Neuroimaging after First Seizure

Aka: Neuroimaging after First Seizure, Seizure Indications for Neuroimaging

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II. Epidemiology

  1. Incidence: Neuroimaging in first non-febrile Seizure Evaluation identifies a structural Brain Lesion
    1. Adults: 33%
    2. Infants <6 months: 50%

III. Techniques: Imaging Studies after first Seizure

  1. See First Seizure Evaluation
  2. 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. New Focal Seizures
      4. Persistently abnormal Neurologic Exam (or symptoms that do not resolve)
      5. Failure to return to neurologic baseline or persistent neurologic deficits
      6. New, non-Febrile Seizure in age <1 year old
      7. Suspected Traumatic cause (e.g. suspected Child Abuse or neglect)
    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
  3. 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

IV. Indications: Adults

  1. See First Seizure Evaluation
  2. 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)
  3. 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)
  4. Deferred outpatient neuroimaging indications (typically MRI Head with Epilepsy specific thin-sliced protocol)
    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

V. Indications: Children

  1. See Unprovoked Seizure in Children
  2. Background
    1. MRI Head is the preferred modality if imaging is absolutely required (no radiation)
    2. MRI in young children typically requires Procedural Sedation and increased resource use
      1. See Procedural Sedation
      2. Consult pediatric neurology if imaging may be deferred to follow-up or tertiary transfer
      3. Larger, tertiary facilities have T3 MRI allowing rapid sequences and shorter MRI time
    3. Anxiolysis alone (single agent Midazolam) may be effective in some children
      1. Midazolam 0.05 mg/kg IV (up to 2 doses at least 3 minutes apart)
      2. Midazolam 0.5 mg/kg intranasal (1/2 in each nostril) using 5 mg/ml up to 10 to 20 mg
    4. References
      1. Claudius and Marin (2023) EM:Rap, Pediatric Pearls: Pediatric Imaging, accessed 10/1/2023
  3. All patients under age 6-12 months (aside from simple Febrile Seizure)
  4. Cognitive or Motor Developmental Delay
  5. EEG with primary Generalized Epilepsy
  6. Head Trauma
  7. Malignancy
  8. Brain Tumor
  9. Prior Cerebrovascular Accident
  10. HIV Infection
  11. Bleeding Disorder or Coagulopathy
  12. Sickle Cell Disease
  13. Hydrocephalus
  14. Prior CNS surgery with shunt
  15. Neurocutaneous Syndrome (e.g. Neurofibromatosis, Tuberous Sclerosis)
  16. Hemihypertrophy
  17. Cysticercosis exposure (e.g. travel to endemic regions)
  18. Abnormal Neurologic Exam
    1. Focal neurologic deficits
    2. Mental status changes persist
    3. Partial Seizure (Focal Seizure)
    4. Postictal neurologic deficit that persists

VI. 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]

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