Depressor Septi Nasi Muscle Resection or Nerve Block

Abstract

In our daily practice, we usually perform the rhinoplasty without considering the dynamic functions.The depressor septi nasi muscle (DSNM) is very important in nose dynamics. Its hyperactivity in some rhinoplasty patients while they smiling or speaking causes a deformity that includes drooping of the nasal tip, elevation and shortening of the upper lip, and increased maxillary gingival show. The dissection of the depressor septi muscle during rhinoplasty can improve the tip-upper lip relationship in appropriately selected patients.

1. Introduction

1.1. Anatomy of depressor septi nasi muscle

The anatomy of the depressor septi nasi has been well studied by Rod Rohrich [1,2]. Is a small, paired muscle located on either side of the nasal septum, has four proximal attachments, footplates of the medial crura, caudal septum, dermocartilaginous ligament and anterior nasal spine, The muscle is divided by the nasal septum into bilateral and symmetric portions. On each of these portions we may observe a division in its fascicles:

• Medial: in medial position, parallel to the nasal septum.

• Intermedial: between medial and lateral.

• Lateral: this one more peripheral to the nasal septum.

They were interdigitated with the orbicularis oris. Like the other muscles of the nose is innervated by branches of the facial nerve and supplied by the facial artery.

Three variation of the depressor septi muscle were delineated (Fig.1-2):

Type I: Inserted fully into the orbicularis oris. 62 %.

Type II: Inserted into the periosteum and incompletely into the orbicularis oris. 22%.

Type III: Showed no or rudimentary depressor septi muscle. 16 %.

Figure 1.

Anatomical variation of the depressor septi muscle.

Figure 2.

Percentages of anatomical variation of the depressor septi muscle.

In some patients (type I and II), animation (particularly smiling) produces a deformity characterized by:

1. A descending nasal tip.

2. A shortened upper lip.

3. An increased maxillary gingival show.

4. A transverse crease in the mid-philtral area.

In 1992 Cachay velazquez described these modifications as rhino-gingivolabial syndrome of the smile (drooping of the nasal tip, elevation and shortening of the upper lip, and increased maxillary gingival show) [3].

It’s important to note that not only produces aesthetic alterations, also produces functional changes, alters the air turbulence.

The aim of treating the muscle with a minimally invasive surgery (permanent) or botulinum toxin (temporary) is decrease the effect of smiling on all four parameters.

Smile test (Wright 1976): Before the operation, during the smile analysis, front and lateral facial photographs of patients in repose and full smile were studied and at follow-up visits (Fig.3) [4,5,6].

Figure 3.

Smile Test, plunging of the nasal tip when smiling.

After the photographs the nasal length (NL) from the radix to the tip, tip projection (TP) from the alar-cheek junction to the tip, upper lip height (UL) and the presence or absence of a transverse upper labial crease (TC) were determined (Fig.4).

Figure 4.

There main parameters used to evaluate the DSNM, NL (nasal length), TP (tip projection) and UL (upper lip height).

2. Surgical treatment of the depressor septi nasi muscle

The main and most important objective of the treatment is to remove the distal tension of the nasal tip, releasing and elevating it (Fig.5).

Figure 5.

After resection of the muscle, the nasal tip is released.

There are two surgical techniques for depressor septi nasi muscle treatment, transnasal and transoral technique. It’s important to note that the two different techniques were not significantly different in decreasing the effects of smiling on nasal length, tip projection, upper lip height, or transverse crease.

Note: Release of this muscle also cause slight ptosis of the upper lip which may not be beneficial in patients with long upper lip.

The authors of this chapter use the transoral technique if the patient have a tethering of the frenulum and use the transnasal technique if you don’t (Fig.6) [7].

Figure 6.

Algorithm for treatment of the DSNM.

• Transoral Technique (Fig.7):

We infiltrate the mucosa, frenulum and the soft tissue with 2% lidocaine with epinephrine 1:50,000, this way we produce analgesia and vasoconstriction, later on with a scalpel blade # 15 make a horizontal upper labial sulcus incision of no more than 10 mm, the depressor septi nasi muscle is released near its origin with the orbicularis oris or periosteum, transposed, and sutured to the contralateral transposed depressor septi nasi muscle (Nylon 4.0). The horizontal incision is closed vertically (vicryl 4.0).

Figure 7.

An artistic illustration of the transoral technique. a) Horizontal upper labial sulcus incision; b, c, d) Transposed and sutured to the contralateral transposed depressor septi nasi muscle; e) Close the horizontal incision vertically.

2.1. Transnasal technique

We infiltrate the membranous septum with 2% lidocaine with epinephrine 1:50,000, with a scalpel blade # 15 we make an incision of no more than 5 mm along the vestibular floor, the depressor septi nasi muscle is dissected and elevated with a dissecting Metzenbaum scissors from its position behind the columella, between the medial crura. Mahe and Camblin have noted that transaction of the depressor septi muscle may fail to produce lasting results because of reattachment of the muscle, that's why we prefer resect a 5-mm segment (Fig.8-9):

Figure 8.

Transnasal technique.

Figure 9.

A) Preoperative patient with gingival smile, lowering of the nasal tip, upper lip shortening. and transverse crease in the mid-philtral area. B) Same patient in the pop period.

3. Nerve block of the depressor septi nasi muscle

For patients who don´t want a surgical treatment, we purpose the blocking of the depressor septi nasi with BNT-A for similar but temporary results, about 4 to 6 months. (Fig.10):

Figure 10.

Nasal-labial angle blocking the m. depressor septi nasi with BNT-A: through the skin.

3.1. Trancutaneous technique

After patient selection, we mark the injection points at the base of the columella, two points at the medial crural footplate and one point between the two medial crura.

With a 1ml syringe and a 30G needle injecting 1 U of BNT-A at each point (Fig.11). After 1 week the results we get are relax the DSNM, enhancement of the nasolabial angle in static and dynamic positions, improvement the transverse crease in the mid-philtral area and prevent the dropping of the nasal tip during smile [8].

Figure 11.

Nerve block of the DSNM technique.

4. Conclusion

An active depressor septi nasi muscle is responsible for descending the nasal tip, shortened upper lip, increased maxillary gingival show and transverse crease in the mid-philtral area. Those deformities can fixed with treatment minimally invasive with a permanent or temporary results

The authors of this chapter prefer the surgical treatment to get permanent results.

Acknowledgments

We would like to extend our grateful thanks to all those who helped make this chapter. Special thanks go to the following people:

To Jose Juri, M.D: Our master in Plastic and Reconstructive Surgery.

To Hector Moina, M.D for his willingness to review the chapter and his unfailing support.

To Gustavo Mouriño, M.D for his unconditional support.

To Alejandro Lucchelli, M.D for his high quality photography.

To Myrian Arenas, surgical scrub nurse, for her dedication.