Differential Diagnosis for Sudden Lethargy and Delirium in a 66-year-old
Single Most Likely Diagnosis
- Sepsis: Given the age of the patient and the sudden onset of lethargy and delirium, sepsis is a highly plausible diagnosis. Elderly individuals are more susceptible to infections, and sepsis can present with non-specific symptoms such as lethargy and altered mental status.
Other Likely Diagnoses
- Acute Stroke: A stroke can cause sudden lethargy and delirium, especially if it involves areas of the brain responsible for consciousness and cognitive function.
- Metabolic Disorders (e.g., Hypoglycemia, Hyperglycemia): Abnormal blood glucose levels can lead to altered mental status, and given the age, diabetes or other metabolic issues could be underlying factors.
- Medication Side Effects: The elderly are often on multiple medications, and certain drugs or drug interactions can cause lethargy and delirium.
- Dehydration: Especially common in the elderly, dehydration can lead to delirium and lethargy due to electrolyte imbalances and decreased blood volume.
Do Not Miss Diagnoses
- Meningitis or Encephalitis: Although less common, these infections can present with sudden onset of lethargy and delirium and are critical to diagnose early due to their high mortality rate if untreated.
- Subdural Hematoma: Especially in the elderly, even minor trauma can lead to a subdural hematoma, which can cause gradual or sudden onset of lethargy and altered mental status.
- Pulmonary Embolism: A large pulmonary embolism can cause sudden onset of symptoms including lethargy due to hypoxia and decreased cardiac output.
- Cardiac Arrest or Myocardial Infarction: These conditions can lead to reduced cerebral perfusion, resulting in lethargy and delirium.
Rare Diagnoses
- Wernicke's Encephalopathy: A condition caused by thiamine deficiency, often seen in alcoholics, but can occur in other conditions leading to malnutrition.
- Hashimoto's Encephalopathy: A rare condition associated with Hashimoto's thyroiditis, presenting with altered mental status and lethargy.
- Creutzfeldt-Jakob Disease: A rare, degenerative, fatal brain disorder that can present with rapid decline in cognitive and motor functions, including lethargy and delirium.