NOTE UNILATERAL VISUAL AGNOSIA A. Mazzocchi, L. Posteraro, G. NuzzP and M. Parma (Clinica Neurologica and 1Clinica Oculistica, University of Parma) INTRODUCTION Visual agnosia is generally regarded as a disorder involving the whole field of vision. Rarely have conditions limited to one visual hemifield been reported and, in addition, these cases were concerned with the inability to recognize only one or two types of stimuli in the left visual field, i.e. colours in the presence of right occipital lesions (Reinhard, 1887; Albert, 1975; Damasio, 1980; Zihl, 1980; Henderson, 1982) or letters and colours following surgical resection of the corpus callosum (Trescher and Ford, 1937; Maspes, 1948). There are, however, three unpublished case reports of hemiagnosia: two associated with a left posterior lesion and involving, respectively, colours and faces (Hyman et al., 1984) and all kinds of visual stimuli (Carbonnel and Charnallet, 1984); one associated with a right posterior lesion and involving images and objects (Tucker and Roeltgen, 1984). Table I summarizes the clinicopathological features of patients with hemiagnosia. The patient reported here had agnosia in the left visual field for all visual stimuli. The associated vascular lesion was located in the right temporo-occipital region with no evidence of corpus callosum involvement. CASE REPORT S.B., a 64-year-old right-handed and right-eyed former printer, with a 5 year school education, had been suffering from a mild form of hypertension for ten years. In 1980 he was hospitalized because of headache, vomiting, left-ear hearing loss and visual blurring. Visual field examination disclosed left homonymous hemianopia. CT-scan showed a right temporo-occipital haemorragic lesion. Four weeks later, his hearing had improved, as confirmed by audiometric examination, and perimetry revealed that the deficit in the left visual field was confined to the upper quadrant. Eighteen months later, the patient developed left hemiplegia. CT-scan did not show any evidence of new lesions. After a month, only a mild spasticity on the left side persisted. A third CT-scan taken six months later was unchanged. In 1982 the patient was referred to our Neuropsychology Service because he complained of "visual difficulties" that could not be accounted for by ophtalmological examination. The patient himself reported that his "eyes see well, the brain does not". Neurological examination showed a mild hemiparesis on the left side with no other abnormalities. Ophtalmological examination revCortex (1985) 21, 309-316 A. Mazzucchi, L. Posteraro, G. Nuzzi and M. Parma 310 TABLE I Major Characteristics of Hemiagnosia in Each of the Reported Cases Authors Pathology Reinhard (1887) Trescher and Ford (1937) Maspes (1948) R parietal and L occipital RVF defect infarctions Splenium surgical section full Albert et al. (1975) Damasio et al. (1980) Zihl and von Cramon (1980) Henderson (1982) Splenium surgical section Neuropsychological disorders L hemifield "color recognition" disorder R tactile agnosia for letters and L hemifield letter agnosia L hemifield impaired recognition of letters, numbers and shapes L hemifield "colour blindness" Visual field full Bilateral infarction in the R superior distribution of posterior quadrant­ cerebral arteries anopia "(CT-scan) full R occipital lobe infarction (CT-scan) R temporo-occipital full haemorrage with splenium involvement Biparietal neoplastic full lesion with splenium involvement Carbonnel and L occipital lesion full (vascular?, toxic?) Charnallet (1984) (CT-scan) Hyman et L occipital vascular lesion R superior al. (1984) quadrant­ anopia Tucker and R occipital vascular lesion L superior Roeltgen quadrant­ (1984) anopia L hemifield "colour recognition" disorder L superior quadrant­ anopic "colour recognition" disorder; L hemifield "colour anomia" L hemifield acromatopsia R hemifield letter, colour and figure agnosia. Bilateral alexia R inferior hemifield acromatopsia and prosopagnosia L inferior hemifield impaired recognition of objects and images R = right; L = left ealed normal visual acuity (10110 in the right; 9110 in the left eye). Visual-field examination (Figure 1) confirmed the presence of left upper homonymous qua­ drantanopia. Evoked visual potentials disclosed a mild delay in the left eye. CT-scan provided evidence of a right temporo-occipital lesion involving the lower optic radiation but apparently sparing the corpus callosum (Figure 2). Neuropsychological Examination Spontaneous speech, writing, reading aloud, acoustic and graphic verbal comprehension were correct (Token Test: 34/36). Correct performances were also obtained on simple calculation, arithmetic, ideomotor and constructional tasks. The score on Progressive Matrices 47 was 30/36. Both verbal and spatial memory performances were in the normal range. Unilateral visual agnosia 311 B. o.om.tro pucllllott _ _ ..., .. _ OOLOM ·­- o - 4 J I I 0 0 . y . i • 00. ~·- ~= ____ --.... ........ COlOR£ )( eo........ st t 3,5 o Fig. 1 - I @2] os ..... -"'o ": .. Visual field examination showing left upper homonymous quadrantanopia. .... 