A total of 100 patients with persistent post-traumatic headache and 100 age- and gender-matched healthy controls were enrolled into this study. Characteristics of the study population and control group are presented in Table 1. Patients’ mean age was 36.0 ± 11.7 years, and 83% were women. The mean number of monthly headache days was 25.4 ± 7.1, and 91% had a migraine-like headache phenotype. Conditions associated with persistent post-traumatic headache were poor quality of sleep (85%), recurrent episodes of neck pain (78%), probable to high risk of anxiety (52%), and probable to high risk of depression (42%). In addition, the proportion of patients with mild, moderate, or severe cutaneous allodynia was 23%, 17%, and 6%, respectively. Additional characteristics of the patient population have been published elsewhere and are also summarized in Table 2 [2, 18].

The median number of TTS was 21 (IQR, 12–31) in patients with persistent post-traumatic headache and 10 (IQR, 6–17) in healthy controls, and the difference was significant (P < 0.001). Compared with controls, patients with post-traumatic headache also had higher left-sided TTS (P < 0.001) and higher right-sided TTS (P < 0.001).

Among patients, TTS was correlated with age (rs = -0.31, P = 0.002), ASC-12 scores (rs = 0.28, P = 0.005), and HADS anxiety scores (rs = 0.20, P = 0.05), (Table 3). No correlations were observed between TTS and monthly headache days (rs = -0.12, P = 0.20), Global PSQ-I scores (rs = 0.13, P = 0.21), HADS depression scores (rs = -0.01, P = 0.89), and headache intensity on the assessment day (rs = -0.07, P = 0.52), (Table 3).

For the left-sided m. temporalis, mean PPT values were lower in patients with persistent post-traumatic headache (157.5 ± 59.9), compared with healthy controls (201.1 ± 65.2; P < 0.001). Mean PPT values obtained from the right-sided m. temporalis were also lower in patients (159.5 ± 63.8), compared with healthy controls (212.3 ± 61.9; P < 0.001). There were no correlations for PPT values from both the left- and right-sided m. temporalis of patients with any of the following variables: age, monthly headache days, ASC-12 scores, Global PSQ-I scores, HADS anxiety scores, HADS depression scores, and headache intensity on the assessment day (Table 4).

For the upper part of the left-sided m. trapezius, mean PPT values were lower in patients (241.6 ± 104.2) than in healthy controls (308.0 ± 114.7; P < 0.001). Mean PPT values obtained from the corresponding right-sided m. trapezius were also lower in patients with persistent post-traumatic headache (277.1 ± 117.0), compared with the control group (317.5 ± 123.0; P = 0.01). Among patients, correlations were observed between age and PPT values in the upper part of both the left-sided (rs = 0.21, P = 0.04) and right-sided m. trapezius (rs = 0.19, P = 0.05), (Table 5). There were no correlations for left- or right-sided PPT values with monthly headache days, ASC-12 scores, Global PSQ-I scores, HADS anxiety scores, HADS depression scores, and headache intensity on the assessment day (Table 5).

Mean PPT values obtained from the middle part of the left-sided m. trapezius were lower in patients with persistent post-traumatic headache (237.2 ± 107.5), compared with healthy controls (281.0 ± 109.2; P = 0.003). Patients also had lower mean PPT values in the corresponding right-sided m. trapezius (251.0 ± 111.0), compared with the control population (311.6 ± 131.3, P < 0.001). No correlations were observed for PPT values from the middle part of both the left- and right-sided m. trapezius of patients with any of the following variables: age, monthly headache days, ASC-12 scores, Global PSQ-I scores, HADS anxiety scores, HADS depression scores, and headache intensity on the assessment day (Table 5).