Syndrome of Nonverbal Learning Disabilities:
The syndrome of nonverbal learning disabilities (NVLD) includes a number of specific, potentially debilitating symptoms. Rourke (1995a) has grouped these into three major areas: neuropsychological deficits, academic deficits, and social-emotional/adaptational deficits. Neuropsychological deficits include difficulties with tactile and visual perception, psychomotor coordination, tactile and visual attention, nonverbal memory, reasoning, executive functions, and specific aspects of speech and language. Deficits in math calculations, mathematical reasoning, reading comprehension, specific aspects of written language, and handwriting are primary academic concerns. Social deficits include problems with social perception and social interaction. Children with this disorder are also seen as having substantially increased risk for internalized forms of psychopathology, primarily anxiety and depression. There has also been evidence to suggest a greater risk for suicide (Rourke, Young, & Leenaars, 1989).
The NVLD syndrome has been described as a distinct diagnostic entity only recently. The foremost researcher in the area is Byron Rourke, although many other individuals have been intimately involved with investigating and treating this disorder (e.g., Fletcher et al., 1992; Johnson & Myklebust, 1967). Perhaps the first written descriptions of the syndrome were prepared by Johnson and Myklebust, although there is no reason to believe the disorder is new.
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).
Some clinicians have also suggested that Asperger's syndrome and NVLD are similar disorders. This is a controversial assertion. Many researchers have questioned the validity of Asperger's syndrome as a distinct diagnostic entity apart from autism (Semrud-Clikeman & Hynd, 1990; Wing, 1991). In essence, the lower functioning children diagnosed with Asperger's may be more properly diagnosed as autistic. In turn, many of the higher functioning children diagnosed with Asperger's syndrome may instead be children with NVLD who have been misdiagnosed.
While the NVLD syndrome has only recently been described in detail (Rourke, 1987, 1989), a number of important articles and two major books have been dedicated to descriptions of the disorder (Rourke, 1989, 1995a). Despite this fact, the syndrome is unfamiliar to many psychologists, diagnosticians, and educators. There is no formal provision under federal special education law recognizing the existence of nonverbal learning disability as a handicapping condition. In most cases, children with this disorder are best classified as Other Health Impaired. Because they may also have specific motor skills deficits, problems with math, social interactional difficulties, and/or emotional disturbances, some of these children may also be appropriately classified as orthopedically handicapped, learning disabled, or emotionally disturbed. This may be particularly appropriate for cases of neurologically acquired NVLD rather than the more common developmental cases of the disorder.
The purpose of this article is to familiarize the reader with the NVLD syndrome and the current state of research on this disorder. Practical guidelines for identifying children at risk, evaluating and diagnosing the syndrome, and making treatment recommendations are emphasized. Finally, a case example with accompanying test data illustrations is provided.
Clinical Description of the Syndrome
Such children are often described as better "auditory learners" than "visual learners." This is related to their greater proficiency with verbal-auditory modalities than tactile-visual modalities (Rourke, 1995a). In addition, they are frequently described as less active and more reluctant to physically explore their environment (Rourke, 1989). This lack of active exploration is believed to be secondary to their lack of proficiency with tactile and visual input (Rourke, 1995a). In effect, because they frequently gain little useful information from manipulating their environment, they seldom do so on their own initiative.
Rourke (1989) provided the first detailed description of the nonverbal learning disability syndrome based on his research into learning disability subtypes (Rourke & Fisk, 1988). More recently (Rourke, 1995a), refined and expanded his description of NVLD symptoms. His model is dynamic in speculating that primary neuropsychological deficits lead to secondary deficits in modality-specific aspects of attention and, more generally, in the extent to which children actively explore their environment. These primary neuropsychological deficits include tactile perception, visual perception, and motor coordination. In turn, these secondary deficits lead to tertiary deficits, particularly in nonverbal memory, abstract reasoning, executive functions, and specific aspects of speech and language. Specific, measurable impairments in academic performance, social functioning, and emotional well being are direct by-products of this constellation of primary, secondary, and tertiary neuropsychological deficits.
