The Boundaries between Asperger and Nonverbal Learning Disability Syndromes

by Bonny Forrest, Ph.D

email: BonForrest@aol.com

                The purpose of this article is to review similarities and differences between Asperger (AS) and Nonverbal Learning Disability (NVLD) Syndromes.  The existence of AS as a separate diagnostic entity from Autism remains controversial.  Much of this controversy stems from the presence of children who have social deficits characteristic of Autism but exhibit lesser degrees of language impairments, and from the use of the age of onset of language deficits to distinguish between the two syndromes.  Perhaps even more contestable is whether a distinction exists between AS and NVLD.  The latter, which has not yet been recognized by the DSM-IV-TR as a diagnostic entity, has been most frequently defined in the literature by a specific neuropsychological profile.  This profile can be very similar to that of children with AS.  The main difference between the two disorders, as they are most frequently defined clinically, is the absence in children with NVLD of restricted interests or special skills.  The diagnostic situation is further complicated, however, by the complex and still-changing definitions of the social deficits observed in NVLD.

Asperger Syndrome

Behavioral Consequences

Attempts have been made to distinguish children with AS on the basis of the functional aspects of their social impairments.  Their social interactions have been described as lacking in empathy, exhibiting poor nonverbal communication and use of speech, and being overly reliant on rote language abilities.  These children are usually aware of their inability to connect to others (Volkmar and Klin, 2000). In addition, the child with AS tends to become an expert in a specific area of interest (e.g., the weather or subway lines).  Although one subgroup of the children with nonverbal disorders of learning described by Johnson and Myklebust (1967) exhibits social deficits, this group does not generally exhibit restricted interests or special skills that would meet the criteria for diagnostic classification as AS. 

Neuropsychological Profiles

Few studies have attempted to validate a neuropsychological profile of children with AS.  The results of this handful of studies, although far from providing a definitive template, seem to suggest that individuals with AS have deficits in fine and gross motor skills, visual motor integration, visual-spatial perception, nonverbal concept formation, and visual memory.  Language skills are generally intact (Klin, Volkmar and Sparrow, 2000).  This profile of neuropsychological assets and deficits is very similar to the NVLD profile described by Rourke (1995), as discussed below.

Nonverbal Learning Disabilities

Behavioral Characteristics

Johnson and Myklebust (1967) were the first to posit the existence of discrete subtypes of nonverbal learning disorders, including one sub-group of children with nonverbal deficits who have deficiencies in social perception.  They defined social perception broadly as the inability of a child to interpret both the emotions expressed by another person and the perception of oneself in relation to the behavior of others.  Such children cannot pretend, anticipate, evaluate the significance of certain aspects of their environment, or comprehend the meaning of facial expressions and gestures or the subtleties of emotions.  They further described the children with difficulties in social perception as having average or above average abilities in language but difficulty using those language skills. 

Neuropsychological Profiles

                Byron Rourke’s (1995) recent research has focused primarily on the combination of neuropsychological assets and deficits that produces as a byproduct the poor social relatedness that Johnson and Myklebust (1967) described as characteristic of only one group of children with NVLD.  Rourke described the neuropsychological deficits in NVLD more specifically in terms of primary, secondary, and tertiary deficits.  The children he studied had primary deficits in tactile perception, visual perception, complex psychomotor activities and the ability to process novel material.  Secondary deficits (secondary because they were related to the basic deficits) included difficulties in tactile attention, visual attention and exploratory behavior.  Tertiary deficits included tactile memory, visual memory, concept formation and problem solving.  According to Rourke (1995), when these neuropsychological deficits interact with assets in auditory perception, simple motor skills and the ability to process rote material, socioemotional or adaptational deficits result. Children with NVLD as described by Rourke (1995) often exhibit extreme difficulty in processing new or complex social situations and interpreting facial expressions.  In novel situations, they rely on repetitious or rote behaviors, because they excel in these skills.  Their interactions with other children are stereotypical and lacking in reciprocity (Rourke and Tsatsanis, 2000).  Children encompassed in Rourke’s (1995) description may manifest these symptoms from birth or as a result of neuropsychological injury or disease.

The young boy examined in the following case report provides a graphic illustration of the difficulties presented when attempting to diagnose a child who exhibits some but not all of the characteristics associated with both AS and NVLD.

