What is the appropriate workup for a patient presenting with possible seizure-like activity?

Workup for Possible Seizure-Like Activity

For patients presenting with possible seizure-like activity, immediately assess vital signs and neurological status, obtain serum glucose and sodium levels, and perform neuroimaging based on risk stratification—with emergent CT for high-risk features or deferred outpatient MRI for low-risk patients who have returned to baseline. 1

Initial Clinical Assessment

Confirm the event was actually a seizure, as 28-48% of suspected seizures have alternative diagnoses including syncope, nonepileptic seizures, or panic attacks. 1 Key features that strongly suggest true seizure include:

• Tonic-clonic movements that are prolonged and begin simultaneously with loss of consciousness 1
• Document precise details: time of onset, duration, focal versus generalized onset, motor activity characteristics, and post-ictal state 2
• Assess Glasgow Coma Scale score, as GCS <15 is associated with higher early seizure recurrence risk 2

Essential Laboratory Testing

Obtain serum glucose and sodium immediately—these are the only laboratory abnormalities that consistently alter acute management and require immediate intervention. 1, 2

Additional targeted laboratory tests based on clinical context:

• Pregnancy test if patient has reached menarche 1
• Calcium and magnesium in patients with known cancer or renal failure 1
• Toxicology screening if any question of drug exposure or substance abuse 1
• Additional tests (CBC, comprehensive metabolic panel) only when suggested by specific clinical findings such as vomiting, diarrhea, or dehydration 1

Neuroimaging Decision Algorithm

High-Risk Features Requiring Emergent CT Head Without Contrast 1, 2:

• Age >40 years
• Recent head trauma
• History of malignancy or immunocompromised state
• Persistent altered mental status or new focal neurological deficits
• Anticoagulation therapy
• Fever (suggesting possible CNS infection)
• Persistent headache
• Focal seizure onset before generalization

CT is useful for rapidly identifying intracranial hemorrhage, stroke, vascular malformation, hydrocephalus, and tumors. 1 However, CT has limited sensitivity—22% of patients with normal neurologic examinations still have abnormal imaging, and CT misses epileptogenic lesions that MRI detects. 1

Low-Risk Patients (Deferred Outpatient MRI Acceptable) 1, 2:

• Young age (<40 years)
• Returned to baseline neurological status
• Normal neurological examination
• Reliable follow-up arrangements available

MRI is the preferred imaging modality for non-emergent evaluation as it is significantly more sensitive than CT for detecting epileptogenic lesions. 1 In children with focal seizures, MRI with dedicated epilepsy protocol shows positive findings in nearly 50% of cases. 1

Electroencephalography (EEG)

EEG is recommended as part of the neurodiagnostic evaluation for apparent first unprovoked seizures. 1 Abnormal EEG findings predict increased risk of seizure recurrence. 1

Lumbar Puncture Indications

Lumbar puncture should be performed primarily when there is concern for meningitis or encephalitis. 1 Specific indications include:

• Fever with meningeal signs
• Immunocompromised patients (perform after head CT) 1, 2
• Clinical suspicion of CNS infection

Risk Stratification for Early Seizure Recurrence

The mean time to first seizure recurrence is 121 minutes (median 90 minutes), with >85% of early recurrences occurring within 6 hours of presentation. 1, 2

Overall 24-hour recurrence rates:

• 19% in all seizure patients 1
• 9% when alcohol-related events and focal CT lesions are excluded 1
• 9.4% in nonalcoholic patients with new-onset seizures (lowest risk) 1
• 25.2% in alcoholic patients with seizure history (highest risk) 1

Risk factors for early recurrence include:

• Age ≥40 years
• Alcoholism
• Hyperglycemia
• GCS score <15
• History of CNS injury (stroke, trauma, tumor) 2

Disposition Decision-Making

Patients with a first unprovoked seizure who have returned to their clinical baseline in the ED need not be admitted. 1, 2

Consider admission if any of the following are present 1, 2:

• Persistent abnormal neurological examination
• Abnormal investigation results requiring inpatient management
• Patient has not returned to baseline
• Provoked seizures where underlying cause requires treatment
• High risk of early recurrence (alcoholics, abnormal GCS)

Special Populations

Neonates (0-29 days) 3:

• MRI head is the preferred imaging modality to evaluate parenchymal brain abnormalities
• Ultrasound may be useful initial bedside imaging for unstable infants
• Underlying cause identified in 95% of neonatal seizures, most commonly hypoxic-ischemic injury (46-65%)

Simple Febrile Seizures (6 months-5 years) 1:

• Neuroimaging is NOT indicated
• MRI abnormalities found in 11.4% did not affect clinical management

Complex Febrile Seizures 1:

• Neuroimaging generally unnecessary unless other neurological indications present
• MRI may be indicated in febrile status epilepticus due to increased association with imaging findings

Critical Pitfalls to Avoid

• Failing to identify hypoglycemia or hyponatremia that may be causing the seizure 1
• Missing structural lesions by not performing appropriate neuroimaging 1
• Assuming alcohol withdrawal as the cause in first-time seizures—this should be a diagnosis of exclusion after searching for symptomatic causes 1
• Allowing oral intake before proper swallowing assessment due to elevated aspiration risk in the immediate post-ictal period 4