This clinical picture — acute fever, focal neurologic deficits, CSF abnormalities, and temporal lobe lesions on CT — is most consistent with which diagnosis?

• A. Herpes encephalitis
• B. Meningitis
• C. Cerebral abscess
• D. Autoimmune encephalitis

Answer: (A)

The key idea is that temporal lobe involvement on imaging with an acute febrile illness and focal neurologic deficits points to herpes simplex encephalitis. HSV encephalitis classically causes rapid-onset fever, altered mental status or focal signs (such as aphasia or seizures), and an inflammatory CSF picture (often lymphocytic pleocytosis with elevated protein; sometimes red blood cells from hemorrhagic necrosis). The temporal lobes are a hallmark site of HSV infection, so CT or MRI showing temporal lobe abnormalities strongly supports this diagnosis. In contrast, meningitis alone would typically lack focal deficits and show a different CSF profile; a cerebral abscess would usually present as a discrete ring-enhancing lesion with mass effect rather than bilateral temporal-lobe involvement and the broader encephalitic picture; autoimmune encephalitis can mimic encephalitis but usually lacks the infectious fever and the characteristic temporal lobe imaging findings. Because HSV encephalitis is a medical emergency, treatment with intravenous acyclovir should be started promptly while confirming with CSF PCR for HSV DNA.