Influences on the fusimotor-muscle spindle system from chemosensitive nerve endings in cervical facet joints in the cat: possible implications for whiplash induced disorders

Abstract

The aim of the present study was to establish if there exists reflex connections from ligamentous structures in cervical facet joints and the fusimotor system of dorsal neck muscles. In seven cats, anaesthetized with alpha-chloralose, bradykinin (BK) of concentrations between 12 and 50 microg was injected into the facet joint between C1 and C2. Recordings were made from single muscle spindle afferents (MSA) originating in contralateral trapezius and splenius muscles (TrSp). Fusimotor induced changes in the sensitivity of the muscle spindle afferents were assessed by recording the responses to sinusoidal stretches of the TrSp muscles. The mean rate of discharge and the depth of modulation of a fitted sine were taken as quantitative estimates of the response. A total of 25 MSAs were recorded, and 21 of these showed clear-cut alterations in their responses to the sinusoidal stretches following Bk. injections into contralateral facet joint. The majority of the responding afferents (13/21) showed changes in their responses indicating an increased activity of static fusimotoneurones, although responses of dynamic and mixed static and dynamic nature were also seen. Local anaesthetics applied to the intraarticular receptors abolished the effects. Injection (i.v.) of a general anaesthetic (pentobarbital) abolished the effects. The results show that there exist reflex connections between receptors in cervical facet joints and fusimotoneurones of dorsal neck muscles, and this might be of importance in the pathophysiology behind whiplash associated disorders (WAD).

Peripheral and Spinal Mechanisms of Pain and Dry Needling Mediated Analgesia: A Clinical Resource Guide for Health Care Professionals

“…In particular, facet joint pain has been shown to activate γ motor neurons and thereby increase the sensitivity of muscle spindles [35][36][37]. In addition, numerous studies have demonstrated that spinal manipulation increases the afferent discharge from mechanoreceptors and subsequently quiets α motor neurons, resulting in reduced EMG activity of paraspinal muscles [38].…”

Dizziness, Unsteadiness, Visual Disturbances, and Sensorimotor Control in Traumatic Neck Pain

“…18,82 After traumatic neck injury, disturbances in sensorimotor control, primarily via altered cervical input, may occur due to a combination of factors. Apart from direct trauma, factors associated with the trauma, such as inflammation, 110 functional impairment, 32 morphological changes to musculature, 29 pain, 66 and psychological distress, 79 may alter cervical input or CNS representation. This can influence cervical reflex connections to the visual and vestibular systems and result in subsequent secondary disturbances.…”

Postural Mismatch in Musculoskeletal Disorders

“…lactic acid, arachidonic acid, bradykinin and serotonin) [36,37]. Moreover, bradykinin injection into cervical facet joints [38] as well as the temporomandibular joint [39] was shown to affect the stretch sensitivity of the neck muscle spindles. Evidence suggests that the acuity of proprioceptive information from muscle spindle afferents can be impaired by fatigue, inflammation as well as trauma [35].…”