Türe, Uğur

British anatomical physiology in the early 19th century evolved from the work of William Harvey, Thomas Willis, and William Hunter, who emphasized cerebral functional localization, integrating physiology and anatomy. This novel perspective was championed by Herbert Mayo (1796–1852). A student of Charles Bell at the Middlesex Hospital in London, Mayo subsequently became a surgeon there in 1818 and later a professor of anatomy and surgery. His experiments on the motor functions of the seventh cranial nerve and sensorimotor functions of the fifth cranial nerve brought him renown. Mayo, inspired by Johann Christian Reil, also conducted the first accurate brainstem dissections, developed innovative tissue preservation methods, and provided detailed descriptions of key fiber tracts. Mayo’s 1822–1823 Anatomical and Physiological Commentaries and 1827 A Series of Engravings Intended to Illustrate the Structure of the Brain and Spinal Chord in Man accurately depicted the corona radiata, cerebellar peduncles, and uncinate fascicle. In his 1842 book, The Nervous System and Its Functions , Mayo discussed the localization of higher brain functions. His dissections remained unmatched until Josef Klingler’s work in 1934. Despite the quality of his work, Mayo has been largely neglected, possibly because of his tumultuous relationship with Bell and later professional difficulties. Nevertheless, Mayo significantly contributed to white matter anatomy and led the search for cerebral localization, subsequently impacting neurosurgery. This article examines his life and work.

OBJECTIVE The term "sagittal stratum" was coined by Heinrich Sachs in 1892 to define a parasagittally oriented white matter layer at the temporo-occipital cortex. Although this term has been widely used for more than 100 years, the description, classification, borders, and involved fibers of the structure vary among authors and remain imprecise. Through fiber microdissection and tractography, the authors aimed to define the sagittal stratum and resolve the uncertainty by revealing the relationship of this structure to other cerebral white matter pathways and the orientation of fibers in it. METHODS Twenty postmortem human cerebral hemispheres were prepared according to Klingler’s method. Fiber dissections were performed under a surgical microscope and with microsurgical techniques. The results of dissection at each step were photographed with 2D and 3D imaging techniques, and 3D photogrammetry techniques were used to create a 360° model. Diffusion tensor imaging and 7T high-resolution MRI were used to confirm the findings. RESULTS This study revisited the 3D organization of white matter tracts in the sagittal stratum through fiber microdissection and tractography. The microneuroanatomical structure of the sagittal stratum and its special organization with fibers from all three fiber systems are demonstrated. The authors’ findings revealed that the sagittal stratum has two layers consisting of four different fiber tracts. Its external layer consists of a long association fiber and a commissural fiber, while its internal layer consists of intertwined projection fibers, including temporo-parieto-occipitopontine fibers and the posterior thalamic peduncle. Detailed microdissection also showed the location of the posterior thalamic peduncle in the most medial site of all posterior hemispheric projection fibers. CONCLUSIONS The structure of the sagittal stratum is distinctive in that it contains all three main fiber systems: association, commissural, and projection. Because of its expansive location in the temporal and occipital lobes, it can be damaged by most neurosurgical pathologies and procedures. The authors emphasize the significance of preserving the sagittal stratum during surgical interventions while also challenging the notion of a "silent" brain, suggesting that the current inability to fully comprehend cerebral function contributes to this misconception. Detailed knowledge of the complex white matter anatomy of the sagittal stratum can guide neurosurgeons in surgical planning and the selection of appropriate surgical approaches with intraoperative orientation for safe surgery and less comorbidity.