A34-year-old man with an 8-year history of multiple sclerosis presents for regularly scheduled follow-up. he reports worsening of his disease and is uncharacteristically irritable, notably complaining about waiting 10 minutes in the examination room. he reports his vision and legs are "worse" and that he has difficulty sleeping. he also mentions that work is going well, but his girlfriend moved out last month. there have been no changes in his prescribed interferon beta and oxybutynin. neurologic examination demonstrates a right relative afferent pupillary defect, a left internuclear ophthalmoplegia, and spastic paraparesis with bilateral extensor plantar responses. he walks with a walker to stabilize his spastic gait. these findings have not changed since his last visit 3 months ago. the neurologist should next ask about