BRAIN AND 38, 576-595 (1990) LANGUAGE Left Occipital Lobectomy and the Preangular Anatomy of Reading SAMUELH. GREENBLATT Brown University Program in Neurosurgery Two patients had alexias after left occipital lobectomies. Case 1 was a 55year-old man with a glioblastoma. At 4 months after surgery he could read slowly, but reading was neither efficient nor pleasant. Case 2 was a 19-year-old male who had a more restricted, medial occipital lobectomy for an encapsulated mesenchymal chondrosarcoma. The tumor did not invade brain initially, and the patient recovered efficient reading after 15 months. It is postulated that Case 2 was able to recover efficient reading because he still had a field of left ventrolateral occipitotemporal cortex connected to homologous cortex on the right. o 1990 Academic Press. Inc. In 1952, Hecaen, de Ajuriaguerra, and David described the effects of occipital lobectomy on reading in seven patients. Their work showed that people who undergo dominant occipital lobectomies usually have severe alexias in the immediate postoperative period. The reading deficit tends to improve with the passage of time, but the patients usually find that reading is neither efficient nor pleasant. The present report describes two patients who had dominant occipital lobectomies. It was concluded that they had separable alexic syndromes, which can be differentiated by their clinical courses, the anatomical locations of their lesions, and the surgical approaches to them. The anatomical differences lead to a The surgery in both cases was performed by the late Kenneth Shulman, M.D., who kindly gave his permission for their presentations. Michael Swerdlow, M.D., provided much appreciated assistance in the followup of Case I. The early neuropsychological testing in Case 2 was performed by Paula Fuld, Ph.D. The later testing in Case 2 was performed by Richard Kovner, Ph.D., and Alice Ancede, under the direction of Steven Mattis, Ph.D. Ms. Ancede provided the reading therapy, which was much appreciated by all. Kytja K. S. Voeller, M.D., reviewed an earlier version of the manuscript and made many valuable suggestions. The two case reports were presented to the International Neuropsychological Society in New York on February 1, 1979. Send requests for reprints to the author at Brown University Program in Neurosurgery, Memorial Hospital of Rhode Island, Pawtucket. RI 02860. 576 0093-934x/90 $3 .OO Copyright 0 1990 by Academic All rights of reproduction Press. Inc. in any form reserved. LEFT OCCIPITAL LOBECTOMY 577 modification of Dejerine’s (1892, 1901; Geschwind, 1962) model of the pathways for reading. From this modified model one can predict the possibility of a third syndrome of alexia after dominant occipital lobectomy, which has been confirmed by at least one case report (Vincent, Sadowsky, Saunders, & Reeves, 1977). The first case followed the typical course described by Hecaen et al. (1952). Thus, it is presented in much less detail than the second, which was investigated more thoroughly. CASE REPORTS Case I This 55year-old right-handed, polyglot salesman had been a voracious reader. Three weeks prior to hospital admission in 1976 he became aware of right-sided visual difficulty. Ten days before admission he began to complain of poor memory and word finding problems. On the day before admission, he found that he could not read his favorite newspaper. General physical examination was unremarkable. Visual acuity was 20/40 bilaterally, but formal visual field testing confirmed the presence of a complete right homonymous hemianopsia. There was a mild rightsided paresis involving the lower face and arm. He could read and write, and there was no anomia. The initial diagnosis was cerebrovascular accident in the distribution of the left posterior cerebral artery. Over the course of the next few days the patient developed ataxia, decreasing fluency, anomia, and alexia with agraphia. Computed tomography (CT) was consistent with glioblastoma multiforme surrounded by edema in the left temporo-occipital region (Fig. 1). This impression was confirmed by cerebral arteriography, which localized the lesion to the left posterior parieto-occipital region. Dexamethasone was started. Twelve days after admission the patient’s spontaneous speech was fluent with no paraphasias. There was some anomia on confrontation testing but no paraphasias. Tactile naming was intact. Color naming and sorting were normal. Repetition was perfect. Auditory comprehension was somewhat limited, but less disturbed than reading. The patient could not read large newspaper headlines or even some single letters. Writing was essentially impossible. He struggled to write his name in barely legible form using block capital letters. He could not copy a triangle. He read 2-digit numbers slowly, and he could not perform mental or written arithmetic. A left occipital lobectomy was performed 13 days after admission. The resection was made approximately 4.5 cm forward along the surface from the occipital tip. It was carried across the occipital lobe from