What is the initial workup for a patient presenting with epilepsy?

Initial Workup for Epilepsy

The initial workup for a patient presenting with epilepsy should include laboratory testing based on individual clinical circumstances, EEG, and neuroimaging with MRI as the preferred modality. 1

Laboratory Testing

• Basic laboratory tests: Order based on clinical presentation and suspicion:

  • Complete blood count
  • Electrolytes (sodium, potassium, calcium, magnesium)
  • Blood glucose
  • Renal function (BUN, creatinine)
  • Liver function tests

• Toxicology screening: Consider across all age groups if there is any suspicion of drug exposure or substance abuse 1

  • Particularly important for cocaine, stimulants, tricyclic antidepressants, antihistamines, and theophylline, which are commonly associated with seizures 1

• Special considerations:

  • Hypomagnesemia is common in alcohol-related seizures 1
  • HIV testing should be considered in patients with risk factors, as HIV patients may have specific etiologies including opportunistic infections 1

Electroencephalography (EEG)

• Standard recommendation: EEG is recommended as part of the neurodiagnostic evaluation for all patients with apparent first unprovoked seizure 1

  • Helps classify seizure type and epilepsy syndrome
  • Abnormal EEG findings predict increased risk of seizure recurrence 1

• Emergency EEG considerations:

  • Consider emergent EEG in patients suspected of being in nonconvulsive status epilepticus or subtle convulsive status epilepticus
  • Also indicated for patients who have received long-acting paralytics or are in drug-induced coma 1

Neuroimaging

• MRI is the preferred modality over CT for epilepsy evaluation 1

  • MRI detects focal brain abnormalities in up to 55% of children with seizures, compared to only 18% with CT 1
  • Approximately 29% of abnormal intracranial findings are not seen on initial CT but are detected on MRI 1

• Timing of neuroimaging:

  • Emergent neuroimaging is indicated for:

    • Patients with postictal focal deficits that do not quickly resolve
    • Patients who have not returned to baseline within several hours after the seizure 1
    • Patients with focal seizures and abnormal neurological examination 1

  • Non-urgent MRI should be considered for:

    • Patients with significant cognitive or motor impairment of unknown etiology
    • Unexplained abnormalities on neurological examination
    • Seizures of partial onset (with or without secondary generalization)
    • EEG that does not represent benign partial epilepsy or primary generalized epilepsy
    • Children under 1 year of age 1

Special Considerations

• Lumbar puncture: Limited value in routine evaluation but should be performed when there is concern for meningitis or encephalitis 1

• Epilepsy protocol MRI: Standard MRI may miss epileptogenic lesions; optimized epilepsy protocol with adequate spatial resolution and multiplanar reformatting is essential for focal epilepsy 1

• Advanced imaging: Consider for drug-resistant epilepsy or when standard workup is inconclusive:

  • FDG-PET for localizing the seizure onset zone in presurgical evaluation 1
  • Ictal/interictal SPECT for localizing seizure focus in drug-resistant focal epilepsy 1

Common Pitfalls to Avoid

1. Relying solely on CT imaging: MRI is significantly more sensitive for detecting epileptogenic lesions 1

2. Missing metabolic causes: History and physical examination may not predict all metabolic abnormalities; consider checking glucose, sodium, calcium, and magnesium levels 1

3. Overlooking toxicologic causes: Drug toxicity is a common cause of seizures, particularly with cocaine, stimulants, and certain medications 1

4. Failure to recognize non-convulsive status epilepticus: Consider EEG in patients with unexplained altered mental status following a seizure 1

5. Inadequate imaging protocols: Standard brain MRI protocols may miss subtle cortical dysplasias and other epileptogenic lesions; specialized epilepsy protocols are preferred 1

By following this structured approach to the initial workup of epilepsy, clinicians can efficiently identify the underlying etiology and guide appropriate treatment decisions to improve patient outcomes.