A 34-year-old woman with breast cancer presents to her physician complaining of increased weakness, lower back pain, and urinary incontinence. She was diagnosed with breast cancer 2 years ago and is undergoing radiation and chemotherapy. Her back pain developed 2 days ago. Physical examination shows lower extremity weakness and hyporeflexia. Which of the following is the most appropriate next step in this patient's care? (A) Obtain a neurologic consultation (B) Obtain an emergency spinal MRI (C) Administer narcotics for pain relief (D) Administer high-dose steroids (E) Perform a lumbar puncture