Distribution of substance P and calcitonin gene-related peptide-like immunoreactive nerve fibers in the rat temporomandibular joint

The density and distribution of substance P-like immunoreactive (SP-LI) and calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibers in rat temporomandibular joint (TMJ) were investigated in whole-mount preparations and frozen sections by immunohistochemistry with the avidin-biotin-peroxidase complex method. Both types of immunoreactive nerves were observed primarily in the joint capsule, the peripheral articular disc, the synovial membrane, and the periosteum. The distribution of CGRP-LI nerves was similar to that of SP-LI nerves. The anterior portion of the joint capsule and disc was most densely innervated, followed by the posterior, lateral, and medial portions. In addition, CGRP-LI nerves were more numerous and more dense in immuno-intensity than SP-LI nerves. In the synovial membrane, many SP- and CGRP-LI nerves terminated in the subsynovial layer, but some branches extended into the superficial synovial lining layer close to the joint cavity. Immunolabeled nerves were prominently located in the disc attachment and peripheral portion of the disc, and occasional nerves were located in the dense collagenous disc band as an actual disc. However, no fibers were detected in the central disc band. Thus, most of the disc was not innervated by any nerves. The present study provides a morphological basis for the possible roles of neuropeptides in endocytosis by synoviocytes, regulation of blood flow in the synovial membrane, nociception mechanisms of the TMJ, and modulation of the inflammatory response in the TMJ.

Thalamic- and cerebellar-projecting interpolaris neuron responses to afferent inputs

Thalamic- and cerebellar-projecting interpolaris neuron responses to afferent inputs from the temporomandibular joint (TMJ) and/or the masseter muscle (Mm) were examined in rats. Of 230 neurons tested, 24 could be antidromically stimulated from the contralateral ventral posteromedial thalamic nucleus (VPM), and 27 of 91 neurons tested were stimulated from the ipsilateral posteromedial part of crus II of the cerebellar cortex. None had dual projections. The thalamic-projecting neurons were recorded in the dorsomedial region of the interpolaris; most cerebellar-projecting neurons were at the medial border of the interpolaris. Ten of 24 thalamic- and 17 of 27 cerebellar-projecting neurons received nociceptive information. Afferent inputs from the TMJ and the Mm converged on 6 of 24 thalamic-projecting neurons and on 16 of 27 cerebellar-projecting neurons. In both the thalamic- and cerebellar-projecting neurons, there was no difference between the non-nociceptive and nociceptive neurons in mean antidromic latency. The results suggest that the interpolaris integrates and relays afferent inputs from deep oral structures.

Responses of trigeminal subnucleus interpolaris neurons to afferent inputs from deep oral structures

Responses of trigeminal subnucleus interpolaris neurons to natural and electrical stimulation of the temporomandibular joint (TMJ) and the masseter muscle (Mm) were studied in the anesthetized rat. Interpolaris neurons could be placed in one of three classes determined by their responses to noxious and innocuous stimuli: Class I, excited by only innocuous stimuli; Class II, excited by only noxious stimuli; Class III, excited by both. In each class, the conduction velocities of the primary afferents were roughly equivalent to those of small-diameter fibers. Approximately 70% of the interpolaris neurons tested received nociceptive inputs from the TMJ and/or the Mm. Most of these neurons had extensive convergence of afferent inputs, including the TMJ, the Mm, and/or the facial skin. The results suggest involvement of interpolaris neurons in the characteristics of deep pain, such as its spread and referral.

The structure and function of the temporomandibular joint

Although characterised by having a synovial membrane lining the nonarticulating surfaces within the joint capsule, in some ways the temporomandibular joint (TMJ) is an atypical joint. This paper highlights the differences between the TMJ and other movable joints with a description of the structure, innervation blood supply and musculature. Also included are details of how the TMJ moves--the effectors of movement and the various reflexes controlling movement of the joint.

