Skip to textbook content
Doctor’s PassportTextbook
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

First seizure and seizure mimics

Neurology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
!
Escalate

A convulsive seizure lasting five minutes or more, recurrent seizures without recovery, persistent hypoglycaemia, ongoing impaired consciousness, pregnancy with possible eclampsia, meningism, acute focal deficit, major injury or cardiorespiratory compromise is a medical emergency requiring ABCDE care and the status or relevant acute pathway.

Synopsis

Stabilise a first suspected seizure, reconstruct the event from positive clinical evidence, identify provoked and cardiac causes, and arrange timely specialist testing without using a normal EEG to dismiss epilepsy.

  • The diagnosis rests first on a detailed account from the patient and witnesses, including before, during and after the event; obtain smartphone video when available and consent permits.
  • A first suspected seizure should prompt a 12-lead ECG because arrhythmia and convulsive syncope can closely resemble epilepsy and may carry immediate cardiac risk.
  • Check capillary glucose promptly and investigate sodium, calcium, infection, intoxication, withdrawal and other provoking factors according to the clinical context.
  • Lateral tongue injury, stereotyped tonic then clonic movements, cyanosis, prolonged post-event confusion and postictal focal weakness increase the probability of a tonic-clonic seizure but none is perfectly specific.
  • Presyncope, pallor, sweating, a situational trigger and rapid recovery favour syncope; brief jerks can occur during cerebral hypoperfusion and do not automatically imply epilepsy.
  • NICE recommends urgent referral after a first suspected seizure for assessment by an epilepsy-experienced clinician, aiming for review within two weeks.
  • When EEG is requested after a first seizure it should be performed as soon as possible, ideally within 72 hours; epileptiform activity supports the diagnosis, while a normal result cannot exclude it.
  • Do not start long-term antiseizure medication reflexively after every provoked or uncertain event; recurrence risk, imaging, EEG, neurological findings and the person’s preferences guide a specialist decision.

Key red flags

Generalised convulsive event

Abrupt loss of awareness followed by tonic stiffening and rhythmic bilateral clonic movements, with post-event confusion and muscle soreness, is strongly suggestive when witnessed as a coherent sequence.

Focal-class clue

A stereotyped sensory, experiential, autonomic or motor aura, unilateral onset, head version, speech arrest or postictal focal weakness suggests a seizure beginning in one cerebral network.

Convulsive syncope

Prolonged standing, pain, heat, nausea, sweating, visual dimming and pallor followed by brief loss of tone, a few jerks and rapid orientation favours reflex syncope; exertional or supine collapse raises cardiac concern.

Acute symptomatic seizure

Fever, meningism, severe metabolic disturbance, recent brain injury, stroke, intoxication or withdrawal points towards an immediate provoking process whose treatment cannot wait for an outpatient epilepsy label.

Investigation priorities

01
Capillary glucose and targeted blood testsFirst step

Find reversible metabolic causes and assess consequences of a prolonged convulsion.

Management branches

ImmediateStabilise and identify provocation

A person presents during or soon after a first suspected seizure.

  1. 1. Protect from injury, use ABCDE, time the event, check glucose and oxygenation, and treat as status if convulsions reach five minutes or recovery fails.
  2. 2. Establish baseline cognition and repeat neurological examination after the postictal period, looking for trauma, meningism, pregnancy-related disease and persistent focal signs.
  3. 3. Obtain ECG and targeted laboratory tests, treating major metabolic, infectious, toxicological or withdrawal causes through the appropriate acute pathway.
  4. 4. Decide whether immediate CT, lumbar puncture, cardiac monitoring or admission is needed; do not defer dangerous-cause evaluation to the epilepsy clinic.
ReconstructDistinguish seizure from mimic

The person is stable enough for a detailed account.

  1. 1. Build a timeline from pre-event symptoms and circumstances through motor sequence, responsiveness, colour, duration and recovery using patient and independent witness accounts.
  2. 2. Seek positive features supporting the Focal or Generalized class and actively compare syncope, functional events, migraine, sleep and movement phenomena.

Key medicines

Buccal midazolam for a prolonged convulsive seizureUse the person’s emergency plan where available; a common adult community rescue dose is 10 mg buccally, while hospital benzodiazepine choice and repeat timing follow the current status protocol.Support airway and breathing, time each dose and avoid repeated unrecorded benzodiazepines because respiratory depression and delayed escalation can follow. Call emergency services under the agreed plan.
Long-term antiseizure treatment after one unprovoked eventThere is no universal starter regimen; a specialist selects a seizure-appropriate medicine and titration when neurological deficit, unequivocal epileptiform EEG, structural abnormality or unacceptable recurrence risk supports treatment.Do not treat an uncertain mimic merely to feel safe. Consider mood, cognition, pregnancy potential, contraception, organ function, interactions, occupation and driving, and explain that abrupt later withdrawal may provoke seizures.
Open full textbook →Answer 2 questions
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG217 epilepsy diagnosis and assessmentCurrent first-seizure referral, ECG, EEG and neuroimaging recommendations.
  • NICE NG217 treatment safety and monitoringNational criteria for considering treatment after a first unprovoked seizure.
  • NICE CG109 transient loss of consciousness recommendationsUK assessment framework for syncope, cardiac red flags and blackout history.
  • DVLA neurological fitness to drive guidanceCurrent legal standards that must be checked for individual seizure and licence circumstances.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
3. Record uncertainty explicitly and avoid over-weighting isolated incontinence, tongue injury or serum biomarkers, which are supportive at most.
  • 4. Ask about previous subtle episodes, febrile seizures, developmental or neurological history, family history and prior brain insults that alter recurrence probability.