Neurnradinlogg Neuroradiology (1987) 29:283-286 @ Springer-Verlag 1987 Alexia without agraphia: Clinical-computed tomographic correlations L. A. Weisberg and M. Wall Department of Neurology and Psychiatry, Tulane University Medical School, Neurology Service of the Charity Hospital, and the Neurology Service of the Veterans Administration Hospital, New Orleans, Louisiana, USA Summary. Four patients with alexia without agraphia had CT lesions which correlated with the clinical findings. All lesions were vascular; two were spontaneous intracerebral hematomas and two were ischemic infarctions in the posterior cerebral artery distribution. The lesions were located in the posterior portion of the dominant hemisphere. The location of the lesion correlated with the presence or absence of visual field abnormalities. ous intracerebral hemorrhage, arteriovenous malformations, intracranial neoplasm, brain abscess and migraine [2-5]. The purpose of this present analysis is to report four patients with alexia without agraphia in which CT verified the pathological lesion and location. Case Reports Case 1 The clinical syndrome of alexia (acquired inability to read) without agraphia (inability to write) is an uncommon disorder [1, 2]. In those cases in which there is pathological verification of the lesion location, abnormal findings are demonstrated in the left occipital lobe usually with involvement of the splenium of the corpus callosum. The syndrome of alexia without agraphia is most commonly caused by ischemic infarction due to occlusive cerebrovascular disease involving the posterior cerebral artery; however it has been also reported in cases of spontane- J.P., a 79-year-old right-handed hypertensive man was without neurological symptoms until the day of admission when he developed fight focal motor seizures. He stated that familiar objects appeared "strange" but he experienced no visual loss. On examination, he was awake and alert with fluent speech. Comprehension and repetition was normal. He had a profound deficit for naming objects (anomia). He was able to write fluently but was unable to read what he had written. He was also unable to name colors. Visual fields were full to confrontation. Detailed tangent screen perimetry Fig.la-c. There is a sharply marginated hyperdense nonenhancing hematoma in the left (reader's right) posterior-inferior temporal region (a) with hypodense edema in the parietal and temporal region (b). The medial occipital cortex and corpus callosum are not involved (e) 284 Fig.2a-c. There is a hypodense sharply marginated nonenhancing lesion which involvesthe posteriorinferior temporal (a) and occipital (b) lobes (both medial and lateral portions), and splenium of the corpus callosum (e) commands well. There were no paraphasias present. He was able to write to dictation. He had moderate difficulty reading and identifying letters. There was a mild hemiparesis with position sense loss and astereognosis of the right hand. His reflexes were brisk on the right side and a right extensor plantar response was present. Tangent screen visual field examination showed a dense right homonymous hemianopsia. CT showed a large hypodense nonenhancing lesion in the posterior cerebral artery distribution (Fig. 2). Case 3 Fig.3 a and b. There is a sharply marginated homogeneous hyperdense subcortical nonenhancing hematoma in the left (reader's right) parietal-occipital region (a). There is a surrounding hypodense region consistent with edema (b). The lesion spares the medial occipital cortex and splenium of the corpus callosum showed no evidence of right homonymous hemianopsia. The remainder of his neurologic examination was normal. CT showed left posterior-inferior temporal hematoma (Fig. 1). Case 2 F.S., a 48-year-old right-handed hypertensive man with a history of chronic alcoholism was well until watching television one evening. He suddenly became unresponsive with stiffening of his upper and lower extremities and his face twisted to the right. The episode lasted 30 to 60 minutes. He was unable to move his right side immediately after the episode. According to his wife, he could not recognize her for the next several days and initially he had difficulty naming and comprehending. When he was examined 7 months later, he was awake and alert with fluent speech and mild word-finding (anomic) difficulty. He was able to repeat and follow three step J.Z., an 83-year-old right-handed hypertensive man was well until he developed vertigo and diminished vision while reading the paper. His family also noted numerous errors with his speech. On examination, his speech was fluent with numerous paraphasias. A mild to moderate anomia was present. There was mild difficulty with comprehension and repetition. He was able to write with occasional errors but completely unable to read. One week later, his language disturbance had cleared except for some occasional word finding difficulty and occasional paraphasic errors. He was able to write well but remained unable to read. Tangent screen visual fields at the time showed right homonymous hemianopsia which was most severe in the superior fields. CT showed a left parietal-occipital subcortical lobar hematoma (Fig. 3). It is uncertain whether this hemorrhage represents a primary hematoma or hemorrhagic infarction. Case 4 C.F., this 50-year-old woman with a history of atherosclerotic cardiovascular disease had no neurological symptomatology until she noticed the 285 Fig.4a-c. There is a sharply marginated hypodense temporal-parietal lesion (a). There is also a hypodense region extending to the lateral occipital