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Crossed aphasia in an illiterate dextral
BRAIN
AND
LANGUAGE
3, 164-172 (1976)
Crossed
Aphasia
in an HIiterate Dextral
AR 83 year old illiterate, right-handed woman developed a persistent nonfiuent aphasia following a right cerebral infarction (crossed aphasia). Computerized axial tomography localized the lesion to the right posterior frontal lobe. It is suggested that the neural mechanisms involved in learning to read and write may be critical for the complete establishment and maintenance of language dominance in the left hemisphere, and that, in this case, the patient’s failure to acquire reading and writing skills altered the normal evolution of language lateraiization and resutted in the right hemisphere assuming the dominant role.
This report details the case of an illiterate, right-handed woman who developed a persistent nonfluent aphasia and left hemiparesis following a right cerebral lesion. Although aphasia following right cerebral lesions in right-handed individuals (crossed aphasia) has been occasionally described, this represents the first documented case of crossed aphasia in an illiterate dextrai, CASE REPORT An 83 year old right-handed woman was admitted to the UCLA Medical Center on July 16,1974, because of the sudden onset of left sided weakness and inability to speak. According to her family, during the 8 months prior to admission she had several transient episodes of difficulty with speech, characterized primarily by a marked reduction in speech output. Following each episode. the patient told them she knew what she wanted to say but couldn’t get the words out. Comprehension was intact during these episodes and there were no associated visual, motor, or somotosensory deficits. On the night of admission, the patient suddenly began to speak very haltingly in a slurred voice. This was shortly followed by a loss of all speech and left sided weakness, including the face. She was taken to the hospital and admitted for evaluation. Examination on admission revealed an 83 year old woman, appearing younger than her stated age and in no acute distress. The blond pressure i Requests for reprints should be addressed to: Adam F. Wechsler, M.D., Neurology Service, 691/180,VA Wadsworth Hospital Center, Wilshire & Sawtelle Blvds., Los Angeles, California 90073. 164 Copyright D Wh hy Academic Press, Inc. All nghrs of reproduction III any form rewrved
CROSSED
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was 120/70 mm Hg, pulse 60/min, respirations 20/min, and temperature 98.6”F. The general physical examination was normal. On neurologic examination, the patient was cooperative and seemed alert. Her speech was limited to a few unintelligible grunt-like sounds. Most simple one-stage verbal commands such as “close your eyes” and “stick out your tongue” were followed correctly, but anything more complicated confused her. She could communicate through gesture when she needed a bedpan. She recognized and identified five of seven common objects shown to her by either nodding appropriately when the correct name was offered by the examiner or by demonstrating the use of the object. She was unable to follow any written commands and attempts at writing produced only a small amount of illegible scribble. (It was only after the initial examination that the full history of the patient’s illiteracy emerged.) Visual fields were full to finger confrontation and optokinetic nystagmus was normal in all directions. There was moderate left facial weakness, and the tongue deviated slightly to the left. She had a severe left hemiparesis, much greater in the arm than leg. Deep tendon reflexes were slightly increased on the left, and there was a left Babinski. There were no grasp, snout, suck, glabellar, or palmomental reflexes. Except for extinction of pinprick on the left on double simultaneous stimulation, the sensory examination was grossly intact. Auscultation of the head and neck revealed no bruits and there were no meningeal signs. Lumbar puncture yielded clear and colorless fluid under normal pressure. The fluid contained no red cells or white cells. The protein was 71 mg/lOO ml and the glucose 87 mg/lOO ml. Skull and chest roentgenograms were normal. An electrocardiogram revealed a sinus bradycardia but was otherwise unremarkable. An electroencephalogram showed focal right hemisphere slowing, most prominent anteriorly. A technetium-99 m pertechnetate cerebral blood flow study demonstrated decreased tracer uptake in the distribution of the right middle cerebral artery; a brain scan disclosed a questionable area of increased tracer uptake in the right posterior frontal region. The above studies were felt to be compatible with the clinical impression of a right cerebral infarction. Course
The patient’s left hemiparesis gradually improved. One month after admission, she still had moderate weakness of the left arm but only mild leg weakess and minimal left facial weakness. The tongue protruded in the midline and although rapid movements of the tongue were mildly reduced, there was no atrophy or obvious focal weakness. The left sided hyperreflexia and left Babinski remained, but no other pathological reflexes could be elicited. Thejawjerk was not increased. Confrontation visual field examination was normal as was somatosensory testing. There was never any incontinence.
