Spinal segmental sensitization as a common origin of chronic non-specific regional musculoskeletal pain: review of its pathophysiology and diagnosis

Musculoskeletal pain involving a region of the spine with radiation to the head, trunk, or extremities is relatively common in daily medical practice, such as upper- neck pain with headache, lower-neck pain and discomfort in the shoulders and arms, or low-back pain with sciatica. The instability of a vertebral segment produces a persistent barrage of nociceptive impulses that trigger peripheral and central sensitization phenomena, affecting the metamere innervated by the corresponding nerve root. This process produces clinical manifestations of hyperalgesia and/or allodynia in dermatomes, myotomes, and sclerotomes with a typical regional distribution known as spinal segmental sensitization (SSS). The activation of new peripheral nociceptive foci within the affected metamere can further aggravate the clinical picture. This disorder is usually classified as non-specific for being a somatosensory nervous system dysfunction without evident structural damage, which can lead to confusion since the magnitude of pain and disability reported by the patient appear to be disproportionate to the findings of auxiliary tests. In the absence of a timely diagnosis and adequate treatment, patients may resort to alternative therapies, which often do not solve the problem. The use of a standardized set of diagnostic criteria will help clinicians identify SSS and help researchers conduct studies in homogeneous populations. This review of its pathophysiology provides a foundation for rationally and systematically establishing the best treatment schemes and thus will benefit the many patients who suffer from this syndrome, which represents a challenge for