Investigations
1st investigations to order
diagnosis is clinical
Test
Tests may be required to identify the source of fever.
Result
seizures associated with fever
Investigations to consider
lumbar puncture
Test
Indicated to rule out meningitis or encephalitis if: presence of suspicious symptoms and signs (e.g., bulging fontanelle, nuchal rigidity) and if age is younger than 12 months; a focal, prolonged, or multiple seizure occurs within 24 hours with prolonged impairment of consciousness; or there is history of persistent irritability or lethargy, or pretreatment with oral antibiotics.
How to perform a diagnostic lumbar puncture in adults. Includes a discussion of patient positioning, choice of needle, and measurement of opening and closing pressure.
Result
normal cells, protein, and glucose
viral studies
Test
Viral studies may be useful in patients with complex febrile seizures and symptoms of encephalitis or encephalopathy.
Result
may be positive
blood culture
Test
Bacteraemia is rare, but meningitis should always be considered.
Result
bacteraemia may be present
EEG
Test
The role of electroencephalography (EEG) in the work-up of febrile seizure remains controversial.[62] There is no evidence that an EEG can be used to predict whether a child will develop epilepsy after a simple febrile seizure. Also, development of epilepsy cannot be prevented by knowledge of EEG findings.[63]
However, acute EEG may have a role following status epilepticus. The FEBSTAT study performed baseline EEGs within 72 hours of an episode of febrile status epilepticus. Review of the baseline EEGs showed a focal EEG slowing or attenuation in a substantial proportion of children. The slowing and attenuation are highly associated with MRI evidence of acute hippocampal injury. These findings may be a sensitive and readily obtainable marker of acute injury associated with febrile seizure epilepsy.[52]
Recurrent simple or complex febrile seizures also do not justify an EEG, as it is of no use in identifying a structural abnormality or in predicting recurrent febrile seizure or the development of epilepsy.[64]
EEG should be considered in all children with complex febrile seizures that recur with afebrile convulsions, or in children who have recurrent febrile seizures and also exhibit developmental delays or abnormal neurological signs and symptoms.[65] One Cochrane review found no evidence to support or refute the use of EEG and its timing after complex febrile seizures among children under the age of 5 years.[53]
Focal EEG slowing or attenuation are present in EEGs obtained within 72 hours following febrile status epilepticus in a substantial proportion of children.[52]
Neurological consultation is needed.
Result
possible focal EEG slowing or attenuation following febrile status epilepticus
brain MRI
Test
Usually normal; may show hippocampal oedema or sclerosis with complex, prolonged, and focal febrile seizure.[52][66][67]
Not indicated with simple type, but should be considered in children with focal seizures, an atypical history with abnormal developmental history, or abnormal neurological examination.
Result
may show acute hippocampal oedema or chronic hippocampal sclerosis
serum sodium
Test
Hyponatraemia may increase the risk for multiple seizures during the same febrile illness.[68] Despite these and other similar reports, the American Academy of Pediatrics does not recommend routine serum electrolytes after a first simple febrile seizure.[1]
Result
may be low (<130 mmol/L or 130 mEq/L)
FBC
Test
Not routinely recommended, but may be required to determine the cause of fever.[43]
Result
variable
capillary blood gluscose
Test
A capillary blood glucose test should be performed on all children who present with a seizure to exclude hypoglycaemia.
Result
usually normal
serum glucose
iron studies
Test
Consider testing if clinically indicated or other blood tests are being performed.[69]
Result
may reveal deficiency
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