medial to lateral in a coronal plane that was almost perpendicular to the falx. Gross total tumor removal was achieved, except at the inferior portion of the occipital lobe, where it was thought that some tumor remained unre- 578 SAMUEL H. GREENBLATT FIG. 1. Case 1. Contrast-enhanced CT showing the extent of the tumor before the occipital lobectomy. Analysis of these slices by comparison to the figures in the atlas of Matsui and Hirano (1978) shows that the tumor extends from the middle temporal and fusiform gyri inferiorly (upper left slice) to the posterior aspect of the deep inferior parietal lobe superiorly (lower right slice). The only follow-up CT was taken when the tumor was recurrent. sected. After surgery, the patient was treated with continued dexamethasone, radiotherapy (5900 rads) and chemotherapy (BCNU). On the day after surgery, the patient was alert. His auditory language was largely unchanged, except that his comprehension was slightly worse and repetition was slightly impaired. He could not read or write. However, 13 days postoperatively, there was striking improvement. His right hemiparesis was difficult to detect, though his right homonymous hemianopsia was unchanged to confrontation testing. Spontaneous speech was fluent with no paraphasias. Confrontation naming, repetition, auditory comprehension, right-left functions, finger gnosis, and written and verbal calculations were all normal. The patient produced an acceptable copy of a drawing of a house, though he still had some difficulty in making a recognizable drawing of a clock. He could read, but very slowly LEFT OCCIPITAL LOBECTOMY 579 was not noted, though he may have been doing it internally. His comprehension was accurate for what little he read. He wrote his name and a short sentence to dictation, but there were grammatical errors in his production of a longer sentence. At 4 months after surgery, the patient was at the zenith of his postoperative recovery. He had no subjective complaints about his auditory language functions in English, Yiddish, or Hebrew. However, he was reading only newspaper headlines and items of necessity. He described his reading difficulty as being like “slow plasma.” On visual confrontation testing, he still had a right homonymous hemianopsia, although there was a suggestion of some medial upper quadrant sparing. His auditory language was normal, with no anomia and good comprehenson. He could read a headline in a magazine quite well. When asked to read some text in Science, he did so very slowly but with good comprehension. He wrote his name and address and copied script perfectly. His written production of a spontaneous sentence was slightly agrammatic: “You Doctor are giving me pretty much attention.” Seven months after surgery he began to show right-sided motor signs. Thereafter his course was one of gradual deterioration until he died a year after surgery. Case 2 This lPyear-old, right-handed, white male university student was initially hospitalized in 1977. He gave a 2-year history of poorly localized headaches and a 2- to 3-month history of episodic visual obscurations, usually on the right. He had bilateral papilledema, normal visual acuities, and a complete right homonymous hemianopsia that did not spare the macula. CT (Fig 2) and cerebral angiography showed a large left medial occipital vascular malformation. Six days after admission, a left occipital craniotomy was performed. An occipital lobectomy was begun 6 cm from the occipital pole and carried into the occipital horn of the lateral ventricle. Vigorous bleeding led to clipping of a posterior medial branch of the posterior cerebral artery. Continued subpial dissection then revealed a very firm tumor mass, which was attached to the straight sinus at the falx-tentorial junction. It was covered by large vascular structures. The procedure was terminated. The patient awoke quickly. He was initially disoriented, and he had some word finding difficulty. Six days after surgery the patient was alert and oriented. His right homonymous hemianopsia was unchanged. Spontaneous speech was normal, but he had some anomias on confrontation testing. Auditory repetition and comprehension were normal. Color naming was disturbed. 580 SAMUEL H. GREENBLATT FIG. 2. Case 2. Preoperative, contrast-enhanced CT showing the size and location of the very vascular tumor in the medial left occipital fossa. The edematous brain anterior and lateral to the tumor has been compressed (but not invaded) by the pressure of the adjacent mass, so it is not valid to try to understand anatomical boundaries by reference to atlases of normal CT anatomy. tive of color blindness. His arithmetic abilities were limited to simple addition. His drawings of a house and a clock were primitive, and he could not copy a simple pseudo-three-dimensional figure. He could copy letters but not words. Reading was very limited. He could read letters, short numbers, and LEFT OCCIPITAL LOBECTOMY 581 some proper names. He tended to spell some words aloud before pronouncing them correctly, but at other times he denied spelling internally when he read. He could write his name and a dictated sentence. There was only one spelling error in his production of a spontaneous sentence: “The weather is very beautiful, yet it’s hazzy.” He recognized even low frequency words spelled aloud for him, but he made errors in spelling aloud words that were spoken to him (e.g., vascular was spelled as “vascaluar.