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Selective Deficit of Visual Size Perception: Two J Neurol Neurosurg Psychiatry: First Published As 10.1136/Jnnp.57.1.73 on 1 January 1994

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Selective Deficit of Visual Size Perception: Two J Neurol Neurosurg Psychiatry: First Published As 10.1136/Jnnp.57.1.73 on 1 January 1994 journal ofNeurology, Neurosurgery, and Psychiany 1994;57:73-78 73 Selective deficit of visual size perception: two J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.57.1.73 on 1 January 1994. Downloaded from cases of hemimicropsia Laurent Cohen, Fran9oise Gray, Christian Meyrignac, Stanislas Dehaene, Jean-Denis Degos Abstract pathways, such as the chiasmatic tumor Hemimicropsia is a rare disorder of reported by Bender and Savitsky," can cause visual perception characterised by an micropsia. Micropsia of neurological origin is apparent reduction of the size of objects most frequently reported as a manifestation when presented in one hemifield. We of temporal lobe seizures.'213 It then affects report two cases of hemumicropsia either the entire visual field, or the object that resulting from focal brain lesions. The the patient fixates at the moment of the first patient was an art teacher and could seizure. It is accompanied by a broad variety accurately depict his abnormal visual of temporal epileptic SyMptomS.7 8 More perception. He subsequently died and his rarely, micropsia can be part of purely visual brain was examined post mortem. In the seizures. It then affects only one half of the second patient, micropsia was assessed visual field, and is accompanied by other by a quantified size comparison task. cerebral visual disturbances, such as meta- The size of a given object is normally morphopsia or dyschromatopsia.415 Apart perceived as constant across any spatial from epileptic phenomena, transient microp- position. Hemimicropsia may thus be sia can also result from migraine,'6 or from considered a limited violation of the size the action of mescaline and other hallucino- constancy principle. Behavioural and genic drugs. anatomical data are discussed in relation Permanent dysmetropsia following focal to the neural basis of visual object per- cerebral lesions is rare and affects lateral ception in humans. homonymous segments of the visual field.'718 It often may be overlooked, because of severe (7Neurol Neurosurg Psychiatry 1994;57:73-78) associated visual impairments,'9 20 or because of the mildness of the functional disability.7 The only probable case of permanent dys- It is now widely acknowledged that different metropsia with satisfactory localisation data types of visual information are processed in was recently reported by Ebata et al,2' with an the brain along anatomically distinct path- unexpected retrosplenial lesion. We describe ways.' Neuropsychology has long provided two cases of pure hemimicropsia following data suggestive of this organisation, through posterior cerebral damage. the description of deficits selectively affecting http://jnnp.bmj.com/ the perception of-for example, colour or Service de Neurologie, movement.2' Building upon these initial clini- Case 1 H6pital de la studies and brain functional The patient was a 50-year-old right-handed Salpetriere, Paris, cal data, animal France imaging in humans have recently allowed a man with no history of psychiatric disorders, L Cohen more systematic and detailed study of these working as an art teacher. Since the age of Service de processing modules.45 There is, however, about 40, he had suffered occasional attacks Neuropathologie, only scant evidence about the neural basis of of ophthalmic migraine. His mother and one on September 30, 2021 by guest. Protected copyright. Hopital Henri Mondor, Cr6teil, size constancy, one major property of the nor- brother had similar ophthalmic migraine. At France mal visual system.6 The size of a given object the age of 44, he had suffered a myocardial F Gray is perceived as constant, whatever its location infarct. On his way to a routine cardiological D6partement de and distance. A correction process allows for consultation, the patient experienced sudden Neurosciences, CHU the location and the size of the retinal projec- left homonymous hemianopia. At the same Henri Mondor, Cr6teil, France tion in the course of object perception. time, he noticed that he could not recognise C Meyrignac Dysmetropsia (also called dysmegalopsia), the face of a friend who was with him at that J-D Degos is a disorder of visual perception charac- moment. He was able to find his way to the Laboratoire de terised by an apparent modification of the hospital. He did not recognise his usual car- Sciences Cognitives et Psycholinguistique, size of perceived objects. Objects appear diologist, nor the other members of the med- INSERM and CNRS, either shrunk (micropsia) or enlarged ical staff. One hour later, right-sided Paris, France (macropsia), relative to their normal size. An throbbing headache began, and lasted for S Dehaene overview of published reports shows that about two hours. The patient was admitted to Address correspondence to Dr L Cohen, Service de micropsia and macropsia result from similar the