Status Epilepticus: Diagnosis and Management

Introduction

Status epilepticus is a medical emergency defined operationally as a seizure lasting more than 5 minutes, or recurrent seizures without full recovery of consciousness between them.¹ This is a deliberate departure from the older textbook definition of 30 minutes: evidence shows that seizures rarely stop spontaneously after 5 minutes, that treatment becomes progressively harder to achieve pharmacologically the longer a seizure continues, and that outcome worsens the longer status persists - so waiting for 30 minutes before acting is now considered a dangerous delay.²

It can occur in a patient with known epilepsy (often precipitated by missed medication or intercurrent illness) or as the first presentation of a new neurological or systemic problem. Management follows a staged, time-driven algorithm that is one of the most frequently examined acute protocols in medicine.

Understanding why the algorithm is timed explains almost every decision within it. During a prolonged seizure, inhibitory GABA-A receptors are progressively internalised from the synaptic membrane while excitatory NMDA receptors are trafficked towards it. This means the brain becomes physically less able to respond to benzodiazepines - which act on GABA-A receptors - the longer the seizure continues. This receptor trafficking is the pharmacological reason why two doses of benzodiazepine that fail should prompt escalation rather than a third dose, and why the entire pathway is driven by the clock rather than by response alone.

In parallel, the metabolic demands of continuous neuronal firing outstrip cerebral oxygen and glucose supply. Early compensatory mechanisms - increased cerebral blood flow, hypertension, tachycardia and hyperglycaemia - fail after roughly 30 minutes, at which point blood pressure and glucose fall, cerebral autoregulation is lost, and excitotoxic neuronal death begins. This transition from a compensated to a decompensated phase is what converts a treatable emergency into one that causes lasting brain injury.

Incidence is in the region of 10-40 per 100,000 per year, and roughly half of cases occur in patients with no prior diagnosis of epilepsy - which is an important corrective to the assumption that status is a complication of established disease. Incidence is highest at the extremes of age, and in older adults acute symptomatic causes such as stroke, infection and metabolic derangement predominate, which is why the search for an underlying cause is as urgent as the seizure treatment itself.

Aetiology

The causes divide usefully into those occurring in someone with established epilepsy, where a precipitant has lowered the seizure threshold, and those representing an acute symptomatic insult in a patient with no prior seizure history. The distinction matters practically: in the first group the priority is restoring antiepileptic levels and identifying the trigger, while in the second the status is a symptom of an acute brain or systemic problem that itself needs urgent treatment.

• Non-adherence to, or abrupt withdrawal of, antiepileptic medication - the single commonest precipitant in someone with known epilepsy
• Alcohol - both acute intoxication and withdrawal
• Metabolic derangement - hypoglycaemia, hyponatraemia, hypocalcaemia, hepatic or renal failure
• CNS infection - meningitis, encephalitis, brain abscess
• Stroke - ischaemic or haemorrhagic, particularly in older adults with no prior seizure history
• Structural brain lesion - tumour, traumatic brain injury
• Eclampsia - in pregnancy or the puerperium
• Drug toxicity or overdose, and certain drugs that lower seizure threshold (tramadol, some antipsychotics, bupropion)
• Febrile illness in young children

Clinical features

Convulsive status epilepticus is usually obvious: continuous or repeated generalised tonic-clonic activity without recovery of consciousness. Non-convulsive status epilepticus is far less obvious and should be considered in anyone with unexplained, persistently reduced consciousness or subtle ongoing twitching, confusion or behavioural change, particularly after a convulsive seizure appears to have stopped but the patient fails to wake up as expected.

• Continuous or repeated tonic-clonic movements
• No return of normal consciousness between seizures
• Autonomic features: tachycardia, hypertension, hyperthermia, sweating
• Risk of hypoxia, rhabdomyolysis and aspiration the longer it continues
• Subtle or absent motor signs in non-convulsive status - look for eye deviation, nystagmoid eye movements, or unexplained fluctuating consciousness

As status continues, the outward appearance can become deceptively quiet. Vigorous convulsive movements may give way to only subtle twitching of the face or fingers, or to nystagmoid eye movements, even while intense electrographic seizure activity persists - a state sometimes called subtle or electromechanical dissociation. This is not improvement, and it is one of the most dangerous points in the illness, because the visible signs prompting escalation disappear while the brain injury continues. It is the principal reason continuous EEG is needed once a patient is sedated or paralysed.

Non-convulsive status epilepticus

Non-convulsive status should be actively considered in any patient with unexplained, prolonged confusion or reduced consciousness - particularly in an intensive care setting, in older adults presenting with delirium of unclear cause, and specifically in a patient who has had a convulsive seizure and then fails to regain consciousness within 20-30 minutes. A prolonged post-ictal state and ongoing non-convulsive status can look identical at the bedside; only an EEG distinguishes them, and the difference determines whether the patient needs further antiepileptic treatment or simply time.

Investigations

Investigation runs in parallel with treatment, not before it - do not delay first-line treatment while awaiting results. In practice the first three actions (glucose, IV access with bloods drawn, and the first benzodiazepine dose) happen essentially simultaneously as a team, rather than sequentially.

