Modified bifrontal interhemispheric approach to aneurysms of the anterior communicating artery with the use of a trephine craniotomy. A review of personal experience with 25 cases.

A modified microsurgical bifrontal interhemispheric approach (small trephine craniotomy) for clipping of aneurysms of the anterior communicating artery (ACoA) is described. This approach has been used in a series of 23 patients with ACoA and 2 patients with distal anterior cerebral artery aneurysms. Feasibility, indications and problems related to this approach to ACoA aneurysms are assessed. Twenty-one patients (84%) made an excellent or good recovery. The result was poor in an 80-year-old patient who was in grade 3 pre-operatively. Three patients of this series died: one of them was pre-operatively in grade 4 and died from pneumonia; the other two died as consequence of unrelated ailments. Incidence and extent of vasospasm was within the normal range, corresponding to the amount and distribution of subarachnoid blood clots. From our experience it can be concluded that this approach is safe and feasible for patients with ACoA aneurysms graded 1-2 (Hunt-Kosnik's grading system) and evaluated as group 1-2 of Fisher's CT classification. But it is not recommended for patients with larger amounts of subarachnoid blood clots. Advantages of this microapproach to ACoA aneurysms are: a) minimal brain damage, b) adequate visualization and anatomical orientation, c) preservation of the olfactory nerves and the gyrus rectus, d) reduced operative time, e) easy clip application to aneurysms pointing in any direction.