“). Bedside testing by other examiners 5 days later showed some improvement in many areas, especially color naming, but reading was only slightly improved. Two weeks after his first surgery, the patient was returned to the operating room and the craniotomy was reopened. More brain tissue surrounding the tumor was removed, and a partial (dorsal) occipital lobectomy was completed. The tumor was attached to the left falx at the confluence of the straight and lateral sinuses. A thin layer of occipital cortex was found between the tumor and the tentorium. At the end of the procedure, the only remaining tumor was a small placode on the torcula, which was electrocoagulated. The final pathological diagnosis was mesenchymal chondrosarcoma (Dahlin & Henderson, 1962). Twelve days after the second procedure the patient could read single sentences with some errors. The errors were corrected by the patient when the misread words were spelled for him. Just prior to discharge, 3 weeks after the second surgery, his speech was fluent with good comprehension. There was still a confrontation anomia and some perseveration when he felt pressured. Right-left orientation and color naming were normal. He had difficulties with arithmetic operations, and there was mild inattention to the right side on the Raven’s test. Reading remained impaired. To overcome this problem, he spelled words to himself or traced them with his finger. He recognized many unread words when they were spelled, but even this device was not totally effective. His writing was quite good. When asked to describe the clothing of his father, who was present in the room, he wrote: “My father is in a blue plaid shirt with dark blue pants.” A follow-up CT scan was obtained at this time (Fig. 3). After discharge, the patient experienced flashes of light in both visual fields. These were thought to be seizures. They were successfully treated with anticonvulsants (phenobarbital and carbamazapine). He returned to his university program on a part-time basis 8 months after surgery. In doing so, he found that reading assignments were not difficult to complete, though testing showed that he continued to use a sounding out method of reading whenever he encountered an unfamiliar word. Two 582 SAMUEL H. GREENBLATT FIG. 3. Case 2. Contrast-enhanced CT obtained 2 weeks after the second craniotomy. In the lowest slice (upper left), the metal clip (metallic artifact) in the left occipital region is actually on the inferior surface of the temporal lobe, with cerebellum medial to it. According to Matsui and Hirano (1978, p. 124), the inferior temporal gyrus lies anterolateral to this site. Thus, it is present in this CT slice of this patient. Essentially the same interpretation applies to the next higher slice (upper right). At its widest extent (lower left), the surgical lesion cuts across the middle temporal and fusiform gyri. LEFT OCCIPITAL 583 LOBECTOMY surgery and chemotherapy was given. Two and a half years later he noted gradual loss of visual acuity in his remaining left visual field. Repeat CT and arteriography showed recurrence of the tumor. Five and a half years after his original surgery, his craniotomy was again reopened, and recurrent tumor was debulked. He had very little useful vision when discharged. Neuropsychological and Reading Tests in Case 2 The results of serial reading tests are shown in Table 1. At 4 months there was an obvious alexia and some element of agraphia. In addition, the results of a Wechsler Adult Intelligence Scale (Wechsler, 1955) at that time showed that there was spatial disorientation, verbal comprehension deficit, mild color anomia (with intact color vision), constructional apraxia, and severe dyscalculia. Finger gnosis, graphesthesia, and verbal short-term memory were intact. The patient was given extensive therapy in reading. At 4 months after surgery, he was reading at the 8.0 grade level. The therapist found that practice improved the patient’s performance, whereas this effect was not seen at 15 months, when his reading grade level was 12.2. Although the patient’s reading abilities recovered quite well, his basic strategy of reading did not change. His preferred and most efficient approach was global (lexical). At 4 months this sufficed only for short words, but at 15 months it was useful for many longer words as well. If the lexical approach failed, he reverted to contextual clues, including word outline and general TABLE I CASE 2. RESULTS OF SERIAL READING WRAT (Jastak & Jastak, 1965) Reading Spelling Arithmetic Gray Oral (Gray, 1967) Reading Comprehension Gray Oral Passage no. 6 Passage no. 7 Passage no. 8 Passage no. 12 