Seizures - afebrile
Red flags
- Seizure without fever but with meningism/reduced consciousness -> still consider CNS infection (encephalitis can be afebrile early)
- New focal signs -> structural lesion
- Prolonged seizure or failure to return to baseline -> status/non-convulsive status
- First seizure in pregnancy with hypertension -> eclampsia even without fever
- Recurrent afebrile seizures with no clear trigger -> unprovoked epilepsy work-up needed
Differential by mechanism
The key distinction this note organises around: afebrile excludes simple febrile seizure as the explanation, so the differential shifts to
- Metabolic: hypoglycaemia, hyponatraemia, hypocalcaemia/hypomagnesaemia, uraemia, hepatic encephalopathy
- Toxic/withdrawal: alcohol or benzodiazepine withdrawal, stimulant use, drug overdose (tricyclics, tramadol, bupropion, isoniazid)
- Structural: stroke, tumour, trauma, prior lesion (epilepsy)
- Unprovoked epilepsy: genetic generalised or focal structural epilepsy
- Eclampsia (pregnancy, even normothermic)
- Cardiac - convulsive syncope from arrhythmia mimicking a seizure
Focused history
- Detailed eyewitness account - onset, semiology, duration, post-ictal state
- Medication and substance history - anticonvulsant adherence, alcohol, illicit drugs, new prescriptions (lowers seizure threshold - tramadol, bupropion, quinolones)
- Renal/hepatic disease history
- Pregnancy status and blood pressure history
- Prior seizures, family history of epilepsy
- Preceding cardiac symptoms (palpitations, chest pain) suggesting a cardiac mimic
Focused examination
- Full neurological exam once post-ictal period settles
- Cardiovascular exam and lying/standing BP, murmurs, irregular pulse
- Signs of chronic liver/renal disease
- Signs of alcohol withdrawal (tremor, autonomic hyperactivity)
- Blood pressure and proteinuria if pregnant
- Tongue laceration, injury pattern supporting a true convulsion
Investigation strategy
- Bedside glucose immediately
- Bloods: UEC, calcium, magnesium, glucose, LFT, ammonia if hepatic disease, FBE, anticonvulsant levels if relevant
- ECG in every case - exclude arrhythmia/long QT as the true cause of the collapse
- CT brain for first seizure, focal signs, or failure to return to baseline; MRI as outpatient for further structural/epileptogenic work-up
- EEG to support epilepsy diagnosis and classify syndrome
- Toxicology screen if substance use suspected
Management
A. Treat identified cause
- Correct metabolic derangement (glucose, sodium, calcium/magnesium)
- Manage alcohol/benzodiazepine withdrawal per protocol (benzodiazepine-based regimen, thiamine)
- Review and cease/adjust seizure-threshold-lowering medications where possible
B. Anticonvulsant decision - same logic as generalised/focal seizure notes
- Provoked seizure with reversible cause corrected: no long-term anticonvulsant needed
- Unprovoked seizure: start anticonvulsant if high recurrence risk (epileptiform EEG, structural lesion, prior brain insult) or after a second unprovoked seizure
- Drug choice by epilepsy type; avoid valproate in women of childbearing potential
C. Special situations
- Eclampsia: IV magnesium sulfate (not standard anticonvulsants), urgent obstetric involvement, deliver if appropriate
- Alcohol withdrawal seizures: benzodiazepine-based withdrawal regimen (e.g. diazepam per symptom-triggered protocol), not routine long-term anticonvulsants
D. Safety
- Driving restriction per jurisdiction, occupational safety counselling
- Address the modifiable driver (alcohol, medication adherence, sleep) as the primary prevention strategy
Traps
- Assuming "afebrile" rules out infection - early encephalitis can present before fever develops
- Missing eclampsia because there is no fever and blood pressure was not checked
- Treating alcohol withdrawal seizures with long-term anticonvulsants rather than a withdrawal protocol
- Not reviewing the medication list for seizure-threshold-lowering drugs (tramadol, bupropion, quinolones)
- Missing a cardiac cause (arrhythmia) when brief myoclonic jerks accompanied a faint
Talk track
Afebrile does not mean benign - work through metabolic, toxic/withdrawal, structural, cardiac-mimic and eclampsia causes systematically with glucose, electrolytes, ECG and CT/MRI as indicated. Treat the reversible cause where found; reserve long-term anticonvulsants for unprovoked seizures with high recurrence risk or after a second unprovoked event, choosing the drug by epilepsy type and avoiding valproate in women of childbearing potential.
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