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Dementia
9 notes available
1 Last Minute Review 2 Alzheimer Disease 3 Frontotemporal Dementia 4 Lewy Body & Parkinson Dementia 5 Vascular Cognitive Impairment 6 Rapidly Progressive Dementias 7 Reversible & Secondary Dementias 8 Mild Cognitive Impairment & Dementia Workup 9 Behavioral & Psychiatric Features
Clinical › Dementia

Rapidly Progressive Dementias

Rapidly Progressive Dementias

What You'll Learn

  • Definition: Subacute cognitive decline progressing to severe dementia within weeks to months (typically <1–2 years from onset) — far faster than typical neurodegenerative dementias
  • Prion disease (sCJD) is the most tested RPD on boards: rapidly progressive dementia + myoclonus + akinetic mutism; MRI DWI cortical ribboning; CSF RT-QuIC (most specific test); EEG periodic sharp wave complexes; mean survival ~5 months
  • Autoimmune encephalitis is the most important treatable RPD: anti-NMDAR, anti-LGI1, anti-CASPR2, anti-GABA-B — always send serum + CSF antibody panels
  • Boards love reversible causes: autoimmune encephalitis, Hashimoto encephalopathy (SREAT), CNS vasculitis, Whipple disease, CNS infections, and metabolic/toxic etiologies are all potentially treatable
  • RPD workup mnemonic — “VITAMINS-D”: Vascular, Infectious, Toxic-metabolic, Autoimmune, Metastatic/neoplastic, Iatrogenic, Neurodegenerative (prion), Systemic/seizures, Demyelinating
  • MRI DWI is the single most useful imaging sequence: cortical ribboning + caudate/putamen restriction in sCJD; mesial temporal FLAIR hyperintensity in autoimmune/limbic encephalitis
  • Brain biopsy is the last resort: reserved for cases where extensive workup is nondiagnostic and a treatable condition remains possible
HighYield Pearls
  • RPD definition: onset → severe dementia in <1–2 yr; ~20–25% have a treatable cause — aggressive workup is mandatory
  • VITAMINS-D differential: Vascular, Infectious, Toxic-metabolic, Autoimmune, Metastatic, Iatrogenic, Neurodegenerative (prion), Systemic/Seizures, Demyelinating
  • Sporadic CJD triad: rapidly progressive dementia + startle/stimulus-sensitive myoclonus + cerebellar/visual/pyramidal signs → akinetic mutism; mean survival ~5–6 mo
  • CJD diagnostics: MRI DWI cortical ribboning + caudate/putamen (± thalamic) restriction (DWI > FLAIR); CSF RT-QuIC (most sensitive & specific); 14-3-3 & tau supportive; EEG periodic sharp wave complexes (~1 Hz) mid-late disease
  • vCJD: younger patient, psychiatric onset, longer course, BSE exposure → pulvinar sign (bilateral posterior thalamic DWI/FLAIR); FFI = D178N PRNP → progressive insomnia + autonomic + cognitive + motor
  • Autoimmune encephalitis — treatable: always send paired serum + CSF autoimmune panel; treat with IV steroids + IVIG/PLEX, escalate to rituximab/cyclophosphamide; PET/CT ± testicular/pelvic US for tumor
  • SREAT (Hashimoto encephalopathy): encephalopathy + seizures + myoclonus + stroke-like episodes; high anti-TPO; dramatic steroid response; relapsing-remitting
  • Wernicke encephalopathy: ophthalmoparesis + ataxia + confusion → IV thiamine BEFORE glucose; untreated → irreversible Korsakoff amnestic syndrome with confabulation
  • PCNSL: periventricular, homogeneously enhancing, restricted diffusion, steroid-sensitive — avoid steroids before biopsy (can vanish the lesion); treat with HD-methotrexate
  • Treatable causes you cannot miss: autoimmune/paraneoplastic, SREAT, B12, thyroid, Wernicke, neurosyphilis, late Lyme, HIV, NCSE, PCNSL, CNS vasculitis, Whipple
🔍 Quick ReferenceClinical / time course · Imaging / EEG / CSF · Treatment
Clinical / time course
  • Rapidly progressive dementia + startle/stimulus-sensitive myoclonus + akinetic mutism → sporadic CJD
  • Young adult, psychiatric/behavioral prodrome + orofacial dyskinesia + autonomic instability + seizures → anti-NMDAR encephalitis (ovarian teratoma)
  • Older man with faciobrachial dystonic seizures (FBDS) + hyponatremia + limbic encephalitis → anti-LGI1
  • Limbic encephalitis + refractory status epilepticus + SCLC → anti-GABA-B; SCLC + chorea + optic neuritis → CV2/CRMP5
  • Encephalopathy + myoclonus + stroke-like episodes + high anti-TPO, steroid-responsive → SREAT / Hashimoto encephalopathy
  • Progressive untreatable insomnia + dysautonomia + motor signs → Fatal Familial Insomnia (D178N PRNP)
  • Ophthalmoparesis + ataxia + confusion in alcoholic/malnourished patient → Wernicke encephalopathy; chronic amnesia + confabulation → Korsakoff
  • Eclampsia / post-transplant on tacrolimus or cyclosporine / severe HTN with cortical blindness + seizures → PRES (RPLS)
    • Imaging / EEG / CSF / labs
    • Cortical ribboning + caudate/putamen DWI restriction (DWI > FLAIR) → sporadic CJD
    • Bilateral posterior thalamic (pulvinar) DWI/FLAIR hyperintensity — “pulvinar sign” → variant CJD
    • EEG periodic sharp wave complexes ~1 Hz → sCJD (mid-late); extreme delta brush → anti-NMDAR
    • CSF RT-QuIC positive → CJD (most sensitive & specific); 14-3-3 & tau supportive
    • Mesial temporal FLAIR hyperintensity, bilateral → limbic / autoimmune encephalitis
    • Parieto-occipital vasogenic FLAIR edema sparing cortex → PRES
    • Periventricular homogeneously enhancing mass with restricted diffusion → PCNSL (steroid-sensitive)
    • Diffuse multilobar FLAIR hyperintensity without mass effect → gliomatosis cerebri pattern (now molecular dx)
    • EEG triphasic waves + asterixis + elevated NH3 → hepatic encephalopathy
    • CSF VDRL positive / reactive serum RPR with cognitive decline → neurosyphilis (general paresis)
    Treatment / pearls
    • IV thiamine before any glucose → Wernicke (precipitable by dextrose in malnourished)
    • IV steroids + IVIG or PLEX, then rituximab/cyclophosphamide → autoimmune/paraneoplastic encephalitis; tumor search with PET/CT
    • Empiric steroid trial with dramatic response → SREAT (Hashimoto encephalopathy)
    • High-dose methotrexate — avoid pre-biopsy steroids → PCNSL
    • IV penicillin G × 10–14 days → neurosyphilis; IV ceftriaxone → late neuro-Lyme
    • Withdraw offending agent + control BP → PRES (usually reversible)
    • Paired serum + CSF autoimmune panel + PET/CT for occult malignancy → standard RPD workup before calling it CJD
    • Brain biopsy → last resort when workup nondiagnostic and a treatable condition remains plausible
    • No disease-modifying therapy — supportive care & counseling → prion disease (sCJD, vCJD, FFI, iatrogenic)
Definition & Approach

