QUANTITATIVE MORPHOLOGICAL ANALYSIS OF THE HUMAN INSULAR CORTEX: A CADAVERIC STUDY

Introduction and Aim: The insular cortex, a concealed fifth lobe of the brain, exhibits significant variability in its gross anatomical organization within the operculoinsular compartment of the Sylvian fissure. This study aimed to comprehensively characterize the morphological patterns and morphometric features of the insular gyri and sulci in a cohort of human cadaveric cerebral hemispheres. Materials and Methods: Fifty-eight formalin-fixed human cerebral hemispheres were meticulously examined to identify variations in the gyri and sulci of the insular cortex. The lengths of these structures were precisely measured using a digital vernier caliper. This investigation was conducted in the Department of Anatomy at Gandhi Medical College, Bhopal. Results: Morphological analysis revealed both typical and variant insular patterns, including discontinuous sulci and fused gyri. Among the observed variations (21%, 85/406 gyri), bifid gyri were most frequent (10.3%, 44/406), particularly affecting the anterior short gyrus (41%, 18/44). Hypoplastic gyri constituted 7.63% (31/406) of variations and were most commonly found in the middle short gyri (58%, 18/31). Trifid gyri were observed in 2.46% (10/406) of cases. Notably, transverse gyri were present in 22.41% (13/58) and accessory gyri in 65.51% (39/58) of hemispheres, while both were absent in 32.76% (19/58). The mean lengths of the insular gyri were: anterior short (24.54mm), middle short (25.04mm), posterior short (34.08mm), anterior long (36.87mm), and posterior long (37.1mm). The mean lengths of the insular sulci were: central insular (35.3mm), superior periinsular (52.48mm), anterior periinsular (24.5mm), inferior periinsular (26.4mm), and posterior periinsular (12.81mm). Conclusion: This study highlights the considerable morphological variability of the insular gyri, with bifid, trifid, and hypoplastic patterns being prevalent. The presence of transverse and accessory gyri, primarily in the anterior insula, contributes to variations in the total number of gyri, making the anterior lobule generally larger but with shorter gyri compared to the posterior lobule. These detailed morphological and morphometric findings of the insular cortex are crucial for neurosurgical planning and understanding individual anatomical differences.