Original article
Diagnostic overshadowing in a population of children with neurological disabilities: A cross sectional descriptive study on acquired ADHD

https://doi.org/10.1016/j.ejpn.2015.04.004Get rights and content

Highlights

  • Acquired ADHD is common in children with neurological disabilities.

  • Acquired ADHD is often underdiagnosed due to diagnostic overshadowing.

  • This finding may have important implications for clinical practice.

Abstract

Aim

Diagnostic overshadowing refers to the underdiagnosis of comorbid conditions in children with known neurological diagnoses. To demonstrate diagnostic overshadowing we determined the prevalence of attention deficit-hyperactivity disorders (ADHD) in a cohort of children with a wide range of neurological disabilities.

Method

The study cohort consisted of 685 children (mean age 10.3 years, SD: 3.1; 425 boys and 260 girls) who visited a tertiary outpatient multidisciplinary clinic for neurological learning disabilities. Patients with ADHD were identified by retrospective chart review using DSM-IV criteria.

Results

The prevalence of ADHD in this cohort was 38.8% (266 children); of these children only 28.2% (75 children) were diagnosed with ADHD before referral.

Interpretation

ADHD is a common problem in children with neurological disabilities and may be underdiagnosed due to overshadowing of somatic, physical or syndromal features of the disability. In our heterogeneous population ADHD was overshadowed in 71.8% of the cases. This finding may have important implications for diagnosis and treatment of mental health needs in children with neurological disabilities.

Introduction

Attention Deficit-Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder in childhood with important implications for the child's functioning in the domain of learning, emotion, behaviour, and social functioning. Polaczyk et al. estimated its prevalence in a systematic worldwide review to be 5.29%.1

The aetiology of ADHD is heterogeneous. On the one hand it is a highly heritable disorder (estimated to be around 70–80% of the genetic variation), on the other hand it can be acquired due to lesions of the brain, other environmental factors such as deprivation or a combination of factors.2 The presence of brain dysfunction is associated with a higher risk of neuropsychiatric problems. This was already described by Graham and Rutter in the classical Isle of Wight study.3 In a population of 11,826 school age children they found that in children with a neurological condition (epilepsy or cerebral palsy) 34.5% also manifested a psychiatric disorder. For children with lesions below the brainstem (like muscular dystrophy or poliomyelitis) the prevalence was 13.3%. They furthermore reported that organic brain dysfunction was not associated with any specific type of psychiatric disorder such as hyperkinetic syndrome or neurotic disorders.

Literature on ADHD in neurological disabilities is fragmented and often restricted to small samples of children using different methodologies and lack of control groups. We reviewed the literature on the prevalence of ADHD in four different child neurological conditions. In children with severe traumatic brain injury, the incidence of ADHD is about one third of the children.4 Max et al. introduced the term secondary attention deficit hyperactivity disorder (SADHD) to better characterize this condition of paediatric psychopathology. The term acquired ADHD has also been used for attention disorders in various neurodevelopmental disorders such as neurofibromatosis type 1 (NF1) where an incidence of ADHD has been reported of 53%.5, 6 In clinical practice only a small percentage of children with NF1 are diagnosed with ADHD.7 For children with cerebral palsy (CP) there is to our knowledge only one population based study on psychiatric comorbidity.8 Bjorgaas et al. found in a Norwegian cohort of 67 children with CP that 50% of the children with mild to moderate motor function problems without intellectual disability, met the criteria of ADHD. Furthermore, in two thirds of children with CP meeting the criteria of ADHD, the attention problems had not been addressed prior to the study. Finally, in boys and young men with Duchenne muscular dystrophy (DMD) the involvement of the brain is now beyond any doubt.9 Recently Pane et al. assessed ADHD in 103 boys with DMD. ADHD was found in 32% of the boys; 18 of them also had an intellectual disability. ADHD was not related to the level of motor ability, nor to the use of steroids.10

There is a growing interest in the neurobehavioral aspects of child neurological conditions, but they may remain underdiagnosed. We hypothesize that the term diagnostic overshadowing applies for ADHD in children with neurological disabilities. Originally, Reiss, Levtan, and Szyszko introduced this term in 1982 to refer to the tendency to attribute behaviour problems in individuals with intellectual disability to this underlying cognitive deficit and therefore underdiagnose a comorbid psychopathology.11 This clinical bias may result in underdiagnosis of attention deficit symptoms without further diagnosis and treatment. This may have important implications for the children's future academic and professional career, which is not only at risk because of physical impairments, but also because of the attention deficits if left untreated. The aim of the present cohort study was to study the prevalence of ADHD in a clinical sample of school age children with a wide range of neurological disabilities in general and, more specific, in children with traumatic brain injury, cerebral palsy, neurofibromatosis type 1, and Duchenne muscular dystrophy.

Section snippets

Methods

Charts of children referred to a tertiary outpatient clinic of neurological learning disabilities in Heeze (Netherlands) for the period 2010–2014 were reviewed. A team of a child neurologist and a (child)neuropsychologist evaluated the children. A total of 863 children were referred with a neurological condition or suspicion of a neurological condition. Informed consent was given by all caregivers. One hundred children were five years or younger, and therefore were excluded because no formal

Results

In our patient population 266 children (38.8%) were given the clinical diagnosis ADHD. Inspection of the medical files at referral showed that 75 of the children (28.2%) had already received a diagnosis of ADHD before referral. Furthermore, the medical history revealed that for 6.1% of the children a previous family history of attention disorders was present. When looking at ADHD in the different medical diagnoses the following frequency distribution of ADHD can be seen: traumatic brain injury

Discussion

The complexity and heterogeneity of child neurological disabilities constitutes a challenge to diagnose ADHD in this group of children. There is a growing scientific interest in the neurobehavioral comorbidities of these disabilities: terms as ‘secondary ADHD’ or ‘acquired ADHD’ are used in literature.

Our descriptive cohort study reports on the clinical data of a heterogeneous sample of children with a neurological disability, referred to a tertiary outpatient clinic. Overall the prevalence

Conflict of interest

None.

References (14)

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