NLD = VIQ > PIQ  ... It Ain’t Necessarily So

 by Pamela B. Tanguay

 

 

For as long as I have heard the term NLD, I’ve understood that the key indicator of this disorder is a WISC VIQ > PIQ. For many years, I blindly accepted this as fact.

When our daughter was recently administered her third WISC over a period of seven years, her historical VIQ > PIQ collapsed to equal scores. Since she was diagnosed some years ago with "classic" NLD by a very qualified neuropsychologist, I was puzzled. My daughter’s NLD characteristics, although improved, have remained constant, so how could the classic VIQ > PIQ suddenly disappear?

Scratching my head, I looked at the subtest scores. Two VIQ subtest scores dropped dramatically--comprehension and arithmetic each dropped 5 points. The remaining verbal scores were consistent with earlier results. The last subtest score that had any notable change was a modest decrease in picture arrangement, which is on the PIQ side of the equation.

As the child ages, the questions presented in the WISC become more difficult, and the "cues" more subtle. Since the comprehension and picture arrangement subtests relate to social skills, and the arithmetic subtest is obviously related to math, drops in these three areas would appear to be consistent with an NLD diagnosis. After all, social and math deficits are hallmarks of this disorder.

So here’s the dilemma…my daughter’s subtest scores appear totally consistent with an NLD diagnosis, right? BUT the experts say that the VIQ > PIQ continues over time, with the spread in favor of a higher VIQ often continuing to increase as the child ages. How can this be so? I was stumped as to how the premise of a continued VIQ > PIQ spread could be supported. In my mind, it was more likely that the VIQ would drop over time, suppressed by the comprehension and arithmetic scores. 

After struggling with this dilemma for almost a year, I found myself in the enviable position of being able to pose the question to Dr. Byron Rourke. "Does the VIQ > PIQ profile continue over time?" Although he personally answered my question, more importantly he clarified the issue from the podium the next afternoon at a conference. His answer? The VIQ > PIQ profile, although common, is not always present, since the verbal score may be suppressed by the comprehension and arithmetic subtest scores. EUREKA!!!!

So what’s the big deal? Information on NLD is finally beginning to surface in the educational environment. Articles are starting to appear in educational trade journals, workshops are being conducted for teachers, parents are educating their school districts, and so forth. If educators latch onto a simple concept such as VIQ > PIQ equals NLD, they may well miss the boat. The old saying "a little knowledge is dangerous," applies here in spades. The sudden absence of the VIQ > PIQ discrepancy does not mean that my daughter is suddenly "cured," and that services should be removed. Subtest scatter in a student’s WISC results is far more important than the averaged scores, and WISC results should never replace a full neuropsychological evaluation and resulting diagnosis.

 

Wechsler Intelligence Scale for Children   The verbal score is based on the following subtests, with most questions being presented verbally and a verbal response required: Information: Factual knowledge, long-term memory, recall. Similarities: Abstract reasoning, verbal categories and concepts. Arithmetic: Attention and concentration, numerical reasoning. Vocabulary: Language development, word knowledge, verbal fluency. Comprehension: Social and practical judgment, common sense. Digit Span: Short-term auditory memory, concentration.   The performance score is based on the following subtests, with information presented visually and generally requiring a nonverbal response: Picture Completion: Alertness to detail, visual discrimination. Coding: Visual-motor coordination, speed, concentration. Picture Arrangement: Planning, logical thinking, social knowledge. Block Design: Spatial analysis, abstract visual problem-solving. Object Assembly: Visual analysis and construction of objects. Symbol Search: Visual-motor quickness, concentration, persistence. Mazes: Fine motor coordination, planning, following directions.