AMMs, as defined by 2000 WHO, are biologically heterogeneous. Recurrence-free survival can be further stratified by location and histological parameters, especially mitotic count, brain invasion, and Ki67 labeling index. Not only brain invasion, but also the presence or absence of brain tissue in surgical specimens should be reported, because the absence of brain invasion, when brain tissue is identified, provides very important positive prognostic information.

Brain invasion assessability is related to meningioma grade and size and can be improved by extensive sampling of meningioma surgical.

The neurovascular relationships in the trigeminal root entry zone were studied in 130 trigeminal root entry zones of 65 cadavers. No history of facial or trigeminal pain had been obtained during life in these subjects. The technique of intravascular injection, which allowed good visualization and evaluation of the neurovascular relationships, is described. A total of 42 examples of contact with the root entry zone and 10 examples of compression were identified. In 30 of the examples of contact, the finding could be related to an artery; in the other examples, it appeared to be due to veins. Of the arterial compressions, the superior cerebellar artery was responsible in 53.8%, the anterior inferior cerebellar artery was responsible in 25.6%, and pontine branches of the basilar artery were responsible for the remaining 20.6%. Only one instance of unequivocal compression by a vein was found. Other anatomical observations of interest are reported. The absence of a history of trigeminal neuralgia in the 7% of examined nerves in which root entry zone showed arterial compression is in marked contrast to the finding of 80% or more in the operative series for trigeminal neuralgia. It seems that vascular compressions may be the predominant but not the sole cause of trigeminal neuralgia.

Intraoperative visual guidance based on 3D visualisation proved to be adequate and accurate for locating superficial brain tumours in cases where transfer of planned surgical targets to the surgical field was possible. Decision about its use should be based on preoperative computer-assisted 3D planning, in which the feasibility of visual matching during surgery can and must be assessed.