THE MYOFASCIAL COMPONENT OF FACIAL PAIN

by Andrew J Gallagher BAppSci(Physio) MAPAMSCM,
Director, Victorian School of Massage, Victoria, Australia

bstract: The presentation of head and neck pain is a complex area of clinical practice. It can involve symptoms arising from a great number of sites relating to conditions of the musculoskeletal, dental and upper respiratory systems.

The term craniomandibular dysfunction (CMD) is being used to describe the complex condition involving abnormal jaw mechanics, associated with facial pain incorporating dysfunction of the masticatory muscles and the temporomandibular joint(9).

As the pain of this disturbance is orofacial, it is more often seen more by dentists than massage practitioners or physiotherapists. However, evaluation of the voluminous literature on the subject reveals a strong myofascial component to the syndrome, involving not only the masticatory muscles, but also those of the cervical region as well. The purpose of this article is to examine the role muscles of the cervical and orofacial regions have in this syndrome, the pain patterns of their associated trigger points, as well as to look briefly at the interrelationship between the two muscle groups and how changes in head posture may affect this relationship.

Introduction

Head, neck and face pain are commonly encountered in the daily practice of therapeutic massage, physiotherapy and indeed medical practice. Muscles as a primary source of pain have long been recognised by massage therapists and sections of the physiotherapy and medical professions. Some of the leading workers in the field of musculoskeletal medicine, such as Vladamir Janda, Janet Travell and David Simon, have constantly brought to our attention through their clinical research the role of muscles and their associated soft tissue investments (fascia) in the aetiology of many clinical syndromes(3).

These syndromes are often poorly managed and sometimes totally misdiagnosed because of the failure of clinicians to recognise and appreciate the significance of muscular dysfunction in the presentation of their patient's signs and symptoms.

Muscles are sensitive structures with a capability to act both as a source of afferent as well as being the target of afferent impulses.

Muscles respond to stimuli, they move, support and protect. In co-ordination with the nervous system, they provide smooth regulated movements which, through sensory feedback to higher centres, is constantly monitored to allow for continual adjustment.

In this article, I would like to review the function of the cervical and masticatory muscles and their development of head and facial pain. Further, once establishing this role, I will review the aetiology of craniomandibular dysfunction, examining the role muscles have in the development and perpetuation of the clinical signs and symptoms of CMD.

Cervical muscles - a review

The cervical musculature is a well known source of head and neck pain and in particular trigger point activity of these muscles quite often presents as head and facial pain, sometimes in association, but not always, with symptoms of the cervical region itself. In particular, trigger points of this region have been well documented(6), as a source of referred pain to the head and face.

Clinically this is often described as tension headache, post whiplash syndrome or sometimes even incorrectly attributed to psychogenic causes.

The muscles of the cervical region that refer pain to the head and face region include:

Upper trapezius

This muscle refers pain in an arc up the side of the neck across the occipital temporal and frontal regions to settle behind the eye. There may also be some referral over the angle of the jaw. The upper fibres can develop trigger points in response to trauma (whiplash), poor posture, as well as over activity due to compensation in shoulder pathology, particularly where the normal synergistic function of the rotator cuff and deltoid are interfered with, resulting in chronic shortening of the upper fibres.

The muscle is also prone to the effects of stress and tension and is often the cause of common tension headaches(5). Trigger points in this muscle may not greatly limit cervical movement, however, palpation of the upper fibres in a routine cervical examination will readily identify tension, with the referred pain of an active trigger point readily provoked by stretch or firm palpation.

Sternocleidomastoid muscle

This particular muscle has been dubbed by Travell & Simon in their book Myofascial Pain and Dysfunction as amazingly complex. This seems an apt description when one considers the muscle's complex function, referred pain pattern and involvement in non pain symptoms such as postural dizziness and imbalance. It also can be the cause of satellite trigger points developing in the masseter and temporalis muscles, which obviously can result in Impairment of craniomandibular function; this fact in itself illustrating the effect that cervical musculature dysfunction can have on the genesis of the controversial craniomandibular dysfunction or TMJ syndrome.

The muscle acts to flex the head, while unilaterally it laterally deviates to the same side whilst rotating to the opposite. It also acts to check hyperextension of the neck as well as resisting forced unprotected movement of the head, as seen in whiplash. The muscle also works with the trapezius to stabilise the head, allowing the mandible to move during talking and mastication.

The muscle functions as an accessory respiratory muscle, hence its tight, overdeveloped appearance often noted in the asthmatic or patient suffering emphysema.