166
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F. WECHSLER
More comprehensive evaluation of higher cerebral functions 1 month after admission revealed the following: The patient was alert, pleasant, and cooperative. There was no evidence of denial of illness, significant frustration, or depression. Her affective responses were consistently appropriate. She produced very little speech, and the speech she did produce was slurred, slightly reduced in volume, agrammatic, and haltingly expressed with great effort. When indicating that she wanted to go to the bathroom, for example, she said only, “Go-bathroom.” She almost never initiated conversation. Her speech contained occasional perseveration but no paraphasia. The patient could hum simple melodies and was slightly.more fluent with words in song than in conversational speech. She was oriented to time, place, and person, and answered correctly simple questions about current events and family data. She recognized and correctly identified most pictures of famous people. Those she failed to name initially were correctly identified when the right name was given by the examiner. She was unable to spell simple three or four letter words, and similar words spelled aloud by the examiner could not be identified. She was able to do only very simple calculations correctly, such as two plus two and ten minus five. She knew there were two nickels in one dime, but thought there were ten nickels in one dollar. Her comprehension was good for simple one-stage commands but she usually had difficulty following more complex instructions. There was agrammatism in repetition, e.g., “It is a nice day outside” was repeated as “nice-outside.” Her ability to name common objects was fairly good but there was occasional phonemic paraphasia, as in “pair” for “chair” and “saw” for “straw”; she consistently selected the correct name of an object when it was offered. Body parts and colors were identified without difficulty, and her ability to demonstrate the use of objects was unimpaired. She could tell the correct time from the wall clock. Although most one and two digit numbers were read correctly, she made frequent errors with numbers containing three digits or more. Some single letters were correctly identified but she was unable to read two or three letter words like go, dog, and cut. She had difficulty writing her own name accurately, with a tendency to perseverate letters and omit syllables. She was unable to write anything else, either spontaneously or to dictation, but was able to copy some printed words despite making frequent errors. She did somewhat better copying simple forms and designs, and her free drawing of a person and a house, although laborious and slightly malformed, was done fairly accurately. Although there was mild buccofacial apraxia to command, manifested by some difficulty performing tasks such as blowing a kiss, puckering her lips, or whistling, she did better imitating the above actions when performed by the examiner. No significant limb apraxia was present. With the exception of her signature, which improved considerably, most of the above language deficits present at 1 month after admission persisted
CROSSED
APHASIA
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essentially unchanged. An EM1 scan performed 5 months after her admission demonstrated a large, well defined area of decreased density in the posterior right frontal region (Fig. l), felt to be most compatible with a cerebral infarction in the distribution of the middle cerebral artery. There was no significant cerebral atrophy and the ventricles were felt to be at the upper limits of normal in size. Past History The patient was born in Russia. There was no history of birth injury and early developmental milestones were apparently normal. (This information was obtained from the patient and from two of her children. Although unable to provide precise details, they seemed reasonably confident in its accuracy.) She came to the United States at age five. Formal schooling ceased after the first grade (the reason for this was socio-economic and not because of intellectual difficulty). She learned to speak Yiddish and English fluently but never learned to read either language. (Although English was the preferred language during the patient’s adult life, she spoke both equally well; following her stroke, she was nearly equally aphasic in both languages and has remained so in her recovery to date.) She could sign her name but was unable to write anything else. She knew how to tell time and could play a few simple card games. In addition to her role as a housewife, she worked as a doctor’s assistant, in a candy store, as a cook, and in a laundry shop; according to her family she performed well in all these occupations. She was married at age sixteen and had four children-all high school graduates and doing well. Her family described her as “well-organized,” “neat,” “well-liked,” and “charming.” They felt there had been some decline in the patient’s memory over the last few years but that it had not been particularly severe or progressive, and that otherwise she had seemed as alert and attentive as ever just prior to her stroke. She has always been strongly right-handed (signing her name, eating, combing hair, needle threading, nail filing, lighting matches, throwing objects), and there is no history of any left-handedness in her family. DISCUSSION
Aphasia in right-handed individuals following right cerebral lesions (crossed aphasia) is extremely rare. Some of the features which have been described as being more characteristic of crossed aphasia in dextrals are familial evidence of sinistrality, predominance of expressive deficits over disturbances in comprehension and in naming, varying degrees of visual-constructive impairment and reading and writing disability, and relatively little apraxia, particularly of the limbs (Brown & Wilson, 1973; Clark & Zangwill, 1965; Ettlinger, Jackson, & Zangwill, 1955; Holmes &
168
ADAM
F. WECHSLER
FIG. 1. Computerized axial tomogram demonstrating a large, well-defined area of decreased density in the posterior right frontal region (arrows) most compatible with a cerebral infarction in the distribution of the middle cerebral artery. The ventricles (v) are at the upper limits of normal in size.