Temporomandibular joint innervation in rats: a horseradish peroxidase study

In the present study, we have used the horseradish peroxidase (HRP) retrograde transport technique to map the trigeminal primary afferent and motor neurons that innervate the temporomandibular joint (TMJ) and the lateral pterygoid muscle (LPM). One to 3.0 microL of 4% wheatgerm agglutinin conjugated horseradish peroxidase (HRP-WGA) solution was introduced unilaterally into the joint cavity of twelve Sprague-Dawley rats. Injections were made from the above, following trephining of the zygomatic arch with a dental bur. Seventy-two hours after surgery, the animals were sacrificed via perfusion-fixation through the left ventricle. The TMJ, both trigeminal ganglia and brain stem were removed, sectioned serially at 50 microns, and reacted according to the tetramethyl benzidine (TMB) technique of Mesulam. Tissues were then examined at the light microscopic level. The injection site showed that the HRP-WGA filled the upper chamber of the TMJ cavity and extended anteriorly to include the LPM. HRP injected into the joint cavity was transported retrogradely to the ipsilateral trigeminal ganglion, where numerous HRP labeled neurons were found. The greatest number of cells were localized in the dorsolateral posterior portion of the ganglion. In the brain stem, numerous labeled cells representing the motor innervation of the LPM were found in a crescent-shaped array on the ventral side of the trigeminal motor nucleus. No labeled cells were found in the mesencephalic nucleus. The results show substantial trigeminal sensory innervation of the TMJ and LPM with no central projection to the mesencephalic nucleus.

Neural elements in the human temporomandibular articular disc

The purpose of this study was to determine the presence and describe the location of neural elements in the articular disc of the human temporomandibular joint. Six articular discs were obtained from three adult human subjects at autopsy. Four discs were cut into segments of known anterior-posterior orientation. The remaining two were processed intact. All tissues were stained in bulk with gold chloride, and frozen, sectioned on a sliding microtome at 70 to 100 microns, mounted on slides, dehydrated, and coverslipped. Nerve fibers were seen penetrating the discs from the pericapsular connective tissue. Structures resembling Ruffini endings, Pacinian corpuscles, and Golgi tendon organs were identified in the pericapsular connective tissue and within the disc. The population density of neural elements was the greatest at the periphery of the disc and progressively decreased towards the center, which was essentially devoid of them. The concentration of neural elements appeared to be greater at the anterior and posterior margins of the disc, with the greatest concentration being posteriorly. These findings support the theory that afferent nerves may arise from neural elements within the disc.

[Evaluation of the status of the stomatognathic system in patients with idiopathic headaches]

The stomatognathic system was assessed in 114 subjects with various types of idiopathic headaches. Stomatognathic system dysfunctions were recognized most frequently in patients with atypical facial pain and headache, and with mixed headache. Much less frequently these dysfunctions were present in patients with migraine or cluster headaches. The obtained results suggest that stomatognathic system dysfunctions should be considered in the pathogenesis of certain headaches.

A multifocal schwannoma of the masseteric nerve causing hemicrania

A case is reported of schwannoma of the right masseteric nerve, invading the pterygopalatine fossa and the parapharyngeal space through the mandibular notch in a 61-year-old woman. The tumor in this case was composed of four various-sized interconnected nodules, simulating a string of beads. The tumor was the cause of the patient's chronic hemicrania, as confirmed by the relief from and disappearance of head pain after surgical removal of the tumor. The most important aspects of this case are the anatomic site of the schwannoma and its uncommon clinicopathologic manifestations; this tumor originated from the masseteric nerve and is the first case reported to straddle the mandibular notch.

The peripheral distribution of trigeminal nerve fibres in the rat temporomandibular joint studied by an anterograde axonal transport method with wheat germ agglutinin-horseradish peroxidase

Wheat germ agglutinin-horseradish peroxidase was injected into the trigeminal ganglion to trace the peripheral distribution of the nerve fibres in the temporomandibular joint. It was transported anterogradely along trigeminal nerve fibres. Horseradish-peroxidase-labelled nerve fibres were found in the anterior and posterior bands of the articular disc, and terminated as nerve endings near the intermediate zone of the disc. However, the intermediate zone itself did not contain any nerve endings. Other nerve fibres penetrated from the subsynovial layer into the synovial membrane and also terminated as nerve endings close to the articular cavity. Thus, this method is suitable for tracing peripheral nerve fibres and nerve endings originating in the trigeminal ganglion.

