Idiopathic toe walking (ITW) is defined as a gait pattern in children aged more than 3 years characterised by the bilateral absence of heel contact with the ground (“walking on tiptoes”). It is a clinical diagnosis that requires ruling out other neurologic or traumatologic–orthopaedic conditions that may cause a similar gait.1,2 Before age 2 years, this pattern is considered normal, and it resolves spontaneously in most children, as demonstrated by a longitudinal study by Engström et al. with follow up of a cohort of Swedish children through age 5 years. Only 30 of the 70 children who toe-walked at the beginning of the study continued to do so at age 5 years.3

Based on several studies, the prevalence of ITW in healthy children is estimated at 7–24%.

In addition to pain and increased instability, children with persistent ITW lose the ability to dorsally flex the ankle, which results in a shortened Achilles tendon.

When it comes to the aetiology of ITW, a hereditary pattern of ITW has been described since the earliest studies. Other studies have proposed impairments in sensory processing and proprioception as the cause of this gait pattern.4–6

The increased prevalence of ITW in children with autism spectrum disorder is well known, but several studies have also reported an association of ITW with other neurodevelopmental disorders. In a sample of 163 children, Accardo et al. found that those with ITW were more likely to have language disorders.7,8 A study in 26 children with ITW by Futagi et al. found that half had neurodevelopmental disorders (mainly hyperactivity and motor impairment) and 4 were in follow up for intellectual disability.9 Another study conducted by Schulman et al. also found an association between ITW in children with language disorders and fine and gross motor delays and visuomotor delays.10

Just as the incidence of ITW is higher in children with neurodevelopmental disorders, there is also a higher probability of its occurrence in association with different learning disorders. Thus, Engström et al. found that out of 51 children with ITW, 39% had motor disorders, 17% impairment in executive function, 25.5% perceptual disorders, 23.5% memory and language disorders, 25% poor social skills and 21.6% emotional/behavioural disorders.11

In Spain, ITW has also been described as a marker of impaired psychomotor development. For instance, a study comparing 56 Spanish school children aged 3–6 years who walked on their toes to children who did not exhibit this gait pattern by means of a psychometric test (CUMANIN) found that the children who toe-walked had a lower score in the developmental questionnaire overall and in specific subscales such as psychomotor development, memory, and verbal and nonverbal development.12

The scarcity of studies addressing the presence of ITW in association with one of the most prevalent neurodevelopmental disorders in Spain, attention-deficit hyperactivity disorder (ADHD), motivated us to conduct this study. Thus, our aim was to assess the potential association of ADHD with the presence of ITW.

We analysed data for children aged 6–18 years that received an ADHD diagnosis based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and with a normal neurological evaluation assessed in the Paediatric Neurology clinic of the Hospital Fundación Jiménez Díaz (Madrid) between January and December 2015.

Every patient included in the study had undergone a psychometric assessment that included a cognitive evaluation and screening for learning disorders. We excluded patients with any of the following: intellectual disability (IQ<70), pyramidal signs on neurologic assessment, presence of significant abnormalities in neuroimaging, autism spectrum disorder, chromosomal disorders or other defined genetic syndromes, or neurologic diseases accounting for the presence of ADHD symptoms (poorly controlled seizures, epileptic encephalopathies such as continuous spike and wave during sleep, and others).

We took a detailed history of ADHD symptoms, including an assessment of their severity by means of the Clinical Global Impression scale (CGI) and the Children's global assessment scale (C-GAS). We also analysed developmental, learning and social characteristics, and the presence of tics, developmental coordination disorders and other factors associated with ITW (family history, pain in lower extremities and frequent falling).

Furthermore, we took biometric measurements with a 360° goniometer with 2 moveable arms measuring 17.5cm each, with an angle scale marked at 2° intervals and a linear scale accurate to 1mm. In each patient, we measured the popliteal angle and the passive ankle dorsiflexion both with an extended and a flexed knee. We defined shortening of the Achilles as a passive ankle dorsiflexion with an extended knee of less than −10° (Fig. 1).

Figure 1.

Measurement of ankle dorsiflexion with the goniometer.

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We performed the statistical analysis with the software SPSS version 22, using the χ2 test.

The incidence of ITW is greater in patients with neurodevelopmental disorders compared to the general population. This association has been well defined, as we have noted above, with ITW found in patients with autism spectrum disorder (19–63%), language disorders (16–22%), cognitive disorders (30%) and learning disorders (20%). However, there is no previous study analysing the prevalence of ITW in patients with ADHD, the disorder that is the leading reason for seeking psychiatric care and found in 3.5% of school-aged children in Spain.13

In our sample, 20.8% of children with ADHD had ITW. Although this gait pattern was more frequent in patients with the combined type of ADHD, the differences between ADHD subtypes were not statistically significant. On the other hand, we found that not all patients with ITW had shortening of the Achilles tendon at the time of the assessment, although it is possible that they would have developed it eventually, since there is a progressive loss of ankle dorsiflexion in patients with ITW, as demonstrated in the work of Engelbert, frequently leading to shortening of the Achilles tendon or other tendons in the dorsal musculature of the lower extremities.14

We found a statistically significant association between ITW and the presence of impairments in social interaction (in the absence of autism spectrum disorder), which was consistent with the higher prevalence of ITW in patients with autism spectrum disorder. We also found a strong association between the presence of ITW and a positive family history of functional equinus in first-degree relatives, which supports the hypothesis that ITW is hereditary. But we did not find an association with other variables under study, such as sex, preterm birth, severity of ADHD, tics, language disorders, motor coordination, reading and writing or other psychiatric comorbidities.

It seems that the presence of ITW in children with neurodevelopmental disorders may stem from impairments in proprioception and sensory processing. Thus, in 1978 Montgomery and Gauger presented a series of cases that suggested that impairments in sensory processing and proprioception may be the main cause of ITW, although their results were not statistically significant.15

Later on, in 2011, Williams et al. performed a study where they assessed patients with and without ITW on a vibration platform and observed that patients with ITW had lower vibration perception thresholds compared to patients with normal gait, as well as poorer coordination. These data support the hypothesis that ITW results from impairments in sensory processing due to which patients require increased proprioceptive input to be able to maintain postural stability.5

Although many of our patients with ITW experienced pain, most of them had never sought medical care for it. We think that the early diagnosis of ITW is essential in order to implement effective treatments (physical therapy, botulinum toxin, orthotics, etc.) capable of preventing the associated symptoms (pain, instability) or surgeries required to treat shortened tendons.

This is the first study that demonstrates the high probability of ITW in children with ADHD. This association is usually underdiagnosed and may be a significant cause of morbidity in these patients.

The main limitations of our study are the lack of a control group and that the sample was obtained from a hospital setting, which may have resulted in a bias towards greater disease severity (although we did not find a significant association between the severity of ADHD symptoms and the presence of ITW).

The authors have no conflicts of interest to declare.