A 42-year-old male carpenter from Delhi presents with a 3-week history of progressive weakness of finger flexion and intrinsic hand muscles. On examination, he has a claw hand deformity (hyperextension at MCP joints and flexion at IP joints of digits 4–5), loss of sensation over the medial 1.5 fingers, and wasting of the hypothenar eminence. He reports no history of trauma or elbow injury. Nerve conduction studies show slowing of conduction velocity across the elbow with preserved conduction distally. What is the most appropriate next step in management?