Seizures - non-convulsive status epilepticus
Red flags
- Persistently altered consciousness after a convulsive seizure should have stopped - the single commonest trigger for suspicion
- Fluctuating confusion/behaviour change in ICU or post-operative patients
- Unexplained coma, especially after any convulsive event or in a critically ill patient
- Subtle motor signs - eyelid fluttering, nystagmoid eye movements, facial/limb twitching easily missed on a brief review
Differential by mechanism
- Post-convulsive NCSE - ongoing electrographic seizure after visible convulsions stop
- De novo absence status - typically in known generalised epilepsy, or new-onset in benzodiazepine withdrawal
- Complex partial (focal) status - fluctuating altered awareness, automatisms
- NCSE in critical illness - underlies a significant proportion of unexplained coma in ICU
- Delirium (toxic-metabolic, infective) - the major mimic and frequent co-traveller
- Encephalitis/encephalopathy
- Persistent sedative/drug effect
- Non-epileptic (psychogenic/dissociative) state
- Structural lesion with fluctuating mass effect
Focused history
- Preceding convulsive seizure, especially if consciousness has not returned to baseline within an expected timeframe
- Known epilepsy type (absence-prone syndromes), medication changes/non-adherence, benzodiazepine or alcohol withdrawal
- Recent illness, sedating medications, ICU admission
- Collateral report of subtle behavioural change - unresponsiveness, staring, automatisms
Focused examination
- Careful search for subtle motor phenomena - eyelid twitching, nystagmus, facial myoclonus, limb jerking
- Level of consciousness and its fluctuation over the assessment period
- Full neurological exam for focal signs (localises focal-onset NCSE)
- Signs of the underlying precipitant - sepsis, toxidrome, structural lesion
Investigation strategy
- EEG is the diagnostic test - clinical suspicion alone cannot confirm or exclude NCSE
- Continuous EEG monitoring in ICU patients with unexplained persistent altered consciousness, especially post-convulsive-status
- Bloods and imaging as for any unexplained encephalopathy (glucose, electrolytes, LFT, ammonia, CT/MRI brain, +/- LP if infective/autoimmune cause possible)
- Trial of IV benzodiazepine with EEG running can be both diagnostic and therapeutic if EEG is unavailable emergently - clinical/EEG improvement supports the diagnosis
Management
1. Benzodiazepine trial (IV lorazepam) - first-line for all types
2. IV second-line antiepileptic (levetiracetam, valproate, or phenytoin) if benzodiazepine fails or NCSE recurs/persists
3. Absence status - typically responds promptly to benzodiazepine; rarely needs escalation to anaesthesia
4. Focal/complex partial NCSE - treat as focal status; escalate per the convulsive status algorithm if refractory
5. NCSE in critical illness / coma - more cautious escalation to anaesthesia than convulsive status - the risks of intubation/sedation in an already critically ill patient must be weighed against uncertain benefit, and this decision should involve neurology/ICU jointly
- Correct metabolic derangement, treat infection, address benzodiazepine/alcohol withdrawal, review sedating drug interactions
- Resume/optimise antiepileptic therapy if non-adherence identified
Traps
- Assuming a post-ictal patient who "should be waking up by now" simply needs more time, rather than getting an EEG
- Missing subtle motor signs (eyelid flutter, minor twitching) on a brief bedside review
- Treating NCSE in critical illness identically to convulsive status - aggressive anaesthesia here carries its own major risks and needs individualised, specialist-guided decisions
- Attributing fluctuating ICU confusion to delirium alone without considering NCSE, particularly after any preceding convulsive event
- Stopping the work-up for a precipitant once EEG confirms NCSE - the seizure and its cause both need treating
Talk track
Suspect NCSE whenever consciousness does not return to baseline after a convulsive seizure, or in unexplained fluctuating confusion/coma - EEG is the only way to confirm it. Treat with the same benzodiazepine-then-second-line-agent sequence as convulsive status, but escalation to general anaesthesia in critically ill patients with NCSE is a more cautious, individualised decision than for convulsive status because of competing risks.
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