Rourke (1995a) also described a number of assets in children with NVLD. These abilities typically measure within the average to above average range relative to normal peers. These strengths include simple motor skills, auditory perception, simple auditory attention, and rote memory for simple verbal material. Language strengths include adequate receptive language, adequate simple verbal expression, and good phonetic analysis. The relative strengths with phonetic analysis demonstrated by children with NVLD frequently lead to good single word recognition and strong spelling skills, particularly for phonetically predictable words. However, they often have difficulty with spelling and decoding phonetically unpredictable sight words.
Neuropsychological Performance Issues
"Cognitive," as used in this context, refers to an individual's abilities rather than to specific acquired skills. This distinction between abilities and skills is an important one. When a cognitive deficit is present, it is reasonable to expect that all skills dependent on that cognitive ability will be hindered to at least some degree. Of course, all measures of ability are at least in part related to the measurement of acquired skills (Anastasi, 1988). For example, the concept of intelligence is a completely valid ability-based construct (e.g., Brody & Brody, 1976; Mattarazzo, 1972). However, all intelligence tests rely on the measurement of acquired skills and knowledge to make inferences regarding underlying ability. Nevertheless, when a cognitive deficit is truly present, difficulties should be expected on all measures requiring skills dependent on that particular cognitive ability. This is similar to the distinction between production deficits vs. mediational deficits as described by Flavell (1970).
"Neuropsychological" refers to both simple and complex cognitive abilities that can be directly or indirectly linked to the integrity of cerebral functioning. The goal of neuropsychological evaluation is to investigate discrete cognitive processes involved in acquiring new information. For example, poor performance on a measure of copying, such as the Developmental Test of Visual-Motor Integration (Beery, 1982), assuming adequate effort has been put forth by the test taker, may be due to any of a number of factors. Problems with visual perception, motor execution, spatial planning, or the integration of visual and motor abilities may result in poor copying of geometric figures. It is the goal of a comprehensive neuropsychological evaluation to attempt to determine which of these factors are involved. Therefore, neuropsychological does not refer to any specific test or set of tests, but rather to a way of thinking about and investigating cognitive functions. In some cases, this may also involve making inferences about the integrity of cortical or subcortical brain regions that subserve specific cognitive processes.
Intellectual functioning. One of the most readily obvious identifying features of NVLD is a significantly higher Verbal IQ score than Performance IQ score on formal measures of intelligence (Johnson, 1987; Weintraub & Mesulam, 1983). This finding is a direct result of the expected discrepancy between verbal, language-based cognitive abilities and nonverbal, visual-spatial cognitive abilities in these children. In general, the greater the magnitude of this discrepancy, the more likely the accuracy of the diagnosis. Of course, Verbal-Performance IQ score discrepancies alone are never diagnostic in the absence of other supporting evidence. Because neither Verbal IQ scores nor Performance IQ scores are "pure" measures of ability, discrepancies between the Verbal Comprehension Index and the Perceptual Organizational Index are frequently better and more stable measures (Kaufman, 1979). A discrepancy of as few as 10 points may be supportive if there is substantial evidence of the disorder in other domains. More typically, a VIQ-PIQ discrepancy of 15 points or more is expected. It is not unusual to find differences of 40 points or more between Verbal and Performance IQ scores in more severely affected individuals (Johnson, 1987).
Executive functions and higher level reasoning. Rourke (1995a) has also identified deficits in executive functioning as among the primary impairments in NVLD (Strang & Rourke, 1983). Executive functions include such higher level abilities as abstract reasoning, logical analysis, hypothesis testing, and cognitive flexibility, or the ability to "shift gears" mentally. The ability to focus, shift, and distribute attention, organize information into memory to aid learning and remembering, and otherwise regulate thought processes are also examples of executive functions. Although similar etiologies have been proposed to explain both nonverbal learning disability and executive dysfunction (i.e., impairments of subcortical white matter), poor performance on measures of executive functioning are not always found in children with NVLD. There is no clear data to indicate how frequently executive functioning deficits occur in the NVLD population. It is the author's experience that such deficits are common in more severe cases of NVLD and quite rare in more subtle cases.
Many measures of executive functioning exist. Some of the more commonly administered measures include the Wisconsin Card Sorting Test (Berg, 1948), the Category Test (Reitan, 1979), the Tower of London (Shallice, 1982), the Trail Making Test (Reitan, 1979), and the Progressive Figures and Color Form Tests (Reitan & Wolfson, 1985). In addition, many tests of attention and working memory could appropriately be considered measures of executive functioning (Pennington, 1994).
