Anatomical study of insula and its relationship with the adjacent structures

Insular lobe is folded deep in the sylvian fissure, and the transsylvian transinsular approach is one of the most commonly used methods for lesions in the insula, basal ganglia, amygdala, and hippocampus. Hence, it is essential for surgeons to master a specific anatomic knowledge of the insula and its adjacent structures. This study aims to locate the insula, measure relevant parameters, and reduce the occurrence of surgical injury and postoperative complications.

One hundred three individuals (53 males and 50 females) were selected randomly, and magnetic resonance imaging-based morphometric analysis was performed. We located the landmark and measured the parameters related to the transsylvian transinsular approach. The parameters and figures in the sagittal, coronal, and axial planes were used to illustrate the anatomical relationship between the insular lobe and its adjacent structures.

The length of the superior limiting sulcus (line A) was 52.05 ± 3.30 mm in the left and 51.56 ± 2.90 mm in the right. The length of the inferior limiting sulcus (line B) was 48.18 ± 3.01 mm in the left and 48.40 ± 3.34 mm in the right. The length of the anterior limiting sulcus (line C) was 22.64 ± 1.47 mm in the left and 22.50 ± 1.57 mm in the right. The length of the central insular sulcus (line D) was 31.36 ± 2.68 mm in the left and 31.52 ± 2.53 mm in the right. The distance from insular apex to brain surface through sylvian fissure (line E) was 19.26 ± 2.21 mm in the left and 19.36 ± 2.26 in the right. The distance from inferior limiting sulcus to the roof of temporal horn (line J) was 9.75 ± 1.38 mm in the left and 9.66 ± 1.18 mm in the right. The angle (θ), which was formed by line J and the vertical line via the inferior limiting sulcus (line I), was 30.51 ± 3.60 degrees in the left and 30.56 ± 3.11 degrees in the right. The distance from insular apex to the lateral side of putamen (line L) was 10.10 ± 1.59 mm in the left and 10.62 ± 1.39 mm in the right. The distance from insular apex to the middle of genu capsulae internae (line K) was 25.73 ± 1.02 mm in the left and 26.50 ± 1.15 mm in the right. Independent-samples t test showed no significant difference of the means between the right side and the left side.

The statistics in our study can help to understand the complicated anatomical structures of insula and its surrounding area. Moreover, the parameters can increase the feasibility and safety of the surgery via transsylvian transinsular approach.