Sadoff, 1966). In the majority of cases described, agrammatism has been present in conversational speech and in repetition. The aphasia encountered in the patient described in this report demonstrated many of the above characteristics. Affection of expressive speech was much greater than the mild to moderate comprehension deficit. There was a tendency to agrammatism both in conversational speech and in repetition. Naming ability was only mildly disturbed. She had a varying degree of difficulty with visual-constructional tasks and, although some buccofacial apraxia was present, no significant limb apraxia was seen.
CROSSED
APHASIA
169
Unlike the majority of previously reported cases, the patient had no evidence of left-handedness in her family. What makes this case unique, however, is the fact that it is the first documented example of crossed aphasia occurring in a right-handed patient who never learned to read or write. Although one cannot rule out with certainty bilateral representation of language function in this patient, or that a lesion of the left hemisphere might also have resulted in aphasia, somewhat against these possibilities is the fact that if such bilateralization of language had indeed been present one would have expected a greater recovery of speech function after a focal lesions than what was observed (Zangwill, 1960). Furthermore, it should be mentioned that as far as could be determined by clinical and radiographical methods, the patient’s syndrome was produced by the single lesion in the right posterior frontal lobe. Clinical and laboratory testing revealed no evidence of any associated lesions in the same or opposite hemisphere. Although the patient did show deficits on the mental status examination which raise the possibility of some diffuse cerebral dysfunction, the overall picture, particularly when viewed in light of the past history, was different from that usually encountered in patients with diffuse dysfunction. On the contrary, the fact that she had successfully raised a family, worked effectively at several occupations, and had always remained alert and attentive despite her advanced age strongly argues against significant dementia. Moreover, the EMI scan did not reveal significant ventricular enlargement or cortical atrophy. There are probably several factors which contribute to the establishment of cerebral dominance in the developing individual. Neuroanatomic evidence of asymmetry of the superior surface of the temporal lobe (Planum Temporale) has been demonstrated in the newborn (Witelson & Pallie, 1973), as well as in the adult (Geschwind & Levitsky, 1968)human brain. Similar evidence of morphologic asymmetry has also been observed to be present in Broca’s area (Wada, 1974). In all these studies the left side has been larger than the right in the newborn as well as in the adult. At first glance, this asymmetrical enlargement in the regions of the major speech areas would seem to support the idea that it is these observed biological differences, rather than subsequent environmental influences, which are the principal determining factors in explaining lateralization of language to the left hemisphere (Witelson & Pallie, 1973). Recent physiologic evidence for hemispheric asymmetry from birth (Molfese, 1972)would also argue in favor of this concept, although it is conceivable that such physiologic asymmetry might very well be just a function of the increased mass of the left hemisphere. Although one cannot ignore the possibility that there is an inborn anatomic substrate which may account for the unilaterality of language, recent experimental evidence demonstrating anatomical changes in the brain in response to environmental factors may have implications for the
170
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importance of experiential factors in determining cerebral dominance. The experiments of Hubel and Wiesel (1962) on kittens demonstrated that precise patterned connections are established from the eye to the brain before birth, but that in the absence of visual input, these patterned connections become irreversibly damaged. Globus and Scheibel (1967) have shown that visual deafferentation in the rabbit results in deformation or loss of dendritic spines from neurons in the animal’s visual cortex. Other experiments producing olfactory deafferentation in rats resulted in a reduction in the dendritic density of the animals’ prepyriform cortex (Jones & Thomas, 1962). Electronmicroscopic studies of deafferented cerebellar cortex demonstrated degeneration of dendritic spines and climbing fibers (Hamori, 1973). Finally, Malkasian and Diamond (1971) showed that neonatal rats raised in an enriched environment had significant greater cortical depths than rats raised in an impoverished environment after 28 days. These studies reveal that environmental factors can produce microstructural changes in the neuronal connections of the brain after their initial formation. Although there is certainly a qualitative difference between the anatomic deafferentation experiments cited above and what might be called a functional hypoafferentation in the case presented, it is conceivable that failure to push certain kinds of input patterns over a given anatomic substrate may only differ in degree from the effects of anatomic deprivation of a specific type of sensory input. Moreover, although the patient did have some language input during her formative years, we really don’t know whether a critical intensity of afferent input through education in written language is necessary for initial lateralization to be maintained. Additional evidence that argues against the idea that the anatomic asymmetry of the cerebral hemispheres uniquely determines left sided language lateralization is the fact that the establishment of language dominance in the left hemisphere can be blocked by acquired left cerebral lesions early in life. In infancy and early childhood, the cerebral hemispheres are not yet specialized for language and either hemisphere is capable of subsequently taking over language function following a unilateral lesion of the opposite hemisphere if the lesion occurs early enough. It is not until after age five that aphasia is usually seen after lesions in the left hemisphere in dextrals and is infrequent after right cerebral lesions (Guttman, 1942), suggesting that by this time considerable lateralization of language function has already occurred. Recent dichotic listening studies (Krashen & Harshman, 1972) support this observation. In this regard, it is of interest that the acquisition of reading and writing skills generally takes place about the same time that left sided lesions first begin to consistently produce aphasia in dextrals and when right cerebral lesions generally no longer do.
