Foramen magnum tumors produce many bizarre symptoms, and several reports have mentioned the pitfalls in diagnosing such tumors. In this report, we confirm such a tumor causing motor disturbance of the contralateral extremities. A 64-year-old male with a 2-year history of numbness of the right extremities and motor disturbance of the left extremities presented to our hospital. Neurological findings were as follows: hypoesthesia of the right hand and both lower legs, weakness of the left extremities, hyperactive deep tendon reflexes in the left upper and lower extremities, and Hoffmann's and Babinski's signs on the left side were present. On MR images, myelogram and CT-myelogram a dumbbell shaped tumor, which showed compression of the cervical spinal cord from the right side at the level of C1-C2, was noted. The tumor was surgically resected, and on histological examination it was diagnosed as a neurinoma. In this case the tumor was situated at C1-C2 below decussation, however, weakness and increased deep tendon reflexes were found in the contralateral extremities. The main function of the upper cervical spine is rotation. The spinal cord is compressed by contralateral lamina during rotational motion of the upper cervical spine. Thus, as noted in the present study, contralateral motor disturbance may occur.