Abstract text (incl. figure legends and references)

Objective: To evaluate whether there are differences in pressure pain thresholds (PPT) over neural structures in the cranio-cervical region and upper limbs between patients who present with headache and those who do not shortly after a whiplash injury

Methods: A case-control study was conducted from September 2020 to February 2021 in a Traumatology Clinic in Madrid, Spain. PPT (N/cm2) were evaluated with an algometer twice over the median, ulnar, radial, supra-orbitaire and greater occipital nerves bilaterally. The evaluator was blinded to the group allocation.

Results: Among 49 consecutive patients who were assessed, 41 eligible patients were included in this study, 22 and 19 with and without headache, respectively.

Baseline differences between groups were found in relation to sex; there were more women in the group with headache (73.7% vs 50% in the non-headache group). No baseline differences were found in age, height, weight and days from the accident to the evaluation. When compared to the non-headache group, significantly lower PPT (mean ± SD; p-value) were found in the headache group for left (20,92±7,4; p=0,031) and right (20.90±8,5; p=0,028) radial nerves, right ulnar nerve (16.64±5,52; p=0,016) left (8.47±2,62; p=0,008) and right (8.79±3,15; p=0,008) supra-orbitaire nerves and left (8.79±3,10; p<0,001) and right (8.64±2,83; p<o,001) greater occipital nerves.

Conclusion:

People who present with headache soon after a whiplash injury show lower PPT over neural structures when compared to those patients who did not develop headache. These findings suggest the presence of greater sensitization in those who develop headache following a whiplash trauma.