COLLATERAL SULCUS MORPHOLOGY IN NORMAL INDIVIDUALS IN MAGNETIC RESONANCE IMAGING OF BRAIN

Collateral sulcus (CS) develops during early stage of the gestation and is well formed at 23rd weeks during pregnancy. The temporal part of the CS continues with limbic ssure and forms a cortical fold. This folding creates a protrusion inside the temporal horn of the lateral ventricle that is named the collateral eminence. The occipital part of CS, which is named as the posterior transverse CS, forms a border between the lingual gyrus and lateral occipitotemporal gyrus. The CS and the occipitotemporal sulcus (OTS) are the prominent landmarks that separate the mesial and lateral temporal lobe. Collateral sulcus angle and depth are used as indirect criteria to look for presence or absence of incomplete hippocampal inversion. AIM: To describe the normal morphological patterns of collateral sulcus in magnetic resonance imaging of brain. OBJECTIVES: 1. To document the range, mean, SD of depth of the collateral sulcus. 2. To determine the collateral sulcus angle range, mean, SD in normal MRI brain. Materials and Methods: A retrospective and prospective observational study was conducted in a tertiary centre using T1 3D MRI images of brain morphological pattern of collateral sulcus in normal individuals for whom MRI brain was normal otherwise was recorded. The MRI images of a total of 250 individuals qualied for the study. Collateral sulcus angle was calculated angle between line drawn horizontal and along depth of collateral sulcus. Results: We arrived at normal distribution of collateral sulcus angle and the mean Collateral Sulcus Angle Degree of the studied patients (N=250) on Right side was recorded as 38.66 degrees with standard deviation of 10.811 degrees. The mean Collateral Sulcus Angle Degree of the studied patients (N=250) on left side was recorded as 42.11 degrees with standard deviation of 13.09 degrees. In current study, we have observed that in all patients with collateral sulcus angle >65 degrees, depth of the collateral sulcus of the corresponding side is </= 7mm. (Mean collateral sulcus depth on right side is 10.1mm and on left side is 10.3mm). Vertical collateral sulcus (> 70 degree from horizontal) and near vertical collateral sulcus (65degree to 70 degree) are observed even with normally appearing properly inverting hippocampus. (Such verticality being possible by shallow depth (as observed in our study) of those collateral sulci). Conclusion: Since collateral sulcus angle and depth are used as indirect criteria to look for presence or absence of incomplete hippocampal inversion, we tried to establish their normal range, mean and SD in 250 normal MRI Brains. We found an abnormal collateral sulcus angle (>70 degrees) in one normal MRI brain study out of 250 study population. Vertical collateral sulcus can be seen as an isolated nding without incomplete hippocampal inversion especially if the collateral sulcus is of shallow depth.