Neuroimaging after First Seizure

1. Epidemiology
   1. Incidence: Neuroimaging in first non-febrile Seizure Evaluation identifies a structural Brain Lesion
      1. Adults: 33%
      2. Infants <6 months: 50%
2. Techniques: Imaging Studies after first Seizure
   1. Step 1: Urgent CT Head (acute to exclude Hemorrhage)
      1. Indicated urgently for at risk patients to exclude conditions that change acute management
         1. Structural cause found in 17% of adults and 8% of children
         2. New onset convulsive Status Epilepticus
         3. Persistently abnormal Neurologic Exam (or symptoms that do not resolve)
         4. Failure to return to neurologic baseline
      2. Patient without risk factors for intracranial pathology
         1. May wait for outpatient imaging typically with MRI Brain
      3. Contrast needed only in HIV or cancer history where tumor or abscess is suspected
   2. Step 2: Routine MRI Head (preferred for structural exam)
      1. Higher efficacy than Head CT in identifying underlying Brain Lesions
      2. No radiation exposure (see Cancer Risk due to Diagnostic Radiology)
         1. Even a greater concern in children in whom radiation exposure carries higher lifetime cancer risk
3. Indications: Adults
   1. All adults should have Neuroimaging after First Seizure (per ACEP and AAN)
      1. Timing of neuroimaging depends on presentation
      2. At risk patients, should undergo urgent Head CT, followed by later MRI Brain
      3. Stable patients may wait to undergo outpatient MRI Brain (if no contraindication for delay)
   2. Urgent neuroimaging indications (typically CT Head)
      1. Acute Head Trauma
      2. Age over 40 years
      3. AIDS
      4. Altered Mental Status persists
      5. Anticoagulation
      6. Fever
      7. Focal neurologic deficit of new onset
      8. Headache persists
      9. Malignancy
      10. Partial Seizure (Focal Seizure)
   3. Deferred outpatient neuroimaging indications (typically MRI Head)
      1. Stable patient and
      2. No urgent neuroimaging indications (see above) and
      3. Reliable patient for follow-up and
      4. Returned to baseline mental status during emergency department evaluation
4. Indications: Children
   1. All patients under age 6-12 months
   2. Cognitive or Motor Developmental Delay
   3. EEG with primary Generalized Epilepsy
   4. Head Trauma
   5. Malignancy
   6. Brain Tumor
   7. Prior Cerebrovascular Accident
   8. HIV Infection
   9. Bleeding Disorder or Coagulopathy
   10. Sickle Cell Disease
   11. Hydrocephalus
   12. Prior CNS surgery with shunt
   13. Neurocutaneous Syndrome (e.g. Neurofibromatosis, Tuberous Sclerosis)
   14. Hemihypertrophy
   15. Cysticercosis exposure (e.g. travel to endemic regions)
   16. Abnormal Neurologic Exam
       1. Focal neurologic deficits
       2. Mental status changes persist
       3. Partial Seizure (Focal Seizure)
       4. Postictal neurologic deficit that persists
5. References
   1. Nocera, Valente, Amanullah (2018) Crit Dec Emerg Med 32(11): 3-9
   2. Dayan (2015) Pediatrics 136(2): e351-60 +PMID:26195538 [PubMed]
   3. Wilden (2012) Am Fam Physician 86(4): 334-40 [PubMed]
   4. Harden (2007) Neurology 69(18): 1772-80 [PubMed]