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171
What are some possible implications for the present case and for cerebral dominance in general? Although one can only speculate on the possible role the patient’s illiteracy played in the clinical picture encountered, the hypothesis I would like to advance is that the neural mechanisms involved in learning to read and write may be necessary for the complete establishment and maintenance of language dominance. Despite the observed anatomic asymmetries of both frontal and temporal speech regions of the brain at birth, it is suggested that over the long epochs that have transpired in the evolution of the human brain, the fullest maturation of critical cell assemblies in the principal language areas of the dominant hemisphere may only have occurred with the development and practice of symbolic operations peculiar to reading and writing. Perhaps in the present case, the patient’s failure to learn to read and write altered the normal evolution of language lateralization and resulted in a shift in the mediation of language function to her “nondominant” hemisphere. There is some support for this hypothesis in the clinical studies of Gorlitzer von Mundy (1957) and Cameron, Currier, and Haerer (1972). Both studies found that the occurrence of aphasia in illiterates with left cerebral lesions is unusual. In addition, there is evidence in the study of Cameron, Currier, and Haerer that the incidence of aphasia is directly proportional to the degree of literacy, suggesting that literacy may play an important role in enhancing lateralization. Of course, since this is only a single case, no definitive conclusions can be drawn. On the other hand, if the above hypothesis has validity the case would serve as an interesting example of the interaction of hereditary and environmental factors in the lateralization of language. REFERENCES Brown, J., & Wilson, F. 1973. Crossed aphasia in a dextral. Neurology (Minneapolis), 23, 907-91 I. Cameron, R., Currier, R., & Haerer, A. 1971. Aphasia and literacy. British Journal of Communication, 6, 161- 163. Clark, B., & Zangwill, 0. 1965.A case of “crossed aphasia” in a dextral. Neuropsychologia, 3, 81-86. Ettlinger, G., Jackson, C., & Zangwill, 0. 1955. Dysphasia following right temporal lobectomy in a right-handed man. Journal of Neurology, Neurosurgery and Psychiatry, 18, 214-217. Geschwind, N., & Levitsky, W. 1968.Human brain: Left-right asymmetries in the temporal speech region. Science, 161, l86- 187. Globus, A., & Scheibel, A. 1967.The effect of visual deprivation on cortical neurons: a Golgi study. Experimental Neurology, 19, 33 I-345. Gorlitzer von Mundy, V. 1957.Zur Prage der paarig veranlagten sprachzentren. Nervenarzf, 28: 212-215. Guttman, E. 1942. Aphasia in children. Brain, 65, 205-219. Hamori, J. 1973. Developmental morphology ofdendritic post synaptic specializations. In K.
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Lissak (Ed.), Recent development of neurobiology in Hungary. Budapest: Akademia Kiado, 4, pp. 9-32. Holmes, J., & Sadoff, R. 1966. Aphasia due to a right hemisphere tumor in a right-handed man. Neurology (Minneapolis), 16, 392-397. Hubel, D., & Wiesel, T. 1962. Receptive fields, binocular interaction and functional architecture in the cat’s visual cortex. Journal of Physiology, 160, 106- 154. Jones, W., & Thomas, B. 1962. Changes in the dendritic organization of neurons in the JournalofAnatomy(London), %,375-381. cerebralcortexfollowingdeafferentation. Krashen, S., & Harshman, R. 1972. Lateralization and the critical period, UCLA working papers in phonetics, 22, 6. Malkasian, D., & Diamond, N. 1971. The effects of environmental manipulation on the morphology of the neonate rat brain. International Journal of Neuroscience, 2, 161-170. Molfese, D. Cerebral asymmetry in infants, children and adults: Auditory evoked responses to speech and music stimuli. Paper presented at the Acoustical Society of America, Miami, 1972. Wada, J. 1974. Morphologic asymmetry of human cerebral hemispheres: Temporal and frontal speech zones in 100adult and 100infant brains. Neurology (Minneapolis), 24, 349. Witelson, S., & Pallie, W. 1973.Left hemisphere specialization for language in the newborn. Brain, 96, 641-646. Zangwill, 0. 1960. Cerebral dominance and its relationship to psychological function. London: Oliver and Boyd. P. 26.
