ABSTRACT: Everyone is aware that when flying at high altitudes, in order to accommodate changes in ear pressure, flight attendants instruct passengers to chew gum or to open their mouth widely.  The two forgotten accessory muscles of mastication, the tensor veli palatini muscle, and the tensor tympani muscle, accommodates the pressure via the eustachian tube to the middle ear.  These two accessory muscles of mastication have been found to also play important roles in treating orofacial pains, including temporomandibular joint pain, facial pain, neck and shoulder pain, as well as the ear symptomology of tinnitus, pressure and pain in the ear, vertigo, and loss or impairment of hearing.  Diagnostic importance to the dental/orofacial pain clinician is the fact that trigeminal pharyngioplasty treatments have shown that a significant portion of patients thought to be suffering from pain of temporomandibular joint, facial, or upper quadrant origins, actually may only be suffering from dysfunction of the two forgotten accessory muscles of mastication, the tensor veli palatini and tensor tympani muscles.
DESCRIPTORS: Tensor Veli Palatini, Tensor Tympani, Trigeminal Pharyngioplasty, Tinnitus, Vertigo, Meniere’s Disease

Embryology

 Embryology of the gestating fetus of a human being’s facial region reveals a branchial arch developing into a mandibular arch; which then develops into the mandible and maxilla.  This double jaw develops from Meckel’s cartilage where the dorsal end of Meckel’s cartilage, with early fibrous connections in conjunction with the pterygoid muscle, gives rise to the ear ossicles, forming the two middle ear bones, the malleus and the incus (1-5).

The blastema of the human embryo which develops into the medial pterygoid muscle also develops into the tensor tympani muscle.  The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle, the tensor tympani muscle, and the tensor veli palatini muscle.  The trigeminal nerve also innervates the other muscles of mastication; the massetter, temporalis and lateral pterygoid muscles, as well as the mylohyoid and anterior digastric muscles.

This suggests early embryologic development of neural patterns established in the brain between the chewing apparatus, pharynx, tympanic cavity, and the eustachian tube; where the mandible and ear bone movements as well as the opening and closing of the eustachian tubes are integrated(6,7).

Anatomy and Function

The tensor tympani muscle originates from the cartilaginous portion of the eustachian tube, on the under surface of the petrous bone, as well as the osseous canal in which the tensor tympani is contained.  It crosses the middle ear by a slender tendon and attaches itself to the manubrium of the malleus.  The tensor tympani muscle tenses the tympanic membrane by drawing the tympanic membrane medially; hence its name, tensor tympani (8).

 The tensor veli palatini muscle originates from the scaphoid fossa of the sphenoid bone and the eustachian tube.  Its eustachian tubal origin is from the superolateral aspect of both the cartilaginous and membranous parts along the entire length of the eustachian tube (8).   There is disagreement in the scientific literature as to whether the tensor veli palatini is a single muscle(10-14) or if this muscle is split into two anatomical and functional parts(15-18).  Descriptions of its tubal origin are also conflicting (19-26).  Simkins felt that the tensor veli palatini muscle functions by closing the eustachian tube when the muscle displaces the eustachian tube’s lateral wall inward (27); while most other researchers presently agree that the tensor veli palatini muscle functions by dilating the eustachian tube; even though these researchers propose different mechanisms of action of this muscle on the eustachian tube (28-34).

Dysfunction of the Tensor Veli Palatini and Tensor Tympani Muscle

After understanding the embryology and anatomy of these two accessory muscles of mastication, it is obvious that dysfunction of these two muscles can effect the middle ear and the eustachian tube’s function, and may cause ear complaints of pain, fullness, tinnitus, vertigo, and hearing impairment or loss.  These complaints are secondary otological manifestations of primary pathological functional changes in the muscular system of the chewing apparatus (35-47).

 Orofacial pain complaints because of dysfunction of these two accessory muscles of mastication include referred pain felt in the temporomandibular joint, in and around the ear, radiation of pain to the temporal region, pain radiation along the ramus of the mandible, pain in the mastoid region, in the cervical region, down the shoulder, and downward along the neck’s sternocliedomastoid muscle (48,49).

