The occipital lobe, the smallest of the cerebral lobes, has three surfaces—dorsolateral, medial, and inferior. Because of the curvilinear aspect of the junction of the posterior falx cerebri and the tentorium cerebelli, the junction of the medial and inferior surfaces of the occipital lobe is somewhat ill defined. Histologically, the lobe is comprised primarily of the three cytoarchitectonic areas, 17, 18, and 19 of Brodmann.

The dorsolateral surface is that cortex posterior to the “occipital line” which extends from the superior extent of the parieto-occipital sulcus superiorly to the “occipital notch” inferiorly; the notch is approximately 4 cm anterior to the occipital pole at the junction of the dorsolateral and inferior surfaces (see Fig. 10.1a). The medial surface is that cortex posterior to the parieto-occipital sulcus superiorly and anterior limb of the calcarine sulcus, which ends just beneath the splenium of the corpus callosum (see Fig. 10.1b). The inferior surface is less well delineated; it includes the posterior part of the temporal lobe, extending behind an arbitrary line between the occipital notch and the isthmus of the cingulate gyrus. Thus, it includes, from lateral to medial, respectively, the posterior part of the inferior temporal gyrus, posterior part of the fusiform (occipitotemporal) gyrus, and the lingual gyrus.

The dorsolateral surface is defined by some as consisting of three, superior, middle, and inferior, occipital gyri. Others fail to acknowledge such a distinction of three gyri, which is my position. In my view it consists of a number of gyri and shallow sulci, which have little, if any, predictability. The cortex of the medial surface that is posterior to the parieto-occipital sulcus and superior to the posterior limb of the calcarine sulcus is the cuneus. That below the sulcus consists primarily of the lingual gyrus. The inferior surface may have gyral names that vary somewhat, depending upon the neuroanatomical text. Thus, these may variously be referred to as the posterior parts of the lingual, temporo-occipital, parahippocampal, and even some of the inferior temporal gyri. These features are illustrated in Fig. 10.1.

The occipital cortex has an array of connectivity with other areas of the cerebrum like other lobes, but it has a very closely associated connectivity with the posterior temporal lobe. This association is significantly reflected in the semiology of the occipital and the posterior temporal seizures.

The semiology of occipital lobe seizures exhibits a remarkable variety, perhaps to a greater extent than other lobes. Its connectivity is such that epileptic foci in the parietal and temporal lobes may disclose characteristics of the semiology that clinically they are initially attributed to those lobes. The reverse is just as likely, i.e., foci in the occipital lobe spreading to the eloquent cortex in other cortical areas, leading to the clinical view that the epileptic foci are in those areas. The majority of seizures arising in the occipital cortex have some remnants of altered vision—altered vision that is usually in the contralateral visual field. These may be alterations in brightness, color, size of objects, appearance of various hallucinations, etc.