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Onset of speech after left hemispherectomy in a nine-year-old boy.
Vargha-Khadem F, Carr LJ, Isaacs E, Brett E, Adams C, Mishkin M
Brain, 1997 Jan;120( Pt 1):159-182

[pdf link to the paper online in Brain]

Case Alex, with Sturge-Weber Syndrome affecting the left hemisphere, failed to develop speech throughout early boyhood, and his comprehension of single words and simple commands remained stagnant at an age equivalent of 3-4 years.

But then, following left hemidecortication at age 8.5 years and withdrawal of anticonvulsants when he was more than 9 years old, Alex suddenly began to acquire speech and language. 

He also showed an unusual degree of residual motor capacity on his right side.

Alex's remarkable progress in learning speech and language, and the development of his other cognitive abilities, were measured periodically from the age of 9 to 15 years. His most recent scores on tests of receptive and expressive language place him at an age equivalent of 8-10 years. Comparison with the level of function attained in these domains by nine other left hemispherectomized patients with early onset of disease and comparable IQ (range, 40-68) but with early development of speech and language, suggests that, surprisingly, Alex has suffered no permanent disadvantage from his protracted period of mutism and severely limited comprehension.

The findings in Alex, as in other left-hemispherectomized patients, indicate definite limits to the cognitive and linguistic capacity of the isolated right hemisphere.

But Alex's achievements appear to challenge the widely held view that early childhood is a particularly critical period for acquisition of speech and language or any of their selective aspects, including phonology, grammar, prosody and semantics.

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