Herpes simplex encephalitis with temporal lobe T2 hyperintensity

A 52-year-old man presents with 3 days of high-grade fever, progressive confusion, personality change with aggressive outbursts, expressive dysphasia, and a complex partial seizure with secondary generalization. Examination reveals neck stiffness, right upper-limb focal motor jerks, and bilateral extensor plantars (GCS 12). Brain MRI demonstrates the findings marked as **D** in the diagram. CSF analysis shows lymphocytic pleocytosis (140 cells/μL, 90% lymphocytes), elevated protein, normal glucose, and red blood cells. HSV-1 PCR is positive. Which of the following is the MOST CRITICAL distinguishing feature of the abnormality marked **D** that differentiates herpes simplex encephalitis from acute middle cerebral artery infarction?