[Atypical metastasis from a colorectal cancer : the pons is undermined !].

Brain metastases occur in 1 to 4 % of patients with colorectal cancer and are unique in 0.5 % of them. Because of their infrequent nature, brain imaging is not recommended in the systematic follow-up of these patients. We report here an exceptional case of a unique brain metastasis in a very unusual position. An 82-year-old patient with a colorectal cancer of the splenic angle that was treated with surgery and adjuvant chemotherapy, developed a series of neurological symptoms over four to six weeks: difficulty swallowing, loss of strength in the four limbs and balance disorders. These symptoms urged the performance of a nuclear magnetic resonance to exclude a central neurological lesion. MRI revealed a nodular tumor of 20 millimeters in the major transverse axis and 17 millimeters in the cerebro-caudal axis, located on the ventral portion of the protuberance. Because of its localization, surgery was not possible and the lesion was treated with Cyberknife radiosurgery. Thanks to the treatment, the lesion decreased in size and the symptoms improved significantly. Despite an initially very poor prognosis in view of the localization of the metastasis, the patient is alive and in excellent general condition more than eight months after the diagnosis of recurrence.