A 50-year-old woman developed discomfort of oral cavity and dysarthria. Her tongue showed a slight left-deviation and atrophy in the left side in a month. Examination with X-p, CT, and MRI showed hypoplasia of the atlas and high cervical ossification of the posterior longitudinal ligament (OPLL) from C1 to C5. Thus, combination of congenital hypoplasia of the atlas and acquired high cervical OPLL reduced a function of hypoglossal nerve, which resulted in the palsy. In a case of unilateral hypoglossal palsy, a possible lesion of foramen magnum should be considered.