AND
LANGUAGE
3, 164-172 (1976)
Crossed
Aphasia
in an HIiterate Dextral
AR 83 year old illiterate, right-handed woman developed a persistent nonfiuent aphasia following a right cerebral infarction (crossed aphasia). Computerized axial tomography localized the lesion to the right posterior frontal lobe. It is suggested that the neural mechanisms involved in learning to read and write may be critical for the complete establishment and maintenance of language dominance in the left hemisphere, and that, in this case, the patient’s failure to acquire reading and writing skills altered the normal evolution of language lateraiization and resutted in the right hemisphere assuming the dominant role.
This report details the case of an illiterate, right-handed woman who developed a persistent nonfluent aphasia and left hemiparesis following a right cerebral lesion. Although aphasia following right cerebral lesions in right-handed individuals (crossed aphasia) has been occasionally described, this represents the first documented case of crossed aphasia in an illiterate dextrai, CASE REPORT An 83 year old right-handed woman was admitted to the UCLA Medical Center on July 16,1974, because of the sudden onset of left sided weakness and inability to speak. According to her family, during the 8 months prior to admission she had several transient episodes of difficulty with speech, characterized primarily by a marked reduction in speech output. Following each episode. the patient told them she knew what she wanted to say but couldn’t get the words out. Comprehension was intact during these episodes and there were no associated visual, motor, or somotosensory deficits. On the night of admission, the patient suddenly began to speak very haltingly in a slurred voice. This was shortly followed by a loss of all speech and left sided weakness, including the face. She was taken to the hospital and admitted for evaluation. Examination on admission revealed an 83 year old woman, appearing younger than her stated age and in no acute distress. The blond pressure i Requests for reprints should be addressed to: Adam F. Wechsler, M.D., Neurology Service, 691/180,VA Wadsworth Hospital Center, Wilshire & Sawtelle Blvds., Los Angeles, California 90073. 164 Copyright D Wh hy Academic Press, Inc. All nghrs of reproduction III any form rewrved
CROSSED
APHASIA
165
was 120/70 mm Hg, pulse 60/min, respirations 20/min, and temperature 98.6”F. The general physical examination was normal. On neurologic examination, the patient was cooperative and seemed alert. Her speech was limited to a few unintelligible grunt-like sounds. Most simple one-stage verbal commands such as “close your eyes” and “stick out your tongue” were followed correctly, but anything more complicated confused her. She could communicate through gesture when she needed a bedpan. She recognized and identified five of seven common objects shown to her by either nodding appropriately when the correct name was offered by the examiner or by demonstrating the use of the object. She was unable to follow any written commands and attempts at writing produced only a small amount of illegible scribble. (It was only after the initial examination that the full history of the patient’s illiteracy emerged.) Visual fields were full to finger confrontation and optokinetic nystagmus was normal in all directions. There was moderate left facial weakness, and the tongue deviated slightly to the left. She had a severe left hemiparesis, much greater in the arm than leg. Deep tendon reflexes were slightly increased on the left, and there was a left Babinski. There were no grasp, snout, suck, glabellar, or palmomental reflexes. Except for extinction of pinprick on the left on double simultaneous stimulation, the sensory examination was grossly intact. Auscultation of the head and neck revealed no bruits and there were no meningeal signs. Lumbar puncture yielded clear and colorless fluid under normal pressure. The fluid contained no red cells or white cells. The protein was 71 mg/lOO ml and the glucose 87 mg/lOO ml. Skull and chest roentgenograms were normal. An electrocardiogram revealed a sinus bradycardia but was otherwise unremarkable. An electroencephalogram showed focal right hemisphere slowing, most prominent anteriorly. A technetium-99 m pertechnetate cerebral blood flow study demonstrated decreased tracer uptake in the distribution of the right middle cerebral artery; a brain scan disclosed a questionable area of increased tracer uptake in the right posterior frontal region. The above studies were felt to be compatible with the clinical impression of a right cerebral infarction. Course
The patient’s left hemiparesis gradually improved. One month after admission, she still had moderate weakness of the left arm but only mild leg weakess and minimal left facial weakness. The tongue protruded in the midline and although rapid movements of the tongue were mildly reduced, there was no atrophy or obvious focal weakness. The left sided hyperreflexia and left Babinski remained, but no other pathological reflexes could be elicited. Thejawjerk was not increased. Confrontation visual field examination was normal as was somatosensory testing. There was never any incontinence.
