Anatomic evaluation of the posterior temporal approach via the Heschl's gyrus to the thalamus, internal capsule, and atrium.

Objective: Posterior temporal craniotomy allows for the exposure of the superior surface of the planum temporale. Heschl's gyrus is the most prominent structure of the planum temporale and can be an anatomical landmark to approach deep brain structures such as the internal capsule, lateral thalamus, and ventricular atrium.

Methods: Ten human cadavers' heads underwent a posterior bilateral temporal craniotomy and the microsurgical dissection of Heschl's gyrus was performed and variables were measured with a neuronavigation system and statistically analyzed.

Results: The mean distance between the keyhole and Heschl's gyrus was 61.7 ± 7.3 mm, the mean distance between the stephanion to Heschl's gyrus was 40.8 ± 6.0 mm, and the mean distance between the temporal lobe and Heschl's gyrus was 54.9 ± 6.9 mm. The length of Heschl's gyrus was 24 ± 7.5 mm, and the inclination angle in the axial plane was 20.0 ± 3.7° having the vertex as its deepest point as the base on the surface of the temporal plane. From Heschl's gyrus, the distance from the surface to the internal capsule was 29.1 ± 5.6 mm, the distance to the lateral thalamus was 34.8 ± 7.3 mm, and the distance to the ventricular atrium was 39.6 ± 7.2 mm. No statistical difference was found between the right and left sides.

Conclusions: Through a posterior temporal craniotomy, the temporal planum is exposed by opening the Sylvian fissure, where Heschl's gyrus can be identified and used as a natural corridor to approach the internal capsule, the ventricular atrium, and the lateral thalamus.