We report the intramedullary growth of a malignant peripheral nerve sheath tumour (MPNST). A 50year-old man developed a severe tetraparesis over a 4-month period. Following irradiation of a chronic tonsillitis during his childhood, the patient had later experienced a number of post-radiation diseases, including a laryngeal cancer that required permanent tracheotomy. Before admission, a magnetic resonance imaging (MRI) study had disclosed a C4-C5 intramedullary lesion. On admission to our Department, the patient had a nearly complete tetraparesis. At surgery, the lesion was exposed through a posterior midline myelotomy. A friable neoplasm, with no clear plane of cleavage, was found. The tumour was subtotally resected. Histological examination, which intraoperatively had not yielded a specific diagnosis, eventually revealed a MPNST, grade intermediate, with ultrastructural and immunohistochemical features consistent with a schwannian differentiation. No postoperative radiotherapy was undertaken. The patient died 9 months later from pneumonial complications. MPNSTs may develop within the spinal cord similarly to their benign schwannian counterpart. The reported sequence of events might support a possible relation between irradiation of the spinal cord and induction, followed by malignant transformation, of intramedullary schwannosis. This unique case must be added to the growing list of radiation-induced spinal cord tumours.