WBR0616

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 32-year-old man is brought to the emergency department for acute change in mental status. According to the wife, the patient has been complaining of a severe headache and high fever that started two days ago. Shortly after admission, the patient begins to seize. He is stabilized with IV lorazepam and valproic acid. Brain MRI of the patient is shown below. Which of the following is most likely to be found in the CSF analysis of the patient? ]]
Answer A	AnswerA::Increased lymphocytes, Increased red blood cells
Answer A Explanation	AnswerAExp::Patients with HSV encephalitis typically have a "viral CSF profile" with elevated lymphocytes. Given the hemorrhagic nature of the illness, xanthochromia (RBCs in the CSF) may be observed.
Answer B	AnswerB::Increased neutrophils, Increased red blood cells
Answer B Explanation	[[AnswerBExp::The CSF of a patient with HSV encephalitis is characterized by increased lymphocytes and not neutrophils. Elevated neutrophil counts are found in bacterial CNS infections.]]
Answer C	AnswerC::Decreased glucose, Increased neutrophils
Answer C Explanation	AnswerCExp::The CSF of a patient with herpes encephalitis is characterized by an unchanged or slightly decreased level of glucose. Glucose level is significantly decreased in bacterial infections of the CNS.
Answer D	AnswerD::Decreased proteins, Increased red blood cells
Answer D Explanation	[[AnswerDExp::The CSF of a patient with HSV encephalitis is characterized by increased proteins.]]
Answer E	AnswerE::Decreased proteins, Increased lymphocytes
Answer E Explanation	[[AnswerEExp::The CSF of a patient with HSV encephalitis is characterized by increased proteins.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::Herpes simplex virus (HSV) encephalitis is a severe central nervous system infection usually associated with HSV type 1 (HSV-1). Although the mechanism of CNS infection is unclear, retrograde axonal transmission appears to be a major pathway. Patients with HSV encephalitis classically present with high grade fever, headache, psychiatric symptoms (Kluver-Bucy syndrome, visual and gustatory hallucinations, etc.), seizures, and focal neurologic symptoms. Physical exam often reveals altered consciousness, papilledema, and cranial nerve defects. Meningeal signs are not very common. Diagnosis should be made promptly although empiric acyclovir therapy should be started immediately in cases of high suspicion. Diagnostic studies include MRI, lumbar puncture for CSF analysis and HSV PCR. Patients with HSV encephalitis has a typical viral CSF profile with elevated lymphocytes, normal glucose, and mildly elevated proteins. Given the hemorrhagic nature of the disease, xanthochromia or increased red blood cells in the CSF can be observed in these patients. MRI imaging reveals temporal lobe involvement (classically isolated temporal lobe encephalitis) with hyperintesity related to intraparenchymal hemorrhage. Significant morbidity and mortality is associated with HSV encephalitis: approximately 10% of treated patients die, and 60% of survivors suffer long-term sequelae. Educational Objective: Herpes encephalitis can be diagnosed by brain imaging and spinal tap. Brain MRI reveals asymmetrical bilateral enhancement of the temporal lobes, while lumbar puncture reveals increased lymphocytes, unchanged glucose level and normal or elevated opening pressure. References: Image courtesy of Dr Bruno Di Muzio, Radiopaedia.org.([| original file here]) ]]
Approved	Approved::Yes
Keyword	WBRKeyword::Herpes, WBRKeyword::Encephalitis, WBRKeyword::HSV-1, WBRKeyword::Temporal lobe, WBRKeyword::Herpes simplex virus, WBRKeyword::Cerebrospinal fluid, WBRKeyword::CSF, WBRKeyword::Xanthochromia
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