Memory functions. Significant discrepancies between verbal and nonverbal memory are also frequently observed. As with other nonverbal functions, NVLD children frequently demonstrate greater impairments on nonverbal memory tasks as the spatial component of the task increases. For example, it is typical to find poorer performance on the Design Memory subtest than the Picture Memory subtest of the Wide Range Assessment of Memory and Learning (WRAML; Sheslow & Adams, 1990). On more simple nonverbal tasks, or those that are more readily verbally encoded, deficits in performance may not appear. For example, both the Visual Memory subtest and the Visual-Sequential Memory subtest of the Test of Visual Perceptual Skills - Revised (Gardner, 1996) frequently score within the average range, particularly for older children. In addition, NVLD children frequently demonstrate problems with more complex measures of verbal learning and memory (Fletcher et al., 1992). This finding is consistent with Rourke's prediction that strengths in verbal learning and memory are largely confined to simple, rote tasks (Rourke, 1995a).
Deficits in executive functions, including working memory, are hypothesized to be responsible for these difficulties on more complex verbal memory measures (Rourke, 1995a). Of course, it is reasonable to expect that NVLD children that do not demonstrate executive functioning deficits will be less likely to show deficits on verbal memory measures. However, weaknesses in nonverbal memory are still likely to be observed.
A good core memory battery for assessing the presence of nonverbal learning disabilities might include the Verbal Selective Reminding Test or the California Verbal Learning Test and selected subtests of the Wide Range Assessment of Memory and Learning, particularly the Story Memory, Picture Memory, and Design Memory subtests. For many children with this disorder, discrepancies can also be found between auditory span of attention, as measured by a digit span test, and spatial span of attention, as measured by the Finger Windows subtest of the WRAML or Corsi blocks (Milner, 1971). In addition, many of these children demonstrate a significantly poor backward digit span with a relatively better forward digit span. The tendency of many children to mentally "visualize" the forward sequence and then "read" it backwards frequently exceeds the NVLD child's capacity to manipulate mental representations.
Language functions. Children with NVLD usually perform well on measures of receptive vocabulary and expressive vocabulary. Some examples of common measures for receptive vocabulary include The Peabody Picture Vocabulary Test (Dunn & Dunn, 1981) and the Receptive One-Word Picture Vocabulary Test (Gardner, 1985). The Expressive One-Word Picture Vocabulary Test - Revised (Gardner, 1990) and the Boston Naming Test (Kaplan, Goodglass, & Weintraub, 1983) are among the best known measures of expressive vocabulary. Among neuropsychologists, these expressive measures are sometimes referred to as "confrontation naming" tasks.
NVLD children sometimes demonstrate weakness in particular aspects of speech and language. As with right hemisphere damage individuals (Ryalls, Joanette, & Feldman, 1987), difficulties with speech prosody and problems understanding and/or expressing emotional intonation are frequently observed in the more severe cases of NVLD. Difficulties with prosody often involve monotone speech with little inflection. Because these children are often hyperverbal in social contexts, their peers frequently see them as droning on relentlessly over boring topics. The deficits these children demonstrate in nonverbal aspects of interaction directly lead to an overreliance on verbalization as a primary means of social interaction. Because the content of their speech is often simple and repetitive, they frequently present as having a restricted range of interests, one of the primary features of Pervasive Developmental Disorder. Difficulties with emotional intonation and affective expression in speech can be measured by asking the child to repeat a neutral phrase within different emotional contexts. For example, they may be asked to state, "I'm going to the store," as if they were angry, sad, or surprised. Similarly, their receptive understanding of the affective tone of language can be assessed by having the examiner repeat this same neutral phrase with different emotional inflections, then asking the child to label the corresponding mood.
Visual-spatial abilities. As already noted, difficulties with visual perception, visual processing, and visual-spatial cognitive abilities are the most prominent features in NVLD (Harnadek & Rourke, 1994). These children frequently demonstrate more impairment on tasks demanding a greater degree of visual processing or involving visual-spatial demands. Measures such as the Judgment of Line Orientation Test are typically very difficult for these children. They may frequently attempt to compensate for these difficulties by employing ineffective strategies, such as attempting to "measure" the angles separating the two lines on the target stimulus with their fingers, then transferring this "measurement" to the response key to determine the answer. Difficulties with copying block designs are also typical. In general, these children have difficulty effectively matching to sample to aid copying, demonstrating deficits in part to whole relationships. They typically have extreme difficulty visualizing the overall gestalt of images, such as required on the Object Assembly subtest of the Wechsler scales.
