By Dr. David Dinklage
There is clearly a great deal of overlap between Aspergers Disorder (AD) and Nonverbal Learning Disabilities (NVLD), so much so that it is possible that the symptoms of each describe the same group of children from different perspectives—AD from either a psychiatric/behavioral perspective, and NVLDneuropsychological perspective. The specific conventions of these diagnoses may lead to a somewhat different group of children meeting diagnostic criteria, but it is not clear that this reflects something “true” in nature. That is, it may only be convention that separates these two groups.
One is reminded of the story of the six blind men who were asked to describe an elephant. Each man grabbed a different part of the creature (the snake-like trunk vs. the tree-like leg) and gave an accurate description from his own particular perspective—but each man thought the others were completely mistaken!
Studies conducted by the Yale Child-Study Group suggest that up to 80% of children who meet the criteria for AD also have NVLD. While there are no studies on overlap in the other direction, most likely children with the more severe forms of NVLD also have AD. Children from both groups are socially awkward and pay over-attention to detail and parts, while missing main themes or underlying principles. However, by convention, the two groups differ in the range of severity. Professionals reserve an AD diagnosis for children with more severe social impairment and behavioral rigidity; some symptoms may overlap with high functioning autism. There are degrees of severity within AD but not to the extent that is acceptable in diagnosing NVLD. These degrees can range from extreme autistic behavior to cases where the social difficulties are very subtle and the academic/cognitive difficulties are more prominent.
Here is a brief outline of the diagnostic criteria for AD and the pattern of neuropsychological finings in NVLD. While the overlap is apparent, the emphasis is different because criteria for NVLD focuses on academic issues as well as specific test findings and is not purely descriptive. This also results in different means of making the diagnosis (testing or observing).
A. Qualitative impairment in social interaction
B. Restricted, repetitive and stereotyped patterns of behavior, interests, and activities.
C. These problems taken together (A plus B) result in significant challenges in the lives of people with AD as they attempt to live in a neurotypical world and meet the expectations of others.
D. There is no general language delay.
E. There is no severe global cognitive impairment.
A. NVLD can be conceptualized as an imbalance in thinking skills—intact linear, detail oriented, automatic processing with impaired appreciation of the big picture, gestalt or underlying theme.
B. It is not nearly as common as language-based learning disabilities, but this may be a phenomenon created by environmental demands (i.e. our societal demands for precision skills in reading assure that even the most subtle language-based LD cases are identified)
C. Typically social/psychiatric concerns are raised before academic problems are identified.
D. While the overlap is not complete, NVLD children may meet the criteria for Pervasive Developmental Disorder Not Otherwise Specified (PDD NOS), Aspergers Disorder, or Schizotypal Personality.
In my practice I have seen a number of children with AD who would not meet the criteria for NVLD in any existing research studies. If these children had participated in the Yale study mentioned earlier in this article, they would probably have been in the 20% of the AD children who did not meet the NVLD criteria. It is possible that the AD children in that 20% may have had very high visual spatial scores, thus masking their over-attention to detail in problem solving. For example, they may have scored very high on the Block Design subtest of the IQ measure (using colored blocks to match a pattern given to them) with little or no appreciation of the gestalt. Their considerable skill and speed at analyzing detail would have allowed them to use this inefficient strategy effectively. With these very bright children, it may be that the tests are not sufficiently sensitive to discern a pattern of NVLD. On the other hand, some children with AD show diffuse difficulties in the language and attention domain, but may not exhibit the pronounced discrepancies associated with NVLD. Nonetheless, they may still struggle with the cognitive difficulties of NVLD. Conversely, a child meeting the criteria for NVLD, may not meet the criteria for AD, even though subtle characteristics of the disorder may be present.
A case example best illustrates how children who clearly have NVLD may not meet the criteria for AD as it is presently understood. I evaluated an eighth grade girl whose parents were concerned about her math performance. She had above average overall ability, but a 24-point discrepancy between her verbal and visual spatial skills on the IQ measure. On the neuropsychological measures, she clearly had the pattern of visual spatial deficits, left sided motor slowing, and poor math ability, while language skills were intact. She did not have any problems with inferential comprehension in reading. One would not even have considered Aspergers Disorder. She had had many good friends through elementary school and felt herself to be part of her peer group. Symbolic play development had been normal and she exhibited no repetitive behaviors. This is unusual in NVLD as well, but since much of the criteria for this neuropsychological diagnosis is cognitive and test-based, it was determined that she met enough of the criteria for a diagnosis of NVLD. I commented in the report that, unlike this girl, most children with NVLD have more social problems, tend to miss the point in social interactions, and have trouble in content areas in school because of inferential reading comprehension problems.
The parents came back to me when she was a senior. She was now isolated from her peers, who complained that she was too literal. Now she was struggling in literature and social studies; her papers tended to be more like lists and less integrated than those of her peers. I don’t believe she was developing a new disorder. She had a classic NVLD, but it was relatively subtle and it required more high-powered peer and academic demands to highlight her social perception and inferential reasoning weaknesses, much the same way that some mildly dyslexic individuals compensate reasonably well and go unnoticed until they flunk out of their first year of college. Given her history of good social adjustment, one would still never diagnose her with AD. One has to wonder whether her neurcognitive functioning indicated AD, but in a much milder form.
Asperger’s Disorder was not originally thought of as having a continuum of severity that included these subtle forms, whereas NVLD did not start with the assumption of more extreme difficulties. As information about AD becomes more widely circulated more and more subtle cases are being identified and the culture is, in some manner, changing the original “intention” of the category. While that may dilute the meaning of the diagnosis, it will more accurately reflect the variety of developmental presentations in nature. As humans, we naturally want to categorize. The complex relationship between NVLD and AD may be an example of categorizing how too rigidly can confuse, rather than clarify, our thinking.
Dr. David Dinklage is Director of Neuropsychology at Cambridge Hospital, and has a private practice in Belmont.