TESTS 4 months after surgery Grade level 15 months after surgery Grade level 7.9 (25 %ile) 7.0 (18 %ile) 3.9 (2 %ile) 12.1 (75%ile) 8.1 (37%ile) 4.9 (8%ile) 8.0 grade level 48% correct 10.6 grade level 74% correct Time (in set) to read same passage 167 set 50 set 127 set 40 set 240 set 51 set 327 set 120 set 584 SAMUEL H. GREENBLATT contextual information. If this failed or was not used, he fell back on a very laborious, letter-by-letter reading method. Nonetheless, spelling aloud was useful only for words with which he was already familiar. ANATOMICAL ANALYSIS Case 1 is representative of the usual alexia syndrome described by HCcaen et al. (1952) after dominant occipital lobectomies. Although the patient recovered some reading abilities, this process was never efficient or enjoyable. There are two important anatomical features in this group of patients: (1) Pathologically, the lesion is usually infiltrative, so there is a reasonable presumption of tissue dysfunction beyond the limits of the surgical resection; and (2) the surgical lesion is either a partial decompressive lobectomy or a complete occipital lobectomy. The surgery in Case 1 removed a large portion of the patient’s left occipital lobe, but it probably did not extend into the posterior parietal lobe. Sparing of the angular gyrus would be predicted from the operative measurements, which were made along the surface of the occipital lobe, measuring forward from the occipital pole. If an occipital lobectomy were carried 4.5 cm forward in a straight line toward the frontal pole, it would invade the parietal lobe, but this kind of surgical measurement is actually made in a curvilinear manner along the brain surface. By the latter method, the parieto-occipital junction (posterior aspect of the angular gyrus) is encountered at a distance of 6 to 7 cm forward from the occipital pole (Greenblatt, 1977). The surgical observation of residual tumor at the inferior aspect of the resection is also important, because the ventral parts of the left occipital lobe are critical for reading (Greenblatt, 1973, 1983; Damasio & Damasio, 1983). Case 2 presents some different clinical and anatomical features. Unlike Case 1, the patient regained efficient reading quite well, although more than a year was required for this degree of recovery to occur. Anatomically, there were also some important differences in Case 2: (1) The lesion was an extra-axial mass attached to the falx near the tentorial junction (Fig. 2). It indented the medial occipital lobe in the region of the calcarine fissure and adjacent gyri, but it did not initially invade neural tissue; and (2) the surgical lesion amounted to a dorsal and medial occipital lobectomy, with invasion of tissue which was immediately adjacent to the tumor. Some inferolateral cortex of the left occipitotemporal area remained intact (Fig. 3). Thus, there are significant clinical and anatomical differences between the postoperative alexias in the “holooccipital lobectomy syndrome” (Case 1) and the “medial occipital lobectomy syndrome” (Case 2). The existence of these two separable syndromes leads to some important conclusions about the normal anatomy of reading in the proficient adult reader. 585 LEFTOCCIPITALLOBECTOMY The Role of the Posterior Lingual and Fusiform Gyri Dejerine’s (1892, 1901) original anatomical model of reading included critical roles for the lingual and fusiform gyri in the occipital lobes on both sides. More recent studies have also reached similar conclusions (Greenblatt, 1973; Benson & Geschwind, 1969). The theory states that visual signals arriving in the right calcarine cortex are transmitted to the adjacent right lingual and fusiform gyri. From there, the signals go through the ventral splenium to the homologous left lingual and fusiform gyri. Thus, “Flechsig’s rule” (Flechsig, 1901; Geschwind, 1965) is fulfilled, because information is transferred across the corpus callosum only between homologous association areas. Visual lexic information from the left calcarine cortex also arrives in these ventral left occipital association areas. The combined signals are then transmitted to the left angular gyrus, probably through the vertical occipital fasciculus (Greenblatt, 1973). But the possibility that reading may eventually recover quite well in the medial occipital lobectomy syndrome is not entirely consistent with the proposition that the left posterior lingual and fusiform gyri are absolutely necessary parts of the normal reading pathways. If they were, the patient (e.g., Case 2) should never recover reading to any degree of normal efficiency, because. those structures are directly invaded by the surgical efforts to remove the tumor. Therefore, some alternative pathway and/or a larger cortical area must be involved. Alternative Pathways Beyond strict adherence to Dejerine’s (1892, 1901) model, at least two different, alternative pathways of reading can be conceived, and both have been proposed. First, as stated by Geschwind (1965), there could be a pathway from right occipital association