Chronic Inflammatory Demyelinating Polyneuropathy

A 52-year-old man presents with a 4-month history of progressive symmetric weakness in both legs and arms, along with loss of vibration sense and proprioception. Examination reveals areflexia and distal wasting. MRI of the spine shows the finding marked **A** in the diagram. Nerve conduction studies demonstrate prolonged distal motor latencies, slow conduction velocities, and conduction blocks in multiple nerves. CSF analysis shows protein elevation with <5 cells/μL. Based on these findings, what is the most likely diagnosis?