We report a 77-year-old man who presented with numbness and weakness of the feet bilaterally, that had progressed over 13 years. He was diagnosed with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) on the basis of nerve conduction studies and a sural nerve biopsy; however, he was inadequately treated and his weakness had progressed. At 76 years of age, he developed spasticity in the legs as well as bladder and rectal incontinences. Gd-enhanced MRI revealed severe compression of the cervical cord by massively enlarged nerve roots. A cervical laminectomy was performed to decompress the cervical cord. A fascicular biopsy of the C5 dorsal root showed a prominent lymphocyte infiltration and edema. Repeated methylprednisolone pulse therapy and IVIg ameliorated the weakness. We concluded that the main cause of nerve root hypertrophy in this patient was active inflammation.