cortex to right angular gyrus and then across the corpus callosum to the left angular gyrus. However, if Geschwind’s alternative pathway were really part of the normal apparatus of high volume, efficient reading, all left occipital lobectomy patients should be able to read soon after surgery. Since this is not the case, it follows that the extra-occipital, right hemisphere pathway is not part of the usual neural mechanism of reading in the normally literate adult. It is also unlikely that this theoretically available pathway is capable of taking over significant lexic functions during recovery from left occipital lobectomy, because the delay of recovery in the medial lobectomy syndrome is so long. The right hemisphere is not retracted or otherwise disturbed during these surgeries, so there is no apparent reason for this intact alternative pathway to require such a long time to take over a function for which it is supposed to be potentially available. Similar time considerations are also relevant to the theoretical possibility of reading by an independent right hemisphere, as an explanation 586 SAMUEL H. GREENBLATT of the recovery in both patients. If it were readily available, it should have appeared sooner. Moreover, Zaidel and Peters (1981) have shown that right hemisphere reading is ideographic, so its syntactic capacities are limited. Thus, right hemisphere reading may account for some of the recovery in Case 1, but it cannot explain the postoperative 12th-grade reading level in Case 2. The second alternative pathway has been proposed more recently by Benson (1982, 1984), who postulates the existence of direct trans-splenial fibers from the right occipital association areas to the left angular gyrus. Objections to this pathway can be raised on several grounds: (1) No such fiber tracts are known to exist in humans; (2) the existence of such a tract would violate Flechsig’s rule (Flechsig, 1901), since it would involve transcallosal connections between nonhomologous cortical association areas; (3) the splenial fibers in this alternative pathway would be connecting ventral occipital cortex on the right with dorsal parietal cortex on the left. This anatomical arrangement would be inconsistent with accumulating evidence that the fibers of the splenium are rather strictly arranged in a layered, dorsal to ventral manner (Greenblatt, Saunders, Culver, & Bogdanowicz, 1980; Ferro, Bravo-Marques, Castro-Caldas, & Antunes, 1983; Pandya & Rosene, 1985); and (4) if this pathway existed, left occipital lobectomy patients should recover reading more thoroughly and more rapidly than they do, because the relevant anatomical areas (especially the splenium) are not directly affected by such surgery. Thus, strong objections can be raised to both proposals for alternative pathways. But Dejerine’s (1892, 1901) model, as originally proposed and more recently interpreted (Geschwind, 1962, 1965; Greenblatt, 1977), does not account for the recovery of reading in Case 2. Therefore, the following discussion proposes a model that invokes a role for the entire field of ventrolateral occipitotemporal cortex of both hemispheres in the pathways for normally efficient reading. A Functional-Anatomical Reading Model of the Preangular Pathways for The modified model is illustrated on the right side of Fig. 4, which omits the intrahemispheric pathways from calcarine cortices to ipsilateral occipital association areas for the sake of clarity. These latter pathways are shown on the feft side of Fig. 4. In essence, the model proposes that lexic information arriving in the nondominant (right) calcarine area is transmitted to the entire field of ipsilateral, ventral occipitotemporal association cortex, medial and lateral. The visual signals then cross to the dominant (left) side through the ventral splenium to the homologous association areas in the dominant occipital lobe (dashed lines in Fig. 4), where they are joined by lexic signals arriving from the left calcarine LEFT OCCIPITAL LOBECTOMY 587 FIG. 4. The drawing on the Iej? shows how a brain was cut to derive the drawing on the right. The most anterior aspect of the removed wedge is in the splenium of the corpus callosum. The upper slice is made through the angular gyrus to the splenium. The lower slices comes out ventral to the occipital tip, so that the calcarine cortex does not extend all the way to the occipital tip in the drawing on the right. See text for explanation of the diagrammatically illustrated tracts. area (solid lines in Fig. 4). The combined signals are transmitted to the left angular gyrus from the entire field of left ventral occipitotemporal association cortex, probably via the vertical occipital fasciculus. The ability of this model to explain the clinical differences between Case 1 and Case 2 can be shown by superimposing their respective lesions on the illustration of the model. In Case 1 (Fig. 5), the combined pathological and surgical lesions involved the medial and lateral aspects of the ventral occipitotemporal cortex. Although the entire right