Problems with drawing or copying are frequently observed. In addition, handwriting may often be poor, at least initially. There is some evidence that children with NVLD are capable of mastering repetitive motor skills with repeated practice over time, despite the fact that they may be particularly weak in acquiring these skills initially. Handwriting, copying of simple shapes, cutting, coloring, pasting, and simple drawing are examples of fine motor skills that frequently improve with age.
One of the better and more dramatic measures for investigating NVLD is the Tactual Performance Test (Reitan, 1979). This task requires the subject to place blocks into a formboard while blindfolded. This measure is arguably the only truly spatial measure in our assessment arsenal because it is performed without the aid of visual input. Because children with NVLD have extreme difficulty "building spatial maps," they frequently perform poorly on this task, often demonstrating little to no learning (Harnadek & Rourke, 1994).
Sensory-perceptual and motor functioning. A number of motor and sensory-perceptual deficits have also been documented in this disorder. Difficulties with tactile discrimination, haptic discrimination, and fine motor coordination are typical. NVLD individuals often demonstrate more difficulty with sensory and fine motor skills on the left side of the body than the right. They almost always demonstrate difficulty with such tasks as finger localization, fingertip number writing, tactile form recognition, and fine motor speed and dexterity on measures such as the Grooved Pegboard Test (Klove, 1963). However, measures of grip strength are usually normal and finger tapping speed is frequently average or near average.
As noted above, children with NVLD are frequently able to achieve average or near-average proficiency on a number of repetitive motor tasks, such as handwriting. They are frequently less coordinated with regard to gross motor activity, particularly when the development of specific skills is required. For example, they may not have difficulty riding a bicycle, but may demonstrate significant difficulty playing competitive sports. In general, these children are far less athletically capable than their peers.
Educational and Academic
Because these children frequently have adequate phonological abilities, they may often be more successful at reading and spelling phonetically predictable words than phonetically unpredictable words. This can sometimes result in a failure to find the expected discrepancies between math and reading or math and spelling on integrated tests such as the Wide Range Achievement Test, even when the diagnosis of NVLD is appropriate. Using more sensitive measures, such as the Woodcock-Johnson Tests of Achievement (Woodcock & Johnson, 1989), can frequently assist the examiner in documenting the discrepancy. Children may sometimes demonstrate better performance on the Word Attack subtest then the Word Identification subtest. More sensitive measures of spelling, such as the Test of Written Spelling - 3 (Larsen & Hammill, 1994) often yield notable discrepancies, with higher standard scores obtained for phonetically predictable words than phonetically unpredictable words.
Another classic finding is the discrepancy between content areas of academics as opposed to more applied aspects. Content areas can be defined as the more basic and mechanical aspects of an academic subject. These include word recognition and word attack for reading; arithmetic calculations within math; and spelling, grammar, and syntax within written language. In contrast, applied aspects of academic subject areas include reading comprehension, math applications (including word problems and algebra), and written composition.
With regard to NVLD children, reading decoding is frequently average while reading comprehension is often poor. Math reasoning is often more impaired than math calculations. They may have difficulty with word problems and almost always struggle with algebra. Within the area of written language, spelling, vocabulary usage, and sentence construction may be adequate. However, children and adults with NVLD frequently have difficulty generating ideas. B. P. Rourke (personal communication, September, 1991) indicated that college students with NVLD may often produce lengthy term papers composed of well constructed sentences that fail to make any substantive points. In this regard, their writing is often "empty" and superficial. The same phenomena are also frequently observed in their pragmatic language, particularly when they are pressed on a specific topic of conversation. Problems with executive functions, integration and synthesis of information, and generalization of knowledge are thought to underlie this content versus applied discrepancy (Rourke, 1995a).
Social Performance Issues
Social judgment and social problem solving are also typically impaired. Some of these impairments are a direct result of problems with perception. In effect, when individuals are unable to accurately perceive a social situation, they are at a significant disadvantage for choosing a correct response. Deficits in reasoning and generalization of knowledge also directly contribute to disadvantages in social problem solving. Furthermore, their behavioral response to similar situations occurring over time may appear very inconsistent and even contradictory.
