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

• Single Most Likely Diagnosis
  • A. Herpes Encephalitis: This is a common cause of encephalitis, particularly in young adults, and can present with altered mental status. The parieto-temporal location is consistent with herpes simplex encephalitis, which often affects the temporal lobes.
• Other Likely Diagnoses
  • B. Meningoencephalitis: This condition, which involves inflammation of both the meninges and the brain, can cause altered mental status and could potentially present with hyperdense lesions on CT due to inflammation or other complications.
  • C. Brain Abscess: Although less common than herpes encephalitis, a brain abscess could present with a hyperdense lesion on CT, especially if it is in the early stages or if there is a significant amount of surrounding edema.
• Do Not Miss Diagnoses
  • Subdural or Epidural Hematoma: Although the question specifies a hyperdense lesion, which could suggest a hemorrhagic or highly cellular process, it's crucial not to miss a hematoma, especially if there's any history of trauma. Hematomas can present with altered mental status and require urgent intervention.
  • Cerebral Venous Thrombosis: This condition can cause hyperdense lesions due to thrombosis and can lead to significant morbidity or mortality if not promptly treated.
• Rare Diagnoses
  • D. Cerebral Hydatid Cyst: While this is a possible cause of a brain lesion, it is relatively rare in many parts of the world and might not be the first consideration unless there's a specific travel or exposure history that increases the likelihood of echinococcosis.
  • Other rare infections or conditions, such as fungal infections or parasitic infections, could also present with similar findings but would be less common and might require specific risk factors or exposures to be considered.