Traumatic atlanto-occipital dislocation is a serious injury that is usually fatal. The number of patients surviving this injury, however, appears to be increasing, and most of these survivors are children. This may reflect an improvement in emergency transport services. Seventeen previously reported cases of patients surviving atlanto-occipital dislocation for more than 48 hours are reviewed and an additional case is presented. Many of these patients had an excellent neurological outcome. The radiographic criteria necessary for the diagnosis of atlanto-occipital dislocation are discussed. Cervical computerized tomography may confirm the diagnosis when necessary. It is suggested that there are three types of atlanto-occipital dislocation; utilizing this new classification, a rationale for treatment is described. Fusion is favored for long-term stability.

The authors present this study of proximal anterior cerebral arteries in the normal human to provide a clearer basis for strategy in aneurysm surgery. They describe patterns of origin of branches, their subarachnoid course, and parenchymal distribution. Branches that originate from the anterior cerebral artery at the internal carotid bifurcation perfuse the genu and contiguous posterior limb of the internal capsule and the rostral thalamus. Proximal 4-mm branches supply the anterior limb of the internal capsule, the neighboring hypothalamus, anteroventral putamen, and pallidum. The remaining anterior cerebral artery proximal to the communicating artery sends branches to the optic chiasm, the adjacent hypothalamus, and the anterior commissure. Heubner's artery arises directly opposite the anterior communicating artery to supply much of the striatum and internal capsule rostral to the anterior commissure. The anterior communicating artery branches supply the fornix, corpus callosum, septal region, and anterior cingulum. The parenchymal distribution of these end arteries may be surmised from the site of origin named vessels. With this anatomical information one can avoid interruption of blood supply to vital structures when dealing with the anterior cerebral artery and its branches.

Distal anterior cerebral artery aneurysms are commonly found near the genu of the corpus callosum. While these aneurysms may be surgically obliterated through a variety of approaches, exposure via the interhemispheric fissure is used by many surgeons. Early identification of the afferent artery may be difficult with this approach, however, particularly if the aneurysm lies just beneath the genu of the corpus callosum. The authors have modified the interhemispheric approach to distal anterior cerebral artery aneurysms by electively exposing the feeding artery through a small anterior callosotomy. While this maneuver is not necessary for all distal anterior cerebral artery aneurysms, it can greatly enhance exposure in the region just below the genu of the corpus callosum. Experience with this technique in five patients is reported. In all cases, the limited anterior callosotomy enhanced surgical exposure. No morbidity could be attributed to the callosotomy in any patient. It is concluded that, when the interhemispheric approach is used, anterior callosotomy improves exposure of the region just below the genu of the corpus callosum and may be a useful maneuver when treating distal anterior cerebral artery aneurysms.

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