Case Report

                M is an eight-year, eight-month-old right-handed male. He has worn glasses since the age of 9 ½ months.  M was slow to crawl (11 ½ months) but walked independently at 14 months. His parents were also concerned that his social skills lagged behind his peers.  M frequently observed other children but was hesitant to engage them in play.  School personnel corroborated these concerns as early as preschool. 

M had three comprehensive assessments, followed by additional testing as part of a research study. 

At the time of the first assessment at four years and ten months, later motor milestones, such as undressing, dressing, and copying shapes, were beginning to emerge. Language skills were described as quite good. His verbal abilities were assessed at the 99^th percentile.  M’s performance revealed deficits, however, in gross and fine motor abilities and sensory integration.

M underwent a neuropsychological evaluation at the age of 5 years, 4 months.  At that evaluation, numbers and their applications (e.g., number of cars in a train) intrigued M.  All verbal skills during this second evaluation were Average to High Average for his age.  Nonverbal skills, in contrast, ranged from 2 ½- to 4-year-old levels.  A diagnosis of PDD-NOS was ruled out during that assessment because of his language skills.  Asperger Syndrome was also ruled out because of his lack of restricted repetitive and stereotyped patterns of behaviors or interests.  M was given a formal diagnosis at that time of NVLD.  A supplemental assessment by the school approximately 6 months later at 5 years, 10 months showed math abilities at the 56^th percentile. 

Finally, at the age of 6 years, 11 months, M underwent a second neuropsychological evaluation.  His performance on the WISC-III is set forth below.  Additional testing revealed above average verbal and significantly impaired nonverbal skills.  Math reasoning abilities on the Wechsler Individual Achievement Test were at the 27^th percentile with a standard score of 91. He also had poor vocal tone, prosody and awareness of the pragmatic uses of language. M’s social relations were better than when he was younger; however, he was reported to have no best friend.  A diagnosis of Learning Disorder, Not Otherwise Specified was given and the prior diagnosis of NVLD was confirmed.        

Overall Intellectual Function-WISC-III Scaled and Standard Scores

Additional testing completed as part of a research study resulted in the following scores:

Achievement-standard scores.

Executive Functions-Z, scaled, T or percentage scores as reported by instrument.

Language-scaled scores.

Sensorimotor-scaled or z scores and percentages as appropriate to the instrument.

Visual-spatial-scaled, standard or percentage scores.

Memory and Learning-scaled scores.

Social and Emotional Functioning-z scores.

Discussion

Although M fits the general neuropsychological profile for both AS and NVLD, he does not have some of the behavioral characteristics required for a diagnosis of AS:  he lacks ascribed interests or special skills in the presence of nonverbal cognitive deficits.  Although M’s interest in numbers at one point was considered a possible precursor to a restricted interest that might be indicative of AS, by the age of 8 that interest was not considered clinically significant.  When three neuropsychologists at separate major Northeastern University Hospitals diagnosed M, each ruled out AS because of M’s behavioral characteristics and relied on the neuropsychological profile and the deficits in social skills to assign an NVLD diagnosis.  A diagnosis of Autism was never discussed.     

In their reports, however, each alluded to the difficulties of diagnosing M with NVLD because he did not exhibit all of its characteristics.  These difficulties would have been even more pronounced if these clinicians had attempted to apply more recent descriptions of NVLD by Rourke (2000a) or his proposed ICD-10 criteria. 

Consistent with Rourke’s (1995) neuropsychological descriptions of NVLD, M’s verbal skills were above average, his mechanical math score on the WRAT-3 was at least 8 standard points lower than his reading score, and he had difficulties with graphomotor activities, tone and prosody.  But M does not exhibit some of the other tertiary and secondary neuropsychological deficits described by Rourke (1995).  In addition, a number of M’s strengths are inconsistent with more recent descriptions of the developmental progression of NVLD (Rourke, 2000a).  Finally, M’s social abilities are inconsistent with those described in Rourke’s (2000a) proposed ICD-10 criteria.

As to M’s other neuropsychological abilities, his visual memory and visual motor integration abilities are relatively intact and are therefore inconsistent with the secondary deficits described by Rourke (1995).  (These abilities may also be inconsistent with a diagnosis of AS.)  His oral-motor praxis abilities were also average.  Finally, although M had mechanical arithmetic difficulties on the WRAT-3, these difficulties did not result in deficits in mathematics in general as described by Rourke (1995). The difficulties are consistent, however, with descriptions by Badian (1983) of children with poor social skills and anarithmetria.

