Oh, the Silence...

From Science Blog (May 2003):

Children with unusually delayed speech tend to listen with the right side of the brain rather than the left side of the brain, according to a study published in the December issue of the journal Radiology. Preliminary study results were presented at the Radiological Society of North America's (RSNA) Annual Meeting in 2002.

Scientists compared 17 sedated speech-delayed (2 to 8 year old) children with 35 controls. The full article is available to subscribers only. For our purposes, we'll use some of the terminology-clarifying introduction:

Speech delay encompasses a broad spectrum of conditions with confusing nomenclature (13) and is classified as a communication disorder of childhood in subsections 315.31 and 315.32 of the Diagnostic and Statistical Manual of Mental Disorders DSM-IV (14). These disorders are characterized by a rate of acquisition of speech skills that is slower than normal.

Speech disorders are differentiated from language disorders. Speech refers to the articulation of sounds, and it is the part of language that deals with communication and cognition. Speech disorders may be due to isolated expressive problems, but comprehension always affects expression. The prevalence of speech delay in 6-year-old children in the United States is 3.8% (15). Speech delay is approximately 1.5 times more prevalent in boys (4.5%) than in girls (3.1%) and varies with communal, racial, and cultural backgrounds (15). Shriberg et al found that 11%–15% of children with persistent speech delay have language impairment, although only 5%–8% of children with language impairment have speech delay (15).

There is no clearly defined predictor for language and speech problems in school-aged children (13). Speech delay has many causes and names, including mixed expressive/receptive language disorder, expressive language disorder, developmental language delay, developmental language disorder, and developmental language impairment (16,17). In a patient with any of these disorders, motor skills are preserved, and the rest of the developmental milestones are acquired at an appropriate age. There are no overt abnormalities or underlying neurologic conditions. These children lend themselves to evaluation with sedation and passive paradigms because of the obvious difficulties of cooperating with task performance and remaining still for the examination.