Does obstetric brachial plexus injury influence speech dominance?

Auer, Tibor and Pintér, Sándor and Kovács, Norbert and Kalmár, Zsuzsanna and Nagy, Ferenc and Horváth, Réka and Kószó, Balázs and Perlaki, Gábor and Kálmán, Bernadette and Komoly, Sámuel and Schwarcz, Attila and Janszky, József Vladimír and Kotek, Gyula and Köves, Mária and Woermann, Friedrich G. (2009) Does obstetric brachial plexus injury influence speech dominance? ANNALS OF NEUROLOGY, 65 (1). pp. 57-66. ISSN 0364-5134

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Abstract

Objective: Right-handedness and left-sided language lateralization is an unresolved mystery With unknown cause/effect relations. Most studies suggest that the language lateralization is related to a fundamental brain asymmetry: right-handedness may be secondary. We analyzed the possibility of an opposite cause/effect relation: whether asymmetric hand usage (as a cause) call influence language lateralization (as a consequence). Methods: We determined language lateralization by functional magnetic resonance imaging in 15 subjects whose upper limb (UL) had been injured at birth because of unilateral damage of the brachial plexus. These subjects were able to use only one (the noninjured) UL perfectly. Results: We found correlation between the severity of right-sided UL injuries and hand usage dysfunction and the degree of left-to-right shift of language lateralization. There was, however, not a complete switch of language lateralization. Interpretation: Right-sided UL injury can induce a left-to-right shift in language lateralization, suggesting that hand usage can influence language lateralization. These findings may contradict the broadly accepted theory that right-handedness is a secondary phenomenon caused by left-sided hemispheric language lateralization. However, the cause/effect problem between asymmetric hand usage and language lateralization is not resolved in this study. Our Findings may support the theory that gestures had a crucial role in human language evolution and is a part of the language system even today.

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