312 A. Mazzucchi, L Posteraro, G. Nuzzi and M. Parma Binocular Visual Gnosia Examination The patient himself reported that he was "much confused", especially when looking at fast-moving pictures (as on television and at the cinema), and that the use of lenses did not help him. However, on central presentation he was able to promptly recognize objects, complex and outline figures, colours, photographs of known places, familiar faces, letters and words. He could read a passage correctly and was able to understand its meaning. He promptly recognized 7 of 11 figures of the Street Completion Test (Street, 1931). When the left visual field was excluded by placing semicircular pieces of paperboard on the right halves of his eye glasses, the patient reported that he could see "far better". Unilateral Visual Gnosia Examination The procedure adopted to examine unilateral visual gnosia was as follows: the examiner was sitting right in front of the patient at a distance of about 50-60 em and checked that the patient maintained central vision. Any trial in which the patient shifted his gaze from central fixation was discounted. The stimuli were random presented to either visual field from the periphery to the center, below the plane of fixation to assure presentation to the lower visual fields, until the patient was able to see the stimulus. Drawn stimuli Fig. 2 - CT-scan section: area of decreased density in the right temporo-occipital region involving the lower optic radiation but apparently sparing the splenium. Unilateral visual agnosia 313 presented with black contours against a white background on pieces paperboard, each stimulus being about 2 by 2 em in size. Table II lists number of trials given for each stimulus category and the percent of correct recognitions in the two visual hemifields. Examination began with simple stimuli, such as horizontal and vertical lines or circles, and went on with the presentation of digits, letters, words, colours, faces and objects. As it is apparent from Table II, all the stimuli presented in the right visual field were correctly recognized; consequently in the following ana­ lysis we will focus on left visual field performance only. Simple Stimulus Recognition Three stimuli consisting of vertical or horizontal lines or of circles were presented arranged in a vertical column, and the patient was requested to point to them from the smallest to the largest: this performance was correct. Also correct was the recognition of simple geometric figures (triangle, square, circle and cross) and of single digits. Letter Recognition (A) Single-letter identification: the patient correctly recognized only two (M and H) out of nine letters presented in the left visual field; for the others he reported to see "only signs". (B) Letter matching: when the task involved matchTABLE II Percentage of Correct Recognition of Stimuli Presented to Either Visual Hemifields Stimuli Horizontal Line Arrangement Vertical Line Arrangement Circle Arrangement Geometric Figure Recognition Number Recognition Single Letter Recognition Letter Matching Same/Different Judgement for Paired Letters: Same Different Single Letter Reading Aloud and Copy: 1st 2nd Words of 4-5-6 letters reading aloud Colour Naming Colour Matching Same/Different Judgement for Paired Colours Object Recognition Face Recognition RVF (100%) (100%) (100%) (100%) (100%) (100%) 515 (100%) LVF (100%) (100%) (100%) (100%) (100%) 219 (17%) 215 (40%) 3/3 (100%) 3/3 (100%) 8/8 (100%) 8/8 (100%) 17/17 (100%) 414 (100%) 2/3 0/3 2/8 3/8 5/8 0/8 0/17 1/4 9/9 (100%) 25/25 (100%) 6/6 (100%) 5/9 (56%) 10/25 (40%) (0%) 0/6 6/6 3/3 3/3 6/6 6/6 9/9 6/6 3/3 3/3 6/6 6/6 (66%) (0%) (25%) (38%) (62%) (0%) (0%) (25%) 314 A. Mazzucchi, L. Posteraro, G. Nuzzi and M. Parma ing a laterally presented letter with its copy in a central array, two letters (L and 0) were recognized immediately, whereas three (V, Band H) were mistaken for L, Rand F respectively. (C) Same/Different judgements for paired letters: in the left visual field the patient recognized two same pairs out of three though remaining unable to name the letters, while for none of the three different pairs could he come to a decision because he "could not see well". (D) Writing down laterally presented letters: only MandL were recognized among the letters presented in the left visual field; A, F and H were recognized only after they had been reproduced on paper, while B and Q were erroneously reproduced for P and D, respective­ ly. Word Recognition None of the words presented in the left visual field were recognized. When the patient was requested to identify the single letters composing the word he iden­ tified E by its "being a square letter... with one piece missing"; he also recognized A, after an attempt to write it down, and C saying "it looks like a circle ... an open one... it's a Cor a G". Colour Naming None of the colours presented in the left visual field was correctly named, and he often merely described them as "light" or "dark". Colour matching: a colour chip was laterally presented