Myofascial pain syndrome and sensitization

Abstract

Myofascial pain syndrome (MPS) is a major musculoskeletal pain that occur in every age group, and has been associated with numerous pain conditions including radiculopathies, osteoarthritis, disc syndrome, tendonitis, migraines, tension type headaches, computer-related disorders, spinal dysfunction, and pelvic pain. Myofascial pain is identified by palpating skeletal muscle for myofascial trigger points (MTrPs). A MTrP is classically defined by Professor Janet G Travell and Professor David G Simons as "a hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. Although the specific pathophysiological basis of MTrPs development and symptomatology is unknown, there are evidences of histological, neurophysiological, biochemical, and somatosensory abnormalities. These emerging findings suggest that myofascial pain is a complex form of neuromuscular dysfunction consisting of motor and sensory abnormalities involving both the peripheral and central nervous systems.Sensitization in corresponding spinal segments plays a major role in the formation of continuous pain in a given part of the body. The term called by Professor Andrew A. Fischer for this phenomenon is "spinal segmental sensitization" (SSS). SSS is a hyperactive state of the spinal cord caused by irritative foci sending nociceptive impulses from a sensitized damaged tissue to dorsal horn neurons. The clinical manifestation of dorsal horn sensitization includes hyperalgesia of the dermatome, pressure pain sensitivity of the sclerotome and myofascial trigger points within the myotomes, which are supplied by the sensitized spinal segment. There are significant elevated levels of substance P, calcitonin gene-related peptide (CGRP), bradykinin, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), serotonin, and norepinephrine in the vicinity of the active myofascial trigger point. Overall, pH was significant lower in the active trigger point. The mechanism consists of the nociceptive stimuli generated in the sensitized areas bombarding the dorsal horn of the spinal cord. This causes central nervous system sensitization with resultant hyperalgesia of the dermatome and sclerotome and spreads from the sensory component of the spinal segment to the anterior horn cells, which control the myotome within the territory of the SSS. The development or amplified activity of MTrPs is one of the clinical manifestations of SSS. The Segmental Desensitization treatment consists of injection of local anesthetic agents in the involved dermatome to block the posterior branch of the dorsal spinal nerve along the involved paraspinal muscles. In addition, local anesthetic injection is applied peripherally near the foci of irritation in local soft tissue, directly into taut bands and trigger points, using a needling and infiltration technique. Stretching exercises, local heat application and additional transcutaneous electrical nerve stimulation (TENS) treatment complete the muscular relaxation after the injections. E...

Sensibilización espinal segmentaria: un síndrome doloroso neuromusculoesquelético desconcertante

“…La persistencia de una noxa que pueda causar o que ya esté ocasionando un daño tisular produce un bombardeo persistente de impulsos nociceptivos que viajan de los nervios periféricos hacia el asta posterior de la médula espinal y los centros supraespinales. Este bombardeo ejerce sobre el sistema nervioso central un efecto de amplificación de las señales nociceptivas que se conoce como sensibilización 28,29 , la cual se manifiesta con una reducción del umbral de los receptores sensitivos y un incremento de la magnitud de la respuesta a los estímulos, pudiendo llegar a desarrollar actividad espontánea 26 .…”

“…Esto, a su vez, conducirá al dolor radicular por alteración del transporte de nutrientes en el tejido neural (al afectar la microcirculación del fluido espinal y sanguínea) y a una respuesta inflamatoria [45][46][47] ocasionada por la compresión, lo cual conllevará a la hipersensibilidad sensitiva y motora. Por lo tanto, en el dermatoma no solo se presentará hiperalgesia y alodinia, sino que además los músculos periféricos pueden sensibilizarse a la acetilcolina circulante, dando lugar a bandas tensas y puntos gatillo miofasciales en el miotoma 19,29,48 que a su vez afectan al esclerotoma correspondiente.…”

Intramuscular Electrical Stimulation Combined with Therapeutic Exercises in Patients with Shoulder Adhesive Capsulitis: A Randomised Controlled Trial

“…According to previous study, increased MTrPs activity in the shoulder region might stimulate the sensitivity of MTrPs in the remote muscles; lead to development of widespread pain in patients diagnosed with myofascial pain syndrome (MPS) of shoulder [ 12 ]. Although the features of altered pain sensitivity within the MTrPs area confirm the peripheral source of nociception, the presence of widespread pain indicates the central sensitization of MTrP [ 13 14 ]. Overall, the optimal management for the deactivation of MTrP might reverse the sensitization process of pain, thereby attenuate the central and peripheral sensitization in musculoskeletal conditions [ 15 ].…”

Update of Extracorporeal Shockwave Therapy in Myofascial Pain Syndrome

“…1 There are emerging findings suggest that myofascial pain is a complex form of neuromuscular dysfunction consisting of motor and sensory abnormalities involving both the peripheral and central nervous systems. [2][3][4][5][6][7][8] Sensitization in corresponding spinal segments plays a major role in the formation of continuous pain in a given part of the body. The term called by Professor Andrew A. Fischer for this phenomenon is "spinal segmental sensitization" (SSS).…”

“…Sclerotomal sensitization revealed as bursitis, enthesitis, epicondylitis and tendonitis occur in the affected distribution innervated by the spinal segment that is upregulate. [2][3][4][5][6][7][8] MPS is a great imitator. Neck or back pain of myofascial origin may mimic radiculopathy with pain radiating down upper or lower limb.…”