Sample

The sample of the present study’s originated from a cross-sectional population study comprising nearly all individuals known with CHARGE in Norway (N = 35) [33]. This primary population (N = 35) demonstrated statistical representativity on several intellectual parameters (i.e., normally distributed), such as the overall measure of intellectual abilities. Basing the selection on age requirements of WISC-V (i.e., age interval [6.0, 16.11]) resulted in a sub-sample of 15 children and adolescent, which equalled most school aged children with CHARGE in Norway. Accordingly, assuming continued representativity, the same parameters should remain valid.

The gender ratio of the 15 children and adolescents was 7 to 8 (7 boys), between the ages of 7.6 and 16.11 (M = 12.7).

The degree of auditory deficits varied among the participants: 3 had a slight auditory impairment, 5 had moderate, and 7 had severe or profound, along with visual challenges: 2 presented average vision, 5 slight impairments, 1 moderate, and 7 severe.

Four participants used sign language while the others communicated by sign supported speech. Notable, Norwegian sign language has the same legal and educational status as Norwegian speech.

The sample was divided into two subgroups. The first subgroup consisted of 8 participants without deafblindness with a mean age of 12.3 years. The second subgroup included 7 participants with mean age of 13.2 years presenting more extensive combined sensory impairments corresponding to a deafblind condition. In Norway, a multidisciplinary team connected to the National Advisory Unit on Deafblindness, Department of the University Hospital og Northern Norway conduct the evaluation and final identification of deafblindness. Accordingly, all the participants had been evaluated by this unit as a part of their ordinary medical follow-up.

Design

This study applied a two-level assessment approach (Fig. 1), in which the 1st level refers to a standardized administration of WISC-V without deviating from the test protocol [32].

Fig. 1

Graphic illustration of the study design

The 2nd level assessment was a continuation of the 1st level using the stop criteria from the level 1 as the starting point for level 2. The main goal of this level was to increase accessibility by providing compensation (i.e., accommodation) for the participants combined sensory impairments, and founded on the principle of augmentative and alternative communication support (AAC) (https://isaac-online.org/english/what-is-aac/).

While the participants standard scores on WISC-V provided a baseline for comparative analyses, the norm data served as control group. The participants degree of hearing and visual impairments was defined as independent variables. A gap between a participant’s test score and expected score (i.e., relevant age norms on WISC-V) should imply the effect of intervening factor(s).

Cognitive measures and arithmetic’s

The subtests Block design, Similarities, Digit span, Matrix reasoning, Coding, Figure weights and Vocabulary of WISC-V [32] estimated the participants cognitive functioning on two levels. A Full-Scale Index referred to their performances after completing the 1st level assessment following standardized procedures. A Global Cognitive Estimate designated an overall score estimated after completing the 2nd level, which included gains in scores due to the provided accommodations. An Estimated Cognitive Difference represented the difference in scores between the two levels.

The test norms of WISC-V evaluated participants’ performances from both levels.

Implementation

The first author, a clinical neuropsychologist, conducted all the anamnestic interviews, preparation, and execution of testing.

Every participant was assigned up to 5 days to undergo all testing. Each day was divided into two working sessions, one morning and one midday, of no more than 45 min. The child’s teacher, a fluent signer, attended all the test sessions.

The 1st level assessment followed standardized procedure, i.e., each participant went through sequentially the items on every subtest until reaching the stop criteria. The assessment proceeded at the same subtest to the 2nd level by enforcing a seamless transition. This involved introduction of different accommodations, starting at the three recently failed test items from the 1st level.

The 4 participants who used sign language as their primary language needed instructions and responses translated (i.e., Norwegian speech to Norwegian Sign Language). Because different grammatical rules apply in Norwegian Sign language compared to Norwegian speech, the wording of the test instructions and verbal subtests had to be changed as illustrated below:

Standardized Question: What is the similarity between Red and Green?

Sign Language Connotation: Red! Green! Similar, how?

Standardized Question: Shy. What does shy mean?

Sign Language Connotation:Shy! Means what?

Standardized Question:Why should we avoid throwing garbage in the nature?

Sign Language Connotation:Garbage in nature, not good! Why?

Each item underwent analysis to evaluate if the change of wording influenced the content and intent. In case of uncertainties the item was excluded for all the participants.

Test accommodations

All the participants received accommodations regardless of their sensory motor impairment. Building on the original Wechsler material and reports from parents’ and teachers’, the accommodations’ final design addressed challenges within hearing, vison, and psychomotor tempo [34]. Furthermore, the categories delineated by Sireci and O’Riordan served as a guideline (i.e., Presentation, Response, and Timing) [27]. The Presentation category included enlargement of test material, application of contrasts and bold print, and framing the working area by Velcro boards (i.e., on the school desk). It also involved repeating instructions, sign supported speech and tactile communication.

The Response category involved alternative augmentative communication beyond speech and pointing, e.g., Velcro patches, crossing out, and tracing to indicate answers.

The Timing category consisted of extra time for completing each test item disregarding the time-limits indicated in the original test protocol.

All 15 received language support (i.e., visual and tactile signs) during the 2nd level assessments.

The visual accommodations included enlargement of print and supplication of contrasts to separate essential information from irrelevant visual noise (e.g., framing of the task at hand with black, brighter colors).

Extra time for task completion served to compensate for the participants’ tempo challenges.

Due to the crucial importance for the present study’s credibility, the discussion includes validations of the provided accommodations.

Statistical analyses

Tests of normality of findings were overall found satisfactory for further statistical investigations. The skewness of the Full-Scale Index (0.97) and Global Cognitive Estimate (1.01) appeared moderate and left-skewed. Their kurtosis equalled 1.23 and 1.17, respectively, indicating a more light-tailed distribution than a Gaussian distribution. The Shapiro–Wilk test turned out significant for both variables (Full-Scale Index: p = 0.04; Global Cognitive Estimate: p = 0.03). The effect size (Cohen’s d) turned out small as expected due to the small sample but given this paper's purpose not precluding further statistical analyses.

Pearson correlations estimated the strength of the associations between the dependent (i.e., Full-Scale Index, Global Cognitive Estimate, and Estimated Cognitive Difference) and independent variables (i.e., age, gender, degree of sensory impairment, including deafblindness). In contrast, paired sample t-tests estimated their difference.

Data analyses used SPSS software (version 29.0) with significance level p < 0.05.