Massa intermedia of the thalamus: an anatomical study using magnetic resonance imaging

Abstract

Purpose: Few studies have explored the morphology of massa intermedia (MI). The aim of the present study was to characterize it using magnetic resonance imaging (MRI). Methods: A total of 205 patients were enrolled in this study. Following initial examinations with conventional MRI sequences, thin-slice coronal and sagittal T2-weighted imaging was performed. For MI localization, the third ventricle was arbitrarily divided into nine areas on the midsagittal image. Results: MI was identified in 93% of the total patients—89% in male and 91% in female patients. Among them, 68% showed a single, styloid-shaped MI with variable thickness and cross sectional configuration, followed by broad and double MIs that were found in 18% and 10% patients, respectively. In the anteroposterior dimension, 99% of the MIs were identified in the middle third area, followed by the posterior third area. In the supero-inferior dimension, 95% of the MIs were identified in the middle third area, followed by the upper third area. With a significant difference, a broad MI was more frequently found in women than in men. Conclusions: MIs are commonly located in the middle third of the third ventricle as a single commissure with high morphological variability. Compared to men, women may have a well-developed, broader MI.