A 36-year-old woman presents with a 2-day history of fever, stiff neck, and headaches. She also was reported to have had one seizure just prior to her admission. The patient has a temperature of 39°C, blood pressure of 120/80 mmHg, and heart rate of 106 beats per minute. A lumbar puncture is performed and her CSF studies reveal the following:
Which of the following is the most likely diagnosis in this patient?
A. Meningococcal meningitisHerpes simplex encephalitis. This question is testing one’s ability to distinguish causes of abnormal CSF values. The patient in this question likely has herpes simplex (HSV) encephalitis, which accounts for almost 20% of viral encephalitis cases and presents with fever, focal seizures, and sometimes aphasia, ataxia, hemiparesis, and behavioral symptoms. HSV encephalitis typically affects the temporal lobes of the brain and has an acute onset. CSF analysis is critical in securing the diagnosis. CSF studies reveal lymphocytosis, elevated protein levels, normal glucose levels, and occasionally increased levels of RBCs due to hemorrhagic destruction of the temporal lobes. To solidify the diagnosis, the most specific test is PCR analysis of HSV DNA in the spinal fluid.
(A, D) Bacterial meningitis will present with low glucose in the CSF. In addition, rather than lymphocytosis, increased neutrophils will be seen on CSF analysis. (C) Fungal meningitis often presents with low glucose like bacterial meningitis, but will accompany a lymphocytosis. The patient in this question has a CSF analysis that is consistent with a viral etiology.