Acquired Aphasia in Children

13 Acquired Aphasia in Children DOROTHY M. ARAM Introduction Children versus Adults Language disruptions secondary to acquired central nervous system (CNS) lesions differ between children and adults in multiple respects. Chief among these differences are the developmental stage of language ac- quisition at the time of insult and the developmental stage of the CNS. In adult aphasia premorbid mastery of language is assumed, at least to the level of the aphasic's intellectual ability and educational opportunities. Acquired aphasia sustained in childhood, however, interferes with the developmental process of language learning and disrupts those aspects of language already mastered. The investigator and clinician thus are faced with sorting which aspects of language have been lost or impaired from those yet to emerge, potentially in an altered manner. Complicating research and clinical practice in this area is the need to account continually for the developmental stage of that aspect of language under consideration for each child. In research, stage-appropriate language tasks must be se- lected, and comparison must be made to peers of comparable age and language stage. Also, appropriate controls common in adult studies, such as social class and gender, are critical. These requirements present no small challenge, as most studies involve a wide age range of children and ado- lescents. In clinical practice, the question is whether assessment tools used for developmental language disorders should be used or whether adult aphasia batteries should be adapted for children. The answer typically de- pends on the age of the child and the availability of age- and stage-appro- 451 ACQUIRED APHASIA, THIRD EDITION Copyright 1998 by Academic Press. All rights of reproduction in any form reserved. 452 Dorothy M. Aram priate measures. With childhood acquired aphasias, the question of how language is altered following a CNS insult is inextricably related to how language learning proceeds. The second major difference between adults and children sustaining language-disrupting neurological insults is the stage of maturity of the CNS at the time of insult. The controversy relating to the degree of early hemispher- ic specialization versus equipotentiality for language (e.g., Kinsbourne & Hiscock, 1977; Lenneberg, 1967) has sparked much of the research in this area during the past 20 years. Although most of the data appear to evidence considerable early brain specialization for language and other higher cognitive functions (Best, 1988; Molfese & Segalowitz, 1988), the remarkable capacity of young children to recover from major cortical insults has been repeatedly reported. That children recover much more rapidly and completely from focal brain lesions than do adult with comparable insults has become a truism that is generall~ although not universall~ supported. The rapidity and level of language recovery in young brain-injured children evidence a degree of functional and presumed neural plasticity far exceeding that in adults (Aram & Eisele, 1992). Most (Bates et al., in press; Eisele & Aram, 1993; Lees, 1993; Vargha-Khadem, Isaacs, van der Werf, Robb, & Wilson, 1992) but not all (Martins & Ferro, 1993; Paquier & Van Dongen, 1993) investigators in this field conclude that the pattern of language loss following lesions in children generally do not correspond to what is observed in adults with similar in- juries. Rather, as Bates et al. (1997) recently have suggested, the data thus far suggest that "innate regional biases in style of information processing lead to familiar patterns of brain organization for language under normal conditions and permit alternative patterns to emerge in children with focal brain injury" (abstract). An immature CNS at the time of insult does not necessarily lead, however, to a more favorable outcome. In some instancesmfor example, conditions resulting in diffuse brain involvement--a brain insult incurred at a young age may be more, rather than less, deleterious, a topic returned to later in this chapter. The essential concern here is that just as the child's language system is in the process of development, so too is the central nervous system, processes that are complete or declining in the adult. Although in many in- stances the immaturity of the child's CNS supports alternatives for greater functional recovery, at other times early insults appear to interfere with pri- mary skills, thus precluding later achievements. Terminology ACQUIRED VERSUS DEVELOPMENTALAPHASIA The term ACQUIRED is used to modify the term APHASIA in children to dis- tinguish language disorders accompanied by known CNS insults from the 13 AcquiredAphasia in Children 453 much more common form of DEVELOPMENTAL APHASIA. Developmental aphasia, also referred to as developmental language disorders or specific language impairment, is manifest when a child fails to learn to talk normal- ly, but a frank neurological basis is not apparent. Indeed, the presence of a frank neurological abnormality typically is established as an exclusionary criterion for the diagnosis of developmental aphasia or developmental language disorder (Benton, 1964; Tallal, 1988). Although many researchers as- sume abnormal neurological functions give rise to the developmental aphasias (e.g., Rapin & Allen, 1988), the search for identifiable brain lesions to account for these developmental disorders has been largely unproductive. Also, the language symptomatology that follows acquired unilateral lesions typically has been found to be less severe and less persistent than is often seen in children with developmental language disorders (Aram & Eisele, 1994). This chapter addresses the language abilities only in children with known brain insults, that is, those with acquired aphasia. ACQUIRED LANGUAGE LOSS VERSUS ACQUIRED BRAIN LESION According to the literature on acquired aphasia in children, even though the lesion is generally acquiredmthrough stroke, tumor, trauma, or some other form of CNS insultmthe language loss is not necessarily "acquired," as frequently the insult occurs before much language has been acquired and therefore not much can be "lost." Few studies have been confined to older children with relatively well developed language at the time of insult; rather most have involved a wide age range at lesion onset, typically extending from pre- or perinatal insults to those incurred during adoles- cence. Indeed, many studies compare outcome as a function of whether the lesion was sustained prior to 1 year of age (the somewhat arbitrary de- marcation for the onset of language) or after 1 year of age, with a broad range of onset ages included in the latter group. Therefore, acquired aphasia, as used here, refers to language discrepancies or abnormalities accompanied by a known brain lesion, irrespective of when during the course of language development that lesion occurred. Nature of the Studies Available Although a more homogeneous age of lesion onset would be desirable in reports of acquired aphasia in children, age is only one of several markedly heterogeneous variables complicating interpretation of the ma- jority of studies addressing this topic. The major methodological problems confounding review of work in this area have been reviewed elsewhere (Aram & Whitaker, 1988). Five variables, typically noncomparable both within and across studies, are of particular note: 454 Dorothy M. Aram 1. AGE OF LESION ONSET was discussed earlier and generally involves a broad spectrum of ages. 2. The NATURE OF THE NEUROLOGICAL INSULTS described in studies are typically diverse, and often include such disparate conditions as tumors, head trauma, herpes encephalitis, and cerebral vascular accidents in a sin- gle study. This chapter draws not only from studies specifically addressing acquired CNS insults and aphasias in children, but also from studies of in- fantile or childhood hemiplegias, as the overlap of children included in these studies is considerable. In an effort to reduce the wide diversity of conditions discussed here, this chapter does not address the hemispher- ectomy or epileptic aphasia literature except when an occasional hemi- spherectomized or epileptic aphasic child has been included in a group study involving heterogeneous causes. 3. EXTENSIVENESS OF BRAIN INVOLVEMENT also varies widely from cir- cumscribed focal lesions to diffuse white and gray matter involvement. Of- ten specification of the degree of actual brain involvement is lacking and can only be inferred from the etiology or clinical pattern. This topic is discussed more fully later in this chapter. 4. AGE AT FOLLOW-UP varies both with respect to chronological age and with respect to time elapsed since lesion onset. A few studies have described language during the acute period of recovery, although most have assessed language status years after lesion onset. 5. The METHOD OF EVALUATIONused in various studies has differed. Un- til the past 15 years, most statements pertaining to language ability were based on nonsystematic clinical observations or on verbal intelligence scores. More recently, most studies have begun to report standardized language tests, and a few have begun to include a more experimental or hy- pothesis-testing approach to the study of acquired aphasia in children. Because very few experimentally rich or methodologically sound studies of relatively homogeneous groups of lesioned children exist, the present review is not restricted to those few studies. Rather,

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