Patient appears confused and disoriented with intact cranial

Discussion in 'USMLE STEP 2 CS' started by Guest, Apr 11, 2009.

  1. Guest

    Guest Guest

    A 57-year-old man is brought to the emergency department after having had a seizure. His wife states that two days ago, he began complaining of a headache and fever and was intolerant to bright light. This morning she noticed he was confused and disoriented. He subsequently developed a tonic-clonic seizure. He has no past medical history and is on no medications. His temperature is 101.2 F, heart rate is 97/min, and blood pressure is 128/85 mm Hg. His pupils are equal and reactive, with normal fundi. There is marked nuchal rigidity.

    Upon physical examination, the patient appears confused and disoriented with intact cranial nerves. The lumbar puncture on the day of admission shows a lymphocytic pleocytosis of the cerebrospinal fluid. Gram stain shows no organisms. The patient is then placed on intravenous acyclovir. Later, during the course of this admission, an MRI of the brain shows increased signal uptake of the right temporal lobe. Final analysis of the cerebral spinal fluid (CSF) shows no growth on bacterial or acid-fast cultures. The VDRL and CSF herpes-antibody test are negative. Which of the following is the next best step in the treatment of this patient?

    (A) Brain biopsy
    (B) Continue the full course of acyclovir and await PCR testing of the CSF
    (C) Continue acyclovir and add ceftriaxone
    (D) Discontinue acyclovir and start ceftriaxone
    (E) Examine CSF for anti-HSV antibodies in four weeks
  2. Guest

    Guest Guest

    (B) Continue the full course of acyclovir and await PCR testing of the CSF
  3. Guest

    Guest Guest

    Explanation:

    This patient most likely has herpes simplex virus (HSV) encephalitis. His clinical presentation, cerebral spinal fluid (CSF) analysis, and MRI findings are very characteristic of HSV central nervous system (CNS) infection. Herpes encephalitis usually presents with fever, confusion, a mild lymphocytic pleocytosis, and temporal lobe involvement on brain scan. In cases like this, the HSV polymerase chain reaction (PCR) would usually be positive in 95 to 98% of patients. In cases where there is a high clinical suspicion of HSV encephalitis, the only indication to stop the course of acyclovir is a negative brain biopsy or a negative herpes DNA, PCR test. There is rarely a need to perform a brain biopsy to exclude herpes encephalitis because of the exquisitely high sensitivity of the PCR test. Antibodies to HSV will rise in the CSF in patients with HSV encephalitis, but rarely before 10 days of illness. The question, however, states that he had a negative antibody test, not a negative PCR for herpes DNA

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