What Is a Rapidly Progressive Dementia?

  • Timeframe: Onset to severe dementia in <1–2 years (many cases progress in weeks to months)
  • Contrast with typical Alzheimer disease (AD): 8–12 year course from onset to severe dementia
  • Key distinction: ~20–25% of RPDs have a potentially reversible cause — aggressive workup is mandatory
  • ~30–60% of RPDs in tertiary referral cohorts are prion disease (heavily referral-biased); ~15–25% are non-prion neurodegenerative (rapidly progressive AD, DLB, FTD); and 15–25% are potentially treatable (autoimmune, infectious, neoplastic, toxic-metabolic)

VITAMINS-D Mnemonic for RPD Differential

Letter Category Examples
V Vascular CNS vasculitis, intravascular lymphoma, cerebral amyloid angiopathy-related inflammation
I Infectious HIV/PML, Whipple disease, neurosyphilis, fungal meningitis
T Toxic-metabolic Bismuth, lithium, heavy metals, Wernicke encephalopathy, hepatic encephalopathy
A Autoimmune Anti-NMDAR, anti-LGI1, SREAT (Hashimoto), neurosarcoidosis, CNS lupus
M Metastatic/Neoplastic CNS lymphoma, intravascular lymphoma, leptomeningeal carcinomatosis, paraneoplastic
I Iatrogenic Immunosuppressants, chemotherapy (methotrexate), radiation, drug toxicity
N Neurodegenerative Prion disease (CJD), rapidly progressive AD, corticobasal syndrome, DLB
S Systemic/Seizures Nonconvulsive status epilepticus, thyroid disease, B12 deficiency, psychiatric (pseudodementia)
D Demyelinating Tumefactive MS, ADEM, CLIPPERS, acute disseminated leukoencephalopathy
💎 Board Pearl
  • The VITAMINS-D mnemonic is the standard framework for RPD workup — boards often test the differential broadly to see if you consider treatable causes before defaulting to CJD
  • Up to 10–25% of cases referred as “probable CJD” ultimately have an alternative (often treatable) diagnosis
🔒

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