The muscle refers two distinct pain patterns from active trigger points depending on which head of the muscle is involved.

The more superficial sternal head gives rise to occipital and vertex pain, as well as supraorbital, temporal and maxillary pain. The deeper clavicular fibres give rise to ear and frontal pain (the frontal pain can be bilateral) as well as retroauricular pain.

Autonomic concomitants of trigger point activity in this particular muscle can include tear discharge and reddening of the conjuctiva, disturbance of vestibular function and space perception as well as postural dizziness. These are similar symptoms resulting from experiments cited by Baldry(2), that involved anaesthetising the first to third cervical nerve roots in monkeys. It is not surprising to learn that the sensory supply of this muscle is the C2 C3 nerves.

The altered sensory information arising from the muscle with trigger points is part of the vital proprioceptive information being relayed to higher centres; thus it is not surprising that functions: such as that of the vestibular apparatus which rely on this information are subsequently disturbed. Active trigger points in the clavicular division have been observed to affect hearing with an immediate improvement once the trigger point has been deactivated.

Patients have also described tinnitus, but this is usually associated with satellite trigger points in the deep head of the masseter muscle rather than the sternocleidomastoid itself.

Splenii muscles

The splenius capitis muscle which arises from the spinous processes of the lower cervical and upper thoracic spine when containing active trigger points can give rise to vertex pain, whilst the splenius cervicis muscle arising from the spinous processes of T3 to T6 and inserting into the upper three cervical transverse processes, refers pain to the temporal area and behind the eye. These muscles are usually involved in cervical syndromes associated with poor posture, injury or work involving awkward neck positions. They are often seen with levator scapulae dysfunction and contribute to the stiff neck syndrome as they can limit rotation movements of the head.
As well as referring pain to the head and face muscles, they can also contribute by trigger point activity and tightness to the increased head forward position which can influence mandibular positioning and accordingly masticatory dysfunction.

Posterior cervical muscles (Semispinales Capitis, Semispinales cervicis)

The semispinales muscles refer pain to the head, the cervicis causing occipital pain, often seen as part of the tension headache syndrome alongside trapezius. The cervicus is often part of the tension headache syndrome, giving rise to a band of pain that when bilaterally involved causes a tight hatband sensation around the head. The focus of pain is often felt over the anterior aspect of the temporal fossa.

This muscle can also cause entrapment of the greater occipital nerve leading to occipital neuralgia due to taut band formation within the muscle. Symptoms of this can include pain. numbness, tingling and burning over the scalp and occipital region. A recent study by Akemi Takawo(1) examining the significance of radiological changes in the cervical spine and prevalence of occipital neuralgia, concluded that on the basis of comparison of the cervical radiographs of symptomatic and non symptomatic patients, there was no real evidence to indicate that compression nerve roots at the neural foramen was a significant cause of occipital neuralgia. In fact. they suggested (although not specifically investigating it) that more attention needs to be paid to the role of muscles, fascia and other soft tissues in the patho genesis of occipital neuralgia.

The clinical finding of occipital neuralgia associated with semispinales trigger points, would clearly support this contention.

Suboccipital muscles

These muscles which include the rectus capitis posterior major and minor, as well as superior capitis oblique, and inferior capitis oblique, are deep muscles which lie deep to the posterior cervical muscles, directly inferior to the occiput. These muscles control the movements of the upper two cervical joints: the alanto-occipital joint at which flexion/extension and lateral tilting of the head occurs and the alanto axial-joint which provides head rotation.

These muscles produce pain patterns similar to that of the semispinales muscle and according to Janda are prone to tightness as part of the cross layered syndrome associated with chronic postural dysfunction which may have its origin in pelvic asymmetries short leg syndrome, or a tight psoas muscle.

Haygure et al (1992, see section on head posture in this article) have clearly demonstrated the relationship between head posture and masticatory muscle balance.

Their research has also shown the adverse effect of head forward posture, which involves upper cervical extension, (which can be caused by trigger points in, or tightness of the sub-occipital musculature) on the position of the mandible leading to masticatory muscle imbalance. which is one of the main features of the craniomandibular Syndrome.

Hence, although the cervical muscles warrant inclusion in this discussion on the basis of their pain referral patterns, they more importantly are a potential source of orofacial pain because of their postural role which influences the position of the TMJ and subsequent masticatory muscle function.

Muscles of mastication

The Masseter muscle has a deep and superficial component The fibres arise from the zygomatic arch and maxilla, attaching to the outer surface of the ramus and angle of the mandible. The superficial fibres elevate, while the deep fibres retrude the mandible. Patients complain of pain referred to the maxilla, upper and lower dentures, TMJ joint, ear and mandibular regions.

