Review Question - QID 215193

A 53-year-old man presents to clinic complaining of trouble walking for the past few months that has been steadily worsening. He notices this issue most when he gets up in the middle of the night to walk into the kitchen for water. He has also noted shooting pains down his legs. He has not seen a physician for the past several years, does not take any medications, has never had surgery, and has no allergies to medications. His temperature is 37.2°C (98.9°F), blood pressure is 138/89 mmHg, pulse is 73/min, respirations are 14/min, and oxygen saturation is 97% on room air. On exam, his pupils at baseline appear as shown in the top panel of Figure A, they appear as in the middle panel in response to light shone in the right eye, and they appear as in the bottom panel upon accommodation. His exam is also notable for a positive Romberg sign and decreased deep tendon reflexes. Which of the following is the most appropriate treatment for this patient?