166
ADAM
F. WECHSLER
More comprehensive evaluation of higher cerebral functions 1 month after admission revealed the following: The patient was alert, pleasant, and cooperative. There was no evidence of denial of illness, significant frustration, or depression. Her affective responses were consistently appropriate. She produced very little speech, and the speech she did produce was slurred, slightly reduced in volume, agrammatic, and haltingly expressed with great effort. When indicating that she wanted to go to the bathroom, for example, she said only, “Go-bathroom.” She almost never initiated conversation. Her speech contained occasional perseveration but no paraphasia. The patient could hum simple melodies and was slightly.more fluent with words in song than in conversational speech. She was oriented to time, place, and person, and answered correctly simple questions about current events and family data. She recognized and correctly identified most pictures of famous people. Those she failed to name initially were correctly identified when the right name was given by the examiner. She was unable to spell simple three or four letter words, and similar words spelled aloud by the examiner could not be identified. She was able to do only very simple calculations correctly, such as two plus two and ten minus five. She knew there were two nickels in one dime, but thought there were ten nickels in one dollar. Her comprehension was good for simple one-stage commands but she usually had difficulty following more complex instructions. There was agrammatism in repetition, e.g., “It is a nice day outside” was repeated as “nice-outside.” Her ability to name common objects was fairly good but there was occasional phonemic paraphasia, as in “pair” for “chair” and “saw” for “straw”; she consistently selected the correct name of an object when it was offered. Body parts and colors were identified without difficulty, and her ability to demonstrate the use of objects was unimpaired. She could tell the correct time from the wall clock. Although most one and two digit numbers were read correctly, she made frequent errors with numbers containing three digits or more. Some single letters were correctly identified but she was unable to read two or three letter words like go, dog, and cut. She had difficulty writing her own name accurately, with a tendency to perseverate letters and omit syllables. She was unable to write anything else, either spontaneously or to dictation, but was able to copy some printed words despite making frequent errors. She did somewhat better copying simple forms and designs, and her free drawing of a person and a house, although laborious and slightly malformed, was done fairly accurately. Although there was mild buccofacial apraxia to command, manifested by some difficulty performing tasks such as blowing a kiss, puckering her lips, or whistling, she did better imitating the above actions when performed by the examiner. No significant limb apraxia was present. With the exception of her signature, which improved considerably, most of the above language deficits present at 1 month after admission persisted
CROSSED
APHASIA
167
essentially unchanged. An EM1 scan performed 5 months after her admission demonstrated a large, well defined area of decreased density in the posterior right frontal region (Fig. l), felt to be most compatible with a cerebral infarction in the distribution of the middle cerebral artery. There was no significant cerebral atrophy and the ventricles were felt to be at the upper limits of normal in size. Past History The patient was born in Russia. There was no history of birth injury and early developmental milestones were apparently normal. (This information was obtained from the patient and from two of her children. Although unable to provide precise details, they seemed reasonably confident in its accuracy.) She came to the United States at age five. Formal schooling ceased after the first grade (the reason for this was socio-economic and not because of intellectual difficulty). She learned to speak Yiddish and English fluently but never learned to read either language. (Although English was the preferred language during the patient’s adult life, she spoke both equally well; following her stroke, she was nearly equally aphasic in both languages and has remained so in her recovery to date.) She could sign her name but was unable to write anything else. She knew how to tell time and could play a few simple card games. In addition to her role as a housewife, she worked as a doctor’s assistant, in a candy store, as a cook, and in a laundry shop; according to her family she performed well in all these occupations. She was married at age sixteen and had four children-all high school graduates and doing well. Her family described her as “well-organized,” “neat,” “well-liked,” and “charming.” They felt there had been some decline in the patient’s memory over the last few years but that it had not been particularly severe or progressive, and that otherwise she had seemed as alert and attentive as ever just prior to her stroke. She has always been strongly right-handed (signing her name, eating, combing hair, needle threading, nail filing, lighting matches, throwing objects), and there is no history of any left-handedness in her family. DISCUSSION
Aphasia in right-handed individuals following right cerebral lesions (crossed aphasia) is extremely rare. Some of the features which have been described as being more characteristic of crossed aphasia in dextrals are familial evidence of sinistrality, predominance of expressive deficits over disturbances in comprehension and in naming, varying degrees of visual-constructive impairment and reading and writing disability, and relatively little apraxia, particularly of the limbs (Brown & Wilson, 1973; Clark & Zangwill, 1965; Ettlinger, Jackson, & Zangwill, 1955; Holmes &
168
ADAM
F. WECHSLER
FIG. 1. Computerized axial tomogram demonstrating a large, well-defined area of decreased density in the posterior right frontal region (arrows) most compatible with a cerebral infarction in the distribution of the middle cerebral artery. The ventricles (v) are at the upper limits of normal in size.
