Surgical neuroanatomy and language

Abstract

Fiber dissection study is an old technique originating in the 17th century and reached its apex with the sophisticated atlas of Ludwig and Klingler in the mid 20th century. Recent advancements in neuroscience, however, have once again highlighted the macroscopic anatomy of the brain, seeking a more precise and detailed map of the cortices and white matters from a new perspective where the brain is organized into a complex network of multiple distinct neural circuits, working more like a dynamic network with plasticity, as opposed to the traditional rigid and localizationistic view. The neural basis of language had once been considered as a simple model consisting of the Broca’s area, the Wernicke’s area, and the arcuate fasciculus connecting the above two cortical areas. However, it has grown to be understood as a larger and more complex model, in which language is processed through two distinct pathways, the dorsal stream and the ventral stream. The superior longitudinal fasciculus/the arcuate fasciculus make up the backbone of the dorsal stream and are associated with phonological processing. The ventral stream consists of a network supported by the inferior fronto-occipital fasciculus and intratemporal pathways and is associated with semantic processing. The frontal aslant tract is a deep frontal tract connecting the supplementary motor area and the Broca’s area and it is associated with the driving of language. It is necessary for every neurosurgeon to have a basic knowledge of the neural basis of language, including both the anatomical and functional aspects for safer surgical planning, and preservation of language.