ItaL J. NeuroL Sci. 4: 365-370, 1982 Inferior cortical altitudinal hemianopia: report of a case Camarda R., Bonavita V. Clinica Neurologica (R), 1a Facoltfi di Medicina e Chirurgia, Universitf degli Studi di Napoli A case of bilateral inferior altitudinal hemianopia of cortical origin is reported Although bilateral altitudinal hemianopias can be caused by more or less symmetrical involvement of visual pathways, it is shown how only three sites of these pathways are likely to be responsible for altitudinal hemianopias in human pathology. Key-Words: Inferior altitudinal hemianopia - - visual pathways - - calcarine lips Introduction Altitudinal or horizontal hemianopias, i.e. the bilateral loss of the upper (superior type) or lower (inferior type) visual fields with the dividing lines going horizontally through the fixation point are undoubtedly among the less common types of visual field defects. According to Guillaumant et al. [4] "... ni les constatations anatomiques, ni les hypothrses pathogrniques ne parviennent ~ donner de l'hrmianopsie horizontale une explication vrritablement satisfaisante". Nevertheless, since visual pathways are retinotopically and symmetrically organised in both left and right hemispheres, a visual field defect along the horizontal meridian of both left and right visual fields must necessarily be considered as a direct consequence of a structural lesion involving symmetrically optic fibers of both left and right visual pathways. This simple pathogenetic principle requiring involvement of visual pathways of both hemispheres explains why bilateral altitudinal hemianopias are such rare conditions and why such cases are so rarely reported in the literature [2, 3, 4, 9, 13]. Case report This 49-year-old housewife was admitted to our Clinic in November 1980. Almost two years before admission she started complaining of recurrent cephalalgia usually at vertex which resolved partially after prolonged (3-4 days) oral intake of aspirin. During November 1979 she suddenly complained of blurring of vision (lastmg about three days). During this time, although normally alert, she was unable to recognize the faces of familar people. Although she recovered quickly, the patient continued to complain of some blurring of vision, especially in the inferior half of the visual field. Although the visual incapacity disoriented her, disrupting her pattern of living and even causing her injury because she could not see obstacles lying in her way, she was unaware of the visual field defect, attributing her visual problems to poor glasses, which she changed frequently. With the worsenlng of the disturbance, her husband requested his wife's admission to our department. Neurologic examination revealed an inferior altitudinal hemianopia by the confrontation method, absence of Wernicke's hemianopic phenomenon, absence of responses to visual threat in the inferior half of the visual fields, a moderate pyramidal left hemiparesis, a slight bilateral "freinage" in the finger-to-nose test, a visual anosognosia - - that is unawareness of hemianopia. Although not properly tested, the Riddoch effect was present in the blind hemifield [8]. The patient in fact was unable to see a static object even if it was larger and brighter than a moving one, but frequently she was able to grasp an object in motion and to indicate roughly the direction of motion. Psychiatric examination showed no abnormali365 The ltalian Journal of Neurological Sciences Fig. 1 Inferior bilateral altitudinal hemianopia .sparing fixation. ties. EEG recording showed sporadic slow waves in both hemispheres. The quantitative visual field examination performed with a Goldmann bowl perimeter showed inferior temporal and nasal quadrantanopia in both visual fields (Fig. 1). Routine laboratory investigations gave normal results. E K G showed generic signs of myocardial damage. CT scan revealed circumscribed areas of low density situated posteriorly and mesially in both occipital regions, but larger on the left than on the right side; moderate enlargement of the lateral ventricles and slight cortical atrophy (Fig. 2). Discussion As already stated, altitudinal hemianopias are not a c o m m o n visual field defect [2, 3, 4, 9, 13]. A m o n g the cases reported in the literature, unilateral forms are numerically preponderant and horizontal hemianopia seems to affect the lower half much more frequently than the upper half of the visual field [9, 14]. Whereas vertical hemianopias express unilateral retrochiasmatic involvement of the visual pathways (homonymous type) or expressions of bilateral chiasmatic involvement of optic nerve fibers (heteronymous type), horizontal hemianopias must necessarily be considered as expressing bilateral and symmetrical involvement of both left and right visual pathways. Theoretically, such a bilateral and symmetrical structural lesion of the visual fibers could occur at any point along their way from retinae to the calcarine lips, but in practice there are only three 366 points along the course of the visual fibers in which such lesion most frequently occurs. These are: 1) the prelaminar portion of both optic nerve heads; 2) the chiasmatic crossing region and 3) the calcarine lips of the occipital cortex. It is