Psychophysic-psychological dichotomy in very early acute mTBI pain: A prospective study

OBJECTIVE: To characterize the pain-related somatosensory and psychological presentation of very early acute patients with a mild traumatic brain injury (mTBI). METHODS: Patients with an mTBI participated in a prospective observational study undergoing clinical, psychophysic, and psychological assessment within 72 hours after the accident. Healthy controls underwent similar protocol. RESULTS: One hundred acute patients with an mTBI (age 36 ± 12.5 [SD] years, range 19-67 years, 42 women) and 80 healthy controls (age 43 ± 14.3 years, range 24-74 years, 40 women) participated. Patients with an mTBI demonstrated a pronociceptive psychophysic response in most tests such as less efficient pressure-pain threshold-conditioned pain modulation (0.19 ±0.19±.09 vs. 0.91±.10 kg, p < 0.001) and lower temperature needed to elicit a Pain50 response (44.72 ± 0.26°C vs 46.41 ± 0.30°C, p < 0.001). Their psychophysic findings correlated with clinical pain measures, e.g., Pain50 temperature and mean head (r = -0.21, p = 0.045) and neck (r = -0.26, p = 0.011) pain. The pain-catastrophizing magnification subscale was the only psychological variable to show a difference from the controls, while no significant correlations were found between any psychological measures and the clinical or psychophysic pain measures. CONCLUSIONS: There appears to be a dichotomy between somatosensory and psychological findings in the very early acute post-mTBI stage; while the first is altered and is associated with the clinical picture, the second is unchanged. In the context of the ongoing debate on the pathophysiologic nature of the post-mTBI syndrome, our findings support its "physical" basis, free of mental influence, at least in the short time window after the injury.