A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 67-year-old man presents to the emergency department with confusion. The patient is generally healthy, but his wife noticed him becoming progressively more confused as the day went on. The patient is not currently taking any medications and has no recent falls or trauma. His temperature is 102°F (38.9°C), blood pressure is 126/64 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a confused man who cannot participate in a neurological exam secondary to his confusion. No symptoms are elicited with flexion of the neck and jolt accentuation of headache is negative. Initial laboratory values are unremarkable and the patient's chest radiograph and urinalysis are within normal limits. An initial CT scan of the head is unremarkable. Which of the following is the best next step in management?
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A
AcyclovirCorrect. Empiric IV acyclovir should be started immediately when HSV encephalitis is suspected, before LP/PCR results — delay sharply worsens outcome.
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B
CT angiogram of the head and neckIncorrect. CT angiography evaluates for vascular causes of altered mental status; fever and no focal deficit make encephalitis more likely than stroke.
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C
PCR of the cerebrospinal fluidIncorrect. CSF PCR is needed to confirm the diagnosis, but treatment must not wait for results — acyclovir is started empirically first.
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D
Vancomycin, ceftriaxone, ampicillin, and dexamethasoneIncorrect. Bacterial meningitis coverage is reasonable to add but the absence of meningismus and the high stakes of missing HSV make empiric acyclovir the more critical next step.
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E
Lumbar puncture for empiric meningitis workupIncorrect. LP and empiric antibiotics would be appropriate if meningitis were suspected, but this confused febrile patient has a non-localizing exam and unremarkable initial workup — HSV encephalitis (treated empirically with acyclovir) is the more dangerous can't-miss diagnosis.
↑ Tap an answer to reveal the reasoning
Answer: A. An elderly man with acute confusion and fever (102°F) without meningismus, with unremarkable initial workup (normal CT, normal urinalysis and chest x-ray), most likely has HERPES SIMPLEX ENCEPHALITIS. HSV-1 is the most common cause of sporadic encephalitis and classically presents with fever, altered mental status, behavioral changes, and sometimes seizures. The cardinal teaching point is that EMPIRIC ACYCLOVIR SHOULD BE STARTED IMMEDIATELY when HSV encephalitis is suspected, because untreated mortality exceeds 70% and delays of even hours worsen outcomes.
Diagnostic workup proceeds in parallel: CSF studies (lymphocytic pleocytosis, elevated protein, often elevated RBCs from temporal lobe necrosis) and CSF HSV PCR are sensitive and specific, but DO NOT delay acyclovir while awaiting results. MRI typically shows temporal-lobe involvement. CT angiography would be for suspected stroke or vascular cause. PCR of CSF is the diagnostic test but acyclovir should be started empirically first. Broad-spectrum bacterial-meningitis antibiotics are reasonable too, but the question asks the BEST NEXT step and HSV encephalitis is the most likely lethal-if-missed diagnosis.
Clinical pearl: empiric acyclovir for suspected HSV encephalitis is one of the highest-impact ED decisions; delay correlates directly with poorer neurologic outcomes.
**Why each option:**
**A.** Correct. Empiric IV acyclovir should be started immediately when HSV encephalitis is suspected, before LP/PCR results — delay sharply worsens outcome.
**B.** CT angiography evaluates for vascular causes of altered mental status; fever and no focal deficit make encephalitis more likely than stroke.
**C.** CSF PCR is needed to confirm the diagnosis, but treatment must not wait for results — acyclovir is started empirically first.
**D.** Bacterial meningitis coverage is reasonable to add but the absence of meningismus and the high stakes of missing HSV make empiric acyclovir the more critical next step.