Sadoff, 1966). In the majority of cases described, agrammatism has been present in conversational speech and in repetition. The aphasia encountered in the patient described in this report demonstrated many of the above characteristics. Affection of expressive speech was much greater than the mild to moderate comprehension deficit. There was a tendency to agrammatism both in conversational speech and in repetition. Naming ability was only mildly disturbed. She had a varying degree of difficulty with visual-constructional tasks and, although some buccofacial apraxia was present, no significant limb apraxia was seen.
CROSSED
APHASIA
169
Unlike the majority of previously reported cases, the patient had no evidence of left-handedness in her family. What makes this case unique, however, is the fact that it is the first documented example of crossed aphasia occurring in a right-handed patient who never learned to read or write. Although one cannot rule out with certainty bilateral representation of language function in this patient, or that a lesion of the left hemisphere might also have resulted in aphasia, somewhat against these possibilities is the fact that if such bilateralization of language had indeed been present one would have expected a greater recovery of speech function after a focal lesions than what was observed (Zangwill, 1960). Furthermore, it should be mentioned that as far as could be determined by clinical and radiographical methods, the patient’s syndrome was produced by the single lesion in the right posterior frontal lobe. Clinical and laboratory testing revealed no evidence of any associated lesions in the same or opposite hemisphere. Although the patient did show deficits on the mental status examination which raise the possibility of some diffuse cerebral dysfunction, the overall picture, particularly when viewed in light of the past history, was different from that usually encountered in patients with diffuse dysfunction. On the contrary, the fact that she had successfully raised a family, worked effectively at several occupations, and had always remained alert and attentive despite her advanced age strongly argues against significant dementia. Moreover, the EMI scan did not reveal significant ventricular enlargement or cortical atrophy. There are probably several factors which contribute to the establishment of cerebral dominance in the developing individual. Neuroanatomic evidence of asymmetry of the superior surface of the temporal lobe (Planum Temporale) has been demonstrated in the newborn (Witelson & Pallie, 1973), as well as in the adult (Geschwind & Levitsky, 1968)human brain. Similar evidence of morphologic asymmetry has also been observed to be present in Broca’s area (Wada, 1974). In all these studies the left side has been larger than the right in the newborn as well as in the adult. At first glance, this asymmetrical enlargement in the regions of the major speech areas would seem to support the idea that it is these observed biological differences, rather than subsequent environmental influences, which are the principal determining factors in explaining lateralization of language to the left hemisphere (Witelson & Pallie, 1973). Recent physiologic evidence for hemispheric asymmetry from birth (Molfese, 1972)would also argue in favor of this concept, although it is conceivable that such physiologic asymmetry might very well be just a function of the increased mass of the left hemisphere. Although one cannot ignore the possibility that there is an inborn anatomic substrate which may account for the unilaterality of language, recent experimental evidence demonstrating anatomical changes in the brain in response to environmental factors may have implications for the
170
ADAM
F. WECHSLER
importance of experiential factors in determining cerebral dominance. The experiments of Hubel and Wiesel (1962) on kittens demonstrated that precise patterned connections are established from the eye to the brain before birth, but that in the absence of visual input, these patterned connections become irreversibly damaged. Globus and Scheibel (1967) have shown that visual deafferentation in the rabbit results in deformation or loss of dendritic spines from neurons in the animal’s visual cortex. Other experiments producing olfactory deafferentation in rats resulted in a reduction in the dendritic density of the animals’ prepyriform cortex (Jones & Thomas, 1962). Electronmicroscopic studies of deafferented cerebellar cortex demonstrated degeneration of dendritic spines and climbing fibers (Hamori, 1973). Finally, Malkasian and Diamond (1971) showed that neonatal rats raised in an enriched environment had significant greater cortical depths than rats raised in an impoverished environment after 28 days. These studies reveal that environmental factors can produce microstructural changes in the neuronal connections of the brain after their initial formation. Although there is certainly a qualitative difference between the anatomic deafferentation experiments cited above and what might be called a functional hypoafferentation in the case presented, it is conceivable that failure to push certain kinds of input patterns over a given anatomic substrate may only differ in degree from the effects of anatomic deprivation of a specific type of sensory input. Moreover, although the patient did have some language input during her formative years, we really don’t know whether a critical intensity of afferent input through education in written language is necessary for initial lateralization to be maintained. Additional evidence that argues against the idea that the anatomic asymmetry of the cerebral hemispheres uniquely determines left sided language lateralization is the fact that the establishment of language dominance in the left hemisphere can be blocked by acquired left cerebral lesions early in life. In infancy and early childhood, the cerebral hemispheres are not yet specialized for language and either hemisphere is capable of subsequently taking over language function following a unilateral lesion of the opposite hemisphere if the lesion occurs early enough. It is not until after age five that aphasia is usually seen after lesions in the left hemisphere in dextrals and is infrequent after right cerebral lesions (Guttman, 1942), suggesting that by this time considerable lateralization of language function has already occurred. Recent dichotic listening studies (Krashen & Harshman, 1972) support this observation. In this regard, it is of interest that the acquisition of reading and writing skills generally takes place about the same time that left sided lesions first begin to consistently produce aphasia in dextrals and when right cerebral lesions generally no longer do.