Rourke’s recent developmental definitions of NVLD suggest that most children with NVLD manifest language deficits at an early age.  M did not.  This age-of-onset criterion, which is not present in earlier descriptions of NVLD, makes NVLD appear more similar to Autism.  See http://www.nldontheweb.org/Byron_Rourke_QA15.htm.   

Rourke has also proposed ICD-10 criteria for NVLD that include behavioral characteristics of a distorted sense of time and extreme social impairment.  See http://www.nldontheweb.org/Byron_Rourke_QA15.htm and http://www.nldontheweb.org/Byron_Rourke_QA18.htm.  How the social deficits in these criteria are qualitatively different from those observed in Autism or AS is unclear.  M did not have a distorted sense of time (e.g., when asked how long it took to tie his shoes, M replied, “For most kids they can do it in about 20 seconds, me it takes about two minutes.”)   M’s social deficits could also not be characterized as extreme.  M did have difficulty adapting to new situations, engaging in reciprocal conversations and judging personal space distances. On the Personality Inventory for Children (Wirt et al., 1977), however, he did not have elevated levels of depression or withdrawal.  His mood lability resulted in a clinically significant elevation of psychosis.  M could name some of the emotions exhibited in the Child and Adolescent Social Perception Measure (Magill-Evans et al., 1995), although he could not tell you how he knew what children in the scenes were feeling.  M’s subtle social deficits seem to be more like those of the subgroup of children described by Johnson and Myklebust (1967) than those described by Rourke (2000b).

Future studies that attempt to distinguish AS and NVLD might investigate any differences in social abilities between the two groups (Volkmar and Klin, 1998). M’s social abilities were poor but they also seemed less compromised than those typically observed in AS.    Rourke and Tsatsanis (2000) have stated that the psychosocial deficits experienced by children who exhibit NVLD “are viewed as the direct result of the interaction” of the neuropsychological assets and deficits (p. 237).  The nonverbal cognitive profile in AS and NVLD has also been described, however, as limiting a child’s ability to make full use of social cues because it affects their ability to process nonverbal stimuli in various modalities.  (Volkmar and Klin, 1998).  Still others have said that children with the NVLD profile may or may not exhibit social deficits.  (Pennington, 1991).    Future research should provide better descriptions of the nature and extent of the social abilities in children with AS and NVLD.  It would also appear that M might not meet the criteria for PDD-NOS specified in the practice parameters by the American Academy of Child and Adolescent Psychiatry and the DSM-IV-TR because his social deficit is not severe and pervasive.  See http://www.guidelines.gov/VIEWS/summary.asp?guideline=001367.  

We are left to speculate as to whether the discrepancies in M’s verbal and performance scores were relied on too heavily in indicating a diagnosis of NVLD.  Given M’s history of poor motor development and current test performance, it appears that most of his cognitive difficulties stem from his motor dyspraxia.  His social difficulties are more appropriately addressed, however, by an NVLD diagnosis.  In the absence of social disability criteria independent of Autism, AS or NVLD, an NVLD diagnosis is frequently used to fill the void and obtain the necessary services.   

In sum, M meets some but not all of the proposed criteria for NVLD.  How many he meets depends on the description of NVLD one uses.  As this article has indicated, the changing and sometimes conflicting protocols and descriptions of NVLD complicate the diagnostic process.

For example, M meets at least five of the eight current criteria for NVLD or “probable NVLD” as described in Rourke’s protocol for children slightly older (nine) than M.  See www.nldontheweb.org/Byron_Rourke_QA18.htm. That protocol is separate from and less comprehensive than Rourke’s qualitative descriptions at www.nldontheweb.org/Byron_Rourke_QA2.htm.  The neuropsychological diagnosis of NVLD is often complicated by the fact that this protocol requires deficits on the Tactile Performance Test and the Target Test, which are infrequently used in assessments.

Additionally, M meets approximately five of the ten “characteristics” described in children under the age of six, and seven of eight of the characteristics described in children seven and above. See  http://www.nldontheweb.org/Byron_Rourke_QA15.htm.  Finally, he meets approximately 6 of 10 of the ICD-10 criteria proposed by Rourke.  See http://www.nldontheweb.org/Byron_Rourke_QA15.htm.   Qualitatively, M is more accurately captured by the descriptions of children with social deficits and nonverbal disorders of learning provided by Johnson and Myklebust (1967) and Badian (1983).