cortex (b). The splenium of the corpus callosum, and medial occipital cortex do not appear to be involved (e) L Discussion R Broca's area ~/ernicke's area Angular gyrus Splenium of corpus catlosum \ %. / Occipital lobe 1 Fig. 5. Possible lesions for alexia without agraphia. The perisylvian language core is composed of Wernicke's area, its outflow, the arcuate fasciculus and Brocas area. Visual information enters this circuit at the angular gyms. Lesion 1 is the classic lesion for alexia without agraphia involving the dominant medial occipital lobe and the splenium. Lesion 2 disconnects visual input from the language core without involving the visual pathways and this thus does not cause a hemianopsia acute onset of visual loss. On examination, her visual acuity was normal and she had a congruous fight superior quadrantanopsia on perimetric visual field examination. Her speech was fluent and without paraphasic errors. She could name, repeat, and comprehend appropriately. She was able to write fluently to dictation but was totally unable to read what she had written. CT scan showed a hypodense temporal-parietal lesion extending to the lateral occipital cortex (Fig. 4). The left angular gyrus is believed to be the center for reading and writing. If there is a left angular gyms lesion, the patient may show both alexia and agraphia. However, if the patient has a pathological process that (a) involves the medial portion of the occipital lobe and the splenium of the corpus callosum and (b) spares the angular gyms, then he may show alexia without agraphia. In this case, the function of writing will be intact because the angular gyms is spared; however reading will be impaired because the primary visual cortex is effectively disconnected from the angular gyrus of the dominant parietal lobe. The patient can see the words but they have no meaning because the visual information does not reach the language area to be processed. Interruption of the fibers of the splenium of the corpus callosum causes an inability to read in the left visual field (hemialexia). Involvement of the medial occipital cortex of the dominant (left) occipital cortex causes a right homonymous hemianopsia (Lesion 1, Fig.5). If the lesion involves only the white matter which connects the angular gyms to the visual (occipital) cortex and spares the optic radiations which are contiguous with the occipital horn of the lateral ventricle then the patient may have no hemianopsia (Lesion 2, Fig. 5). Occlusion of the posterior cerebral artery is the most common cause of alexia without agraphia. If there is occlusion of the entire vascular supply of the left posterior cerebral artery there may be ischemic infarction involving the occipital lobe (including the visual calcarine cortex), medial portions of the temporal lobe, thalamus and splenium of the corpus callosum. These patients may have alexia without agraphia. In addition they may exhibit 1. right homonymous hemianopsia, 2. color naming defects (color anomia) and 3. verbal memory loss (amnesia). The hemianopsia is due to involvement 286 of the calcarine cortex or the underlying white matter. Color anomia is present if the lesion involves the corpus callosum dorsal to its inferior one third [6]. The memory disturbance is believed to result from medial temporal (hippocampal and parahippocampal) cortex involvement. Figure 2 illustrates an extensive lesion that caused such syndrome. Alexia without agraphia may also occur with less extensive lesions, if they involve the optic radiations or primary visual (calcarine) cortex and the periventricular white matter but spare the corpus caUosum. These patients have an accompanying hemianopsia but no defect for color naming or memory. Alexia may occur in association with a less extensive visual field defect e.g. right superior quadrantopia due to involvement of the inferior portion of optic radiations. Such an association implies an inferior occipital lesion in the dominant hemisphere adequate to produce the syndrome as seen in Case 4. Most uncommonly, alexia occurs without visual field defect as occurred in Case 1. This occurs with lesions which involve the association fibers that traverse the occipital-temporal cortex but spare the optic radiations. It is important to perform meticulous visual field examinations that include assessment of the central and peripheral visual fields, otherwise one may miss a central visual field defect [7-9]. The sine qua non for the syndrome is this disconnection of visual information from the angular gyms. References 1. Damasio AR, Damasio H (1983) The anatomic basis of pure alexia. Neurology 33: 1573-1583 2. Greenblatt SH (1977) Neurosurgery and the anatomy of reading: a practical review. Neurosurgery 1:6-14 3. Utti RJ, Donat JR, Romanchuk K (1984) Pure alexia without hemianopia. Arch Neurol 41:1130 4. Judd T, Gardner H, Geschwind N (1983) Alexia without agraphia in a composer. Brain 106:435-437 5. Nicole S (1982) Alexia without agraphia: a case studied by means of computed axial tomography. Eur Neurol 21: 361-365 6. Ajax ET, Schenkenberg T, Kosteljanetz M (1977) Alexia without agraphia and the inferior splenium. Neurology 27: 685-688 7. Casto-Caldes A, Salgedo V (1984) Right hemifield alexia without hemianopia. Arch Neurol 41:84-87 8. Greenblatt SH (1973) Alexia without agraphia or hemianopsia. Brain 96:307-316 9. Wall M (1985) The importance of evaluating the central visual field in occipital lobe lesions. Arch Neurol 42:309 Received: 17 July 1985 Leon A. Weisberg M.D. Department of Neurology and Psychiatry 1415 Tulane Avenue New Orleans, LA 70112 USA