Similarities Between Tinnitus and Pain

Chronic pain and tinnitus share analogous anatomical and pathophysiological mechanisms leading to similarities in clinical presentation and resulting in common treatment approaches. Yet, there is an important difference as well. Acute pain is the result of activation of specific dedicated pain pathways, for which there is no tinnitus counterpart. Chronic pain is slightly more prevalent than tinnitus, 25% vs. 15%, and both symptoms are on the rise, also being comorbid. Clinically, both are entirely subjective symptoms that can be associated with suffering in 20% of patients. Chronic pain can be associated with allodynia and hyperpathia, and tinnitus with hyperacusis and misophonia. Both can have a wind-up phenomenon. Both share electrophysiological similarities in that alpha oscillatory resting state activity is replaced by theta-gamma cross-frequency coupling in the respective sensory cortex. The presence of pain and tinnitus results from an imbalance between two pain and tinnitus provoking pathways and one descending pain and noise cancelling pathway, respectively. The thalamocortical dysrhythmic activity present in the lateral pathway is embedded in the triple cognitive network, essential for conscious perception and related to pain or tinnitus-related suffering. The transition from acute to chronic pain and tinnitus is related to maladaptive learning via conditioning, based on abnormal connectivity between the nucleus accumbens and the descending pain and noise canceling pathway, respectively. The persistence of chronic pain and tinnitus may be linked to neuroinflammation, which is the result of genetic and epigenetic factors, combined with altered microbiome.