well known that throughout the extent of their entire course from retina to occipital cortex, the optic fibers are grouped and topographically organised according to the retinal quadrants from which they arise. Accordingly, axons of ganglion cells located in the temporal half of the retina throughout the extent of the optic nerve have an identical temporal, spatial location, whereas ganglion cell axons from the nasal half of the retina lie in the medial portion of the nerve and fibers coming from the upper retinal quadrants are dorsally located while the lower ones are ventrally located. This geometrical grouping is still present in the chiasmal crossing, since fibers from the upper quadrants, uncrossed temporal and crossed nasal fibers of both retinae, in this region are dorsally located and those from the lower quadrants are ventrally located. Posterior to the optic chiasm and throughout the course of the optic tract such spatial distribution develops some intricacies, since there is a twisting of the optic fibers and axons from the upper retinal quadrants gradually assume a dorsomedial location while these from the infenor quadrants assume a ventro-lateral position. Since this twisting is maintained in the optic radiations, fibers carrying peripheral vision from the upper and lower retinal quadrants (uncrossed temporal and crossed nasal) assume a Camarda: Inferior altitudinal hemianopta Fig. 2 Successive tomographic section& after contrast medium injection, demonstrating a bilateral occipital infarction. dorsal and a ventral position respectively, whereas fibers carrying macular vision form the intermediate portion of the geniculo-calcarine pathways. At the occipital cortex level, fibers dorsally located in the optic radiations terminate on the upper lips of the calcarine fissures whereas fibers ventrally located in the radiations terminate in the lower lips of the fissures. At the end of the fiber course from retinae to cortex, the retino-calcarine topographic relationship, taking into account the upper lips of the calcarine fissures and the upper quadrants of both retinae, is as follows: left temporal and right nasal quadrants are represented on the upper left calcarine lip and right temporal and left nasal quadrants are represented on the upper right calcarine lip (obviously the same topographic relationship holds for the ventral retinal quadrants and the ventral calcarine lips). Since the retino-calcarine topographic relationship involves the peripheral-macular extent of the quadrants, the visual field's cortical representation along the antero-posterior planes is such that in each lip the binocular visual field appears to be located in the posterior two thirds of the calcarine lips whereas the temporal crescents, that is the peripheral, monocular, portions of the visual field lying just outside the binocular visual field are located in the anterior third of the lips. Bearing in mind the brief summary of the visual pathways course just outlined, we can try to locate the bilateral and symmetrical lesion of the visual system in our patient. The absence in the patient's history of any sequential involvement of the visual fields of both eyes, the absence of unilateral or bilateral optic disc edema or of the pseudo Forster-Kennedy syndrome, the absence of unilateral or bilateral optic atrophy and the sudden but bilateral appearance of the horizontal field defect allow us to exclude anterior ischemic optic neuropathy (AION) [5] as a cause of the visual field defect. Because of the retinotopy of the chiasmal crossing, the optic fiber involvement responsible for the patient's inferior altitudinal hemianopia could be due to an internal hydrocephalus or a third ventricle tumor)pressing{ on the dorsal aspect of the chiasm [7]. Once again, the absence of any historical and clinical signs of such a lesion and above all, the absence of Wernicke's hemianopic phenomenon, although this is difficult to elicit, allow us to exclude clinically any chiasmatic involvement of (*) Opticochiasmatic arachnoiditis [1] as a cause of altitudinal hemianopia at chiasmal crossing level, though the most frequent cause adduced, is undoubtedly the least satisfactory since there is no convincing anatomical connection between the visual field defect and the impli cated noxa [15]. 367 The Italian Journal of Neurological Sciences the visual pathways and to consider as suprageniculate, posterior to the lateral geniculate body, the site of the bilateral involvement of these pathways. The absence of straight margins in the field defects in the two eyes, their congruity and macular sparing all stressed by the perimetric maps, further indicate as bilateral the cortical involvement of the visual system clinically located in both left and right entire superior lips of the calcarine fissures. The time-honored concepts of the course of the visual pathways previously outlined and the scheme of the retinotopic organization of the visual, striate cortex have both been well documented in man since the beginning of this century [6, 11]. Therefore, they apparently require no further amendment. Some points, however deserve further comments. First of all, although in a recent survey [12] the effectiveness of CT in delineating