Isolated and transient tics are fairly common in childhood, ranging from 11–20% in different studies [20–22]. Diagnostic issues may arise in certain circumstances due to the waxing and waning nature and heterogeneity of tic symptom presentation [15]. Additionally, only a few studies have evaluated how many children with transient tics would become cases of Tourette syndrome or chronic tic disorder over time [23]. In this study, we tried to delineate the clinical features and follow-up outcomes in pediatric patients with tic disorders. We identified the complexities associated with tic disorders, including tic severity and related impairment, lag time to diagnosis, percentage of concomitant neuropsychiatric conditions, and predictors of clinical outcomes. The results of our study would help in better understanding of tic disorders.
We found that the mean age of 6.9 years for the onset of tics was higher than that reported in other studies, which ranged between 4 and 6 years for onset [5–7]. Mild tic symptoms may initially go unrecognized by caregivers and become noticeable only with increasing severity, which may account for the higher mean age at onset in this study. Consistent with previous studies by Robertson et al. [24], we found a higher proportion of tic disorders in males than females in our study. With regard to initial tic symptoms, eye blinking was observed most frequently, accounting for more than half of tic symptoms in patients (50.4%). Previous studies have also noted that tics usually begin in the head and face, with eye blinking being the first and the most common tic [25, 26].
Children with tic disorders have a higher likelihood of concomitant neuropsychiatric conditions [27]. Our results identified ADHD as the most commonly reported comorbid neuropsychiatric disorder, a finding consistent with previous research [28]. Tics are often not the most enduring or impairing problem in children with tic disorders; other coexisting neuropsychiatric conditions are often a greater source of impairment than the tics themselves [29]. Comorbid ADHD symptoms may have an undesirable impact on social, academic, and behavioral functions and can negatively impact quality of life and global psychosocial functioning [30–32]. Carter et al. [33] found that children with ADHD and tic disorders have more behavioral problems and poorer social adaptation compared to children with tic disorders only. Moreover, it has been postulated that the presence of ADHD in patients with tic disorders is correlated with higher rates of other neuropsychiatric comorbidities, such as OCD, anxiety disorders, anger control disorders, mood disorders, and personality disorders [5]. Our data noted a similar trend in that children with moderate to severe tics had more co-occurring neuropsychiatric disorders than those with mild tics, although the differences were not statistically significant. At a more general level, our results align with previous research showing that children with tic disorders may have increased healthcare needs and require supplemental mental health or educational services and support [34]. Therefore, clinical assessment of pediatric patients with tic disorders warrants a thorough evaluation for coexisting ADHD and other neuropsychiatric problems.
In our study, a relatively short lag time to diagnosis following the onset of tic symptoms was observed, with a mean duration of 13.3 months. This lag is significantly shorter than the 3 to 8 years delay reported in previous studies [5, 18]. The shorter time to diagnosis identified in our study is comparable to findings from more recent studies [16, 35]. In addition, time lag from when tics were first noticed to diagnosis was negatively correlated with tic severity. Growing awareness of tic symptoms among physicians and the availability of health information to patients and their families may be important factors in shortening the time to diagnosis [16]. Timely diagnosis of tic disorders may enable patients and their families to have access to optimized medical, psychological, and educational treatment and other support services [35].
We also found that patients with motor tics as the initial manifestation experienced less time to diagnosis than those with vocal tics. Patients with only vocal tics experienced relatively longer times to diagnosis compared to those with only motor tics or combined motor and vocal tics. Because throat clearing, sniffling, coughing, and grunting are the most common types of vocal tics, patients with vocal tics can often be misdiagnosed as having common pediatric conditions such as a cold, asthma, or allergy, which may contribute to diagnostic delay [4, 16].
With regard to follow-up outcomes, the vast majority of patients (83.2%) reported improvement in their tics over time in our study. Tics reach their apex early in the second decade of life and then usually improve during adolescence [26]. According to Bloch et al. [6], more than three-quarters of children with childhood tic symptoms had fewer tics or were completely tic-free at follow-up, while less than a quarter had moderate or greater tics at follow-up. Though questions regarding the clinical predictive factors of follow-up outcomes arise frequently in clinical practice, previous studies have not successfully identified reliable predictors of follow-up outcomes. Prognostic issues can be difficult to address clinically because tic disorders have a complex range of possible symptom combinations and comorbidities [36]. In our study, we attempted to delineate the demographic and clinical factors that could be used to predict the future course of tic disorders. There were, however, no associations between future tic severity and gender, age of tic onset or diagnosis, lag time to diagnosis, subtypes of tic disorders, types of initial tic symptoms, tic severity at diagnosis, presence of neuropsychiatric comorbidities, or treatment utilization. Although we did not uncover robust clinical predictors of the course of tic disorders, our findings may provide a useful platform for further long-term follow-up studies regarding this issue.
Our study is limited by its retrospective nature. Drawing our patient sample from a single referral center likely influenced the lack of statistical significance. Thus, larger prospective studies or collaborative trials are warranted to elucidate the complex interaction of tic severity, comorbidities, and tic-related impairment and reveal the predictors of long-term follow-up outcomes.