Résumé
The authors experienced a case of cystic cerebellar astrocytoma which showed sudden respiratory arrest after an uneventful operation. Preoperative cerebrospinal fluid diversion was not performed despite moderate hydrocephalus because we thought that complete removal of tumor enables the cerebrospinal fluid pathway to be reconstitute. After full awakening from anesthesia postoperatively, the patient's mentality deteriorated again rapidly with sudden respiratory arrest. Brain CT scan taken immediately after revealed no specific finding except moderate hydrocephalus which was the same degree as the preoperative one. This hydrocephalus was alleviated and the patient recovered slowly. We postulate several pathogenic mechanisms for this unusual event. First, chronic compression of fourth ventricle resulted in marked subependymal gliosis and obliteration of outlets of fourth ventricle. Therefore, postoperative reaccumlation of cerebrospinal fluid in ventricles caused serious pressure effect on the lower brain stem with resultant sudden respiratory arrest. Second, sudden decompression of brain stem might induce marked hemodynamic change in the brain stem. Third, there was some traction injury to brain stem by gravity in the sitting position. We suggest that preoperative cerebrospinal fluid diversion and its adeqaute postoperative maintenance is important in posterior fossa tumor surgery in cases with obliteration of perimesencephalic cistern and fourth ventricle, and with brain stem compression or angulation in preoperative magnetic resonance images.