contributing factor or cause of seizures. Glucose measurement should be performed with a fast bedside assay (eg, Dextrostix).

The CBC may show elevation of the white blood cell (WBC) count in patients with infection. However, an elevated WBC count may be due to demargination, returning to reference ranges over 12-24 hours.

Calcium and magnesium measurement may be important, especially for infants fed with cows' milk. It is also valuable in older patients with disorders that may produce imbalances in these elements (eg, renal failure, hypoparathyroidism).

Other necessary tests may include urine/serum toxicology, especially in teenagers with unexplained seizures. If school-aged children who have cats (particularly kittens) at home present with unexplained mental status changes and prolonged seizures, evaluate for catscratch fever by measuring indirect fluorescent antibody titers to Bartonella henselae. A lumbar puncture is commonly indicated in children with GTCSE, especially those with unexplained fever or mental status changes preceding or following the seizure episode.

Continued evaluation

Continue evaluation after seizures are controlled. Basic tests recommended by the Epilepsy Foundation Working Group on Status Epilepticus include liver function tests (LFTs), toxicology screen, and brain imaging.^[14]

After an SE episode, perform a lumbar puncture for individuals with fever or other evidence of CNS infection. Remember that febrile convulsive status may be associated with CNS infection without typical meningeal signs. Brain imaging should be part of the workup for status epilepticus prior to lumbar puncture for patients with acute neurologic changes suggesting increased intracranial pressure.

A treatment algorithm is shown in the image below.

Imaging studies are indicated in patients with GTCSE once they are stabilized. A head CT scan is the best diagnostic imaging study, particularly if intracranial hemorrhage, midline shift, or mass lesion is suspected.

In many centers, head CT scanning is available on an emergency basis. If CT scanning is unavailable and the patient is stable and has no signs of increased intracranial pressure, CT scanning can be temporarily deferred.

Perform an imaging study for all patients who have histories of neurologic (including mental status) changes and for patients who have actual deficits on the neurologic examination that persist after cessation of seizures.

Brain imaging should be part of the workup for SE prior to lumbar puncture for patients with acute neurologic changes suggesting increased intracranial pressure.

Children with complex partial seizures preceding or leading to the episode of GTCSE should undergo brain MRI. In many centers, CT scanning is performed in the ED because MRI services are often unavailable after hours. If not immediately available, MRI should be performed in the following days.

Brain imaging may be unnecessary for patients who have already had MRI performed as part of a workup for epilepsy or when the cause or precipitant for their episode of SE is obvious (eg, low anticonvulsant levels, acute infection).

On follow-up, many patients with documented a priori normal MRI findings may develop an increased T2, diffusion and fluid attenuated inverted recovery (FLAIR) signal. This is especially true in cases of prolonged partial seizures leading to secondary GTCSE. Most of these changes are due to transient vasogenic or cytotoxic edema.

The EEG helps in differentiating convulsive SE from pseudoseizure (nonepileptic or psychogenic seizure). Nonconvulsive status epilepticus (NCSE) may need to be differentiated from postictal state–related depression and unresponsiveness from metabolic encephalopathies (renal and hepatic) as well as anoxic encephalopathies. This is especially the case when treatment with anticonvulsant medication does not improve the patient’s alertness.

Patients who ultimately require continuous infusion with a barbiturate or benzodiazepine should undergo continuous EEG monitoring.

During a prolonged seizure, EEG manifestations follow a sequence of partial (focal) EEG seizures, leading to discrete generalized tonic-clonic seizures that eventually become fused (ie, continuous EEG seizure). Rhythmic lateralized or generalized discharges later appear to slow in frequency and may appear similar to periodic lateralizing epileptiform discharges (PLEDs).

A patient who arrives at the ED may be at any of these EEG stages; historical information concerning seizure progression usually correlates somewhat with stage. Patients at the later stages of EEG with GTCSE may be more difficult to treat.

Patients who cannot be aroused following a seizure should have an EEG performed to rule out subclinical SE. An EEG can confirm the seizure pattern and help indicate the most appropriate long-term treatment, if necessary.

Seizures not responding to appropriate therapy in 60 minutes or to the first- and second-lines drugs (initial doses of benzodiazepines, IV phenytoin/fosphenytoin, and phenobarbital) should be considered refractory status epilepticus. Prolonged refractory status epilepticus (seizures persisting beyond 24 h) needs further workup if routine blood work, MRI of the brain, and microbiological studies in serum and cerebrospinal fluid (CSF) do not provide clues to the etiology of the seizures. The following investigations are considered:

• Urine organic acids, porphyrins (porphyria), and sulfites (sulfite oxidase deficiency and molybdenum co-factor deficiency)
• Serum T4, T3, thyrotropin, and antiperoxidase antibody (autoimmune epilepsy)
• Serological markers for collagen-vascular disorders
• Serum and CSF NMDA-R antibody, ultrasound/CT/MRI of testes and abdomen to look for solid tumors (anti NMDA-R antibody encephalitis)
• Other paraneoplastic antibodies (anti Hu, Yo, Ri)

If the patient continues to be in refractory status epilepticus beyond 72 hours, additional investigations are suggested, as follows:

• Repeat MRI brain with gadolinium
• Cerebral angiography (CT angiography or conventional 4-vessel angiography) to look for evidence of vasculitis
• CSF neurotransmitters

If the above-mentioned investigations do not identify the etiology of seizures within a week, brain biopsy may be considered.