Causes of Dysfunction of the Tensor Veli Palatini and Tensor Tympani Muscles

These two accessory muscles of mastication, the tensor veli palatini and the tensor tympani, can develop myofascial trigger points with shortening of the muscle by the same means that any muscle of mastication can develop pain, which would include direct or indirect trauma to the masticatory muscles (50-52).

Dysfunction of the tensor veli palatini and tensor tympani muscles can also be caused by parafunctional activities of bruxism.  Bruxism is defined as the clenching or grinding of the teeth during nonfunctional movements of the mandible, and is regarded as mandibular parafunctional behavior (53-55).  When this occurs during sleep it is termed nocturnal bruxism (56,57).  Most individuals engage in nocturnal bruxism activity at some point in their lives (58) .  The tissues of the masticatory system will generally adapt to this behavior (59).  In some individuals, their capacity for adaptation will be exceeded by the cumulative forces of this mandibular parafunctional behavior, resulting in pain and dysfunction of the masticatory system (60).  The etiology of nocturnal bruxism is a sleep disorder related to the patient’s waking emotional state that is centrally mediated and precipitated by emotional stress (61).  Nocturnal bruxism behavior has been observed to be related to periods of emotional or physical stress (62) as well as to the anticipation of stress (63).  Experimentally produced stress has resulted in increased jaw muscle activity (64,65).  Nocturnal bruxism can generate incredible forces resulting in significant loads to the masticatory musculature and to the TMJ complex.  The average working force that can be delivered to a natural tooth is 175 psi (66).  Nocturnal bruxism activity can increase that force to 300 psi, with reported cases of 100,000 (67) to 175,000 psi (68).  As a result of stress, there can be an initiation or aggravation of bruxism (69-81).  Additionally, many patients are being treated by their psychiatrists for stress, and are being given prescriptions of SSRI type medications.  A side effect of SSRI medications is grinding of the teeth (82).  Therefore, stress can cause or aggravate the tensor veli palatini and tensor tympani muscles to shorten, and form trigger points.

Dysfunction of the tensor palatini and tensor tympani muscles can be due to referred pain from facial, neck, shoulder, pectoralis, soleus, and even metatarsal muscles, causing secondary myofascial pain in these two forgotten accessory muscles of mastication, causing trigger points and shortening of these muscles (83-85).

Dysfunction can also be caused by a Temporomandibular Disorder with hyperactivity of the masticatory muscles, as well as its associated innervation of muscles by the same trigeminal nerve that can cause primary or secondary reflex contraction in the tensor veli palatini and tensor tympani muscles (86-89).

Additionally, any otolaryngological cause of blockage or pressure changes within the eustachian tube, such as sinus and ear infections, could also cause trigger points in the tensor veli palatini and tensor tympani muscles with sudden or prolonged shortening of the muscle fibers.

 History of the Trigeminal Pharyngioplasty Procedure

The trigeminal pharyngioplasty surgical procedure was developed at White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic in 1994.

Patients with facial pain, with or without one or more complaints of pain in and around the ear, pressure in the ear, vertigo, and tinnitus received trigeminal pharyngioplasty treatment with 75% success in complete or partial improvement of their condition.

Tympanograms were taken on each patient immediately before and after the procedure.  The patients’ subjective reporting of success was objectively matched to tympanographic readouts showing normalization of tympanic membrane pressure.

Clinically, patients reported improvement in hearing impairment with objectively documented audiograms taken before and after the trigeminal pharyngioplasty procedure was performed.

Patients with palpable trigger points and taut bands of the facial, neck, and shoulder musculature, with cervical and mandibular restrictions in range of motion, and classical textbook referral patterns of pain from the neck and shoulders musculature to the facial region; subjectively reported and demonstrated objective improvement after the trigeminal pharyngioplasty was performed.

 After years of performing the trigeminal pharyngioplasty; surgical finesse has shown that adhesions of the tensor veli palatini muscle in the Fossa of Rosenmüller are finger-lysed in the procedure.  These adhesions reappear and require repeated lysis, unless adjunctive treatments are performed both by the treating dentist, and the patient follows a rehabilitative regimen.

