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[[File:WBR0616.jpg|400px]]
[[File:WBR0616.jpg|400px]]
 
|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.
|Explanation=Herpes simplex encephalitis (HSE) is a rare, but severe viral infection of the human [[central nervous system]]. The majority of cases of herpes encephalitis are caused by herpes simplex virus-1 (HSV-1). HSE is thought to be caused by the retrograde transmission of virus from a peripheral site on the face following HSV-1 reactivation, along a nerve axon, to the brain. Most individuals with HSE show a decrease in their level of consciousness and an altered mental state presenting as confusion, and changes in personality. Increased numbers of white blood cells can be found in patient's cerebrospinal fluid, without the presence of pathogenic bacteria and fungi. Patients typically have a [[fever]] and may have [[seizures]]. Imaging by CT or MRI shows characteristic changes in the temporal lobes as depicted in the image. Definite diagnosis requires testing of the cerebrospinal fluid (CSF) by a lumbar puncture which mainly increased lymphocytes. Patients with suspected herpes encephalitis should be treated with acyclovir immediately while waiting for test results.
|AnswerA=Increased lymphocytes, Increased red blood cells
|AnswerA=Increased lymphocytes
|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.
|AnswerAExp=The [[CSF]] of a patient with herpes encephalitis is characterized by increased [[lymphocytes]].
|AnswerB=Increased neutrophils, Increased red blood cells
|AnswerB=Increased neutrophils
|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.
|AnswerBExp=The [[CSF]] of a patient with herpes encephalitis is characterized by increased [[lymphocytes]] and not [[neutrophils]].  Elevated neutrophil levels is found in bacterial infection.
|AnswerC=Decreased glucose, Increased neutrophils
|AnswerC=Decreased glucose
|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.
|AnswerCExp=The CSF of a patient with herpes encephalitis is characterized by an unchanged level of glucise. Glucose level is decreased in bacterial infection.
|AnswerD=Decreased proteins, Increased red blood cells
|AnswerD=Increased glucose
|AnswerDExp=The [[CSF]] of a patient with HSV encephalitis is characterized by increased proteins.
|AnswerDExp=The CSF of a patient with herpes encephalitis is characterized by an unchanged level of glucise. Glucose level is decreased in bacterial infection.
|AnswerE=Decreased proteins, Increased lymphocytes
|AnswerE=Decreased proteins
|AnswerEExp=The [[CSF]] of a patient with HSV encephalitis is characterized by increased proteins.
|AnswerEExp=The [[CSF]] of a patient with herpes encephalitis is not characterized by decreased proteins level.
|EducationalObjectives=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.
|EducationalObjectives=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.([[http://radiopaedia.org/cases/herpetic-encephalitis-1|original file here]])<br>
|References=Image courtesy of Dr Bruno Di Muzio, Radiopaedia.org.([[http://radiopaedia.org/cases/herpetic-encephalitis-1|original file here]])<br>
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Herpes, encephalitis, HSV 1
|WBRKeyword=Herpes, Encephalitis, HSV-1, Temporal lobe, Herpes simplex virus, Cerebrospinal fluid, CSF, Xanthochromia
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 15:32, 10 October 2014
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.([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
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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