hemisphere and splenium were intact, the lexic signals in the right hemisphere had very little association cortex with which to connect in the left hemisphere. The patient’s partial recovery of reading can probably be attributed to some remaining function in the left ventral occipital lobe, but it was insufficient to mediate the high volume, rapid information processing that is characteristic of normal adult reading. In Case 2, on the other hand, a large field of left ventrolateral occipitotemporal association cortex remained uninvaded (Fig. 6). DISCUSSION Review of Other Cases Prior to the study of Hecaen et al., in 1952, there were a few scattered reports of reading and writing deficits in patients who had various surgical invasions of their dominant occipital lobes (Foerster, 1929; Vincent, 588 SAMUEL H. GREENBLATT FIG. 5. A diagrammatic superimposition of the lesion in the hololobectomy syndrome on the anatomical model of the preangular tracts for reading. See text for further explanation. David, & Puech, 1930; German & Fox, 1934; Hoff & Potzel, 1937). Unfortunately, the clinical and/or anatomical information in these reports is not sufficient to allow adequately detailed analysis of those cases. Among the seven patients studied by Hecaen et al. (1952), their cases 1, 2, 5, and 6 had lesions and clinical courses that were paradigmatic of the syndrome of alexia after dominant occipital hololobectomy. Those four right-handed patients had large left occipital lobectomies for infiltrating lesions, but the surgical margins largely spared the angular gyri, as evidenced by rapid recovery of writing after surgery. Reading re- FIG. 6. A diagrammatic superimposition of the lesion in the medial lobecfomy syndrome on the anatomical model of the preangular tracts for reading. See text for further explanation. LEFTOCCIPITALLOBECTOMY 589 covered much more gradually, though sometimes with fair accuracy if it was done slowly. Cases 1 and 5 were followed until their deaths at 7 months and 3 years, respectively, but the end results in cases 2 and 6 were not reported. Among the remaining three patients studied by HCcaen et al. (1952), two are irrelevant to the present discussion. Their case 4 had a large left intraventricular meningioma, which was removed through an occipital lobectomy that invaded the temporal and parietal lobes. That patient had persisting alexia, agraphia, and acalculia. Case 7 was a young, righthanded, bilingual male who had slowly improving alexia without agraphia after a right occipital lobectomy for a tubercle. The possibility of mixed dominance and/or the unlikely presence of another lesion makes this otherwise fascinating case difficult to interpret. Case 3 of Hecaen et al. (1952), was a 40-year-old, right-handed male notary, who had papilledema, an inferior right quadrantanopsia, finger angosia, and acalculia. His only language deficit was a distinct difficulty in reading. At surgery he was found to have a large left falx meningioma that reached forward as far as the posterior cuneus. At 9 months after surgery, his reading was almost normal to formal testing, except for some hesitations. He was still acalculic, but he had no other language deficits. However, he could not return to his occupation as a notary, and he read very little for pleasure. Despite the fact that this patient had a benign, medial occipital meningioma, his anatomical situation was not comparable to the present Case 2. The tumor was more dorsally located, and the resection involved a large part of the dominant occipital lobe. In effect, he had a hololobectomy for a benign lesion, and his postoperative reading did not recover full efficiency. The literature contains only one other case of a surgically removed, left medial occipital (falx) meningioma with an adequate description of the patient’s reading. In 1949, Petit-Dutaillis, Chavany, and Fenelon reported a 44-year-old right-handed male businessman, who presented with headache and progressive reading difficulty. At craniotomy, the bulk of the tumor was removed, but some of its dural attachment could only be coagulated. After surgery, the patient’s complaints of headache and alexia disappeared completely. No visual field defect was mentioned either before or after surgery. However, the patient returned 2 years later with generalized fatigue, alexia, sensory aphasia, acalculia, and a right lateral homonymous hemianopsia. The craniotomy was reopened 27 months after the original surgery. According to the authors’ text and diagrams, a complete left occipital lobectomy was performed, seemingly including resection of the left ventrolateral occipital cortex. Two and a half weeks later, the right lateral homonymous hemianopsia remained, but with some macular sparing. Reading was normal by formal testing. At 3 months after the second surgery, visual field testing showed sig- 590 SAMUEL H. GREENBLATT nificant restoration of vision in the right upper quadrant of both eyes. He could read, but he did not like to. The preservation of some of the patient’s right upper visual field