PD Dr Jan Mehnert, Dr Einav Gozansky, Hagen Pöhlmann | Novel insights into pain processing

Introduction: Factors mediating Pain Chronification (Mehnert)

Some acute pain patients develop chronic pain syndromes, although their acute (peripheral) pain is already cured, while others do not. Factors driving this decision are widely unknown. During my recent research on episodic and chronic migraine, I was able to identify two factors: integration of pain in multisensory processing and the descending pain processing pathway.

Part 1: Multisensory Integration in chronic low-back pain (Gozansky)

Multisensory integration (MI) enhances perceptual reliability by combining inputs across senses, playing an important role in every-day life. Evidence suggests that MI is altered in some pain conditions, like migraine or fibromyalgia, but it is unclear whether this reflects a general feature of pain conditions or is specific to some disorders in which the perception in other senses is also altered. We examined pain-related MI in healthy individuals, patients with chronic low back pain (cLBP) and episodic migraine using reaction-time paradigms and a pain-induced flash illusion. Both groups showed robust multisensory facilitation, race model violations, and comparable susceptibility to pain-induced illusions, regardless of stimulation site. These findings indicate preserved multisensory integration in cLBP, suggesting that MI alterations in chronic pain are not universal but disorder-specific.

Part 2: The causal role of the cerebellum for the descending pain processing pathway (Pöhlmann)

The processing of pain in the central nervous system can be divided into an ascending and a descending pathway. While sensory input flows from 1st order neurons through the thalamus into the cortex, cortical output flows back into these first order neurons through the periacqueductal grey (PAG) and the rostral ventromedial medulla (RVM). Nevertheless, in nearly all studies on pain processing also the Cerebellum shows high activity. We can show that the cerebellum plays a causal role in the descending pain processing pathway modulating the incoming pain signals.