Differential Diagnosis for Young Patient with Altered Mental Status and Parieto-Temporal Hyperdense Lesion on CT Brain

• Single Most Likely Diagnosis
  • A. Herpes Encephalitis: This is the most likely diagnosis due to the location of the lesion (parieto-temporal) which is typical for herpes simplex encephalitis, a condition known to cause severe and potentially fatal brain infection, often presenting with altered mental status.
• Other Likely Diagnoses
  • B. Meningoencephalitis: Infections that cause both meningitis and encephalitis can present with a variety of symptoms including altered mental status and could potentially show hyperdense lesions on CT due to inflammation or other complications.
  • C. Brain Abscess: Although less common than herpes encephalitis in this specific context, a brain abscess could present as a hyperdense lesion, especially if it is encapsulated and contains purulent material. Symptoms can include altered mental status, fever, and focal neurological deficits.
• Do Not Miss Diagnoses
  • Subdural or Epidural Hematoma: These conditions, although not infectious, can present with altered mental status and could appear hyperdense on CT due to blood accumulation. They are emergencies requiring immediate surgical intervention.
  • Cerebral Venous Thrombosis: This condition can cause hyperdense lesions due to thrombosis and could lead to altered mental status. It's crucial not to miss this diagnosis as anticoagulation is the treatment, which is different from the treatment for infectious causes.
• Rare Diagnoses
  • Primary Brain Tumors: Although rare in the acute presentation of altered mental status, certain tumors like glioblastoma could appear as hyperdense lesions on CT, especially if they have hemorrhagic components.
  • Cerebral Arteritis or Vasculitis: These conditions can cause a variety of neurological symptoms including altered mental status and could potentially show hyperdense lesions on imaging due to inflammation of blood vessels. They are less common but important to consider in the differential diagnosis.