Neuroscience · Year 2 · from Neuroscience
Case 2: Herpes Simplex Encephalitis with Limbic Involvement
Patient Presentation
Demographics: 34-year-old female
Chief Complaint: Fever, confusion, and strange behavior for 2 days
History of Present Illness: The patient's husband reports she developed a fever and headache three days ago, which she attributed to a flu. Over the following two days, she became increasingly confused, had difficulty finding words, and exhibited bizarre behavior including repeatedly asking the same questions and becoming agitated when watching television, saying the people on screen were "talking about her." She had one episode witnessed by her husband where she "stared blankly and smacked her lips" for about 2 minutes followed by confusion.
Physical Examination:
- Vital signs: BP 128/76, HR 102, T 38.9C, RR 20
- General: Appears unwell, intermittently agitated
- Neurological:
- Mental status: Oriented to person only; unable to remember three words after 5 minutes; paraphasic errors; intermittent agitation
- Cranial nerves: Intact
- Motor: Right arm drift, 4+/5 strength right upper extremity
- Sensory: Intact
- Reflexes: Brisk on right side
Workup:
- CT head without contrast: Subtle hypodensity in left temporal lobe
- MRI brain: T2/FLAIR hyperintensity involving the left medial temporal lobe (hippocampus, parahippocampal gyrus, amygdala) with extension to the insular cortex; mild enhancement; similar but less extensive changes on the right
- Lumbar puncture: Opening pressure 180 mmH2O; WBC 125/mm3 (85% lymphocytes); protein 78 mg/dL; glucose 58 mg/dL (serum 102); RBC 450/mm3
- CSF HSV PCR: Positive for HSV-1
Diagnosis: Herpes simplex encephalitis (HSE) with bilateral medial temporal lobe involvement
Treatment:
- IV acyclovir 10 mg/kg every 8 hours for 21 days
- Levetiracetam for seizure prophylaxis
- Supportive care in ICU
Clinical Course: The patient's fever resolved within 48 hours. Her agitation improved over 5-7 days. At discharge after 3 weeks, she demonstrated significant anterograde amnesia, being unable to form new memories of events during hospitalization. At 6-month follow-up, she had persistent memory impairment and required assistance with complex tasks but could perform basic activities of daily living independently.
Clinical Pearl: HSV-1 has a predilection for the medial temporal lobes (limbic structures) due to viral latency in the trigeminal ganglion with spread along meningeal branches. The bilateral hippocampal involvement explains the severe anterograde amnesia seen in survivors. Early acyclovir treatment significantly improves outcomes, so empirical treatment should begin immediately when HSE is suspected.