the anatomical extent of an occipital lobe infarction and in providing a useful clinico-pathological correlation with the visual field defects have been widely emphasized, this correlation appears to be effective only when visual field defects along the vertical meridian are taken into consideration. In these circumstances we agree completely that the usual brain CT scans do delineate the anatomical extent of occipital lobe infarction. However, because of the peculiarity of our patient's occipital lesion we have doubts about the effectiveness of CT in all cases. We firmly believe that CT scans along the sagittal planes could be the only effective orientation for a visual field defect along the horizontal meridian, as in our patient. Secondly, according to the history and the CT images there is no doubt about the vascular, ischemic origin of the patient's upper calcarine lips structural lesion. Generally speaking, the patient's history points to a minor completed stroke in the vertebrobasilar territory but the peculiarity of the visual field defect we observed allows us to locate the vascular territory involved even more accurately. It is well known that in humans the calcarine arteries supply the visual striate cortex but perhaps it is less well known that they supply most but not all of this area. Branches from the posterior temporal and from the parieto-occipital arteries, all originating from the posterior cerebral artery, and occipital branches of the middle cerebral artery together with the calcarine arteries constitute a functional unit supplying the A I Cereb _ ~ _ ~ , , ~ ~lv '~-I,. ~ ---. ', Par'occipital .... -. ,1 \ Post. Temp. A Post. Temp. A. _ \ "" Mid. Cereb. A . " " Par'occipital "" Artery Fig. 3 A. Diagram of the visual striate area of a left hemisphere. The walls of the calcarine fissure have been completely separated to show the most frequent vascular subdivisions of the striate area. B. The right half of the visualfield of each eye, showing the portion of the fieldprojecting to each vascular subdivision of the visual area. (adapted from Smith and Richardson, 1966) 368 Camarda: Inferior altitudinal hemianopia A M UBCA C A PTA ~ POA B . LBCA / / LBC/~, J PTA / MOA f POA f UBCA Fig. 4 A. Diagram of the visual striate area of a left hemisphere. The walls of the calcarine fissure have been completely separated to show the supposed vascular subdifisions of the striate area of the patient reported herein. B. The right half of the visual field of each eye, showing the portion of the field projecting to each vascular subdivision of the visual area. MCA =middle cerebral artery; PTA =posterior temporal artery, POA=parieto-occipital artery; UBCA=upper branch of calcarine artery," LBCA=lower branch of calcarine artery; CA =calcarine artery. (redrawn according to Smith and Richardson, 1966). striate areas. According to Smith and Richardson [10] the course and branching of these arteries are not constant from person to person but vary a great deal. Nevertheless from the specimens studied post mortem some conclusions have been firmly established by these authors: namely, the posterior temporal artery commonly supplies the posterior part of the lower calcarine lip and, as its largest contribution to the supply of the visual areas, all the lower calcarine lip and the posterior half of the upper calcarine lip; the middle cerebral artery supplies the posterior half of the upper calcarine lip; the parieto-occipital artery supplies a small part of the anterior portion of the upper calcarine lip (Fig. 3). As far as the calcarine arteries are concerned, course and branching are extremely variable. Thus it is not easy to describe a single pattern of their cortical distribution. Nevertheless, in a high percentage (33%) of the specimens studied by Smith and Richardson the calcarine artery, as it approaches the calcarine fissure, branches into two longitudinal vessels, the upper one supplying the upper calcarine lip and the lower one the lower calcarine lip, that is all strips of cortex that receive the projections from the homonymous contralateral ventral and dorsal sectors respectively of the two visual fields (Fig. 4). Thus on the basis of the most frequent distribution of the calcarine supply of the striate cortex we can say tentatively that our patient's affected vascular district in both hemispheres was supplied by the upper calcarine arteries and by the parieto-occipital arteries. The macular sparing observed in the perimetric maps was a consequence of the preserved blood supply, through the occipital branches of the middle cerebral artery, which spares the foveal cortical representation of both upper calcarine lips. 369 The Italian Journal of Neurological Sciences Sommario Viene descritto un caso di emianopsia altitudinale inferiore di origine corticale. Sebbene l'emianopsia altitudinale possa essere provocata da una compromissione pifi o meno simmetrica, ma sempre bilaterale, delle vie visive lungo il loro decorso dalla retina alla corteccia visiva, viene sottolineato come in patologia umana tale compromissione pu6 istaurarsi solo a tre diversi livelli lungo il decorso di tali vie. A d d r e s s reprints requests to: Prof. V. 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