The occipital lobe convexity sulci and gyri

Laboratory investigation

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Object

The anatomy of the occipital lobe convexity is so intricate and variable that its precise description is not found in the classic anatomy textbooks, and the occipital sulci and gyri are described with different nomenclatures according to different authors. The aim of this study was to investigate and describe the anatomy of the occipital lobe convexity and clarify its nomenclature.

Methods

The configurations of sulci and gyri on the lateral surface of the occipital lobe of 20 cerebral hemispheres were examined in order to identify the most characteristic and consistent patterns.

Results

The most characteristic and consistent occipital sulci identified in this study were the intraoccipital, transverse occipital, and lateral occipital sulci. The morphology of the transverse occipital sulcus and the intraoccipital sulcus connection was identified as the most important aspect to define the gyral pattern of the occipital lobe convexity.

Conclusions

Knowledge of the main features of the occipital sulci and gyri permits the recognition of a basic configuration of the occipital lobe and the identification of its sulcal and gyral variations.

Article Information

Address correspondence to: Raphael Vicente Alves, M.D., Institute of Neurological Sciences, Praça Amadeu Amaral, 27 andar 5, São Paulo, SP, Brasil, 01327-010. email: raphaelvalves@yahoo.com.br.

Please include this information when citing this paper: published online February 17, 2012; DOI: 10.3171/2012.1.JNS11978.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    A: Left occipital lobe convexity. It is possible to identify in this specimen the most common occipital convexity sulci described in the literature. The blue line represents the parietooccipital-preoccipital line. The lateral occipital sulcus is not continuous with the superior temporal sulcus. B: Left occipital lobe convexity. The distal extremity of the intraparietal sulcus is at the level of the parietooccipital-preoccipital line and reaches the transverse occipital sulcus at this point C: Posterior view showing the connection of the transverse occipital sulcus and intraoccipital sulcus. These 2 hemispheres show that the connection occurs at a right angle (resembling the letter T). On the left side, the distal extremity of the intraoccipital sulcus courses inferiorly; thus the superior branch of the transverse occipital sulcus is coursing in the direction of the occipital pole. On the right side it is possible to identify the most common pattern of connection between the transverse occipital and the intraoccipital sulci. D: Right posterior view. There is an angle of approximately 45° between the branches of the transverse occipital sulcus (as in the letter Y). E: Right posterior view. There is an angle of approximately 45° between the branches of the transverse occipital sulcus, but the inferior branch of the transverse occipital sulcus has the same course as the intraoccipital sulcus toward the occipital pole. AOS = anterior occipital sulcus; IOS = intraoccipital sulcus; IPS = intraparietal sulcus; LOS = lateral occipital sulcus; LS = lunate sulcus; STS, superior temporal sulcus; TOS = transverse occipital sulcus.

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    A: Posterolateral view of the right hemisphere. The lateral occipital sulcus is continuous with the superior temporal sulcus. The calcarine fissure is identified reaching the lateral occipital surface on the left hemisphere. The lateral occipital sulcus is located in relationship with the calcarine fissure when it is identified reaching the occipital convexity. B: Posterolateral view of another specimen. The lateral occipital sulcus is continuous with the inferior temporal sulcus. CF = calcarine fissure; ITS = inferior temporal sulcus.

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    A: Lateral view of the left hemisphere. The anterior occipital sulcus partially separates the occipital lobe from the temporal lobe. B: This specimen has the 2-gyrus pattern. The lateral aspect of the occipital lobe is divided into 2 main parts by the lateral occipital sulcus. The superior occipital gyrus is highlighted in green, and the inferior occipital gyrus is highlighted in yellow. C: The same specimen as in Fig. 2A. The superior occipital gyrus (green) and inferior occipital gyrus (yellow) are separated by the lateral occipital sulcus.

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    A: Posterolateral view of the right hemisphere. The inferior branch of the transverse occipital sulcus has the same course as the intraoccipital sulcus and is a continuation of that sulcus toward the occipital pole. It reaches the lateral occipital sulcus next to the occipital pole. B: This specimen has the 3-gyrus pattern. The lateral aspect of the occipital lobe is divided into 3 main parts by the lateral occipital sulcus and the inferior branch of the transverse occipital sulcus. The superior occipital gyrus (green), the inferior occipital gyrus (yellow), and the middle occipital gyrus (blue) are highlighted.

  • View in gallery

    A: Left occipital lobe convexity. In nonatrophic specimens with anatomical variations, it is sometimes difficult to recognize the basic morphology of the superolateral aspect of the occipital lobe. In this hemisphere, a small and less well-defined transverse occipital sulcus is merged with the lunate sulcus, with the superior and middle occipital gyri being separated by this connection. B: Highlighted specimen showing the superior occipital gyrus (green), the inferior occipital gyrus (yellow), and the middle occipital gyrus (blue).

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    A: Posterolateral view of the left hemisphere. The 3-gyrus pattern was identified in only 30% of the specimens, and in these cases the middle occipital gyrus seemed to be the most posterior part of the angular gyrus posterior to the parietooccipital-preoccipital line. Infrequently, the middle occipital gyrus exhibits a distinct configuration such as illustrated in this figure. B: The same specimen with highlighting distinguishing the superior occipital gyrus (green), inferior occipital gyrus (yellow), and middle occipital gyrus (blue). Ang. gyrus = angular gyrus; SMG = supramarginal gyrus.

  • View in gallery

    A: Posterolateral view of the left hemisphere. In this specimen, the lunate sulcus is identified, and it partially isolates the occipital pole from the superior and inferior occipital gyri. It is possible to identify gyral connections with the superior and inferior occipital gyri (asterisk). B: Posterior view of another left hemisphere. Frequently the superior and the inferior occipital gyri converge posterior to the distal extremity of the lateral occipital sulcus to form the occipital pole. IOG = inferior occipital gyrus; SOG = superior occipital gyrus.

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    Illustrative drawings based on descriptions and/or images from the following authors who have studied the occipital lobe convexity: Testut and Jacob (A), Flores (B), Williams and Warwick (C), Ono (D), Rothon (E), Duvernoy (F), and Yaşargil (G). TO = inferior transverse occipital; MOG = middle occipital gyrus; MTO = middle transverse occipital; SOS = superior occipital sulcus; STO = superior transverse occipital.

  • View in gallery

    Illustrative drawing showing the most characteristic and consistent patterns of the occipital sulci and gyri found in this study to compare with the literature descriptions. Left: The 2-gyrus pattern. Right: The 3-gyrus pattern. CS = central sulcus; SF = sylvian fissure.

References

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