This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S., Subject name: Medicine
An 18-year-old man develops fever, headache, confusion, and generalized seizures. On examination, he is moving all his limbs, but incoherent. A CT scan shows bilateral, small, low-density temporal lobe lesions. CSF shows mononuclear cell pleocytosis, increased protein, and normal glucose. The EEG shows bilateral periodic discharges from the temporal leads and slow-wave complexes at regular intervals of 2-3/sec. Which of the following is the most appropriate next step in management? 
Select and explain. 
A. angiography, B. observing response to therapy, C. cerebral biopsy, D. acute viral titers
B: observing response to therapy
Answer: B: observing response to therapy 
Explanation: The patient's findings strongly suggest herpes simplex encephalitis. This is generally caused by herpes simplex virus type 1 (HSVI). When the disease is suspected, appropriate antiviral therapy (acyclovir) should be started immediately. CT scan is not helpful in diagnosis because it becomes positive only late in the disease, but MRI scans may be helpful. Brain biopsy, once the diagnostic test of choice, is the most definitive test but is rarely performed.