Interpersonal intimacy is frequently impaired, although problems forming close personal attachments may not be noticed until late childhood or early adolescence when dating begins. Rourke (1995a) speculated that these difficulties with establishing intimacy are directly related to the lack of "tactile-perceptual and psychomotor prowess required for smooth affectional encounters" (p. 17). Difficulty maintaining meaningful friendships may also occur. As already noted, problems with speech prosody and expressive language may lead to increased rejection by peers.
Another major characteristic of individuals with NVLD is a lack of adaptability (Rourke, 1995a). In general, children, adolescents, and adults with this disorder respond poorly to novel circumstances. The ability to deal with changing circumstances is a fundamental aspect of social competency. It is also an important aspect of normal social development. The difficulties with reasoning, flexibility, and problem solving in NVLD individuals, combined with their other cognitive deficits, place them at a substantial disadvantage for coping with the changing circumstances of day-to-day life.
The lifelong difficulties with academic and social functioning most NVLD individuals endure contribute directly to their problems with emotional adjustment. Some of these difficulties with internalizing emotional problems can be demonstrated in early childhood. However, problems with anxiety and depression are much more common through adolescence and into adulthood. Rourke et al. (1989) indicated that the frustrations many individuals with NVLD face culminate when they attempt to enter the workforce. They rarely make good impressions during job interviews. They are also more likely to demonstrate difficulties getting along with coworkers. Visual-spatial difficulties and problems with reasoning and judgment make them more accident prone and less successful in many occupations (Rourke et al., 1989).
As these children develop into later infancy and more advanced motor abilities begin to emerge, they are often poorly coordinated. They may participate only minimally during feeding and play times. Acquisition of simple self-help skills is often delayed. Furthermore, once they begin to walk, they may appear clumsy and are often more likely to bump into things or break objects around the house. As Rourke (1995a) indicated, it is not unusual for these children to be labeled as hyperactive or diagnosed with an Attention Deficit Hyperactivity Disorder during the preschool and kindergarten years. Their poor social judgments can often be interpreted as problems with impulsivity. Furthermore, the poor motor coordination resulting from their tactile and visual-spatial deficits increases the likelihood they will be identified as disruptive or destructive.
Difficulties with daily living skills related to eating, dressing, and simple grooming may be noted. In particular, motor abilities necessary for dressing-such as fastening fasteners and learning to tie shoes-are frequently impaired. The acquisition of early preacademic skills related to coloring, cutting, and pasting is also typically delayed. In many cases, these children show little to no interest in working with puzzles, blocks, Legos, or other developmentally appropriate materials. Unfortunately, it is the author's experience that it can be difficult to obtain accurate information regarding a child's proficiency for building puzzles and for working with blocks and other construction materials from parent interviews. Sometimes parents will report that their children demonstrate normal interest and proficiency in these types of tasks even when objective observers would rate them poorly. Generally, parents are more reliable and accurate in reporting levels of proficiency for dressing, cutting, coloring, and pasting.
NVLD children frequently demonstrate initial difficulties acquiring early academic skills. Problems with letter and number recognition, difficulty with one-to-one correspondence in counting, and problems with copying letters and numbers are common. Printing and drawing also are frequently poor. With repeated practice, most NVLD children develop normal proficiency with these types of tasks. Rourke (1995a) suggested that these children eventually acquire normal or nearly normal proficiency on these types of tasks regardless of whether or not they receive early physical intervention such as occupational therapy. It is not unusual to find a history of early involvement in occupational therapy and other related services.
In the preschool and beginning elementary school years, children with NVLD typically demonstrate difficulty getting math, reading, and writing "off the ground." It is common for them to have difficulty acquiring recognition of letters and numbers because of the inherent visual-spatial aspects involved in early acquisition. With frequent practice, they become more successful at these tasks and eventually profit from the development of the necessary symbol systems required for the early development of reading and math concepts. As already noted, often letter formation and handwriting are initially poor, but typically improve over time.