Adhesions can start forming within one day, if immobilization of muscles is present (90). Since a primary cause of the adhesions and the re-occurence of those adhesions on the tensor veli palatini muscle in the Fossa of Rosenmüller is due to immobility caused by shortening of the muscle fibers; an Anterior Midline Point Stop (AMPS) appliance must be made and used in conjunction with the trigeminal pharyngioplasty procedure.  The AMPS appliance and its therapeutic use has been described by Schames J, et al.(91) .

An AMPS appliance has been used and documented in the scientific literature over the past 30 years by prosthodontic dental specialists for the reduction in muscular activity as well as in the reduction of pain in the muscles of mastication (92-116).

Use of the AMPS appliance helps prevent dysfunction of both the tensor veli palatini and tensor tympani muscles of mastication by direct mobilization of these two muscles, as well as preventing secondary reflex contraction by the associated innervation of the trigeminal nerve of the other masticatory muscles (117-120).

 The patient performing therapeutic motion exercises utilizing the ramp on the AMPS appliance, helps mobilize all the muscles of mastication, including the tensor veli palatini and tensor tympani muscles, and prevents adhesions from reoccurring (121).

Trigger point injections into primary sources of referred pain from the masticatory muscles, as well as from the facial, neck, and shoulder muscles will also help prevent shortening of the tensor veli palatini muscle inducing the formation of adhesions (122).

Trigeminal Pharyngioplasty

Please Note: We advise dentists to receive appropriate hands-on training before performing the trigeminal pharyngioplasty procedure.

A unilateral or bilateral trigeminal pharyngioiplasty can be performed with or without topical application of bupivicane spray.  This depends on the dentist’s or patient’s wish to have the oro-pharynx anesthetized, which may result in difficulty in swallowing.

 Instructions to the patient consists of thorough explanations of the procedure and its possible complications, where the patient is also informed that they will have a gag reflex with the uncomfortable procedure of having a gloved finger in the back of their throat, while the dentist counts slowly from 1 to 3 or 5.  The patient must be instructed not to instinctively bite the dentist’s finger, nor to grab the dentist’s hand.  Post operative discomfort can consist of an irritated throat that can last from one to two days.  Since finger-lysis of adhesions on the tensor veli palatini’s surrounding mucosa is performed, there can be some minimal bleeding.  Patients report drainage in their throat from the eustachian tube area which can last for several weeks.  During the procedure, the patient may hear the lysis of the adhesions, with a “popping” sound occurring, due to the accommodation of the eustachian tube, which allows equilibration of middle ear pressure.

The dentist, using a sterile gloved, shortly manicured, index finger, slides the finger medially past the retromolar pad to the posterior aspect of the soft palate.  This finger is to slip underneath the soft palate, and to slide in a posterior superior lateral direction into the Fossa of Rosenmüller.

To help slip the index finger underneath the soft palate, the patient is advised to say “Aah”, which raises the soft palate.  If the patient has a longer soft palate, the dentist is advised to move his finger towards the uvula and cause the patient to gag.  As the gag reflex occurs, the soft palate is momentarily raised.  The dentist must slip his index finger underneath and behind the soft palate just as the gag reflex occurs.

Please Note: If a pulse is palpated, discontinue the procedure immediately, because of the proximity of the carotid artery which lies beneath the mucosal tissue.  A perceptible pulse may indicate an aneurysm of the carotid artery.

  If no pulse is palpated, the dentist slowly counts from one to three or five, while carefully and gently sliding the index finger from the superior portion of the Fossa of Rosenmüller, in an inferior lateral direction along the torus tubarius at the orifice of the eustachian tube in the oral cavity, finger-lysing any adhesions and massaging the muscle area.  A functional tensor veli palatini muscle causes the torus tubarius to be soft and fleshy, while a dysfunctional tensor veli palatini muscle causes the torus tubarius to be hard and seemingly unpliable.  Repeated trigeminal pharyngioplasty procedures, with use of an AMPS appliance, and therapeutic motion exercises performed by the patient returns the torus tubarius to a soft, fleshy feel, confirming a functional tensor veli palatini muscle.

