Deciphering Persistent Orofacial Pain - PIFP

Persistent non-dental orofacial pain is common yet poorly characterised, and its pathophysiology remains largely unknown. Two clinically similar entities are distinguished: post-traumatic trigeminal neuropathic pain (PTNP), in which peripheral nerve damage is demonstrable, and persistent idiopathic facial pain (PIFP), in which peripheral findings are typically absent - pointing to an altered central processing of trigeminal nociceptive input. This monocentric study characterises the peripheral and central mechanisms of PIFP by comparing PIFP patients with age- and sex-matched healthy controls using a combination of non-invasive peripheral and central approaches.

The study comprises two work packages. The peripheral work package uses quantitative sensory testing (standardised DFNS protocol) to test the hypothesis that PIFP patients retain an intact peripheral nervous system. The central work package uses functional MRI with standardised trigemino-nociceptive stimulation to characterise brainstem network dynamics, testing the hypothesis that PIFP patients exhibit a central trigeminal processing disturbance at the brainstem level. In PIFP patients, the functional MRI is repeated before and after a local-anaesthetic nerve block in the pain area, additionally distinguishing patients whose pain is completely abolished by the block from those with persistent pain despite it. The overarching aim is to characterise the pathophysiological basis of PIFP and thereby advance the mechanistic understanding of persistent orofacial pain.