Midbrain volume in brain herniation: A volumetric analysis in operative traumatic brain injury

This study primarily aimed to assess the volumetric attributes of the midbrain and perimesencephalic structures preoperatively and following surgical interventions in patients diagnosed with brain herniation secondary to traumatic brain injury (TBI).

We evaluated patients based on radiological findings and clinical symptoms indicative of brain herniation. We performed semi-automated segmentation of the intracranial structures most relevant to trauma and of interest for the current study, such as hematoma, ventricles, midbrain, and perimesencephalic cisterns. Using preoperative and postoperative computed tomography scans, we measured and analyzed the volume of these structures. Patients were grouped based on their discharge Glasgow Coma Scale (GCS) scores: GCS 15 and non-GCS 15.

From May 2018 to February 2020, we included 20 patients in the study. Our volumetric analysis revealed that preoperative midbrain volume (5.84 cc vs. 4.37 cc, P = 0.034) was a significant differentiator between GCS 15 and non-GCS 15 groups. Preoperative midbrain volume remained significant in univariate (odds ratio [OR] = 2.280, 95% confidence interval (CI) = 1.126-5.929, P = 0.04) and multivariate logistic regression analysis (adjusted OR = 3.204, 95% CI = 1.228-12.438, P = 0.038) even after adjusting for age, sex, and admission GCS score. We identified a cut-off point of 4.86 ccs in preoperative midbrain volume, which demonstrated a discriminatory performance of 0.788 area under the receiver operating characteristic curve, 80.0% accuracy, 77.8% sensitivity, and 81.8% specificity between the two groups.

Our findings suggest that patients presenting with lesser midbrain compression preoperatively tended to have improved clinical outcomes postsurgery. Thus, we propose that this preoperative midbrain volume cut-off point holds predictive value for clinical outcomes within our cohort.