A 35-year-old physical therapist presents with right-sided back and leg pain. For the last 4 months, he has taken anti-inflammatory medications and performed exercises on his own. While his back pain has improved slightly, his leg pain remain severe and interferes with his ability to sleep and work. Examination reveals positive ipsilateral and contralateral straight leg raise at 30 degrees. He has mildly diminished big toe dorsiflexion strength on the right side. There is a small patch of diminished sensation on the dorsum of the foot. MRI scans are shown in Figures A and B. What is the most appropriate next step in treatment?