hospital. Two days later, left hemianopia Neurologie, H6pital de la causes,7- but micropsia occurs much more had almost completely disappeared but the Salpetriere, 47 Boulevard de I'H6pital, 75651 Paris frequently. prosopagnosia was still severe. The patient CEDEX 13, France. Monocular micropsia can result from reti- could not identify the members of his family Received 27 November nal oedema causing a dislocation of the visually, although he recognised them readily 1992 and in revised form 8 February 1993. receptor cells.'0 Exceptionally, lesions affect- upon hearing their voices. In addition, the Accepted 15 February 1993 ing other parts of the extracerebral visual patient had some difficulty analysing complex 74 Cohen, Gray, Meyrignac, Dehaene, Degos Figure 1 Sample gyrus and the inferior part of the middle J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.57.1.73 on 1 January 1994. Downloaded from drawings ofsymmetrical objects by thefirst patient. occipital gyrus (fig 3). This region corre- The left half is consistently sponds to the lower part of the lateral aspect larger than the right half. '..I\\ of areas 18 and 19. More anteriorly, the '.\I1\ .'. I infarct successively affected the depth of the k. inferior temporal sulcus, part of the middle .f- " 4' ,1;, .. temporal gyrus, and the depth of the superior f ;- I- iI.... b I -.. temporal sulcus. The occipitotemporal gyrus I -~~tI and the angular gyrus were spared. The cervi- cal and intracranial arteries were normal. is/ I' Ni This completely haemorrhagic watershed 4 infarct was interpreted as a consequence of 11IPISI .1I, transient arterial vasospasm having occurred simultaneously in the carotid and verte- brobasilar systems. A \I/ Case 2 ,\,V/ . The patient was a 60-year-old right-handed woman, working as a secretary, with no his- tory of previous neurological or psychiatric visual scenes. He would describe isolated disorders. She underwent surgery for a devi- parts of the scene, mostly picking out the ated nasal septum. On the fourth day follow- region on the right handside, but had ing surgery, she presented with progressively difficulties perceiving the visual field as a increasing visual disorders. Firstly, she com- coherent whole, a behaviour suggestive of plained that objects and faces would disap- simultanagnosia with slight left spatial pear from her view although she could see neglect.22 Finally, he complained that he had part of them. She could see her daughter's special difficulty perceiving depth, propor- earring, but not her daughter's face, or a hook tions, and symmetry. There was no sensory in the wall between two windows, but not the or motor deficit, aphasia, alexia, or apraxia. windows themselves. Having got up from her One week later, prosopagnosia and simul- bed, she turned back but could not see the tanagnosia had receded. Visual field was nor- bed any more. Secondly, she would miss mal on Goldmann perimetry. The patient objects she tried to reach, such as a glass of complained, however, that objects falling in water. She was unable to follow a moving tar- his left visual field appeared somewhat shrunk get visually. In addition to these complex and compressed. He felt it particularly diffi- visual impairments, she was confused, disori- cult to appreciate the symmetry of pictures. ented in time and space, and had anterograde When drawing, he spontaneously tended to amnesia. The condition worsened until the compensate for his perceptual asymmetry by second day. Then confusion, disorientation drawing the left half of objects slightly larger and amnesia receded rapidly. than the right half (fig 1). He was also pre- One week later, simultanagnosia was still sented with truly symmetrical patterns, which present: the patient could not visually grasp http://jnnp.bmj.com/ he perceived as smaller on the left than on the the whole of an object, although she per- right. When asked to correct them so as to ceived isolated details. Visual field was grossly make them look symmetrical, he either normal on confrontation. The ability to reach expanded the left part of the pattern, or for targets in the right visual hemifield was reduced its right part (fig 2). In a sample of severely impaired, indicating unilateral optic six spontaneous or corrected drawings of ataxia. The patient spontaneously reported symmetrical objects, linear measures in the that people's left eye (the one she saw on her on September 30, 2021 by guest. Protected copyright. left half were on the average 16% larger than right) seemed to be smaller and lower than the corresponding measures in the right half. their right one. Her difficulties in dressing The patient did not mention any anomaly of and eating apparently resulted from her colour or movement perception, which were impaired ability to reach rather than from not further explored. ideomotor apraxia. There was no prosopag- Ten days after onset, CT showed a hypo- nosia and colours were perceived normally. dense area in the right occipital region. A There was no sensory motor deficit; oral lan- diagnosis of migrainous stroke was pro- guage comprehension and production were posed.23 The patient died 27 months later normal.
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