A 35-year-old man came to the hospital showing signs of worsening dysesthesia on his right hand. The dysesthesia started on his right hand and then spread to his forearm in two months. It also appeared on his left hand transiently. Initial MR imaging revealed a high signal intensity lesion at Th1-Th10 with an irregular margin (presyrinx state) below C3 on T2WI. The legion extended up to the medulla oblongata rapidly. Corticosteroid therapy lead to a slight improvement in dysesthesia symptoms but did not last. Immunosuppressant was also ineffective. Further examination using Gd enhanced MR imaging in a neurosurgery clinic in a university hospital revealed a spinal tumor at the Th10 level. A tumor resection was performed and dysesthesia improved. Pathological analysis showed hemangioblastoma. Presyrinx and syrinx above Th1 disappeared after the operation. It is necessary to search the whole spine carefully for the possibility of a tumor in the case of steroid resistant progressive spinal lesions with an unknown origin. And we stress the importance of timely surgical intervention regardless of idiopathic or secondary syringomyelia. We would like to report this clinical course presenting MR imaging and discuss the mechanism of forming syringomyelia based on the hypothesis of the alteration of CSF flow.