Introduction

Otitis media is a very common condition in the pediatric population. This diagnosis can include effusion, depending on the patient. Otitis media is a primary problem of the Eustachian tube. Control of the Eustachian tube’s dilation is by the tensor veli palatini (TVP) and the levator veli palatini (LVP).[1] Both of these are muscles reside in the head, specifically near the palatal region, and they both technically originate from the Eustachian tube itself. In particular, the TVP has been targeted more as being the muscle with the most influence on the Eustachian tube’s ventilation and function. Many studies do not agree on the importance of the LVP, and some even argue that it is not relevant to the Eustachian tube’s function, other than the LVP's anatomical derivation. Some reports note the TVP’s significance in connecting the soft and hard palates via the palatal aponeurosis, but this functionality is not why the TVP is classically notable. Because of this structuring of the TVP, when the muscle constricts, it acts to aid in swallowing.[2]

Structure and Function

The tensor veli palatini originates from the inferior surface of the cartilage of the Eustachian tube, the scaphoid fossa, and the sphenoid bone’s spine. The muscle then wraps around the pterygoid hamulus, becoming tendinous, becoming a fan-like aponeurosis attaching to the palatine aponeurosis and horizontal aspect of the palatine bone.[3][4][5] Hypomochlia that control the force vectors dictates the muscle's functions. The hypomochlia include the following: pterygoid hamulus, lateral Ostmann fat pad, and the medial pterygoid muscle. The muscle has two layers. The lateral layer increases drainage and protection when contracted, while the medial layer increases ventilation.[6][4] The TVP’s ventilation ability of the Eustachian tube involves equilibrating air pressure to atmospheric pressure.[7] The portion of the TVP responsible for the ventilation is called dilator tubae because of its ability to dilate and open the Eustachian tube.[4]

The tensor veli palatini is also a component of the soft palate at its midline.[3] Some studies argue that an additional function is velar movement; if the TVP contracts, this increases the swallowing mechanism and decreases airway resistance.[4] Others think that the TVP should be considered a muscle of mastication because, like the masticators, they all have the same embryological origin.[5] These other functions are integral to the head and neck region, but only limited studies discuss the TVP’s additional functionality.

Embryology

The tensor veli palatini begins to develop as early as 6 weeks into gestation. It originates from the first pharyngeal arch’s mesenchyme, specifically from the medial blastema.[5][8] Because the TVP is near the pharyngotympanic tube, it is considered a paratubal or peritubal muscle. The tensor tympani is a muscle that is also considered a paratubal/peritubal muscle because of its proximity to the pharyngotympanic tube. Like the TVP, the tensor tympani also is developed at the same time in gestation.[8]

Blood Supply and Lymphatics

The tensor veli palatini receives its blood supply from the maxillary artery, a branch of the external carotid artery, just below the mastoid bone. The lesser palatine branch of the maxillary artery enters through the maxillary tubercle and emerges through a foramen in the lesser palatine.  In some patients, the lesser palatine branch anastomoses with the greater palatine branch.[9]

Nerves

This muscle's innervation is by the motor part of the mandibular nerve. The mandibular nerve is CNV3 of the trigeminal nerve.[6][5] This nerve also supplies the medial pterygoid.[10] The medial pterygoid and the TVP can work together to open the Eustachian tube and play a role in mastication. The TVP's innervation allows for an understanding of the vast functionality of the muscle.

Muscles

The muscle is at the base of the skull, in the shape of an inverse triangle. The motion of the muscle is activated when a patient swallows or yawns.[6] This motion opens the Eustachian tube because normally, this tube remains closed.[1] The TVP has a close association with the tensor tympani. Recent studies have shown that in some patients, both the TVP and the tensor tympani are connected forming a complex, or a digastric muscle.[8] In these patients, the tensor tympani has similar functions as the TVP. 

Physiologic Variants

There is controversy over the tensor veli palatini’s association to the hamulus. Some studies have shown bursa involvement, others have shown attachments, and some even argue that there may be ethnic properties involved. When considering cleft palate patients, the fanned aponeurosis only reaches the hard palate and fails to hit the soft palate.[4] Research has shown some lateral bundles of the TVP to be continuous with the buccinator muscle. Some medial bundles of the TVP were responsible for creating the palatine aponeurosis.[11] These variants don’t typically alter the function of the TVP.

Surgical Considerations

Some surgeons, when performing palatoplasties, actually cut the tendinous portion of the tensor veli palatini. Palatoplasties are done to surgically correct cleft palates. Interestingly enough, in this patient population, the TVP is anatomically altered.[4]

Clinical Significance

Middle ear disease, like otitis media, have various probable mechanisms; one mechanism, in particular, involves the tensor veli palatini. Because the TVP is effective in opening the nasopharyngeal orifice, it can cause Eustachian tube dysfunction via obstruction if the muscle loses its function.[12] Other forms of obstruction are inflammation, invasion, and paralysis.[10] Because the TVP is called dilator tubae in specific anatomical regions, this emphasizes its significant role in the Eustachian tube's function.

Because of TVP’s minor role in the palatal function, the TVP is theorized to be dysfunctional in a patient with cleft palates. A recent study found that in these patients with cleft palates, the TVP is positioned more medially, as well as have a decrease in the volume of the muscle and the length.[2] This positioning may be important in the future to aid in diagnosing more mild cleft palate deformities.

Other Issues

Of other clinical importance is the ability to use electromyography on the tensor veli palatini muscle. There would be a decrease in activity in the TVP’s electromyography results if the ear were subject to a current bout of otitis media.[7] This technique can theoretically be used in the future to dictate if a child has an otitis media diagnosis and may help quantify the number of occurrences to discuss myringotomies with parents.