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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

Reversible & Secondary Dementias

Reversible & Secondary Dementias

What You'll Learn

  • NPH classic triad — gait apraxia (first & most responsive to treatment), subcortical dementia, urinary incontinence; Evans index >0.3; lumbar tap test improves gait → VP shunt
  • B12 deficiency — subacute combined degeneration + cognitive decline; methylmalonic acid is the most sensitive marker (elevated even when B12 is borderline normal)
  • Hypothyroidism — most common endocrine cause of reversible dementia; always check TSH in every dementia workup
  • Hashimoto encephalopathy (SREAT) — high TPO antibodies, subacute cognitive decline ± seizures/myoclonus, dramatically steroid-responsive; diagnosis of exclusion
  • Neurosyphilis — CSF VDRL is highly specific (~100%) but insensitive (~50%) — a positive CSF VDRL essentially confirms neurosyphilis. CSF FTA-ABS is highly sensitive; a negative CSF FTA-ABS effectively rules out neurosyphilis. FTA-ABS can be false-positive from peripheral blood contamination. Treat with IV penicillin G
  • Depression pseudodementia — patient complains of memory loss (vs. anosognosia in AD), gives “I don’t know” answers, mood symptoms precede cognition → treat depression and cognition improves
  • Medication-induced — anticholinergics are the biggest culprit; always review medication list before diagnosing neurodegenerative dementia
HighYield Pearls
  • Give parenteral thiamine promptly in any suspected Wernicke encephalopathy (alcoholic, bariatric, hyperemesis gravidarum); give it with or just before glucose because a glucose load can precipitate Wernicke in thiamine deficiency — but never withhold or delay glucose in symptomatic hypoglycemia. Triad = ophthalmoplegia + ataxia + confusion; untreated → irreversible Korsakoff amnesia with confabulation.
  • NPH = ventriculomegaly out of proportion to atrophy: Evans index >0.3, callosal angle <90°, DESH sign; lumbar tap test improvement in gait → predicts shunt response. Gait apraxia comes first and responds best; incontinence comes last and responds least.
  • B12 deficiency — check MMA + homocysteine: both elevated even when serum B12 is borderline normal; classic picture = subacute combined degeneration + sensorimotor neuropathy + megaloblastic anemia + dementia ± glossitis; treat with IM cobalamin.
  • CSF VDRL vs FTA-ABS: CSF VDRL is highly specific (~100%) but insensitive (~50%) — positive essentially confirms neurosyphilis. CSF FTA-ABS is sensitive — negative rules it out. Treat with IV penicillin G for 10–14 days; never substitute with benzathine PCN.
  • SREAT (Hashimoto encephalopathy): subacute encephalopathy ± seizures, myoclonus, stroke-like episodes; high anti-TPO/Tg antibodies; dramatically steroid-responsive. Beware: anti-TPO is common in elderly euthyroid women — confirm with steroid response before attributing cognitive decline to SREAT.
  • Autoimmune encephalitis mimicking dementia: LGI1 → older man + faciobrachial dystonic seizures + hyponatremia (highly treatable, immunotherapy-responsive); NMDAR → younger woman + psychiatric + dyskinesias + screen for ovarian teratoma; CASPR2 → Morvan syndrome. Send paired serum + CSF panel.
  • Medication review & deprescribing: anticholinergics (oxybutynin, diphenhydramine, TCAs), benzodiazepines, opioids, anticonvulsants (topiramate, phenobarbital), metoclopramide, Z-drugs — use STOPP-START / Beers criteria. Always exhaust med review BEFORE diagnosing a neurodegenerative dementia.
  • Pseudodementia clues: patient complains of memory loss (vs anosognosia in AD), answers “I don’t know” rather than confabulating, recent/abrupt onset, prominent neurovegetative symptoms, prior psychiatric history → treat depression and cognition improves.
  • Chronic subdural in the elderly anticoagulated patient: can present as subacute “dementia” without clear trauma history; non-contrast CT or MRI is mandatory; surgical drainage / burr hole / MMA embolization is curative.
