Neurosurg Focus 28 (2):E2, 2010 The cerebral sulci and gyri GUILHERME CARVALHAL RIBAS, M.D. Department of Surgery, University of São Paulo Medical School—LIM-02, Hospital Israelita Albert Einstein, São Paulo, Brazil The aim of this study was to describe in detail the microanatomy of the cerebral sulci and gyri, clarifying the nomenclature for microneurosurgical purposes. An extensive review of the literature regarding the historical, evo- lutionary, embryological, and anatomical aspects pertinent to human cerebral sulci and gyri was conducted, with a special focus on microneuroanatomy issues in the field of neurosurgery. An intimate knowledge of the cerebral sulci and gyri is needed to understand neuroimaging studies, as well as to plan and execute current microneurosurgical procedures. (DOI: 10.3171/2009.11.FOCUS09245) KEY WORDS • brain gyrus • brain mapping • brain sulcus • cerebral cortex • cerebral lobe LTHOUGH there is no strict relationship between atized surgical procedure.23 As early as ~ 10,000 years brain structure and function, current knowledge ago, cranial trephination was performed “successfully” shows that the two are closely interrelated. The (that is, with new bone formation after the procedure) in Abrain is divided into regions and subdivided into more the neolithic cultures of Europe, and there are findings specific zones, although there is increasing evidence that dating to 2000 years ago in South America, where the the borders between those zones are much blurrier than practice was particularly common in the pre-Incan and was previously thought.35 Therefore, it is essential that Incan cultures of Peru.26 Despite this historical context, neurosurgeons have an intimate knowledge of brain mi- knowledge of the anatomy of the brain in general and of croanatomy, not only to improve their understanding of its surface in particular is quite recent.23,26,38 neuroimaging studies, but also to allow them to plan and The first significant contributions to neuroanatomy perform neurosurgical procedures while considering par- were made during the Golden Age of Greek civilization. ticular brain functions. Hippocrates (460–370 BC), who is considered the father In the relatively new field of microneurosurgery, the of medicine, posited that the brain was responsible for development and use of the transcisternal, transfissural, mental activities and convulsions, whereas some impor- and transsulcal approaches80,84,85 have established the sul- tant Greek philosophers, such as Aristotle (384–322 BC), ci as fundamental landmarks on the brain surface. The believed that the heart was the seat of intellectual, per- well-known variability in cortical function1,2,17,47,53,75 calls ceptual, and related functions.23 for the aid of cortical mapping techniques to precisely In Alexandria, Egypt, then a Greek city that was par- identify specific sites related to cortical function. Never- ticularly advanced in cultural terms, human dissections, theless, detailed knowledge of the structure and form of which had until then been forbidden in Greek society, be- the cerebral sulci and gyri continues to be mandatory for gan to be performed in ~ 300 BC. There, Herophilus (ca. neuroimaging as well as intraoperative guidance. Once 335–280 BC), a follower of Hippocrates and considered identified, the cerebral sulci can be used by the neurosur- the father of anatomy, studied the brain and its ventricles geon either as microneurosurgical corridors or simply as as well as the cerebellum, distinguished the motor nerves cortical landmarks.61,62 from sensory nerves, and described the confluence of A review of the literature regarding the historical, the cranial venous sinuses, whose name was originally evolutionary, embryological, and anatomical aspects of derived from his own name (“torcular herophili”). One the cerebral sulci and gyri was conducted to establish of his contemporaries and compatriots, Erasistratus (ca. detailed descriptions of these structures, as well as their 310–250 BC) studied the comparative anatomy of the groupings in the brain lobes, for microneurosurgical pur- brain surface and had already hypothesized that there poses. was a relationship between intellect and gyral complex- ity. 23 Historical Aspects Despite the importance of the Greek contribution, the Interest in the human brain dates back to antiquity, most widely known anatomical descriptions of classical and cranial trephination is probably the oldest system- antiquity are those of Galen (130–199 AD), who studied Neurosurg Focus / Volume 28 / February 2010 1 Unauthenticated | Downloaded 09/29/21 05:29 PM UTC G. C. Ribas FIG. 1. Renaissance illustrations of the brain sulci and gyri with a configuration that resembles the small bowel disposal. Left: By Andreas