Synopsis
Treat rapid cognitive decline as an urgent syndrome, identify reversible inflammatory, infectious and toxic causes, and investigate possible prion disease with national specialist and infection-control support.
- Rapidly progressive dementia evolves over weeks or months rather than years and is a diagnostic emergency because autoimmune, infectious, metabolic, toxic and neoplastic causes may be reversible.
- First distinguish delirium, depression and non-convulsive status from a true progressive cognitive syndrome using attention, arousal, collateral timing and EEG where indicated.
- Sporadic CJD commonly combines rapidly progressive cognitive decline with myoclonus, gait or limb ataxia, visual symptoms, pyramidal or extrapyramidal signs and later akinetic mutism.
Key red flags
Rapid cognitive decline with myoclonus, cerebellar or visual dysfunction and pyramidal or extrapyramidal signs is characteristic of sporadic CJD but not pathognomonic.
Investigation priorities
Identify prion-associated cortical or striatal restriction and structural, inflammatory, vascular or neoplastic alternatives.
Management branches
Cognition and function have deteriorated substantially over weeks or a few months.
- Stabilise physiology, assess attention and consciousness, review medicines and toxins, obtain collateral chronology and treat seizures, sepsis, hypoglycaemia or suspected encephalitis without avoidable delay.
- Perform detailed neurological examination and urgent blood, MRI and EEG assessment, selecting lumbar puncture after structural and procedural safety review.
Key medicines
Aciclovir for suspected viral encephalitisUse the local emergency intravenous weight- and renal-adjusted regimen immediately when herpes encephalitis remains plausible; do not await all CSF results.
Clonazepam for distressing myoclonusBegin with a low specialist or palliative dose and titrate cautiously to comfort while preserving useful alertness where possible.