  • AAN core/common dementia workup: medication review, depression/delirium/sleep screen, CBC, CMP, TSH, B12, and structural neuroimaging (MRI > CT). Add RPR/VDRL, HIV, inflammatory/autoimmune labs, CSF, EEG, and genetic tests when history, age, tempo, exam, or risk factors support them — per AAN 2001 (reaffirmed), routine syphilis (and HIV) screening is not justified without risk factors or suggestive evidence. Expand aggressively for early-onset or rapidly progressive: folate/MMA/homocysteine, ANA, ESR/CRP, paraneoplastic + autoimmune encephalitis panels, ceruloplasmin (young → Wilson), heavy metals, ammonia, CSF including Aβ42/p-tau biomarkers and 14-3-3/RT-QuIC if prion suspected.
🔍 Quick ReferenceClinical · Workup / labs · Treatment
Clinical phenotype
  • Magnetic gait, “wet, wacky, wobbly” → Normal pressure hydrocephalus (NPH)
  • Ophthalmoplegia + ataxia + confusion in alcoholic / bariatric / hyperemesis → Wernicke encephalopathy
  • Anterograde amnesia + confabulation after untreated Wernicke → Korsakoff syndrome
  • Frontal disinhibition + delusions of grandeur + Argyll Robertson pupil → General paresis (neurosyphilis)
  • Sensory ataxia + lightning pains + Charcot joints → Tabes dorsalis (neurosyphilis)
  • Older man with faciobrachial dystonic seizures + hyponatremia + cognitive decline → LGI1 autoimmune encephalitis
  • Young woman with psychiatric symptoms + orofacial dyskinesias + autonomic instability → Anti-NMDAR encephalitis (screen for ovarian teratoma)
  • Subcortical executive dysfunction + apathy in advanced HIV/AIDS → HIV-associated neurocognitive disorder (HAND) / AIDS dementia complex
  • Myxedema facies + bradycardia + delayed-relaxation (“hung-up”) reflexes + cognitive slowing → Hypothyroid dementia
  • Patient complains of memory loss + says “I don’t know” + neurovegetative symptoms → Depressive pseudodementia
  • Subacute dementia in elderly anticoagulated patient after minor fall → Chronic subdural hematoma
  • Insomnia + autonomic dysfunction + ataxia in mid-life (Italian/familial) → Fatal familial insomnia (prion) — consider in atypical RPD
Workup / labs / imaging
  • Elevated MMA + homocysteine with borderline serum B12 → B12 deficiency
  • Ventriculomegaly out of proportion to atrophy + Evans index >0.3 + callosal angle <90° + DESH sign → NPH
  • Positive CSF VDRL (highly specific) / negative CSF FTA-ABS rules out → Neurosyphilis
  • High anti-TPO/anti-thyroglobulin antibodies + encephalopathy ± myoclonus → SREAT / Hashimoto encephalopathy
  • Medial temporal FLAIR hyperintensity + PET temporal hypermetabolism → Limbic / autoimmune encephalitis
  • Asterixis + triphasic waves on EEG → Hepatic (or uremic) encephalopathy
  • Low ceruloplasmin + Kayser-Fleischer rings in young patient with cognitive/movement change → Wilson disease
  • Crescentic extra-axial collection on CT, often mixed density, midline shift in elderly → Chronic subdural hematoma
  • STOP-BANG positive + AHI elevated on polysomnography in “dementia” patient → OSA-related cognitive impairment
  • CSF Aβ42 low + p-tau high → Underlying Alzheimer pathology (helps rule in AD when picture is ambiguous)
Treatment / pearls
  • IV thiamine BEFORE glucose → Wernicke encephalopathy (glucose-first precipitates the syndrome)
  • IM cobalamin replacement → B12 deficiency (oral can work but IM if neuro symptoms)
  • IV penicillin G × 10–14 days (never benzathine PCN alone) → Neurosyphilis
  • Levothyroxine replacement → Hypothyroid dementia; high-dose steroids → SREAT (dramatic response is part of the diagnosis)
  • Ventriculoperitoneal (VP) shunt after positive tap test → NPH (gait responds best, incontinence least)
  • Surgical evacuation / burr hole / middle meningeal artery embolization → Chronic subdural hematoma
  • Antiretroviral therapy (ART) + treat opportunistic infections → HAND / AIDS dementia complex
  • IVIG / high-dose steroids / rituximab; remove teratoma if present → Autoimmune encephalitis (NMDAR, LGI1, CASPR2)
  • CPAP therapy → OSA-related reversible cognitive impairment
  • Deprescribe anticholinergics / benzodiazepines / opioids (STOPP-START / Beers) → Medication-induced cognitive impairment
  • Treat the depression (SSRI ± psychotherapy ± ECT) → Pseudodementia — cognition recovers as mood improves
  • Lactulose + rifaximin → Hepatic encephalopathy; chelation (penicillamine, trientine, zinc) → Wilson disease
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