The TMJ and the middle ear: structural and functional correlates for aural symptoms associated with temporomandibular joint dysfunction

Several anatomic relationships existing between the ear and the temporomandibular joint have been proposed to account for the presence of aural symptoms that occur in some patients with temporomandibular joint dysfunction. There are a plethora of functional hypotheses for aural symptoms relating to disturbed functions of the eustachian tube (as well as neuromuscular relationships and neurovascular functions integrating with these hypotheses). Investigators explain the presence of aural symptoms relative to the anatomic relationship of the middle ear to the TMJ as hypothetically due in part to the "tiny ligament," the sphenomandibular ligament, or the diskomalleolar ligament. This article reviews hypotheses, explanations, and current research on this controversial issue.

Convergence patterns of afferent information from the temporomandibular joint and masseter muscle in the trigeminal subnucleus caudalis

Convergence patterns of afferent information from the temporomandibular joint (TMJ) and the masseter muscle (Mm) in the trigeminal subnucleus caudalis in response to natural stimulation were examined in anesthetized rats for a better understanding of masticatory pain phenomena. All neurons tested (135) could be placed in one of the following three classes according to their responsiveness to natural stimulation in the TMJ and/or the Mm: Class I neurons, excited by only innocuous stimuli; Class II neurons, excited by only noxious stimuli; Class III neurons, excited by both. Afferent inputs from the TMJ and the Mm converged on 108 (80%) of the 135 neurons. Of these convergent neurons, 79% received nociceptive information from the TMJ and/or the Mm. The results suggest that convergent caudalis neurons that receive nociceptive information from the TMJ and/or the Mm may be important to referred pain associated with dysfunction of the masticatory system.

Origin of sympathetic and sensory innervation of the temporo-mandibular joint. A retrograde axonal tracing study in the rat

The cells of origin of sensory and sympathetic innervation of the temporo-mandibular joint were studied by the intraaxonal transport method. Horseradish peroxidase or lectin-conjugated horseradish peroxidase was injected into the temporo-mandibular joint unilaterally in adult rats. Labelled cells were observed ipsilaterally in the superior cervical and stellate sympathetic ganglia, in the sensory trigeminal ganglion and in the second to fifth dorsal root ganglia; none were found contralaterally. The results are discussed in relation to the hypothesis that a nervous mechanism might be involved in the pathogenesis of joint inflammation.

Sensory innervation of the temporomandibular joint in the mouse

The sensory innervation of the temporomandibular joints (TMJs) of 8 STR/IN mice was investigated by means of light and electron microscopy. Through the cutting of complete semithin sections in series it was possible to investigate the joints thoroughly. Additionally, one joint with its nerve supply was reconstructed three-dimensionally with a computerized three-dimensional programme. The reconstruction was based on one complete semithin section series. The joint's nerve supply originates from the nervus auriculotemporalis and additionally from motor branches of the n. mandibularis: n. massetericus, n. pterygoideus lateralis and the nn. temporales posteriores. The greatest number of nerve fibres and endings is located in the dorsolateral part of the joint capsule. They lie only in the stratum fibrosum and subsynovially. Neither the stratum synoviale nor the discus articularis contain any nerve fibres or endings, whereas the peri-articular loose connective tissue is richly innervated. The only type of nerve ending observed within the joint was the free nerve ending, which is assumed to serve not only as a nociceptor but also as a polymodal mechanoreceptor. Merely within the insertion of the musculus pterygoideus lateralis at the collum mandibulae single stretch receptors of the Ruffini type were observed. Ultrastructurally, they correspond to those described in the cat's knee joint. Neither lamellated nor nerve endings of the Golgi or Pacini type were observed in the joint or in the peri-articular connective tissue. The unexpected paucity of nerve fibres and endings in the TMJ itself of the mouse suggests that the afferent information from the joint is less important for position sense and movement than the afferent information from muscles, tendons and periodontal ligaments.

Fine structure of calcitonin gene-related peptide-immunoreactive nerve fibres in the rat temporomandibular joint

The distribution and fine structure of these nerve fibres was examined by immunoelectron microscopy. CGRP-immunoreactive fibres were seen in the nerve bundles, blood vessels and periosteum around the condyle as well as in the disc. These nerve fibres were unmyelinated and had diameters varying from 200 to 600 nm. They were completely or partially enclosed by Schwann cell cytoplasm and did not form synaptic contact with any cells. CGRP-immunoreactive nerve fibres may be sensory nature and this peptide could be involved in pain transmission and neurogenic inflammation.

