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NLD and Asperger's Disorder

Joe Palombo

Nonverbal Learning Disabilities, Chapter 11, pages 205-218

Neuropsychological Features of NLD and Asperger's Disorder

Using Rourke's (1989a) profile of assets and deficits in NLD, Volkmar and Klin (1998; Klin, 1994; Klin, Volkmar, Sharrow, Ciechette, & Rourke - 1995; Klin & Volkmar, 1997; Klin, Volkmar, 1994; Volkmar; Klin, Sebaltz Rubin & Bronen, 2000) set out to differentiate Asperger Syndrome from high-functioning autism (HFA). They found an overlap among some of the neurocognitive features of NLD and Asperger's disorder, but not with HFA. They concluded that Asperger Syndrome and HFA are different disorders. This conclusion left open the nature of the relationship between NLD and Asperger Syndrome, although they had found earlier that children with NLD do not exhibit the full clinical syndrome of Asperger Syndrome (Klin et al., 1995; Klin & Volkmar, 1997).

As we saw, Rourkes (1989a) theory proposed that the children's social behaviors are the product of their primary neuropsychological deficits. He interprets the results of the Klin (Klin et al.; 1995) study as indicating that an "overwhelming concordance between AS (Asperger Syndrome) and NLD was obtained" (Rourke & Tsatsanis, 2000, p. 245; see also Gunter, Ghaziuddin, & Ellis, 2002). Rourke and Tsatsanis (2000) state that "a "strikingly similar pattern of behavior and adaptive functioning" exists between NLD and Asperger Syndrome (p. 244). They conclude: "[I]t is of note that there is convincing preliminary evidence to indicate ~{correspondence in the neuropsychological profiles of the two groups. The pattern of neuropsychological assets and deficits that is manifest in NLD seems also characteristic of AS [Asperger syndrome]" (p. 246).

In several publications Volkmar and Klin, who report on their extensive studies of autism and Asperger's disorder, concur that although the diagnoses of NLD and Asperger's disorder are derived from different disciplines- the former from neuropsychology and the latter from psychiatry-some features of the disorders overlap. In the discussion of a case, Klin states that "Although AS and NLD are not mutually exclusive diagnoses (because they belong to different nosologies or classification systems) they often co-occur" (2004, p. 192). Children with Asperger's disorder have NLD, but many children with NLD do not have Asperger's disorder. Finally, their KIin and Volkmars (2003) review of current research leads them to conclude that "the state of discussions of the nosologic status of AS is . . . problematic, given that studies cannot be necessarily compared because of the adoption of different diagnostic definitions, and there has been no comparison across different diagnostic schemes with regard to the relative usefulness of each of the schemes (pp. 7-8). Given the absence of clarity in the features that might characterize Asperger's disorder, the issue of its relationships to NLD presents difficult challenges.

It appears to me that the greatest overlap in symptomatology between NLD and Asperger's disorder lies in the neuropsychological deficits. Both groups of children have deficits in nonlinguistic perception and tend to have executive function difficulties. Were we to limit ourselves to this perspective in making a differentiation, we would find it difficult to demarcate the two disorders. This is not the case for the other two perspectives, the social and intrapersonal.