Diagnostic Imaging Pathways - Paediatric, Seizure
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This pathway provides guidance on imaging children with unexplained seizures.
Date reviewed: May 2017
Date of next review: May 2019
Published: September 2017
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The relative radiation level (RRL) of each imaging investigation is displayed in the pop up box.
| SYMBOL | RRL | EFFECTIVE DOSE RANGE |
 | None | 0 |
 | Minimal | < 1 millisieverts |
 | Low | 1-5 mSv |
 | Medium | 5-10 mSv |
 | High | >10 mSv |
Teaching Points
Teaching Points
- A seizure is defined as “a transient episode of clinical signs and symptoms due to abnormal, synchronous and excessive neuronal discharge in the brain, particularly the cerebral cortex”
- This pathway presents an approach to the investigation and management of unexplained seizures in a paediatric population
- Seizures in younger children differ significantly from those in older children and adults. Children younger than six have less complex behaviours, particularly with focal seizures with impairment of awareness
- History, clinical examination, laboratory investigations and EEG (or Video-EEG) form very important initial steps in diagnosing epilepsy and semi-acute/chronic seizure forms
- Imaging provides further proof to suspected aetiology or its contrary, provides prognostic information, may direct the treatment being planned, helps in localization of the epileptic focus and helps in surgical planning when structural abnormalities are detected
- A significant abnormality on imaging is rare in the absence of a specific seizure pattern, abnormal neurology or an abnormal EEG finding
- Simple febrile seizures do not require imaging
- US should be the first imaging modality for evaluating neonatal seizures though MRI will often also be required
- Imaging, preferentially MRI, is indicated in partial seizures and generalized seizures accompanied by abnormal neurologic findings or other risk factors
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Seizures
- A seizure is defined as “a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain” 1, 2
- Epilepsy is a condition of recurrent seizure activity over a prolonged period with no obvious precipitants.
- Numerous seizure and epilepsy classification systems are available and a widely referenced model was put forth by the International League against Epilepsy (ILAE). 3, 4 Although there are several classification systems present of which many are contended, it is well known that seizures in childhood vary significantly from adults and there are several well recognised epileptic disorders unique to infancy and early childhood. Recognising the syndromes and specific forms of seizures is paramount to administer a tailored management plan
- Apart from acute post-traumatic causes, MRI when available is the imaging modality of choice when feasible owing to its lack of ionising radiation, excellent soft tissue and contrast resolution and versatility but may need general anaesthesia in a significant number of children 5
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Neonatal Seizures
- There is a relatively higher risk of seizures in neonatal period owing to inherent low threshold to excitability of brain cells at this age and the high risk of brain injury in peri-natal period. Pre-term infants have a higher incidence of seizures than term infants 6, 7
- Hypoxic ischemic encephalopathy is the most common cause of seizure in both term and preterm infants. Intracranial haemorrhage is the second leading cause 5
- Timely and accurate diagnosis of seizures in this age group can prevent or reduce the brain damage and reduce the seizure burden 5
- Head ultrasound is the first modality of choice in a majority of these patients because of the ease of use, lack of ionising radiation and portability 5
- Magnetic Resonance Imaging can detect hypoxic ischemic encephalopathy, arterial and venous strokes, structural brain developmental abnormalities, neuro-cutaneous syndromes and inborn errors of metabolism. Diffusion imaging has added sensitivity to routine spin-echo sequences 5, 8, 9
- Computed Tomography can be useful when suspecting skull fractures or haemorrhage but involves exposing highly sensitive neonatal brain to ionising radiation 5, 8
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Febrile Seizures
- Febrile seizures occur in a child of age between 3 months to 5 years and are associated to a febrile illness with no evidence of intra-cranial infection 5
- Febrile seizures are the most common type of childhood seizures 10
- Febrile seizures can be simple - lasting < 15 mins with no atypical features and do not recur within the next 24 hours. Complex/atypical febrile seizures can last for >15 mins, may have focal features and can recur within the next 24 hours 5
- Simple febrile seizures do not need any imaging tests other than routine lab investigations to look for the source of infection if not evident 5, 11, 12
- Complex febrile seizures occasionally have an underlying cause such as meningitis, encephalitis or underlying trauma which may benefit from an MRI or CT scan. 5, 12 The diagnostic yield of imaging tests for detecting a lesion is increased in the presence of an abnormal neurological examination or an abnormal laboratory investigation 13, 14
- Whilst MRI may provide more diagnostic information, CT may be preferable depending on age and waiting time for MRI
- There is increasing evidence that hippocampal swelling and diffusion restriction on MRI particularly in complex febrile seizures may point to an increased likelihood of developing mesial temporal sclerosis in later life which may be another indication for imaging tests in these seizures 5
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Generalised Seizures
- Generalised seizures occur when the entire cerebral cortex of both cerebral hemispheres is aberrantly excited diffusely from the onset 1
- Generalised seizures include infantile spasms, absence seizures, tonic-clonic, atonic and myoclonic seizures.
