Review Question - QID 213828

This patient is presenting with a fever, confusion, and MRI demonstrating edema in the temporal lobe, which is concerning for herpes simplex virus (HSV) encephalitis. HSV encephalitis on lumbar puncture presents with an elevated lymphocyte count, an elevated protein, and a normal glucose.

HSV encephalitis is a high mortality disease that can present with vague symptoms including fever and altered mental status. In meningoencephalitis, patients may have meningeal irritation as well. Any patient suspected of having encephalitis should have a lumbar puncture and polymerase chain reaction performed (as well as culture for bacterial etiologies) to confirm the diagnosis of HSV encephalitis. The initial lumbar puncture findings of HSV encephalitis include an increased red blood cell count, an increased cell count that is predominantly lymphocytes, an increased protein, and a normal glucose. Prior to confirming the diagnosis of HSV encephalitis, patients should be started on acyclovir as this is a high mortality condition.

Figure/Illustration A is an MRI scan of the head demonstrating inflammation in the temporal lobe (red circle) which can be seen in HSV encephalitis.

Incorrect Answers:
Answer 2: Increased lymphocytes, increased protein, and a low glucose would be seen in a fungal meningitis or tuberculosis, which would present with the classic symptoms of meningitis and would be treated with antifungal agents (amphotericin B and 5-flucytosine followed by fluconazole if cryptococcal meningitis in a HIV patient) or rifampin, isoniazid, pyrazinamide, and ethambutol for tuberculosis.

Answer 3: Increased neutrophils, increased protein, and decreased glucose correspond to bacterial meningitis, which is typically empirically treated with vancomycin and ceftriaxone until the culture confirms the agent and sensitivity.

Answer 4: Increased red blood cells, normal protein, and normal glucose would be seen in a subarachnoid hemorrhage which presents with a severe/sudden thunderclap headache and meningeal signs. Though the red blood cell count will be elevated in HSV encephalitis, the predominant cell type is lymphocytes, and the protein would also be elevated.

Answer 5: Normal cell count, increased protein, and normal glucose would be seen in an inflammatory condition such as Guillain-Barre syndrome, which presents with an ascending flaccid paralysis typically after a viral or bacterial infection (most commonly Campylobacter jejuni). Treatment is IVIG or plasmapheresis and intubation if the patient cannot ventilate/oxygenate.

Bullet Summary:
HSV encephalitis presents on lumbar puncture with a normal glucose, elevated protein, an elevated cell count with a lymphocytosis, and an increased RBC count.