Toxic and metabolic disorders can cause confusion, staring, abnormal movements, myoclonus and reduced responsiveness. Some provoke genuine acute symptomatic seizures; others create seizure-like episodes without epileptic activity.
The same illness can cause both seizures and mimics
Severe hypoglycaemia, sodium disturbance, uraemia, liver failure, intoxication and withdrawal can provoke epileptic seizures.
The same disorders can also cause delirium, tremor, asterixis or myoclonus that is not itself a seizure.
Myoclonus is particularly misleading
Multifocal jerks can occur in renal failure, hepatic encephalopathy, drug toxicity and other metabolic states.
Myoclonus should therefore not be assumed to represent generalised epilepsy without EEG and clinical context.
Delirium can fluctuate dramatically
Toxic-metabolic encephalopathy often causes impaired attention, fluctuating consciousness, sleep-wake reversal and behavioural change.
These features can be mistaken for focal impaired-awareness seizures or non-convulsive status epilepticus.
EEG can support both sides of the differential
EEG may show diffuse slowing or characteristic periodic patterns in metabolic encephalopathy.
However, critically ill patients can also develop true electrographic seizures, so abnormal background activity does not exclude simultaneous epilepsy.
Medication toxicity can imitate neurological worsening
Sedatives, opioids, antidepressants, antipsychotics and antiseizure medicines themselves can cause confusion, tremor or movement abnormalities.
Polypharmacy and renal or hepatic impairment increase this risk.
Treating the physiology may be more important than adding antiseizure medication
When the event is caused by a correctable metabolic disturbance, definitive treatment is correction of that disturbance.
Long-term antiseizure medication is not automatically indicated after every acute symptomatic seizure.
Related reading
Sources and further reading
- Seizures as a cause of altered mental status
- A neurologist’s approach to delirium: toxic metabolic encephalopathies
Evidence checked: September 2026.