- Patients with generalised seizures and no neurological findings do not require imaging 5
- New-onset seizures with abnormal neurologic findings and recurrent seizures with varying seizure characteristics warrant neuro-imaging. Urgent neuro-imaging is advocated on the presence of post-ictal focal neurologic defects and semi-urgent neuro-imaging for cognitive and unexplained motor deficits, seizures with partial features, sinister EEG findings and children under 1 year 15
- MRI has higher diagnostic yield than CT but may require general anaesthesia in children and may not be available as freely as CT 15, 16
- When an underlying trauma is suspected, urgent CT scan should be the first choice to rule out intracranial haemorrhage which may need urgent neurosurgical intervention
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Partial (Focal) Seizures
- Focal seizures occur when the aberrant neuronal discharge occurs focally from one of the cerebral cortices. Focal seizures can undergo secondary generalisation when the focal discharge spreads across rapidly to trigger a diffuse neuronal discharge and sometimes the distinction between a primary generalised seizure and secondary generalised seizure becomes very difficult from history alone 2
- Partial seizures most often result from focal structural brain abnormalities. Hence, the positive yield of neuro-imaging in seizures with focal origin is significantly higher than generalised seizures 5, 17
- MRI is considerably more sensitive than CT, particularly with subtle developmental abnormalities and small foci of haemorrhage 5, 15, 16
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Intractable Seizures
- MRI is the most sensitive imaging modality for this relatively uncommon group of patients who may benefit from surgical management aimed at reducing the seizure-burden 5
- Functional brain imaging with Single-Photon Emission CT (SPECT) and Flouorine-18-2-flouro-2-deoxy-D-glucose positron emission tomography (FDG-PET) are also being used to map epileptic foci 5
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Magnetic Resonance Imaging (MRI)
- Apart from acute posttraumatic causes, MRI when available is the imaging modality of choice when feasible owing to its lack of ionising radiation, excellent soft tissue and contrast resolution and versatility but may need general anaesthesia in younger children 5, 15, 16, 18
- Magnetic Resonance Imaging can detect hypoxic ischemic encephalopathy, arterial and venous strokes, structural brain developmental abnormalities, neuro-cutaneous syndromes and inborn errors of metabolism 8, 9
- In partial seizure, MRI outweighs CT in the majority of situations and should be the preferred investigation except in children less than 2 years of age where non-accidental head injury is suspected 15, 16
References
References
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- Fisher RS, Cross JH, French JA, Higurashi N, Hirsch E, Jansen FE, et al. Operational classification of seizure types by the International League Against Epilepsy: Position Paper of the ILAE Commission for Classification and Terminology. Epilepsia. 2017;58(4):522-30. (Guidelines). View the reference
- Seizures and epilepsy in children: Classification, etiology, and clinical features [Internet]. 2016 [cited May 04, 2017]. Available from: (Review article). View the reference
- Berg AT, Berkovic SF, Brodie MJ, Buchhalter J, Cross JH, van Emde Boas W, et al. Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005-2009. Epilepsia. 2010;51(4):676-85. (Guidelines). View the reference
- Engel J, Jr. Report of the ILAE classification core group. Epilepsia. 2006;47(9):1558-68. (Guidelines). View the reference
- National Guideline Clearinghouse (NGC). Guideline summary: ACR Appropriateness Criteria® seizures — child Rockville MD: Agency for Healthcare Research and Quality (AHRQ); 2012. Available from: (Guidelines). View the reference
- Ronen GM, Penney S, Andrews W. The epidemiology of clinical neonatal seizures in Newfoundland: a population-based study. J Pediatr. 1999;134(1):71-5. (Level III evidence). View the reference
- Lanska MJ, Lanska DJ. Neonatal seizures in the United States: results of the National Hospital Discharge Survey, 1980-1991. Neuroepidemiology. 1996;15(3):117-25. (Level III evidence). View the reference
- Seshia SS, Huntsman RJ, Lowry NJ, Seshia M, Yager JY, Sankaran K Neonatal seizures: diagnosis and management. Zhongguo Dang Dai Er Ke Za Zhi. 2011;13(2):81-100. (Review article). View the reference
- Krishnamoorthy KS, Soman TB, Takeoka M, Schaefer PW. Diffusion-Weighted Imaging in Neonatal Cerebral Infarction: Clinical Utility and Follow-Up. Journal of Child Neurology. 2000;15(9):592-602. (Level III evidence). View the reference
- Sfaihi L, Maaloul I, Kmiha S, Aloulou H, Chabchoub I, Kamoun T, et al. Febrile seizures: an epidemiological and outcome study of 482 cases. Childs Nerv Syst. 2012;28(10):1779-84. (Level III evidence). View the reference
- Oluwabusi T, Sood SK. Update on the management of simple febrile seizures: emphasis on minimal intervention. Curr Opin Pediatr. 2012;24(2):259-65. (Review article). View the reference
- Kimia AA, Bachur RG, Torres A, Harper MB. Febrile seizures: emergency medicine perspective. Curr Opin Pediatr. 2015;27(3):292-7. (Review article). View the reference
- Kimia AA, Ben-Joseph E, Prabhu S, Rudloe T, Capraro A, Sarco D, et al. Yield of emergent neuroimaging among children presenting with a first complex febrile seizure. Pediatr Emerg Care. 2012;28(4):316-21. (Level III evidence). View the reference
- Hardasmalani MD, Saber M. Yield of diagnostic studies in children presenting with complex febrile seizures. Pediatr Emerg Care. 2012;28(8):789-91. (Level III evidence). View the reference
- Hsieh DT, Chang T, Tsuchida TN, Vezina LG, Vanderver A, Siedel J, et al. New-onset afebrile seizures in infants: Role of neuroimaging. Neurology. 2010;74(2):150-6. (Level III evidence). View the reference
- Berg AT, Testa FM, Levy SR, Shinnar S. Neuroimaging in children with newly diagnosed epilepsy: A community-based study. Pediatrics. 2000;106(3):527-32. (Levl III evidence). View the reference
- Sharma S, Riviello JJ, Harper MB, Baskin MN. The role of emergent neuroimaging in children with new-onset afebrile seizures. Pediatrics. 2003;111(1):1-5. (Level II/III evidence). View the reference
- Gaillard WD, Chiron C, Cross JH, Harvey AS, Kuzniecky R, Hertz-Pannier L, et al. Guidelines for imaging infants and children with recent-onset epilepsy. Epilepsia. 2009;50(9):2147-53. (Guidelines). View the reference
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