Cerebral Lateralization and Cognitive Deficits After Congenital Hemiparesis Anneli Kolk, MD, PhD, and Tiina Talvik, MD, PhD The purpose of this study was to investigate whether and how handedness is related to the processes of cerebral lateralization and cognitive performance in children with congenital insult. Fifty-six children (31 males and 25 females) with congenital hemiparesis and 14 control subjects were investigated. Of these chil- dren, 32 had a left hemisphere lesion, and 24 children had a right hemisphere lesion. There were 30 right- handed, 23 left-handed, and three ambidextrous chil- dren in the study group. The neuropsychologic as- sessment was performed using the NEPSY (a developmental neuropsychological assessment of child development) test battery. We found that 41% of the hemiparetic children and 72% of the children with a left hemisphere lesion were left-handed. In children contralateral to lesion handedness (no evidence of interhemispheric transfer of functions), we found dif- fuse cognitive deficits with impaired language abilities and poor visuomotor and narrative memory process- ing. In contrast, children with ipsilateral to brain lesion handedness (interhemispheric transfer of functions) demonstrated minimal or moderate side-specific cog- nitive dysfunction. Right-handed children with a right hemisphere lesion had attention, spatial, and short- term memory problems; left-handed children with a left hemisphere lesion had receptive language and visuomotor difficulties. Handedness combined with neuropsychologic assessment is a reliable indicator of the processes of cerebral reorganization after early brain insult. © 2002 by Elsevier Science Inc. All rights reserved. Kolk A, Talvik T. Cerebral lateralization and cognitive deficits after congenital hemiparesis. Pediatr Neurol 2002; 27:356-362. Introduction The discovery of hemispheral asymmetry or lateraliza- tion process (i.e., the degree to which each side of the brain is dominant [or specialized] for a specific cognitive function) will enhance our understanding of neurobehav- ioral development and recovery processes. Intrahemi- spheric lateralization of functions, such as handedness, language, visual abilities, and other less easily conceptu- alized behaviors, is an important developmental indicator in brain-damaged children. Explanations of anomalous cerebral lateralization in adults can be categorized into two main types—natural and pathologic. Natural is based on the individual variants of mechanisms that induce typical asymmetries and could be genetic [1] (the right shift theory [i.e., rs+ gene]). Pathologic cerebral specialization is the result of various pathologies, such as cerebral palsy, stroke, epilepsy, and traumas. Despite a lively and continuing interest in this area [2-7], the localization of specific cerebral functions (e.g., memory, speech, visuomotor precision) after early brain damage remains imperfectly understood. Different terms, such as atypical cerebral lateralization, pathologic hand- edness, shifts in hemispheral control, anomalous cerebral organization, brain plasticity, and typical or atypical reorganization of brain functions are used in the literature to describe the brain’s deviant functional organization. The purpose of our study was to investigate whether and how handedness is related to the processes of cerebral lateralization and cognitive development in children with early brain insult. Patients and Methods Fifty-six children (31 males and 25 females) with congenital hemipa- resis and 14 control subjects were investigated. Of these children, 32 had a left hemisphere lesion, and 24 had a right hemisphere lesion. There From the Department of Paediatrics, University of Tartu; Unit of Neurology, Children’s Clinic of Tartu University Clinics; Tartu, Estonia. Communications should be addressed to: Dr. Kolk; Department of Paediatrics; University of Tartu; Unit of Neurology; Children’s Clinic of Tartu University Clinics; Lunini 6, Tartu 51014, Estonia. Received January 29, 2002; accepted May 8, 2002. 356 PEDIATRIC NEUROLOGY Vol. 27 No. 5 © 2002 by Elsevier Science Inc. All rights reserved. PII S0887-8994(02)00451-4 ● 0887-8994/02/$—see front matter