A 46 year-old man admitted to neurosurgery department with complaints of ataxic gait and decreased sensation in left extremities which were developed when he was 34 years old and aggravated slowly. 25 years ago he developed progressive weakness of intrinsic muscles of right hand. He was diagnosed as Arnold-Chiari Malformation type I. Under the diagnosis of atlantoaxial instability, the patient was treated with operation of craniocervical fusion and laminectomy at C2-C3 level. Despite these treatment, ataxic gait, motor weakness and sensory dissociation was not improved. After the patient was transferred to rehabilitation department, he received comprehensive rehabilitation program. The patient's functional independence measurement(FIM) score at admission was 72 and improved to 104 discharge. The patient was discharged with the state of the monocane ambulation. Like this case, Arnold-Chiari malformation associated with syringomyelia with the evidence of muscle atrophy, ataxia have poor prognosis, therefore early diagnosis and proper managements along with comprehensive rehabilitation is critical in obtaining the best outcome.