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What are some possible implications for the present case and for cerebral dominance in general? Although one can only speculate on the possible role the patient’s illiteracy played in the clinical picture encountered, the hypothesis I would like to advance is that the neural mechanisms involved in learning to read and write may be necessary for the complete establishment and maintenance of language dominance. Despite the observed anatomic asymmetries of both frontal and temporal speech regions of the brain at birth, it is suggested that over the long epochs that have transpired in the evolution of the human brain, the fullest maturation of critical cell assemblies in the principal language areas of the dominant hemisphere may only have occurred with the development and practice of symbolic operations peculiar to reading and writing. Perhaps in the present case, the patient’s failure to learn to read and write altered the normal evolution of language lateralization and resulted in a shift in the mediation of language function to her “nondominant” hemisphere. There is some support for this hypothesis in the clinical studies of Gorlitzer von Mundy (1957) and Cameron, Currier, and Haerer (1972). Both studies found that the occurrence of aphasia in illiterates with left cerebral lesions is unusual. In addition, there is evidence in the study of Cameron, Currier, and Haerer that the incidence of aphasia is directly proportional to the degree of literacy, suggesting that literacy may play an important role in enhancing lateralization. Of course, since this is only a single case, no definitive conclusions can be drawn. On the other hand, if the above hypothesis has validity the case would serve as an interesting example of the interaction of hereditary and environmental factors in the lateralization of language. REFERENCES Brown, J., & Wilson, F. 1973. Crossed aphasia in a dextral. Neurology (Minneapolis), 23, 907-91 I. Cameron, R., Currier, R., & Haerer, A. 1971. Aphasia and literacy. British Journal of Communication, 6, 161- 163. Clark, B., & Zangwill, 0. 1965.A case of “crossed aphasia” in a dextral. Neuropsychologia, 3, 81-86. Ettlinger, G., Jackson, C., & Zangwill, 0. 1955. Dysphasia following right temporal lobectomy in a right-handed man. Journal of Neurology, Neurosurgery and Psychiatry, 18, 214-217. Geschwind, N., & Levitsky, W. 1968.Human brain: Left-right asymmetries in the temporal speech region. Science, 161, l86- 187. Globus, A., & Scheibel, A. 1967.The effect of visual deprivation on cortical neurons: a Golgi study. Experimental Neurology, 19, 33 I-345. Gorlitzer von Mundy, V. 1957.Zur Prage der paarig veranlagten sprachzentren. Nervenarzf, 28: 212-215. Guttman, E. 1942. Aphasia in children. Brain, 65, 205-219. Hamori, J. 1973. Developmental morphology ofdendritic post synaptic specializations. In K.
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Lissak (Ed.), Recent development of neurobiology in Hungary. Budapest: Akademia Kiado, 4, pp. 9-32. Holmes, J., & Sadoff, R. 1966. Aphasia due to a right hemisphere tumor in a right-handed man. Neurology (Minneapolis), 16, 392-397. Hubel, D., & Wiesel, T. 1962. Receptive fields, binocular interaction and functional architecture in the cat’s visual cortex. Journal of Physiology, 160, 106- 154. Jones, W., & Thomas, B. 1962. Changes in the dendritic organization of neurons in the JournalofAnatomy(London), %,375-381. cerebralcortexfollowingdeafferentation. Krashen, S., & Harshman, R. 1972. Lateralization and the critical period, UCLA working papers in phonetics, 22, 6. Malkasian, D., & Diamond, N. 1971. The effects of environmental manipulation on the morphology of the neonate rat brain. International Journal of Neuroscience, 2, 161-170. Molfese, D. Cerebral asymmetry in infants, children and adults: Auditory evoked responses to speech and music stimuli. Paper presented at the Acoustical Society of America, Miami, 1972. Wada, J. 1974. Morphologic asymmetry of human cerebral hemispheres: Temporal and frontal speech zones in 100adult and 100infant brains. Neurology (Minneapolis), 24, 349. Witelson, S., & Pallie, W. 1973.Left hemisphere specialization for language in the newborn. Brain, 96, 641-646. Zangwill, 0. 1960. Cerebral dominance and its relationship to psychological function. London: Oliver and Boyd. P. 26.