Isolated dystonia of trunk and neck muscles without involvement elsewhere has been termed segmental axial dystonia--a rare disorder. We report a 31-year-old man who developed marked dystonia of paraspinal muscles and progressive scoliosis 6 months after a closed head injury. Computed tomography (CT) disclosed three small areas of encephalomalacia, one involving the head of the caudate nucleus. Treatment with trihexyphenidyl resulted in significant improvement of the dystonia and scoliosis.