The muscles act to close the jaw clenching into centric occlusion. The deeper fibres help to retrude the mandible.

The masseter and temporalis muscles function together, with the temporalis more involved in mandibular balance and posture(8).

The patient complains of pain which is similar in nature to that which arises from the temporomandibular joint. Opening of the mouth is restricted; this restriction is more likely to be caused by trigger points in the superficial rather than the deep fibres of the masseter muscle.

Travel & Simon in Volume 1 of the Trigger Point Manual cite causes of unilateral tinnitus which they put down to referred motor activity of the Stapedius muscle of the tympanic membrane. Spasm of this muscle they say could cause oscillation of the middle ear ossicles.

This symptom has also been observed by the same authors in cases of intracapsular TMJ disease, probably explained by the facial connection of the TMJ to the middle ear.

In cases of bilateral tinnitus, other causes would need to be excluded.

Overstress of this muscle can be brought about by various activities - bruxism or forcible contraction of the muscle (cracking nuts or ice - Travell & Simon) or by occlusal disharmony. This muscle is also one to respond to increased states of emotional or psychological stress, resulting in long periods of contraction and development of the pain-tension-ischaemia cycle.

An increase in contractile activity at rest, as seen in occlusal disharmony is likely to be a significant cause of trigger point activity. (see Travell & Simon p.224-225 for details)

Other causes include overstretching of the muscle as in a prolonged dental procedure, direct trauma or satellite trigger points caused by sternocleidomastoid trigger point activity(8).

Temporalis

The temporalis muscle is a fan-shaped muscle arising from the temporal bone and fascia of the temporal fossa and inserting into the condylar process of the mandible. The muscle acts to close the jaw, retrude the mandible and unilaterally it deviates the mandible to the same side.

Trigger points in the muscle can refer pain to the temporal region and upper denture. The patient can complain of hypersensitivity of the upper teeth, with headache (temporal) but rarely is mandibular function affected. However, the patient may be aware of premature tooth contact.

Patients primarily complain of pain and are aware of restricted mouth opening (this is usually more restricted if the masseter muscle is involved).

Activation of trigger points can come about through bruxism, occlusal imbalance or due to direct trauma. (One patient I treated developed temporal trigger point as the result of being hit in the temporal region by a following ski lift.) Travell and Simon also cite auto accidents or forced mandibular compression due to constant cervical tractions as being among other traumatic causes of trigger point activity in the muscle (folate deficiency can also cause restlessness of the masticatory muscles).

Excessive gum chewing and mouth breathing have also been cited by Travell & Simon as causing trigger points in the muscle. Referred pain from the trapezius muscle may also result in satellite trigger points in temporalis.

Lateral pterygoid

This muscle lies deep to and behind the coronoid process and zygomatic arch. It has a superior and inferior division. The upper branch attaches in front of the sphenoid bone and behind the capsule of the TMJ.

The lower head arises from the lateral pterygoid plate and inserts behind to the neck of the mandible.

Pain from trigger points in this muscle is felt over the cheek and TMJ joint.

The muscle opens and protrudes the jaw bilaterally and laterally deviates it unilaterally (to the opposite side).

The superior division exerts traction on the disc at the level of condylar head on jaw closure.

Overactivity or trigger point shortening of the superior division fibres therefore displaces the disc forward and impedes its return to its normal, position on the closure of the jaws.

The inferior division pulls the condylar head forward and down so that condyle can translate over the posterior surface of the eminence - a movement essential for full opening.

Myofascial trigger points in this muscle can cause or be the result of premature teeth contact.

Those patients diagnosed as suffering myofascial pain dysfunction display symptoms similar to those described by Travell & Simon (p263) as being due to active trigger points in the lateral pterygoid muscle (pain in the TMJ muscular tenderness and malocclusion).

Because the pain referred from this muscle and other masticatory muscles includes the TMJ and teeth, it is not surprising that much treatment has been 'misdirected to the joint and teeth with frustrating results' Travell & Simon p263).

Medial pterygoid

This muscle arises from the angle of the jaw (inside surface and above to the lateral pterygoid plate).

It acts to elevate the mandible and laterally deviate it to the opposite side. Pain from active trigger points is felt inside the mouth (tongue, pharynx and hard palate) as well as over the TMJ, mandible and in the region of the lateral pterygoid muscle.

