A 32-year-old woman with known Pott disease (T10–T11 involvement) is 3 months into anti-tuberculous therapy (HRZE). She now presents with acute-onset paraplegia (lower limb weakness, sensory level at T10, absent ankle reflexes). MRI shows cord compression from a large epidural abscess with cord signal changes. She is neurologically deteriorating despite ATT. What is the most appropriate next step?