Clinical Reasoning: A young man with acute encephalopathy, loss of vision, and upper motor neuron signs

A 22-year-old man with no significant medical history presented at the hospital emergency department with a 1-day history of confusion and gradual loss of vision. Seven days before the presentation, he started complaining of holocranial headache, which was initially mild but eventually progressed to become severe in intensity, associated with nausea and vomiting, and was not responsive to paracetamol. There were no associated seizures.