gms | German Medical Science

Objective: Modern MRI techniques have improved the planning of surgery to remove lesions in or around the temporal lobe. Since MRI-based morphometric analyses of the temporo-mesial and para-hippocampal regions as part of it have not yet been performed, the present study was undertaken to obtain relative normative morphometric data of the middle cranial fossa (MCF) in order to obtain individualized bony and cerebral landmarks for approaches to the tentorial notch in skull base surgery and in the post-operative follow-up.

Method: Median-sagittal MRI scans from 30 MPRAGE-sequences of individual brains without pathological lesions were analyzed. The AC-PC line (anterior commissure-posterior commissure line) with vertical lines through AC and PC were chosen as reference lines.

Results: In our morphometric study we described two different measures in the MCF on the right and the left side respectively: 6.30 (0-18) mm above the suprameatal process on the right, and 6.05 (1-14) mm above the suprameatal process on the left. The deepest zone of the MCF is mainly located posteriorly to the tuberculum articularis, presenting a distance from tuberculum in the posterior direction of 6.20 (0-13) mm and 6.70 (0-15) mm, on the right and on the left respectively. The parahippocampal gyrus is bordering over the tentorial notch with a mean distance of 0.8 cm, at the level of the amygdala.

Conclusions: Knowledge of these volumes will allow for the exact planning of surgical approaches to the temporal mesial region and tentorial incisure, for example the subtemporal approach and the surgery of epilepsy, in order to avoid brain damage during retraction or manipulation. Furthermore since the measure, the distances and the curvature of the floor of the MCF present a highly individual variability, an exact pre-operative morphometric study is very important in order to choose the best surgical planning.