Object: An extended retrosigmoid approach can offer sufficient space for clip reconstruction
of high-riding posterior inferior cerebellar artery aneurysms. We conducted a quantitative
anatomical analysis on the glossopharyngo–cochlear triangle (GCT) and structures within
it.
Methods: Extended retrosigmoid craniotomies were performed on ten sides of cadaveric heads,
and the GCT was identified in each specimen. The length of the base and the area of
the GCT were measured. The depth of the vertebrobasilar system and the abducens nerve
to the GCT were measured. The proximal and distal exposable and controllable points
on the vertebrobasilar system were identified. The length from those points to the
dural entry point of the vertebral artery were measured, and the superoinferior distance
from those points to the inferior edge of the foramen magnum were recorded to establish
approach algorithms based on the preoperative imaging. Other factors related to accessibility
via the GCT were investigated.
Results: The mean (±SD) area of the GCT was 45.7 ± 12.55 mm2. Through the GCT, the mean depths of the proximal exposable point, proximal controllable
point, distal controllable point, and distal exposable point of the vertebrobasilar
system were 12.2 ± 4.79, 14.7 ± 5.22, 18.9 ± 3.68, and 22.3 ± 4.01 mm, respectively;
the mean depth of the abducens nerve was 14.3 ± 1.42 mm. The mean lengths between
the dural entry point of the vertebral artery to the proximal exposable point, proximal
controllable point, distal controllable point, and distal exposable point of the vertebrobasilar
system were 30.5 ± 8.09, 33.8 ± 9.00, 43.1 ± 8.74, and 48.0 ± 7.86, respectively;
the mean superoinferior distances from the foramen magnum to those points were 23.1 ± 7.39,
24.7 ± 8.25, 30.0 ± 9.56, and 32.6 ± 7.79 mm, respectively. The lower segment of the
vertebrobasilar system was more superficial in the setting of a high-lying vertebrobasilar
junction (VBJ) than a low-lying VBJ.
Conclusion: We describe the parameters of the GCT in an extended retrosigmoid approach for high-riding
posterior inferior cerebellar artery aneurysms and evaluate the spatial relationship
of the neurovascular structures within it, its relationship to the position of the
vertebrobasilar junction, and the effect of a protruding jugular tubercle on this
approach. Finally, two potential algorithms are offered for preoperative patient selection.
