A 48-year-old man presents with the inability to extend his left foot since yesterday. He has had worsening numbness over the dorsum of his left foot and anterior left leg (inferior to the knee), for the past five weeks; and intermittent discomfort and paresthesia over the same region for the past five years. He had not sought medical attention for this. He reports no significant weight changes recently. There is no history of recent or old trauma to the affected region. He has been in good health otherwise, with unremarkable medical and surgical histories. He took acetaminophen (paracetamol) for the pain. He is not on any other medications or supplements. His family history is unremarkable. He only drinks socially—about 1 to 2 standard drinks per week. He does not smoke or use recreational drugs.