Conclusions        

Although the neuropsychological descriptions of children with AS and NVLD are similar, behavioral criteria may be used to distinguish the two disorders.  The diagnosis is complicated, however, by three factors.

First, at present, most clinicians see NVLD as a neuropsychological rather than behavioral diagnosis. 

Second, the exact nature and causes of the behavioral and social deficits associated with NVLD are poorly understood.  In fact, it is not clear that all children with NVLD have these deficits.  According to Johnson and Myklebust (1967), children with nonverbal deficits of learning such as visual-spatial difficulties may or may not experience social deficits.  Rourke’s (1995) criteria do not seem to require a behavioral or social deficit, and, in the vast majority of his work, he discusses social deficits primarily as a consequence of neuropsychological problems.  Rourke’s (2000a) more recent descriptions, however, seem to include a requirement of extreme social deficits for a diagnosis of NVLD.

Third, different definitions of NVLD carry with them different conclusions about the ability to distinguish it from AS.  Rourke and Tsatsanis (2000) have noted that the NVLD description applies to children with AS. Rourke’s proposed ICD-10 criteria would seem to imply, however, that NVLD is a separate diagnostic entity from AS.  

Given the present state of research into and definitions of AS and NVLD, AS and NVLD can most usefully be seen clinically -- as M’s diagnostic history indicates -- as behaviorally distinct with neuropsychological similarities.  

References

Badian, N. A. (1983). Dyscalculia and nonverbal disorders of learning.  In H. R. Myklebust (Ed.). Progress in learning disabilities, Vol. 5 (pp. 235-264). New York: Grune & Stratton.

Johnson, D. &  Myklebust, H. (1967).  Learning disabilities: Educational principles and practices.  New York: Grune & Stratton.

Klin, A, Volkmar, F.R., and Sparrow, S.S. (2000). Asperger Syndrome.  New York: The Guilford Press.

Klin, A, Volkmar, F.R., Sparrow, S.S., Cicchetti, D.V. & Rourke, B.P. (1995).  Validity and neuropsychological characterization of Asperger syndrome: Convergence with NVLD syndrome.  J. Child Psychology and Psychiatry, 36 (7) 1127-1140.

Magill-Evans, J., Koning, C., Cameron-Sadava, A. & Manyk, K. (1995).  The Child and Adolescent Social Perception Measure.  Journal of Nonverbal Behavior, 19 (3), 151-169.

Pennington, B. (1991).  Diagnosing learning disorders.  New York: Guilford Press.

Rourke, B. (2000a).  Webpage at http://www.nldontheweb.org/Byron_Rourke_QA15.htm located within: http://www.nldontheweb.org/Byron_Rourke_hompage.htm.

Rourke, B. (2000b).  Conference on nonverbal learning disabilities.   Speech and materials presented in New Haven, CT. 

Rourke, B. (Ed.) (1995).  Syndrome of Nonverbal Learning Disabilities: Neurodevelopmental Manifestations.  New York: The Guilford Press.

Rourke, B. (1987).  Syndrome of nonverbal learning disabilities: The final common pathway of white-matter disease/dysfunction?  Clinical Neuropsychologist, 1(3), 209-234.

Rourke, B.P. & Tsatsanis, K.D. (2000).  Nonverbal learning disabilities and Asperger Syndrome. In Klin, A., Volkmar, F. and Sparrow, S. (Eds.) Asperger Syndrome (pp. 231-253). New York: The Guilford Press.

Volkmar, F.R. & Klin, A. (1998).  Asperger Syndrome and nonverbal learning disabilities.  In Schopler, E. and Mesibov, G. B. (Eds.) Asperger Syndrome or High Functioning Autism?  Current issues in autism (pp. 107-121). New York: Plenum Press.

Volkmar, F.R. & Klin, A. (2000).  Diagnostic Issues.  In Klin, A., Volkmar, F. and Sparrow, S. (Eds.) Asperger Syndrome (pp. 25-71). New York: The Guilford Press.

Wirt, R., Lachar, D., Klinedinst, J. and Seat, P. (1977).  Personality inventory for children.  Los Angeles: Western Psychological Corporation.