Abstract
Aims Attention deficit hyperactivity disorder (ADHD) is one of the most frequent neurocognitive impairments in neurofibromatosis type 1 (NF1) and a well-known risk factor for intellectual dysfunction in general. Since NF1 is per se associated with intellectual difficulties, this comorbidity may be crucial for the cognitive development of affected patients. In our study, we investigated if attention deficits are associated with intellectual functioning in NF1 and if children with NF1 plus ADHD differ in their intellectual and attention profiles from children affected by NF1-only or ADHD only. Methods 111 children aged between 6 and 12 years (53 NF1 plus ADHD, 28 NF1-only, 30 ADHD-only) performed the German version of the intelligence test WISC-IV and a continuous performance test (T.O.V.A.) to assess attention functions. Parents completed questionnaires about everyday attention and executive functions (Conners 3®, BRIEF). Results Children with NF1 plus ADHD showed significantly lower intelligence test scores (full-scale IQ: 89.39 [1.40]) than patients with NF1-only (full-scale IQ: 101.14 [1.98]; p < .001), and intellectual functioning correlated significantly with attention performance in NF1 (p < .001). As compared to NF1-only, attention, and executive functioning were impaired on several dimensions (T.O.V.A., Conners 3® and BRIEF) in NF1 plus ADHD. ADHD-only was associated with significantly higher problem scores regarding hyperactivity/impulsivity and inattention (Conners 3®). NF1-only was associated with inattentiveness when compared to the normative sample of the T.O.V.A. Conclusion NF1 is associated with variable attention problems. Severe attention deficits appear to be a risk factor for intellectual dysfunction in NF1, more than NF1 without attention deficit. NF1 plus ADHD presents a specific cognitive profile, which differs from that of NF1 and from neurotypical ADHD.
Highlights
Neurofibromatosis type 1 (NF1) is an autosomal dominant single-gene disorder, affecting the nervous system
Our study may help to substantiate NF1-typical cognitive characteristics and to elaborate differences between NF1 plus ADHD (NF1ADHD) and NF1-only, as well as NF1ADHD and attention deficit hyperactivity disorder (ADHD)-only: (1) Firstly, we assumed that ADHD symptoms are a specific risk factor for intellectual functioning in NF1. erefore, (a) we expected patients with NF1-only and ADHDonly to perform significantly better on measures of intellectual functions than patients with NF1ADHD
A er correcting for the effect of the covariate, significant main effects were observed for all four WISC-IV subscales (verbal comprehension: 퐹(2, 111) = 5.498, 푀푆퐸 = 106.80, 푝 = .005; perceptual reasoning: 퐹(2, 111) = 5.094, 푀푆퐸 = 137.36, 푝 = .008; working memory: 퐹(2, 111) = 7.858, 푀푆퐸 = 131.03, 푝 = .001; processing speed: 퐹(2, 111) = 5.842, 푀푆퐸 = 163.78, 푝 = .004), with the NF1ADHD group performing significantly worse than the NF1control group on all subscales and performing worse than the ADHDcontrol group on the subscale working memory (Table 2)
Summary
Neurofibromatosis type 1 (NF1) is an autosomal dominant single-gene disorder, affecting the nervous system. It has an incidence rate of one in 2600–3000 individuals. NF1 is characterized by a wide range of physical complications [1] and is considered to cause a variety of cognitive dysfunctions [2]. Over and above unspecific attention problems, up to 50% of all NF1 patients present ADHD-like symptoms and fulfil the diagnostic criteria for attention deficit hyperactivity disorder (ADHD) [2, 4,5,6] according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) [7]. Since the ADHD-diagnosis is based exclusively upon behavioral criteria, ADHD-like symptoms in NF1 may consequentially be International Journal of Pediatrics diagnosed as ADHD, even if etiology and developmental course of these symptoms are unknown so far and the high prevalence does not suggest a simple comorbidity
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