Structural connectivity of the human massa intermedia: A probabilistic tractography study

Absence of the interthalamic adhesion (ITA) as a neuroanatomical association or risk factor for neuropsychiatric disorders: A systemic review and meta-analysis

Background

This study aimed to provide an up-to-date account of the frequency of "the absence of interthalamic adhesion (AITA) as a risk factor or association" in healthy subjects and neuropsychiatric patients. Owing to the increased interest in the contribution of ITA to neurological function in previous literature, a meta-analysis of its frequency and sex dependency is required.

Aim

This study aimed to study whether the AITA is associated with neuropsychiatric disorders.

Settings and Design

This study is a meta-analysis and systemic review.

Methods and Material

Literature searches were conducted in PubMed, Web of Science, and Google Scholar using the keywords "interthalamic adhesion," "massa intermedia," "adhesio interthalamica," and "adhesion" along with the Boolean operators (OR, AND, and NOT). Three reviewers independently assessed the abstracts and full texts for validation based on the inclusion criteria. The meta-analysis was performed using Microsoft Excel 2019 for descriptive studies and RevMan 5.2 for comparative studies.

Results

The incidence of absent ITA was 15.3% in healthy subjects and 28.76% in neuropsychiatric subjects. The relative probability of AITA was 2.30 [95% confidence interval (CI), 1.96-2.70] in neuropsychiatric illness. Healthy men were 1.91 times more likely, and men with neuropsychiatric disorders were 1.82 times more likely to have absent ITA than women.

Conclusions and Relevance

In this study, a consistent association of AITA with psychiatric disorders was observed, rendering the condition to be treated as an associated risk factor affecting the function of the habenula nuclear complex via the stria medullaris thalami. A cohort or longitudinal study is needed to compare the incidence of psychiatric disorders in individuals with or without ITA and to calculate the attributed risk.

The Prevalence, Location, and Dimensions Of Interthalamic Adhesions and Their Clinical Significance: Corpse Brain Analysis

Background  Interthalamic adhesion (ITA) or massa intermedia is a midline rod-like neural structure interconnecting the medial surfaces of two thalami. Its absence is considered as a midline defect associated with schizophrenia spectrum disorder. The present study aimed to determine the prevalence, location, and dimensions of the ITA in South Asian brains. Materials and Methods  One hundred midsagittal sections of adult cadaveric brains were examined for the presence or absence of ITAs, their location about the lateral wall of the third ventricle, and their dimensions. Results  ITA was found in 86 sections. In two cases, it was double. There was no significant relationship between the incidence of ITAs and sex ( p  > 0.05). The ITA was most commonly located in the anterosuperior quadrant. The horizontal diameter was 4.61 ± 1.17 mm, and the vertical diameter was 3.10 ± 0.78 mm. In all cases, the horizontal diameter was longer than the vertical. The average area of the ITA was significantly larger in females (17.56 ± 5.26 mm ² ) than in males (13.62 ± 5.22 mm ² ) ( p  = 0.025). Conclusion  Presence of ITA is common in South Asian brains, with usual location in the anterosuperior quadrant of the lateral wall of the third ventricle. The cross-sectional area of the ITA was significantly larger in females than in males. No correlation was found between the surface area of the ITA and the length of the third ventricle.

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

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.

Structural connectivity of the human massa intermedia: A probabilistic tractography study

The role of massa intermedia (MI) is poorly understood in humans. Recent studies suggest its presence may play a role in normal human neurocognitive function while prior studies have shown the absence of MI correlated with psychiatric disorders. There is growing evidence that MI is likely a midline white matter conduit, responsible for interhemispheric connectivity, similar to other midline commissures. MI presence was identified in an unrelated sample using the Human Connectome Project database. MI structural connectivity maps were created and gray matter target regions were identified using probabilistic tractography of the whole brain. Probabilistic tractography revealed an extensive network of connections between MI and limbic, frontal and temporal lobes as well as insula and pericalcarine cortices. Women compared to men had stronger connectivity via their MI. The presented results support the role of MI as a midline commissure with strong connectivity to the amygdala, hippocampus, and entorhinal cortex.