In the early elementary school years, children with NVLD may demonstrate average to above average academic performance. This is sometimes true as early as the first grade, but is frequently seen in the second through fourth grade, particularly for children with more minor forms of the disorder. Of course, those children that are more severely affected may never demonstrate average levels of academic proficiency. Unfortunately, as this more successful group of NVLD children progress into middle school, particularly through the fifth through seventh grades, they often begin to have difficulty maintaining their academic performance. For math in particular, affected individuals rarely exceed a sixth grade equivalent, even as adults (Rourke, 1995a). Difficulties with executive functioning, problem solving, and memory for more complex and meaningful verbal and nonverbal material make it difficult for them to maintain their prior levels of performance (Rourke, 1995a). The author has encountered more than one situation in which school personnel have been reluctant to classify a NVLD child as learning-disabled in their middle school or high school years, despite significant intellectual-achievement discrepancies, because they did not demonstrate early academic deficiencies.
As already noted above, phonological awareness and the acquisition of phonics often are strengths for NVLD children. They are typically far more proficient in word recognition and spelling than in math. However, this discrepancy may not be obvious until the fourth or fifth grade, largely because of the simple nature of the math tasks that are presented to them. While they frequently have difficulty rapidly retrieving math facts, particularly with regard to learning the multiplication tables, normal variability between children in the earlier grade school years makes it possible for NVLD children to still score within the average gross range for math at this age. However, Rourke (1995a) indicated that these children rarely exceed a fifth or sixth grade level of proficiency in math. Difficulties with reading comprehension, thinking and reasoning, novel problem solving, and written expression are frequently more obvious as these children progress into the later elementary and middle school years.
Frequently, number of practical deficits emerge, particularly with regard to mathbased survival skills related to time, money, and measurement. These children often have difficulty with the concept of time. This often applies to the calendar as well as the clock. Learning to tell time is almost always difficult, particularly on an analog clock. These children may have difficulties naming the days of the week or months of the year in order, but typically succeed after much practice. Problems with time management and scheduling may persist into adulthood. Their ability to recognize and discriminate coins is often slow to develop. More fundamentally, they have difficulty acquiring money concepts. These difficulties frequently persist into adulthood and are manifest as difficulties with budgeting, balancing a checkbook, making change, and doing comparison shopping. Difficulties with measurement concepts are most obvious on tasks requiring estimation. Children and adults with NVLD are often confused by systems and units of measurement and may make outrageous estimations regarding size, distance, or quantity. They may, for example, describe a basketball player as 20 feet tall, even if given comparative information, such as the height of the basketball rim from the floor. These outrageous estimations are particularly common for younger children who manifest this disorder. Older children and adults with NVLD may manifest problems with cooking and household management. Doubling and halving the size of a recipe are examples of tasks that are particularly difficult for these individuals.
Because of their relatively stronger language-based abilities, it is not uncommon for higher functioning NVLD individuals to complete college or even obtain a masters degree. However, their difficulties with social skills and higher level cognitive abilities frequently lead to frustration on the job or difficulty finding employment. Problems with planning and organizational skills can further impair their ability to functional well at home and on the job. Less than satisfactory social relationships and difficulties with developing intimate relationships, as already described above, can prove particularly frustrating. For these and other reasons, symptoms of depression and anxiety are common (Rourke & Fisk, 1981; Rourke et al., 1989; Weintraub & Mesulam, 1983).
Prevalence and Incidence
There are also differences between individuals with developmental NVLD compared to those with neurologically acquired NVLD disorders. It does appear, however, that the incidence of NVLD has been on the rise over the past 10 to 15 years (B. P. Rourke, personal communication, September, 1991). Advances in neonatology have resulted in the survival of more significantly premature and potentially neurologically compromised children than ever before. While prematurity itself is not necessarily a risk factor for later cognitive problems (Siegel, 1983), saving more premature infants does increase the pool of potentially at-risk children.
A number of conditions affecting white matter areas of the brain have been found to lead to the NVLD syndrome (Rourke, 1995). Some examples of neurological disorders leading to white matter deficits and NVLD symptoms include callosal agenesis (Smith & Rourke, 1995), hydrocephalus (Fletcher, Brookshire, Bohan, Brandt, & Davidson, 1995), metachromatic leukodystrophy (Dool, Fuerst, & Rourke, 1995), multiple sclerosis (White & Krengel, 1995), encephalomyelitis, certain types of traumatic brain injuries (Ewing-Cobbs, Fletcher, & Levin, 1995), and toxic encephalopathies (White & Krengel, 1995). There is less direct evidence to implicate defects in white matter as causal in developmental cases of the disorder.
