The purpose of the present study was to examine the prevalence of headache after pediatric TBI and to investigate factors associated with the probability of developing headache in a post-acute TBI sample, also in comparison with matched controls from the general German population, which has not been done to date.

When controlling for age, sex, and the presence of chronic health conditions, the differences in the relative frequency of reported headaches between children and adolescents from the post-TBI and general populations do not exceed 5%. Overall, the results indicate no significant increase in the odds of headache in children and adolescents in the post-acute TBI phase compared with matched controls. However, there is an age effect, suggesting that the probability of reporting headache increases with age in children and adolescents.

An increasing tendency for children and adolescents to suffer from headaches has been reported in recent years [32]. Our findings on the prevalence of headache in the matched control sample of 44% are largely consistent with previous findings [32, 33]. Given the high prevalence of headache in (relatively) healthy young people, it is particularly important to understand the impact of a traumatic event such as TBI on the development and persistence of headache, also in terms of differential diagnosis. Since headache has a negative impact on HRQoL [34], particularly in terms of physical functioning and social and psychological well-being [35], it is important to treat it to allow children and adolescents to lead a normal life.

The prevalence of headache in the TBI sample reaches 46%, which exceeds the previously reported frequency of non-specific chronic headache after TBI [7]. Given that the vast majority of the sample sustained mild TBI without detectable neuroimaging abnormalities, this finding deserves special attention. On the one hand, this relatively high prevalence may be due to the way headache was defined in the present study. The post-TBI version of the PCSI requires an assessment of symptom intensity compared with the pre-injury period, which may be affected by recall bias and is not sufficient to make a clinical diagnosis. On the other hand, it may be an indication of headache onset independent of the traumatic event. Post-concussion symptoms in general have repeatedly been found to be TBI-independent, following non-brain injuries or occurring in otherwise healthy populations [36]. In light of these considerations, the high frequency of self-reported headache in the post-acute phase of TBI suggests the need for further attention, special clinical implications (e.g., thorough medical history review, appropriate diagnosis, and timely treatment), and long-term follow-up of affected children and adolescents.

Headache intensity correlates with that of other symptoms, and vice versa, especially in adolescents. However, it is not evident whether other symptoms cause the development of headache or whether headache contributes to the development of more/additional symptoms. Some recent reviews have reported the presence of a greater number of other symptoms as critical to the development of headache both after TBI [3] and in the general pediatric population [37]. Therefore, screening for multiple symptoms such as fatigue, sleep disturbance, difficulty concentrating, clumsiness, etc. in addition to headache would provide a more accurate symptom profile after pediatric TBI and guide further intervention strategies. By comparing the scores of children and adolescents after TBI with those of the general population, conclusions could be drawn more easily. Such reference values have recently been provided for two age-adjusted German post versions of the PCSI [18, 20] and are recommended for use in both clinical and research settings.

According to some studies, different types of headaches in children and adolescents tend to peak around 13 to 15 years of age [38,39,40]. Headaches can be a common symptom of a changing and maturing body, caused by hormonal changes, growth stimulation, but also by other reasons such as physical or mental health problems [37]. In this case, post-TBI headaches may also be exacerbated. For this reason, appropriate developmental considerations and a detailed differential diagnosis should be made [41].

In contrast to previous studies [2, 3, 8, 9], other factors such as gender, repeat TBI, time since injury, TBI severity, presence of lesions on neuroimaging and chronic health complaints had no significant association with post-TBI headache. However, both gender and repeat TBI remained in the reduced model by elastic net regulation, indicating importance of both factors.

Our findings are indicative at least in the post-acute phase of TBI, but are not generalizable to the acute TBI setting. In conclusion, we recommend paying special attention to the multiple symptoms reported and to the age of the patients, complemented by a thorough diagnosis and comparison with children and adolescents from the non-TBI population, to prevent symptom burden, also in the post-acute TBI phase.

The present study is the first to examine the occurrence of headache in children and adolescents after TBI in comparison with the general population. However, some limitations should be noted. First, the information on headaches was based on a single self-report item with a different type of response scale for children and adolescents, which may have overestimated the prevalence. Therefore, we were unable to distinguish between different types and pattern of headache (e.g., migraine or cluster headache [42]). Further research focusing on different types of headaches may contribute to a better understanding of headache incidence, also in comparison with non-TBI populations. Second, the study sample is a post-acute sample with a relatively long time since injury. Although time since injury does not appear to significantly influence outcome, further studies in acute post-injury populations are indicated, especially given that we cannot distinguish whether the occurrence of headache is directly related to TBI or caused by other conditions or recall bias. Third, longitudinal studies at multiple time points would clarify the course of headache after TBI. In addition, a more consistent assessment of the presence of chronic health conditions in both samples would allow for more accurate comparisons of the occurrence of headache with or without TBI. Finally, some factors known to influence the development of headache, such as migraine (including family history), could not be included in the model due to small case numbers or unavailability of data. In addition, the interaction terms could not be considered because of the group size of some variables included in the model. Overall, further studies are recommended to improve the understanding of this common post-TBI symptom.