Microsurgical anatomy of the sagittal stratum

BACKGROUND

The sagittal stratum (SS) is a critical neural crossroad traversed by several white matter tracts that connect multiple areas of the ipsilateral hemisphere. Scant information about the anatomical organization of this structure is available in literature. The goal of this study was to provide a detailed anatomical description of the SS and to discuss the functional implications of the findings when a surgical approach through this structure is planned.

METHODS

Five formalin-fixed human brains were dissected under the operating microscope by using the fiber dissection technique originally described by Ludwig and Klingler.

RESULTS

The SS is a polygonal crossroad of associational fibers situated deep on the lateral surface of the hemisphere, medial to the arcuate/superior longitudinal fascicle complex, and laterally to the tapetal fibers of the atrium. It is organized in three layers: a superficial layer formed by the middle and inferior longitudinal fascicles, a middle layer corresponding to the inferior fronto-occipital fascicle, and a deep layer formed by the optic radiation, intermingled with fibers of the anterior commissure. It originates posteroinferiorly to the inferior limiting sulcus of the insula, contiguous with the fibers of the temporal stem, and ends into the posterior temporo-occipito-parietal cortex.

CONCLUSION

The white matter fiber dissection reveals the tridimensional architecture of the SS and the relationship between its fibers. A detailed understanding of the anatomy of the SS is essential to decrease the operative risks when a surgical approach within this area is undertaken.

Clinical implications of sagittal stratum damage: Laterality, neuroanatomical developmental considerations, and functional outcomes

Background

The sagittal stratum (SS) is an important white matter (WM) structure that provides the anatomic substrate for cortico-cortical and cortico-subcortical axial interconnections necessary to overcome sensory, cognitive and motor processes. SS damage due to diseases or surgical lesions often results in significant functional losses, mainly involving serious language, visual processing, and cognitive deficits. These risks are maximized in older adults because of age-related WM degeneration.

Methods

In this comprehensive review, the research aims to synthesize research conducted on anatomy-functional roles that concern the SS, damage, and surgical outcomes. This would then separate studies that employed high neuroimaging advanced techniques, such as diffusion tensor imaging, combined with intraoperative mapping performed during awake surgery. Key attention areas will, therefore, be trajectories pointing toward lateralization of the SS tracts, age-related vulnerabilities, and the effectiveness of surgical strategies in preserving SS integrity.

Results

The review indicates that the pattern of SS damage is associated with lateralized deficits stemming from left-sided lesions, while language and vision are affected by right-sided. Older adults, already bearing significant WM degeneration, therefore, stand at a significantly greater risk of overall cognitive decline from compounding losses due to SS damage. However, advanced neuroimaging tools and refined surgical techniques have made the preservation of SS pathways much more effective, reducing long-term deficits.

Conclusion

Intraoperative preservation of SS integrity is crucial for the reduction of functional deficits and enhancement of the outcomes. Customized surgical techniques that consider tract lateralization and age-related changes are required. Further research in this area is needed.

Whole-brain gray matter volume and fractional anisotropy of the posterior thalamic radiation and sagittal stratum in healthy adults correlate with the local environment

The impacts of air pollution, local climate, and urbanization on human health have been well-documented in recent studies. In this study, we combined magnetic resonance imaging (MRI) brain analysis with a questionnaire survey on the local environment in 141 healthy middle-aged men and women. Our findings reveal that a favorable environment is positively correlated with gray matter volume (GMV) in the frontal and occipital lobes, cerebellum, and whole brain, as well as with fractional anisotropy (FA) in the fornix (including the fornix stria terminalis), posterior thalamic radiation (PTR), sagittal stratum (SS), and whole brain. Among these, significant correlations between the local environment and whole-brain and cerebellar GMV, PTR, and SS FA remained after Bonferroni correction. Additionally, the positive relationship between the local environment and whole-brain GMV was further supported by principal component analysis (PCA). This is the first study to demonstrate that healthy adult brain structure, as indicated by GMV and FA values, can be influenced by the local environment.