Ear stuffiness may also be present. The muscle works with masseter and temporalis to close the jaw. Bilaterally it assists the lateral pterygoid in protrusion, whilst unilaterally it assists in deviation to the opposite side, alongside the lateral pterygoid.

Patients describe pain from opening the mouth, chewing or clenching the teeth. Pain is also often experienced on swallowing.

Trigger points can develop secondary to lateral pterygoid dysfunction or occlusal disharmony in response to trigger points in the contralateral muscle.

Digastric muscle

Arises from the symphysis of the mandible with the posterior belly inserting to the mastoid notch.

The posterior belly refers pain to the upper part of the sternocleidomastoid muscle, the throat and under the chin.

The anterior belly (less commonly) refers pain to the four lower incisor teeth and the alveolar ridge between them,

With a fixed hyoid bone, this muscle assists in depressing, that is, opening the mouth. Bilaterally the digastric muscles act to retrude the mandible.

With the mandible bred, the muscle lifts the hyoid bone.

Although not as important as the lateral pterygoid in mouth opening, its action is necessary to fully open the mouth. EMG studies would indicate that the muscle is strongly recruited in coughing and swallowing actions.

Apart from pain, the patient will describe difficulty swallowing. The sternocleidomastoid muscle (upper portions) is tender to touch as a result of trigger point activity in the digastric, but palpation reveals the absence of but bands In the sternocleidomastoid itself.

This muscle usually develops trigger points in association with other muscles of mastication as part of the craniomandibular syndrome.

Head posture

The preceding review of the myogenic causes of head pain clearly illustrates the potential of the cervical masticatory muscles to cause the pain associated with CMD.

Further to this. the interrelationship between these two groups of muscles is also of considerable importance when trying to fully understand the symptoms of CMD.

A recent study demonstrates the postural changes of the craniovertebral region alongside morphological changes of cervical region, were significantly different between their study group (patients suffering symptoms of craniomandibular dysfunction) and the healthy control group, whilst morphological changes of the dentition (over bite or incisor inclination) were not significantly different between the two groups.

Further. straightening (improved posture) of the cervical spine was observed after stomatagnathic treatment was carried out. Logically, this 'straightening' is associated with relief of symptoms related to muscular imbalance in the stomatagnathic system These postural changes were maintained at a six month follow up.

In addition, the authors also suggest that the reverse relationship can also exist, that is head posture can influence stomatagnathic function. To support this, they quote the sliding cranium theory(7).

The theory can explain how head posture may perpetuate, if not initiate, craniomandibular dysfunction. The theory proposes that as the cranium bends backwards, the occiput is translated anteriorly causing a simultaneous shift of the whole maxillary dentition in relation to the mandible whish must be forced anteriorly to obtain occlusal support. This will probably affect the muscular balance in its sup porting mechanism, particularly the lateral pterygoid muscle.

As Huggare et al pointed out in their study, head forward position (hyperextension of the upper cervical spine) is often seen in patients who present with orofacial pain. In this author's experience, correcting this upper cervical hyperextension can often give relief of pain, which on initial examination appears to be coming from the masticatory muscles alone. Further ignoring this postural fault and treating the masticatory muscles alone in my experience leads to recurrence of masticatory muscle pain, even when initial treatment appears to have successfully normalised the muscle length, and, as a result, function.

Craniomandibular syndrome

The dental profession has long recognised the muscular component of craniomandibular pain syndromes. Often described as TMJ pain dysfunction syndrome, there has been a steadily growing volume of literature since the dentist Colsen first described the syndrome in 1934, as involving painful hypomobility of the TMJ with associated spasm And tenderness of the masticatory muscles. He also described many associated symptoms including headache, deafness, tinnitus, a sensation of fullness of the ear, vertigo and throat pain.

There are three major views on the aetiology of craniomandibular syndrome, an extensive discussion of these appears in Travell & Simon Vol 1, l71-173, and in practice all three views to an extent overlap and certain patients' presentation may lend greater support to one view or another.

However, it is not surprising that many authors feel that components of each theory co-exist and contribute to the development of the syndrome.

The three theories proposed are:

Muscular

This theory strongly argued by Travell & Simon looks at the problem from the perspective of muscle imbalance, focusing naturally enough on the masticatory musculature, Examination of pain patterns from active trigger points (see previous section on masticatory muscles) certainly supports this theory, as these correspond with the symptoms experienced by patients. In addition, some of the more bizarre symptoms of CMD such as tinnitus, dizziness, hearing impairment, can also be explained on the basis of impaired muscle function, in particular trigger points and muscle shortening.

It is important to appreciate that muscle changes do not necessarily involve increased EMG activity and should not be referred to as spasm.