Vesalius, 1543.65 Right: By Raymond Vieussens, 1684. Reprinted from Vieussens R: Nevrographia Universalis. Frankfurt: Georgium Wilmelmum Künnium, 1690. anatomy in Alexandria, returned to Greece, and finally highly regarded Cerebri Anatome, which featured il- settled in Rome, where he was surgeon to the gladiators lustrations by the renowned architect Christopher Wren and performed dissections, primarily on animals.38 (1632–1723). In addition to describing the group of ar- The Middle Ages, roughly from the 4th to the 14th teries surrounding the base of the brain (now known as century, is well known to have been poor in terms of scien- the circle of Willis), Willis introduced a variety of terms, tific developments in general. Although there were some including neurology, hemisphere, lobe, corpus striatum, contributions from individuals in certain regions—in the peduncle, and pyramid, and showed a relationship be- Arabic world, from Avicenna (980–1037 AD), who some tween the cerebral gyri and memory.23 authors credit with the first representation of the brain, Raymond Vieussens (1644–1716) published the fa- made in ~ 1000 AD;69 and in Europe, from Mundino dei mous Neurographia Universalis in 1690,76 describing in Luzzi,69 who, in 1316, performed the first human dissec- detail the “centrum semiovale” and other cerebral struc- tions reported in Europe—anatomical studies were quite tures but still illustrating the brain surface similarly to the limited, principally because of the prohibition against the small bowel.23,69 Godefroid Bidloo clearly displayed the dissection of human cadavers. During the Renaissance, central sulcus in his atlas and textbook published in 1685,69 this prohibition was finally lifted, which led to the progres- and subsequently Félix Vicq d’Azyr (1748–1794), famous sive development of all anatomical knowledge. The most for describing the mamillothalamic tract, also described preeminent figure in this field was undoubtedly Andreas the precentral and postcentral convolutions and coined Vesalius (1514–1564), professor of anatomy and surgery at the term uncus.69 Later, Johann Christian Reil (1759–1813) the University of Padua, who published the textbook De provided a comprehensive description of the insula, which Humanis Corporis Fabrica,65 in which he pointed out the had been identified by Bartholin in 1641.23,69 In 1827 Her- many errors made by Galen, outlined the distinctions be- bert Mayo, student of the renowned anatomist and surgeon tween white matter and gray matter, and described various Charles Bell (1774–1842), published illustrations of the other aspects of brain anatomy.23,38,69 corona radiata and the internal capsule as well as other Although Vesalius provided intricate anatomical de- important tracts.74 In 1829, the Italian anatomist Luigi Ro- scriptions, especially of the ventricular cavities and their lando (1773–1831) published his text Della Strutura degli related deep neural structures, illustrations of the brain Emisferi Cerebrali,63 becoming the first author to accurate- convolutions, including those of Vesalius, continued to ly portray the cerebral sulci and convolutions, including the show them in a chaotic arrangement. Among other nota- central sulcus, which later received his name and is still ble Renaissance authors were the great Leonardo da Vinci occasionally referred to as the fissure of Rolando.23,74 (1472–1519), who, in addition to his elegant descriptions It was the German physiologist Friedrich Arnold of the brain ventricles, created beautiful illustrations of (1803–1890) who first used the terms frontal, parietal, the brain surface,12 and Julius Casserius (ca. 1545–1616), and occipital to describe the cranial bones. In a text pub- who depicted the brain convolutions, which were at that lished in 1851,5 Arnold recognized only the sylvian fis- time understood to resemble the small bowel (Fig. 1).69 sure and the parietooccipital sulcus (then known as the In 1663 Franciscus de la Böe (1614–1672), also known internal perpendicular fissure) as anatomically constant as Dr. Sylvius, described the lateral cerebral sulcus, which sulci. He did not recognize any organized arrangement therefore came to be known as the sylvian fissure.23 among the cerebral gyri, and he described the temporal In 1664 Thomas Willis (1621–1675) published his region as an anterior extension of the occipital region. 2 Neurosurg Focus / Volume 28 / February 2010 Unauthenticated | Downloaded 09/29/21 05:29 PM UTC The cerebral sulci and gyri TABLE 1: Mammalian cortical development* Primitive Cortex: Allocortex Medial Cortical Ring: Mesocortex Lateral Cortical Ring: Isocortex (3 layers) (6 layers) (6 organized layers) limbic structures paralimbic structures & insula parainsular & other neocortical structures