Yes! Well done. Tricky right? The initial CSF profile was not very impressive, but you correctly sensed that something fishy was going on here. This patient had a suspicious finding on MRI with the right-sided hemispheric (mainly temporal, occipital, insular) cortical diffusion restriction, along with right frontal-maximal LPDs on cEEG. While the patient's CSF profile did not have a pleocytosis, and his HSV PCR was initially negative, this imaging and EEG finding are just too suspicious for HSV to let go. CSF WBC count can actually be normal in a minority of patients. Specifically, one retrospective study from 2013-2018 found that 22% of patients had a normocellular CSF profile on admission! A 2022 paper from Critical Care Medicine found that in patients admitted to the ICU and were later found to have HSV encephalitis, 4% of patients had an initial negative HSV PCR. Low rate, but not zero. Additionally, about 94% of patients with HSV encephalitis ended up having an abnormal brain MRI; we can't and shouldn't use MRI to rule out HSV, but it's helpful to know if abnormalities are present. In terms of the other antimicrobials, with the pretty unimpressive WBC, something like pneumococcal or meningococcal meningitis is probably less likely, so it'd be reasonable to stop IV vancomycin and ceftriaxone (latter also helps cover GNRs). Listeria will generally produce a moderate pleocytosis, and often will have normal cultures, so not totally unreasonable to continue for now. The key with this answer choice was really recognizing that HSV is still a major consideration.
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