What's your name again? A review of the superior longitudinal and arcuate fasciculus evolving nomenclature

Abstract

Studies of the superior longitudinal fasciculus (SLF) have multiplied in recent decades owing to methodological advances, but the absence of a convention for nomenclature remains a source of confusion. Here, we have reviewed existing nomenclatures in the context of the research studies that generated them and we have identified their agreements and disagreements. A literature search was conducted using PubMed/MEDLINE, Web‐of‐Science, Embase, and a review of seminal publications, without restrictions regarding publication date. Our search revealed that diffusion imaging, autoradiography, and fiber dissection have been the main methods contributing to tract designation. The first two have been particularly influential in systematizing the horizontal elements distant from the lateral sulcus. Twelve approaches to naming were identified, eight of them differing considerably from each other. The terms SLF and arcuate fasciculus (AF) were often used as synonyms until the second half of the 20th century. During the last 15 years, this has ceased to be the case in a growing number of publications. The term AF has been used to refer to the assembly of three different segments, or exclusively to long frontotemporal fibers. Similarly, the term SLF has been employed to denote the whole superior longitudinal associative system, or only the horizontal frontoparietal parts. As only partial correspondence can be identified among the available nomenclatures, and in the absence of an official designation of all anatomical structures that can be encountered in clinical practice, a high level of vigilance regarding the effectiveness of every oral or written act of communication is mandatory.

Supramarginal Gyrus and Angular Gyrus Subcortical Connections: A Microanatomical and Tractographic Study for Neurosurgeons

“…In this study, these four segments were named as three horizontal segments numbered superior longitudinal fasciculus I(SLF-I), SLF-II, SLF-III and AF [ 18 ]. In studies with alternative nomenclature, it has been accepted that these fiber groups are separate anatomical structures [ 1 ].…”

“…Neuroradiology and neuroanatomical studies have been gaining importance in recent years in neurology, neurosurgery and basic neuroscience in understanding white matter structure [ 1 ].…”

“…The supramarginal gyrus (SMG) and the posterior superior part of the temporal lobe, which we want to focus on, are important regions for the language of the white matter pathways [ 1 ]. Our aim was to focus on the SMG and angular gyrus AnG, which are important areas for speech paths, and to examine the subcortical connections (superior longitudinal fasciculus II (SLF II), superior longitudinal fasciculus III (SLF III), arcuat fasciculus (AF), middle longitudinal fasciculus (MdLF)) of this region only microanatomically and through the DTI/FT by preserving the pre-central and post-central gyrus, creating a topographic dominance, and to provide a perspective to neurosurgeons.…”

The influence of regions of interest on tractography virtual dissection protocols: general principles to learn and to follow

“…For a neuroanatomist? More than any other protagonist of the current study, the neuroanatomist faces the crucial question of the definition and denomination of a given white matter pathway, especially when confronted with the question of its virtual dissection in tractography (Mandonnet et al, 2018;Panesar and Fernandez-Miranda, 2019;Porto de Oliveira et al, 2021;Vavassori et al, 2021).…”

The Arcuate Fasciculus and language origins: Disentangling existing conceptions that influence evolutionary accounts

“…In the first part of this review, we tackle a major challenge that confronts present-day researchers seeking to investigate the AF: There is currently poor consensus about the anatomical definition of the AF (e.g., where it terminates in the frontal and temporal lobes), and its nomenclature (e.g., whether it is considered part of, or distinct from the Superior Longitudinal Fasciculus (SLF) or Middle Longitudinal Fasciculus (MdLF)). This is primarily driven by the fact that, since its discovery, the methodologies used to study and delineate the AF (e.g., blunt dissections, diffusion MRI tractography, neural tract-tracing) have been constantly evolving, resulting in different descriptions and naming of the AF (e.g., Oliveira et al, 2021;Vavassori et al, 2021). As such, we start the current review with an overview of how the definition and nomenclature of the AF have evolved along with the emergence of different methodologies in the field.…”