Which of the following is NOT a differential diagnosis for syncope?

• A. Pneumonia
• B. Hypotension/shock
• C. Sepsis
• D. Stroke

Answer: (A)

Syncope is a temporary loss of consciousness caused by a brief drop in cerebral blood flow, so what you’re evaluating are conditions that directly or rapidly reduce brain perfusion. The most immediate causes are sudden drops in blood pressure or cardiac output (hypotension or shock), which deprive the brain of blood flow right away. Sepsis can lead to septic shock, another route to profound hypotension and syncope. Stroke is a neurologic event that can present with loss of consciousness, though it usually comes with focal neurological findings rather than a pure, brief loss of consciousness.

Pneumonia, however, is an infection in the lungs and does not directly cause transient loss of consciousness. It might contribute to hypoxemia or, in severe cases, to sepsis, but these are indirect pathways rather than direct, primary causes of syncope. Hence pneumonia is not a differential diagnosis for syncope in the usual clinical evaluation.