Lostosarcome est la deuxime tumeur maligne primitive de los, la plus frquente aprs le mylome. Il atteint habituellement les os longs. La base du crne est exceptionnellement touche. ce propos, nous rapportons un cas dostosarcome de la base du crne suivi dans notre service. Il sagit dune jeune fille de 23 ans admise pour pistaxis bilatrale, cphales et chute de lacuit visuelle puis ccit. Lexamen clinique a retrouv une ccit bilatrale avec exophtalmie. LIRM du crne a montr une volumineuse masse de la base du crne tendue la rgion nasosinusienne. La patiente a t opre par voie rhinoseptale mais la tumeur tait volumineuse et a t juge inoprable. La biopsie a conclu un ostosarcome ostoblastique. Le bilan dextension (TDM thoracique et chographie hpatique) tait normal. Une chimiothrapie premire tait prvue suivie dune association radiochimiothrapie mais la patiente est dcde par volutivit tumorale avant dentamer tout traitement. Lostosarcome de la base du crne est trs rare. Le traitement est bas sur une chirurgie la plus complte possible suivie dune association radiochimiothrapie. Le pronostic est dfavorable, la mdiane de survie ne dpassant pas six mois.

Osteosarcoma, usually observed in long bones, is the second most frequent primitive malignant bone tumor after myeloma. The skull base is an exceptional localization. We report a case of skull base osteosarcoma managed in our department. A 23-year-old female was admitted for bilateral epistaxis, headache, decreasing visual acuity then blindness. Physical examination revealed bilateral blindness and exophthalmia. Cranial magnetic resonance imaging showed a voluminous mass in the skull base extending to the nasosinusal area. A rhinoseptal surgical approach was used but the tumor was so huge that excision was impossible. The biopsy identified at an osteoblastic osteosarcoma. Search for extension (chest computed tomography and abdominal ultrasonography) was negative. Chemotherapy was to be delivered before combination chemoradiotherapy but the patient died before any treatment could be started. Osteosarcoma of the skull base is very rare. The treatment is based on surgery which should be as complete as possible followed by chemoradiotherapy. Prognosis is poor. Median survival is around six months.