Right-Hemisphere dysfuntion vs NLD

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http://www.nldontheweb.org/roman.htm

Nonverbal learning disabilities represent a discrete and separate diagnostic entity. However, some of the symptoms identified are similar to those described for other disorders. Individuals with right hemisphere dysfunction (Semrud-Clikeman & Hynd, 1990; Weintraub & Mesulam, 1983), Asperger's syndrome (Klin, Sparrow, Volkmar, Cicchetti, & Rourke, 1995; Semrud-Clikeman & Hynd, 1990; Wing, 1981), and "central processing disorders" (Rourke, 1982) each possess a number of symptoms that overlap with those seen in NVLD. Nevertheless, these disorders can be differentiated through proper assessment.

For example, right hemisphere dysfunction may produce a number of specific deficits not seen in the typical NVLD presentation (Ardila & Ostrosky-Solis, 1984). These may include more severe speech prosody deficits, more pronounced deficits with planning and organization, and more severe tactile-spatial deficits. Separate theoretical developmental models have emerged that emphasize the role of the right cerebral hemisphere (Goldberg & Costa, 1981) versus the role of subcortical white matter systems (Rourke, 1987) to explain deficits common to both conditions. Overall, however, these models may be more complementary rather than contradictory in that they both yield accurate predictions regarding deficits under somewhat different circumstances (Rourke, 1995a).

Yeah, Rouke's current "white matter" theory as I understand it is that white matter is somehow damaged in NLD. Since the right hemisphere contains a large percentage of white matter, NLDers have trouble with things associated with right hemisphere function, like visual-spatial stuff, abstract thinking, social skills, prosody, etc.

NLDers almost have a mini-version of what someone might develop after a right hemisphere stroke (Right Hemisphere Syndrome). NLDers don't usually have the more severe symptoms though, like neglect or visual agnosia, and the symptoms they have in common are also less severe.

I think Rourke has had difficulty demonstrating a strong, unambiguous correlation between white matter damage and NLD though. Like someone might have leukodystrophy (disorder involving degeneration of white matter), but not NLD, while their sibling without leukodystrophy or visible white matter abnormalities might exhibit symptoms of NLD. So there's definitely something there, but more work still needs to be done.

http://en.wikipedia.org/wiki/Lateraliza ... n_function
http://www.hemihelp.org.uk/