Differential diagnosis of seizures with fever
The following diagnostic possibilities exist, these not being mutually exclusive.
1. The convulsion is not an epileptic seizure nor an anoxic seizure but is a rigor or an hallucination or febrile myoclonus or febrile ataxia.
2. The seizure is a febrile syncope similar to a syncope suffered by adults with influenza and fever.
3. The seizure is a syncope due to ventricular tachyarrhythmia precipitated by fever Brugada syndrome (a sodium channelopathy with several ECG patterns).
4. The seizure represents the presence of a gene for one or other type of epilepsy, albeit genetic analysis may not be practicable.
5. The febrile seizure, especially if prolonged and lateralized (hemiclonic) may be the start of Dravet syndrome or severe myoclonic epilepsy of infancy (SMEI), with a mutation in SCN1A.
6. The febrile seizure may be a manifestation of an SCN1A mutation in a family with GEFS+ (genetic epilepsy with febrile seizures plus).
7. The seizures may reflect static focal pathology even if the infant or child has had no previously known neurological signs.
8. Febrile seizures may represent the onset of a chronic progressive pathology such as Alpers disease due to a mutation in the nuclear mitochondrial gene POLG1.
9. The febrile seizures may be a manifestation of an acute encephalopathy due to a central nervous system infection such as pyogenic or tuberculous meningitis, herpes simplex encephalitis or human herpes virus 6 or 7 infection.
10. The febrile seizure may be a manifestation of a metabolic encephalopathy, the encephalopathy having been precipitated by the catabolism of the febrile illness. In this case the febrile seizure may be a tonic non-epileptic one with loss of ability to localize pain due to brain herniation.
Investigations relate to the question being asked:
1. Is there a treatable disorder?
Irrespective of the age of the child and whether it be the first, second, third or fourth febrile seizure, it is incumbent upon the paediatrician to think whether there could be an underlying pyogenic, tuberculous, herpesvirus or other intracranial infection.
The primary investigation is lumbar puncture with pressure measurement and CSF examination, unless failure to localize pain or other signs suggest that brain herniation is likely.
2. Is there evidence of acute encephalopathy?
Blood and CSF studies may indicate viral infections such as human herpes virus 6 but this will not influence management.
3. Is there evidence of a preexisting static lesion?
Answering this question is not usually helpful and brain MRI is not indicated.
4. Is there evidence of an underlying progressive disorder?
Atypical features, such as unexpectedly high CSF protein, may he a clue to an underlying mitochondrial disorder, in particular mutations in POLG1.
5. Will the febrile seizures recur?
An EEG examination will not answer this question.
6. Can one predict later epilepsy?
EEG examination will not answer this question.
A structural lesion on brain MRI might be predictive but such an investigation is not normally justified.
A pathogenic mutation in SCN1A indicates the beginning of Dravet syndrome and may be helpful for guiding antiepileptic therapy later.
7. Was this vaccine encephalopathy or vaccine damage?
No investigation can support an allegation of' vaccine damage', but finding a pathogenic mutation in SCN1A is a convincing alternative explanation. The best known explanations for deterioration after DTP vaccine are as follows: (1) the start of Dravet syndrome; (2) a mitochondrial disorder, such as due to a mutation in POLG1; (3) metabolic decompensation as in (undiagnosed) glutaric aciduria type 1.
Febrile regression
- The onset of eIF2B-related disorders may be with fever-related acute regression but not febrile seizures.MRI and CSF asialotransferrin should clarify. Acute necrotizing encephalopathy and bilateral striatal necrosis - probably related nuclear pore disorders
Source:
Mary D. King, 2009. A Handbook of Neurological Investigations in Children. 1 Edition. Mac Keith Press.
Add comment