Two results deserve particular attention because they change management directly. Sodium is important not only as a cause of seizures but because rapid correction of chronic hyponatraemia carries its own serious risks, so the rate of correction must be controlled rather than simply normalised. Antiepileptic drug levels, where the patient is already on treatment, distinguish genuine treatment failure from non-adherence or underdosing - a distinction that determines whether the answer is a higher dose of the existing drug or the addition of a new one.

A pregnancy test should be performed in any woman of childbearing age, since eclampsia is managed with magnesium sulfate rather than the standard antiepileptic algorithm, and missing it means giving the wrong treatment entirely.

• Capillary and laboratory glucose - immediately
• U&Es, calcium, magnesium, LFTs - to identify a metabolic precipitant
• FBC and CRP, blood cultures - if infection is suspected
• Antiepileptic drug levels - if the patient is on treatment, to check adherence
• Arterial blood gas - for hypoxia and lactic acidosis from prolonged seizure activity
• CT head - if a structural cause or new focal lesion is suspected, once the patient is stabilised
• Lumbar puncture - if CNS infection is suspected, once safe to perform
• Continuous EEG monitoring - essential in refractory status and to confirm non-convulsive status epilepticus, and to confirm that clinical seizure activity has actually stopped once treatment is given (motor activity can cease while electrographic seizures continue)

Management

Immediate (0-5 minutes)

• ABCDE assessment: airway (recovery position, airway adjunct if needed, avoid inserting anything between clenched teeth), high-flow oxygen, IV access
• Check capillary glucose immediately - give IV glucose (or IM/buccal glucagon if no access) if hypoglycaemic
• Give IV thiamine (Pabrinex) if alcohol excess or malnutrition is possible, before or alongside glucose, to avoid precipitating Wernicke encephalopathy
• Note the time the seizure started - the whole algorithm below is timed from seizure onset

Stage 1 - first-line (5-10 minutes)

A benzodiazepine is first-line, chosen by route according to what is available:

If the seizure continues, the same dose is repeated once, generally after 5-10 minutes, before moving on to second-line treatment - do not give further repeated doses of benzodiazepine beyond this without escalating³, since respiratory depression risk rises and further doses are unlikely to succeed where two have already failed.

Stage 2 - second-line (10-30 minutes, 'established status')

If seizures continue despite two doses of benzodiazepine, give an IV loading dose of one of the following, chosen partly by what the patient already takes and local protocol:

• Levetiracetam IV loading dose - increasingly favoured as first choice for its favourable side-effect profile and lack of significant interactions
• Sodium valproate IV loading dose - avoided if pregnancy is possible or there is known hepatic disease
• Phenytoin IV loading dose - requires cardiac monitoring during infusion because of the risk of arrhythmia and hypotension, and is slower to give than the alternatives

Stage 3 - refractory status (30-45 minutes and beyond)

Treat the cause

Alongside anticonvulsant treatment, actively search for and treat a reversible precipitant - correcting a metabolic derangement, treating infection, or reversing a toxic ingestion may be what actually stops the seizures, and status may not respond fully to anticonvulsants alone if the underlying trigger is not addressed.

Complications

• Hypoxic brain injury from prolonged seizure activity and inadequate airway protection
• Aspiration pneumonia
• Rhabdomyolysis and acute kidney injury from sustained muscle activity
• Cardiac arrhythmia, particularly with phenytoin infusion or from autonomic surge
• Hyperthermia
• Cerebral oedema and, rarely, permanent neurological injury from prolonged status
• Complications of intubation and sedation in refractory status

Red flags

Prognosis

Mortality from status epilepticus rises substantially the longer it continues untreated, and is significantly higher in refractory status requiring general anaesthesia. Outcome is strongly influenced by the underlying cause - status due to a reversible metabolic derangement generally has a better prognosis than status due to an acute structural brain injury such as stroke or encephalitis. Prompt, staged treatment following the time-driven algorithm is the single most important factor a clinician can control.

Three factors dominate prognosis, and only one is modifiable at the bedside: the underlying aetiology, the duration of status before it is controlled, and the patient's age and comorbidity. Aetiology is the most powerful of the three - status provoked by antiepileptic non-adherence in a young person with known epilepsy usually resolves with treatment and a return to baseline, while status caused by hypoxic-ischaemic brain injury after cardiac arrest carries a very poor outlook almost irrespective of how quickly the seizures are stopped.

Survivors of prolonged status may be left with cognitive impairment, particularly affecting memory, and a substantially increased risk of subsequent epilepsy. After recovery, every patient needs a clear plan addressing why status occurred: reviewing adherence and antiepileptic dosing, identifying and treating any newly discovered structural or metabolic cause, providing a written rescue medication plan (usually buccal midazolam) for the patient and family, and giving explicit driving advice, since the DVLA rules for seizures apply in full.

A brief word on psychogenic non-epileptic status, which accounts for a meaningful minority of apparent status presentations and is a recognised cause of unnecessary intubation. Features that should raise suspicion include prolonged episodes with preserved oxygenation and a normal arterial blood gas, asynchronous or fluctuating movements, resistance to eye opening, and failure to respond to escalating doses of antiepileptic drugs. The difficulty is that misdiagnosing genuine status as psychogenic is far more dangerous than the reverse, so the safe approach is to treat as epileptic status while arranging urgent EEG rather than withholding treatment on clinical suspicion alone.