for the patient to recognize it among six centrally presented alternatives. He correctly matched only one (yellow) of the four colours. Same/ Different judgements for paired colours: the patient's responses were correct for five pairs out of nine, the judgement being based on the different shades of the colours. Object Recognition Twenty-five common objects were presented. All were promptly recognized in the right visual field, but only ten in the left visual field. When urged by the examiner, the patient was able to describe the physical features of the objects­ e.g., a candle was "a grey thing, about 15 em long, with the upper part tapering off"; a fork "a long and narrow thing, three-pronged at top"- but this did not help him identifying the first fifteen objects. For the last ten stimuli the spon­ taneous use of such an analytic strategy was more successfull and he promptly recognized three items, and seven after· some delay - e.g. a hammer was "a long thing, with something smaller across its top... could be a hammer". Face Recognition Black-and-white photographs of faces were presented to either visual hemi­ field asking the patient to identify their sex and approximate age. Responses were always correct in the right visual field,but he always failed in the left visual field even when critical details such a baldness, mustaches and long hair were pointed to by examiner. The patient said he could only see "photographs". Unilateral visual agnosia 315 DISCUSSION The present case confirms that hemiagnosia does exist and contextually points out that it may occur not limited to a particular type of stimuli, but involving all types of testable visual material. On binocular vision and in the right hemifield the patient was able to identify all the stimuli presented. In the left hemifield, by contrast, he showed: a) an upper quadrantanopia; and b) inability to recognize any type of material in the lower quadrant, which was free from significant primary sensory loss. An analysis of his performance in different testing conditions intimates that the impairment was already apparent at the stage in which sensory data must integrated in a gestalt, prior to the level of semantic identification. His failures in matching-to-sample tasks, in writing down a letter presented to the left of the fixation point and in discriminating such a basic feature of a face photograph as its sex suggest an "apperceptive" rather than an "associative" deficit and his behavior in the object identification task, where the stimulus was eventually recognized after its different parts had been described, concurs in showing an analytic rather than a gestaltlike strategy. Since the lesion was located in the lateral temporo-occipital function of the right brain, the case can be taken as evidence that the visual information received by the primary sensory area must first be processed in the visual association cortex of the temporal lobe before being forwarded to the semantic identification system of the left hemisphere, which would otherwise work an incompletely analyzed material. The majority of cases of hemiagnosia concern right brain-damaged patients showing faulty recognition in the left visual field (see Table I) and can therefore be interpreted in the frame of the hemispheric specialization for visual process­ ing, with the right side engaged in gestalt recognition and the left side in semantic identification (Mishkin, 1972; Horel and Misantone, 1974). There have also been, however, short reports of right hemiagnosia following left occipital damage and involving figure recognition (Carbonnel and Chamal­ let, 1984; Hyman et al., 1984). It is difficult to account for them in the absence of detailed information, but they underline the need to carefully control the ability to recognize stimuli in each visual field, a procedure usually neglected by neu­ rologists. ABSTRACT A case of unilateral visual agnosia for all types of stimuli limited to the left visual hemifield and associated with a right occipital temporal vascular lesion is reported. Questions raised by this case of hemiagnosia as compared to previous ones are discussed. Acknowledgement. The authors wish to thank Professor Ennio De Renzi for his critical reading of the manuscript and helpful suggestions. This study was partially supported by grant from C.N.R. (Consiglio Nazionale delle Ricerche) N. 8302194.04/115.10423. 316 A. Mazzucchi, L. Posteraro, G. Nuzzi and M. Parma REFERENCES ALBERT, M., RECHES, A., and SILVERBERG, R. Associative visual agnosia without alexia. Neurology, 25: 322-326, 1975. CARBONNEL, S., and CHARNALLET, A. Hemispheric specialization and classification tasks. Second European Workshop on Cognitive Neuropsychology: an interdisciplinary approach. Poster session, Bressanone, 1984. DAMASIO, A., YAMADA, T., DAMASIO, H., CORBETT, J., and MCKEE, J. Central achro­ matopsia: behavioral, anatomic and physiologic aspect!;. Neurology, 30: 1064-1071, 1980. HENDERSON, V.M. Impaired hue discrimination in homonymous visual fields. 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