speaks for the integrity of some of his left inferior occipital cortex, despite the authors’ description of a nearly complete left occipital iobectomy. Therefore, it may well be that some of the ventrolateral cortex was also preserved. From the foregoing review of the available literature, it is concluded that the present Case 2 and the patient of Petit-Dutaillis et al. (1949) are unique in their anatomical details and in the fact that they recovered some degree of efficient reading. Thus, there is only one other case that directly supports the anatomical model which was derived from Case 2. However, the modified model is substantiated by a rather different case, whose clinical aspects can be predicted from it. The Lateral Dominant Occipital Lobectomy Syndrome Consideration of the model shown in Fig. 4 leads to the prediction of a third syndrome of alexia after partial dominant occipital lobectomy, which should be associated with limited ventroiuteral lesions of the left occipitotemporal cortex (Fig. 7). Moreover, the model predicts that such patients should enjoy considerable recovery of reading if the original lesion and the surgical invasion are truly limited to the lateral aspects of the posterior dominant hemisphere. One such case has been observed, by Vincent et al. (1977). They described a 61-year-old woman who had a meningioma of the left lateral tentorium at the temporo-occipital junction. She had been a voracious reader, but her reading efficiency had been gradually declining for 2 years. After uneventful excision of her FIG. 7. A diagrammatic superimposition of the lesion in the lateral lobectomy syndrome on the anatomical model of the preangular tracts for reading. See text for further explanation. LEFT OCCIPITAL LOBECTOMY 591 tumor, her reading abilities gradually improved over a year’s time, though not quite to her premorbid level of efficiency (Vincent & Reeves, 1980). Cases of pure alexia due to ventrolateral occipital lesions may be supportive of the modified model only if the lesion is limited to the cortex. Alexia without agraphia can be caused by a purely subcortical lesion that disconnects the left angular gyrus from the entire field of the left ventral occipital cortex. This disconnection syndrome can be predicted from Dejerine’s original model (1892, 1901). It has been described alexia” by Greenblatt (1976, 1983) and confirmed by as “subangular others (Pirozzolo, Kerr, Obrzut, Morley, Haxby, & Lundgren, 1981; Ducarne, Bergego, & Gardeur, 1983). Therefore, accurate anatomical interpretation of alexia due to a left ventrolateral occipital lesion requires knowledge of whether the lesion involved the underlying occipitotemporal white matter. If the white matter is involved, the anatomical mechanism of the alexia may be simply subangular, and the role of the ventrolateral occipital cortex would be moot. Among the three cases of alexia with left ventrolateral occipital infarctions described by Johansson and Fahlgren (1979), one had a complete right homonymous hemianopsia and two had right upper quadrant defects. Therefore, the infarctions in those patients could have caused alexia by some combination of cortical and subangular lesions. The same caveat must be applied to the single case of alexia after restricted left lateral occipital infarction (patient 13) in the extensive series of Damasio and Damasio (1983). That patient also had a right homonymous hemianopsia. On the other hand, Henderson, Friedman, Teng, and Weiner (1985), reported a single case of a patient who had pure alexia without hemianopsia due to an intracerebral hemorrhage in the inferior occipitotemporal cortex. In this case and that of Vincent et al. (1977), it is reasonable to conclude that the patients’ alexias were caused by their cortical lesions. Finally, it is important to remember that the model shown in Fig. 4 is meant to portray only that part of the pathway for reading which is “preangular,” as that term has been used by Greenblatt (1983). Lexic signals arriving at both primary visual cortices are conducted to the region of the left angular gyrus along these pathways, but the latter region is somehow more central to the process of reading. The exact boundaries of the left parietal cortical area that is involved with reading have never been precisely determined. However, Nielsen’s (1939) analysis showed quite convincingly that the extent of this cortex is largely that of Brodman’s area 39 (angular gyms), usually with some anterior extension into the first temporal gyrus (i.e., toward Wemicke’s area). Thus, in the anatomical model derived from the study of acquired alexias in adults, the known brain areas that support reading are: (1) the preangular structures in the modified model (Fig. 4), and (2) the left angulotemporal region of cortex defined by Nielsen (1939). 