Recommendations for Treatment and Intervention
The following are some standard cautions used by the author to aid families of NVLD children in monitoring potential areas of future difficulty. A behavioral social skills intervention may be necessary to address inadequate social perception and poor social problem-solving skills. Practical day-to-day activities sometimes require more effort for children and adults with NVLD. These actvities include difficulties with mechanical or fine motor operations (e.g., repairing things, using simple tools, building models or puzzles), or difficulties with common tasks requiring math and nonverbal skills, such as cooking. Compensatory techniques can sometimes be helpful, such as relying on a compass, asking for a list of specific landmarks along travel routes, carefully following recipes and instruction manuals, and making procedural notes during tasks to document the steps already completed.
Reading graphs, maps, and charts is often difficult because of the spatial requirements of these tasks. Therefore, asking for written comments to explain graphs, getting verbal directions, or reading figure captions and legends carefully can prove helpful. Similarly, music instruction may be effortful. Reading notes, recognizing tunes, keeping rhythm, and following patterns are tasks that are often quite demanding for people with NVLD. When these problems with music are present, it is important to de-emphasize participation in these types of tasks.
It may also be difficult for these individuals to listen to oral presentations and take notes. If this occurs, compensatory techniques such as using a tape recorder during lectures should be considered. Timed tests may not accurately reflect actual knowledge or ability because problems with rapid processing of visual-spatial information and problems with higher level reasoning often make it difficult for individuals with NVLD to perform well when time is a factor. Allowing additional time or completely removing time constraints reduce this problem. Explicit directions, orally administered, may be difficult to follow if the child is unclear how to proceed perceptually. In this sense, the comment, "I see what you mean" may be appropriate; if a child with a nonverbal learning disability cannot mentally "picture" what they have been asked to do, they may fail on the task despite their capability of success. Having a teacher or "peer tutor" check periodically to determine that the individual is proceeding correctly can help.
Many practical difficulties can be observed in the classroom. Copying math problems or other assignments from a book or chalkboard, writing lengthy reports, or drawing maps could require too much effort. In general, activities requiring drawing, copying, and writing are often difficult for children and adults with NVLD. It may be necessary to have others assist with these tasks, perhaps by providing teacher outlines or having other students offer copies of their own papers.
The ability to solve computational math problems is frequently poor because of misalignment of columns of numbers, poor recall of math facts, or a lack of conceptual understanding. Each type of difficulty may require a different type of intervention, such as using paper with columns, encouraging use of a calculator, or providing examples of proper procedures for solving the problem. Conceptually, math topics related to fractions, decimals, percents, geometry, and trigonometry are typically particularly difficult. In addition, "survival math" concepts involving time, money, and measurement concepts are sometimes poor. Additional tutoring and instruction may be required and physical models and manipulative aids may prove necessary to teach the basic concepts.
Some individuals with NVLD have difficulty with creative writing, book reports, essays, and term papers. Because of their stronger verbal abilities, these individuals often write lengthier passages using good vocabulary and well-constructed sentences. Unfortunately, the result is often rambling and "empty," failing to convey anything of substance and sometimes never "getting to the point." Teaching them to create and follow outlines and providing editorial assistance with rough drafts may prove helpful. They often need additional time to complete and revise these writing assignments.
In addition to these cautionary examples, it is important to consider the appropriateness of special education. There are no formal criteria defining special education eligibility for children with NVLD. The direction of the discrepancy between Verbal and Performance IQ scores, whereby Performance IQ exceeds Verbal IQ, presents a particular difficulty. When a child demonstrates significantly better performance than verbal abilities, nonverbal measures of intelligence are frequently administered as alternative measures of "potential" (e.g., The Test of Nonverbal Intelligence; Brown, Sherbenou, & Johnsen, 1990). Furthermore, children with visual impairments or upper extremity hemiparesis are routinely evaluated using only the verbal subtests from measures of intelligence to establish their "potential." These "alternate" means for assessing general intelligence are commonly accepted by nearly all school districts. However, many school districts do not recognize the Verbal IQ score in isolation as a means for calculating discrepancy-based eligibility for special education in NVLD children. This persists despite the fact that these children are frequently incapable on visual-spatial measures as visually impaired children are. Also, there are no commercially available verbal intellectual measures for nonverbally disabled children that are analogous to the Test of Nonverbal Intelligence.