After trigeminal pharyngioplasty procedures are performed, most patients report improvement in ear pressure; hearing impairments; ear, facial, and temporomandibular joint area pain; as well as neck and shoulder pain.  Restrictions in cervical range of motion improve, as well as documented 5-10 mm increases in maximum interincisal opening of the mouth occur.

Tinnitus symptoms have been noted to decrease immediately or over time.  Please note that some patients may report an increased pitch in their tinnitus complaint, and they should be informed of this prior to the procedure.  We have found that this decreases or resolves over time, however, no guarantees can be made.

If needed, the trigeminal pharyngioplasty can be repeatedly performed after a two week interval, during which time the patient wears their AMPS appliance at night, and performs the therapeutic motion exercises with the AMPS appliance for 10 minutes every hour of the day.

Conclusion

The two forgotten accessory muscles of mastication, the tensor veli palatini and tensor tympani muscles, have been found to play important roles in treating orofacial pains, including temporomandibular joint pain, facial pain, neck and shoulder pain, as well as ear symptomology of tinnitus, pressure and pain in the ear, vertigo, and loss or impairment of hearing.

Otolaryngological symptoms of ear pain, pressure, tinnitus, vertigo, hearing impairment, and hearing loss have always been associated with Temporomandibular Disorders(123-149) .  Ear symptoms have been attributed to trigger point referral patterns in the sternocliedomastoid, cervical paraspinal and/or the upper trapezius muscles(150).  Palpation of masseter, medial pterygoid, and sternodiedomastoid musculature; as well as palpation of the space anterior to the lateral pterygoid muscle; and palpation of the temporomandibular joint itself, has shown to reproduce or intensify patient’s ear complaints (151-154).  Bruxism and ear symptoms, have been associated, and are commonly found among patient’s complaints (155-162).  Most importantly, many studies have shown that improvement in ear symptoms occurs after treatment for Temporomandibular Disorders, where an appliance alone was the predominate treatment that was used by patients (163-171).

 Meniere’s disease’s classical triad of symptoms of tinnitus, vertigo, and fluctuating hearing loss, has also been shown to be associated with tenderness to palpation of the masticatiory cervical, and upper quadrant musculature; as well as tenderness to palpation of the temporomandibular joint (172-173).

The trigeminal pharyngioplasty procedure performed in conjunction with an AMPS appliance, therapeutic motion exercises, as well as trigger point injections to associated masticatory, cervical, and upper quadrant musculature (if injections are required), can help treat dysfunction of the forgotten accessory muscles of mastication, the tensor veli palatini and tensor tympani muscles.  The treatment of these accessory muscles of mastication, the tensor veli palatini and tensor tympani muscles, has shown to improve orofacial, temporomandibular joint, cervical, and shoulder pain complaints; and has also shown to be associated with the relief of ear pain, ear pressure, tinnitus, vertigo, and/or hearing impairment or hearing loss.

Diagnostic importance to the dental/orofacial pain clinician is the fact that trigeminal pharyngioplasty treatments have shown that a significant portion of patients thought to be suffering from pain of temporomandibular joint, facial, or upper quadrant origins, actually may only be suffering from dysfunction of the two forgotten accessory muscles of mastication, the tensor veli palatini and tensor tympani muscles. 

1. Joseph Schames, D.M.D. is the Co-Director of White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic in Los Angeles, California.  He is a Diplomat of the American Academy of Pain Management.

2. Mayer Schames, D.D.S.  is a Clinical Director of White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic in Los Angeles, California.  He is a Diplomat of the American Academy of Pain Management.

3. James P. Boyd, D.D.D. is Director of Research and Senior Clinical Instructor of White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic in Los Angeles, California.

3. Euel L. King, D.D.S. has been the Director of White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic in Los Angeles, California for 30 years.  He is a Diplomat of the American Academy of Pain Management.

4. Seymour Ulansey, M.D. is a Board Certified Anesthesiologist, and the Director of Medicine at White Memorial Medical Center’s Craniofacial Pain/TMJ Clinic.  He is a Fellow of the International College of Surgeons.