592 SAMUEL H. GREENBLATT ADDENDUM A Note on the Functional Pathophysiology of Brain Tumors During the course of this paper’s review, the referees and the editor raised important issues concerning the effects of edema and other problems of interpreting tumor cases. Rather than inserting a few comments about these issues into the text in a random fashion, I thought it might be more effective and coherent to deal with them in this addendum. For the past several decades, the paradigmatic model for localization studies in neuropsychology has been ischemic infarction (nonhemorrhagic stroke). This model produces the most definitive results, because the tissue within the definable area of infarction is completely dead; therefore, its purported functions should be completely eliminated. With the advent of CT [and, more recently, magnetic resonance (MR)] imaging, the area of brain damage can be defined quite well in living subjects. However, studies of stroke patients with concurrent positron emission tomography (PET) and CT have shown that the areas of brain dysfunction are not necessarily coextensive with the areas of damage as defined by CT (Kushner, Reivich, Fieschi, Silver, Chawluk, Rosen, Greenberg, Burke, & Alavi, 1987). When tumor cases are used for localization studies, there are other difficulties. These problems can be summarized under three headings: cerebral edema, brain tissue infiltration, and mass effects. Cerebral edema. Any structural lesion in the brain (including ordinary strokes) can induce an increase in the water content of the surrounding brain, because such lesions alter the blood/brain barrier. However, tumors (and abscesses) are notorious for causing this problem. The issue then arises whether the area of edematous brain is dysfunctional. Penn (1980) has shown that this is not necessarily the case, even when severe edema is seen on CT. In Cases 1 and 2 of the present report, the issue is somewhat moot, because the peritumoral edema that was present preoperatively (and possibly related to the patient’s preoperative findings) had largely resolved by the time of the extensive postoperative testing that is the focus of this report. Nonetheless, the dysfunctional role of cerebral edema remains a significant conundrum in any localization studies involving tumors and other mass lesions. Tissue infiltration by intrinsic (glial) brain tumors. When a tumor arises from tissue elements that are intrinsic to the brain, it is difficult to know how much dysfunction this growth causes in low grade tumors, because the tumor is growing among the normal tissue elements. If such a tumor is highly malignant (e.g, the present Case l), its functional effect is even harder to sort out, because of several factors: (1) There is an infiltrating (outwardly growing) periphery of the tumor, which may actually be in the peritumoral edema that is seen on CT, or even beyond it (Burger, Dubois, Schold, Smith, Odom, Crafts, & Giangaspero, 1983); (2) the LEFT OCCIPITAL LOBECTOMY 593 center of the tumor is often necrotic, but that dead tissue may be mostly tumor cells rather than actual brain tissue; and (3) the mass of the tumor may have a compressive effect on adjacent tissue, similar to what happens in the tissue surrounding an extrinsic tumor (see below). However, once a surgical decompression has been done, the mass effect should be relieved-until the tumor mass recurs (e.g., Case 1). Muss effects. If an intracranial tumor arises from tissue elements that are not intrinsic to the brain (i.e., neither glial nor neuronal), then its major effect on the nearby brain is mechanical-the tumor pushes and thereby squeezes the brain. The paradigmatic example of this tumor type is the meningioma, which purportedly arises from arachnoidal cap cells. Although the tumor in Case 2 turned out to be malignant, it behaved like a meningioma during the time of this patient’s followup as reported here, because it remained extra-axial. That is, the tumor tissue remained outside of the neuraxis until late in the patient’s course. In a theoretical sense, a metastasis to the brain is also an extrinsic mass, as long as it grows as a separate, noninfiltrating lump within the brain tissue. In practical terms, however, this may be only a nicety of definition. For all types of tumors, the truly critical factor is time. In general, brain tissue does not tolerate rapid (hours to weeks) distortion; it becomes severely dysfunctional under such conditions. However, a slowly growing tumor (many months to many years) may cause amazingly little dysfunction, apparently because the adjacent brain retains much of its normal viability and connections. This factor probably accounts for the relatively late onset of symptoms and some of the recovery in Case 2. Thus, in trying to figure out behavioral localization in such cases, the focus of the analysis should be on the extent of the surgical removal of the distorted brain tissue surrounding the lesion. Despite all of the above difficulties (and others not described here), part of the purpose of this addendum is to make a plea for the judicious use of tumor cases in neurobehavioral correlation studies. They may teach us some things that strokes can not-for a very simple reason. 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