Depending on their particular presentation, NVLD children may be classified as learning-disabled (particularly in the area of math), as emotionally disturbed due to their social and emotional problems, or as eligible for occupational therapy because of their motor needs. Simply classifying NVLD children as learning disabled overlooks the extent of their true needs. Similarly, classifying them as eligible for special education on the basis of emotional or social deficits is insufficient to address the global problems presented by this disorder. A holistic approach to intervention must address academic deficiencies, motor and sensory needs, social competency, and emotional well being.
Clinical Case History: Developmental NVLD in a
C. K. had consistently performed poorly academically and had been placed in a self- contained classroom for children with behavior disorders for the past several years. He had no friends at school or at home and was frequently picked on by other children. Because of his desire to be accepted socially, he frequently attempted to imitate the actions of other delinquent adolescents, particularly gang members. C. K. had been assaulted by other adolescents on several occasions after flashing gang signs. When interviewed by the school counselors, it became apparent that he had no idea what the gestures meant. He stated that he was simply copying some of his other classmates. Most of his special education teachers described him as a polite and caring adolescent. He was typically received favorably by adults outside his immediate family.
Higher level reasoning was characterized by significant perseveration on the Wisconsin Card Sorting Test. Perseveration occurs when an individual repeatedly uses an incorrect problem solving strategy despite feedback that the strategy is wrong. It also frequently signifies an inability to consider or derive alternative solutions or strategies. Sequencing and ability to switch mental sets were also extremely poor on the Trail Making Test, Part A and Part B. Verbal learning and memory was poor on the Selective Reminding Test with erratic performance across learning trials and poor delayed recall for the material. Unexpectedly, C. K. also demonstrated moderate impairment for recall of meaningful paragraph length stories on the Story Memory subtest of the Wide Range Assessment of Memory and Learning. Many children with NVLD perform better on such semantic memory tasks. As expected, nonverbal memory functions were very poor and deteriorated in direct relation to the level of difficulty involved as seen by his poorer performance on the Design Memory subtest (Example 1, Example 2) compared to the Picture Memory subtest of the WRAML.
Receptive vocabulary was low average on the Peabody Picture Vocabulary Test - Revised, consistent with his performance on the Vocabulary subtest of the WISC-III. His poor confrontation naming abilities on the Boston Naming Test and poor expressive fluency on the Controlled Oral Word Association Test reflected the commonly seen deficits in more sophisticated aspects of expressive language that are characteristic of NVLD. The Controlled Oral Word Association Test (Benton & Hamsher, 1989) is a measure that allows the subject 60 seconds to generate a list of words, excluding proper nouns, beginning with a particular letter of the alphabet.
C. K. also demonstrated the hallmark of NVLD, impaired visual-spatial perception. Some examples of his poor copying of designs on the Developmental Test of Visual-Motor Integration are included (Example 1, Example 2, Example 3). His ability to copy block designs was also extremely poor. All aspects of sensory-perceptual and fine motor abilities scored within the impaired range. However, there was no evidence of poorer left hand versus right hand performance. Fingertip number writing, a task more dependent on right hemisphere processing, was much poorer than finger localization, a task often related to functioning of the angular gyrus in the left hemisphere.
One diagnostic complication was the presence of more language problems than would ideally be seen in this disorder. The fact that most of C. K.'s verbal subtests were at least low average, his Verbal Comprehension Index was technically within the Low Average range, reading and spelling were adequate, and receptive vocabulary was low average, suggest that there is probably not an additional primary language disorder present. However, some NVLD children do demonstrate other cognitive deficits, including severe language disorders. This does not necessarily preclude the diagnosis. However, it must be carefully demonstrated that the pattern is not simply one of global cognitive dysfunction.
Most neuropsychologists agree that at least three signs of NVLD must be present to make the diagnosis likely. These include a VIQ greater than PIQ discrepancy, math poorer than reading and spelling, and evidence of significantly poor social interaction. C. K. had each of these signs, as well as many additional features of the disorder. There was substantial reason to believe that many of his psychiatric problems were a direct result of an undiagnosed NVLD. In addition to a lifetime of difficulty with learning and socialization, he was dismissed by teachers and his parents as unwilling to work on his behavior problems. In fact, after his parents and doctors were informed of the NVLD diagnosis, they were much more supportive of C. K. and more tolerant of his behavior and learning problems.
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