[Response properties of single sensory units innervating human temporomandibular joint]

The purpose of this study was to examine the response patterns of single sensory units innervating the human temporomandibular joint to the displacements of the mandibular head. 13 single sensory units were recorded from the auriculotemporal nerves of five adult subjects by the method of microneurography and the response patterns were analyzed. The results obtained were as follows: (1) The response patterns of the same unit to the directions of the mandibular movements were classified as Slowly Adapting Type and Fast Adapting Type according to the characteristics of their adaptation. (2) The threshold value of the Fast Adapting Type was higher than that of the Slowly Adapting Type. (3) Increasing the rate of the mandibular opening movements in the initial stage, the firing frequency of the units increased in the response pattern of the Slowly Adapting Type. It was concluded that the sensation in the directions of the displacements of the mandibular head can be induced by the response patterns of the impulses in the nerve fibers innervating the temporomandibular joint.

Peptidergic innervation of the temporomandibular disk in the rat

The peptidergic innervation of the temporomandibular disk was investigated in the postnatal young rat by using an indirect immunofluorescence method. Calcitonin gene-related peptide-containing nerve fibers were located around the blood vessels and terminated as free nerve endings in the disk. These nerve fibers may be of a sensory nature.

Functional anatomy of the temporomandibular joint

Some of the features of the anatomical structures of the temporomandibular joint are outlined, and a brief account of development and nerve supply is followed by consideration of some of the biomechanical aspects of the muscles of mastication.

Localization and central projections of primary afferent neurons that innervate the temporomandibular joint in cats

Primary afferent neurons that innervate the temporomandibular joint (TMJ) in cats were labeled by injecting a 2-5% solution of wheatgerm agglutinin bound to horseradish peroxidase into the joint capsule and capsular tissues in 14 cats and processing the brain stem and trigeminal ganglia using the tetramethylbenzidine method described by Mesulam (1978). The perikarya of ganglion cells that innervate the TMJ ranged in diameter from 15 to 109 microns and were primarily located in the posterolateral portion of the trigeminal ganglion. The central processes of these neurons entered the brain stem in middle pons and were distributed to all portions of the sensory trigeminal nuclei. However, the majority of labeled fibers and greatest density of terminal labeling were observed in the dorsal part of the main sensory nucleus and the subnucleus oralis of the spinal trigeminal nucleus. Very few labeled fibers were observed in the spinal tract of the trigeminal nerve below the obex. However, evidence for axon terminals was consistently observed in laminae I, II, and III of the medullary dorsal horn. These findings concur with physiological evidence showing that information from the TMJ influences neurons in rostral (Kawamura et al., 1967) and in caudal (Broton et al., 1985) portions of the trigeminal sensory nuclei.

Distribution of substance P-like immunoreactive nerve fibers in temporomandibular joint soft tissues of monkey

The distribution of substance P-immunoreactive and silver impregnated nerve fibers in the temporomandibular joint soft tissues of the Macaca fascicularis monkey was investigated in frozen sections. The pattern of substance P-immunoreactive structures in the soft tissues and periosteum of the temporomandibular joint was compared with the distribution of silver impregnated nerve fibers within these tissues. Presence of substance P-immunoreactive fibers was demonstrated in the temporomandibular joint capsule, disc attachments, fascia, adjacent periosteum and within the interfascicular connective tissue of the lateral pterygoid muscle. The overall distribution corresponded to that of silver impregnated nerve fibers. Substance P-immunoreactive nerve fibers were found in the adventitia of arteries in all vascularized temporomandibular joint soft tissues but could not be found in the adventitia of veins. No substance P-immunoreactive or silver impregnated nerve fibers were seen in the dense collagenous tissue forming the disc. Substance P is suggested to influence the major features of inflammation and to play a role in acute and chronic pain conditions.

A modified auriculotemporal nerve block for regional anesthesia of the temporomandibular joint

A technique for producing regional auriculotemporal nerve analgesia is described. Undesirable side effects have been minimized by avoiding facial nerve branches and blood vessels, and injection at the site of the nerve trunk.