[Improvement in brain circulation by microsurgical bypass anastomoses].

On the basis of 100 patients operated during the last ten years at the Neurosurgical University Clinic of Zurich the experiences with the extra-intracranial bypass anastomosis for stroke patients are examined. The risks of this surgery are low (morbidity 2%, mortality 3%) and the patency rate is high (94.3%). The main purpose of this intervention is to prevent or minimize further strokes. This risk was decreased from 40% of non operated cases in the literature to 4.2% in this series. Severe neurological deficits are not improved by surgery. The procedure is therefore indicated for mild forms of cerebral ischemia (TIA's and mild strokes), when the disease is caused by an appropriate obstruction of the internal carotid artery and/or middle cerebral artery which are inaccessible to surgery of the neck. For this latter reason preoperative carotid angiography is mandatory. To avoid unnecessary angiography, the carotid Doppler ultrasound test and dynamic brain scanning are valuable, non invasive screening methods for indicating angiography in eah individual case.