The Myrtiformis Muscle: Identification of a Forgotten Entity That Is Distinct From the Depressor Septi Nasi Muscle

Abstract

Introduction: Nasal musculature anatomy is a topic that plastic surgeons pay attention to. However, the presence and role of the myrtiformis muscle (MM) remain controversial. To elucidate these aspects, an anatomy-based study was conducted.

Materials and methods: Seven midsagittally split and two total cadaver head's nasal bases, embalmed with modified Larssen solution (MLS), were dissected for MM anatomy. The features of this muscle were photographed, and a video of its function was recorded.

Results: It was found that MM originates from the maxillary alveolar process and continues as two heads, one reaching the alar base with spicular fibrotendinous endings and the other extending to depressor septi nasi fibers. Owing to its bi-vectoral muscle fibers, MM is found to constrict the nares by simultaneously forcing the alar base and lowering the columella. It was also found that left-sided muscles were larger than right-sided muscles.

Conclusions: The MM is found to be a constrictor muscle of the nares in this study, contrary to recent observations.

Keywords: anatomy; cadaver; facial muscle; nose; rhinoplasty.

Figure 1. The left half of a cadaver head with a right-inferior oblique view. The green pin was used to retract the OOC and skin laterally.

Observed is the tip of the periosteal elevator (black arrow) that has lifted the body of the MM right after its periosteal insertion. The wire hook strains the fibers of MM (*) that reach the columellar base (C) by joining the DSN muscle. The body of the MM (over the periosteal elevator) continues toward the base of the left nasal ala. P: Hard palate, SAA: Superior alveolar arch, VM: Vestibular mucosa, SM: Nasal mucosa of septum, LL: Lower lip, V: Left nasal vestibulum, OOC: Orbicularis oris complex, MM: Myrtiformis muscle, DSN: Depressor septi nasi

Figure 2. Antero-inferior view of the left nasal base. The blue pin retracts the folded mucosa and OOC. The red, green, and yellow pins are inserted vertically into the LLC base.

Trajectories of the pins show the fibrotendinous endings of the MM. These fibers reach the base of the LLC. On the lower part of the figure, the MM body with a transparent millimetric scale sheet can be seen. Black arrows indicate the insertion line of detached MM. *: fibers to the superficial layer of orbicularis oris-DSN fusion, DSN: Depressor septi nasi, A: Nasal ala, S: Nasal septum, Mi: Median incisor teeth, Li: Lateral incisor teeth, Ca: Canine teeth, OOC: Orbicularis oris complex, MM: Myrtiformis muscle, LLC: Lower lateral cartilage

Figure 3. Superficial plane of the lateral dissections. The LLSAN (*), zygomaticus minor (Z), and transverse part of the nasal (T) muscles can be seen on the same plane under laterally deviated SMAS (S).

SMAS: Superficial musculoaponeurotic system, So: SMAS over the orbicularis oris muscle, F: fibrolamellar tissue of the nasal wing, **: orbital fibers of orbicularis oculi, LLSAN: Levator labii superioris alaeque nasi

Figure 4. Second plane of dissection. The orbicularis oris (O), and LLSAN (L) muscles were detached and deviated laterally. The ILS (i), a part of the OOM, originates medially to the canine teeth juga (C).

It is clearly demonstrated that the branches of the infraorbital nerve and vessels (*) are placed between the superficially placed LLSAN, zygomaticus minor, and OOM and the deeply placed MM. LLSAN: Levator labii superioris alaeque nasi, ILS: Incisivus labii superioris, OOM: Orbicularis oris muscle, MM: Mirtyformis muscle

Figure 5. The deepest plane of dissection. The orbicularis oris (O), LLSAN muscles (L), and branches of infraorbital nerves (*) have deviated laterally. Medial fibers of the MM (M) curve acutely to insert the fibroareolar tissue (F) of the nasal wing (indicated by the long arrow). Lateral fibers are longer and slope medially to insert the fibrous tissue covering the LLC and accessory cartilages (indicated with short arrows). A lateral fibromuscular tissue bundle forms a border-like structure for MM (b).

C: The tip of the juga alveoli of the canine teeth, T: transverse part of nasalis muscle, MM: Myrtiformis muscle, LLSAN: Levator labii superioris alaeque nasi, LLC: Lower lateral cartilage

Figure 6. An anterior view illustration of the location and action of the MM

Left: MM is in the deeper plane than the DSN (*) and OOM. The DSN and OOM are depicted as faded. Right: Two-headed arrows pointing out the vectors of muscle forces. Dotted lines show the new position of LLC and medial crura when the muscles are contracted bilaterally. MM: Myrtiformis muscle, DSN: Depressor septi nasi, OOM: Orbicularis oris muscle, LLC: Lower lateral cartilage, ULC: Upper lateral cartilage, MX: Maxilla Illustration created by author Servet Celik