The results of tight muscles lead to altered TMJ mechanics, including hypomobility, and as elsewhere in the body, can also lead to increased wear on joints and eventual degenerative changes.

Malocclusion can result from tightened muscles, as the normal synergist agonist relationships are disturbed, leading to a loss of smooth co-ordinated movement.

A specific example of the effect of muscle activity of TMJ function can be seen in the lateral pterygoid which, because of its attachment to the disc of the TMJ joint when tight, can displace the disc forward, thus impeding its return to a normal position on closure of the jaw.

Psychological theory

This theory proposes that most of the symptoms are due to stress, tension or emotional upset, leading to increased muscular activity as seen in bruxism, especially at night. Nocturnal bruxism has long been regarded as a symptom of stress.

Even the Bible, when referring to extreme states of distress, refers to 'a great wailing and gnashing of teeth.' Psychological tests on patients have often revealed stress related behaviour, anxiety and poor coping skills in these patients.

It is thought that eventually bruxism and clenching lead to changes in the dentition and muscles, when then lead to TMJ disorders, muscular imbalance and eventual malocclusion.

Malocclusion theory

This theory is supported by the fact that when treated by use of splints to prevent premature contact, patients receive considerable relief of symptoms. Permanent relief can then be obtained by revising the occlusion. Even within this school of thought, there are some divisions of opinions, with some authors believing the occlusal disharmony causes the muscular dysfunction, while others are more concerned about TMJ mechanics being the end result.

The cause of premature contact can be due to trigger points in the masticatory muscles and in fact Schartz, cited in Travell & Simon, recommends relief of all muscular tightness before splinting.

It has been argued that after an initiating activity such as prolonged dental work, stress or trauma, the malocclusion that results could perpetuate trigger point activity, which is responsible for most of the pain experienced by the patient. Further, the disturbed muscle function and proprioception caused by, trigger points has been shown to cause malocclusion and alter TMJ biomechanics.

As stated at the outset, this is a complex and much written about subject. However, in all three theories presented, muscular dysfunction plays a role, with interplay between psychological and dental factors, leading to the entity described in the literature as craniomandibular syndrome.

Whether muscular dysfunction causes, perpetuates or is a result of malocclusion depends on which authors one reads.

However, all agree that somewhere along the line they become involved. The relationship between malocclusion and muscular dysfunction could well be the ultimate chicken or the egg situation.

Conclusion

Regardless of which theory one subscribes to in relation to the origin of craniomandibular dysfunction, muscles are of considerable importance when looking at clinical symptoms.

Many of the described features of the syndrome can be explained on the basis of muscular dysfunction of the masticatory muscles alone.

Further not only are the muscles of the cervical region capable of referring pain to the head and face but also because of their role in controlling head posture they can directly influence mandibular positioning leading to bio-mechanical changes which place more stress on the muscles of mastication contributing to the symptoms of CMD.

It is therefore critical that both cervical and masticatory muscles are examined for shortening and TP activity.

Failure to do so may well result in perpetuating factors continuing to maintain established CMD even if these factors were not responsible for the condition in the first place.

References

1 Akemi Takawo, Shinicki Migao, Jun Feramato "Clinical analysis of occipital neuralgia'. Abstract from the proceedings of the 5th International Headache Conference 1991.

2 Baldrv, PE, (1989) 'Acupuncture, trigger point and musculoskeletal pain', Churchill Livingstone, London.

3 Gallagher, A (1989) Course notes: Introduction to trigger Point Therapy. Victorian School of Massage, Melbourne.

4 Huggare, A 'Head Posture and Cervicovertibral and Craniofacial Morphology in Patients with Craniomandibular dysfunction', The Journal of Craniomandibular Practice Volio No. 3.

5 Janda, AV (1988) 'Muscles and cerviogenic pain syndromes'. In Grant R (ed) Physical Therapy of the Cervical and Thoracic Spine 1988, New York, Church Livingstone ch9.

6 Lewis, J. 'Muscle imbalance its effect of posture and function a review of the Janda Approach', Australian Massage Therapy Journal Vol 5, No. 1.

7 Makotskv (1989) 'The effect of head posture on muscle contact position: The sliding cranium theory'. Journal of Crandiomandibular Practice 7: 286-292.

8 Travell S, Simon D, (1983) 'Myofascial Pain and Dysfunction: the trigger point manual', Williams and Wilkins Baltimore.

9 Uppgaard, R 'Conservative and successful treatment of temporomandibular dysfunction in a private rural practice'.