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Mr. B is a previously healthy 70-year-old man who underwent right upper lobectomy for localized squamous cell lung cancer 5 days ago. On morning rounds, he comments that he is in a military barracks and that he is ready to go home.

Image not available.What is the differential diagnosis of delirium and dementia? How would you frame the differential?

Delirium and dementia are both syndromes of neurologic dysfunction. Both present as a “change in mental status.” Their similarities end here. Whereas delirium is acute, usually reversible and nearly always has an underlying, non-neurologic etiology, dementia is chronic and seldom reversible. The definitions of these syndromes, as included in the DSM-IV-TR follow:


  1. Delirium

    1. Disturbance of consciousness with reduced ability to focus, sustain, or shift attention.

    1. Cognitive change that is not better explained by dementia.

    1. Symptoms develop rapidly (hours to days) and tend to vary during the day.

    1. History, physical exam, or laboratory data suggest that a general medical condition has directly caused the condition.

  2. Dementia

    1. Impaired memory plus at least 1 of the following:

      1. Aphasia (inability to produce or comprehend language)

      1. Apraxia (inability to execute purposeful movements)

      1. Agnosia (inability to recognize objects by feel)

      1. Impaired executive functioning (eg, abstracting and organizing)

    1. Symptoms must also impair work, social, or personal functioning.


Because any illness can cause delirium in a susceptible patient, the differential diagnosis of delirium is long and needs to consider a broad range of illnesses, comorbidities, and medication effects. The differential diagnosis of dementia is more finite; disorders have been listed in order of their approximate prevalence as etiologic factors.


  1. Delirium

    1. Metabolic

      1. Dehydration

      1. Electrolyte abnormalities

      1. Hyperglycemia or hypoglycemia

      1. Acidosis or alkalosis

      1. Liver disease

      1. Hypoxia or hypercarbia

      1. Uncontrolled thyroid disease

      1. Azotemia

      1. Thiamine deficiency (Wernicke encephalopathy)

    1. Infectious disease

      1. CNS infection

      1. Systemic infection of any kind

      1. HIV

    1. Cerebrovascular event

      1. Ischemic stroke

      1. Hemorrhagic stroke

      1. Vasculitis

    1. CNS mass

      1. Tumor

      1. Subdural hematoma

    1. Cardiovascular

      1. Myocardial infarction

      1. Heart failure

      1. Arrhythmia

    1. Drugs

      1. Alcohol withdrawal

      1. Diuretics

      1. Anticholinergics

      1. Nonsteroidal antiinflammatory drugs

      1. Corticosteroids

      1. Digoxin

      1. Opioids

      1. Antidepressants

      1. Anxiolytics

    1. Miscellaneous

      1. Fecal impaction

      1. Urinary retention

      1. Sensory deprivation

      1. Severe illness

  2. Dementia

    1. Alzheimer dementia

    1. Dementia with Lewy bodies

    1. Vascular dementia

    1. Frontotemporal dementia

    1. Alcohol-related

    1. Uncommon dementias

      1. Subdural hematoma

      1. Hypothyroid

      1. Vitamin B12 deficient

      1. Infectious

        1. Syphilis

        1. Prion disease

      1. Normal-pressure hydrocephalus

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Mr. B was previously healthy with only mild chronic obstructive pulmonary disease. His surgery went well but was complicated by transient hypotension and excessive blood loss. He was extubated on postoperative day 3. On postoperative day 4, his wife noted some confusion. The medical team did not detect any abnormalities when they evaluated him.

Today, postoperative day 5, he is more confused. He is oriented only to person. He is unable to answer any minimally complicated questions.

Image not available.At this point, ...

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