Does obstetric brachial plexus injury influence speech dominance?
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) can 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.


CONCLUSIONS
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.
Auer
Tibor
T
Department of Neurology, University of Pecs, Pecs, Hungary.
Pinter
Sandor
S
Kovacs
Norbert
N
Kalmar
Zsuzsanna
Z
Nagy
Ferenc
F
Horvath
Reka A
RA
Koszo
Balazs
B
Kotek
Gyula
G
Perlaki
Gabor
G
Koves
Maria
M
Kalman
Bernadette
B
Komoly
Samuel
S
Schwarcz
Attila
A
Woermann
Friedrich G
FG
Janszky
Jozsef
J
D000293:Adolescent; D000328:Adult; D020516:Brachial Plexus Neuropathies / Q000150:complications* / Q000209:etiology*; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology; D002648:Child; D036861:Delivery, Obstetric / Q000009:adverse effects*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood; D013064:Speech Disorders / Q000209:etiology* / Q000473:pathology; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D055815:Young Adult
D010100:Oxygen