---

Nasofacial Angles, Facial Aesthetic Metrics & the SLAD-R Procedure

---

PART 1: KEY NASOFACIAL ANGLES AND FACIAL AESTHETIC METRICS

Facial Proportions - The Classic Framework

• The face is divided into 5 equal vertical segments, demarcated laterally by the outer ear, lateral canthi, and medial canthi.
• Each fifth approximates the width of one eye = intercanthal distance.

• Upper third: trichion to glabella
• Middle third: glabella to subnasale
• Lower third: subnasale to menton

• Subnasale to stomion = 1/3 of lower facial height
• Stomion to menton = 2/3 of lower facial height

---

The Powell and Humphreys Nasofacial Angle System

---

1. Nasofrontal Angle (NFA)

---

2. Nasofacial Angle (NFcA)

---

3. Nasolabial Angle (NLA)

---

4. Nasomental Angle (NMA)

---

5. Mentocervical Angle (MCA)

---

Summary Table: Powell and Humphreys Angles

---

Nasal Projection and Rotation Metrics

• Occurs along an arc with radius based at the external auditory canal (Cummings).
• Rotation increases along the upper arc and decreases along the lower arc.

• Nasal tip projection ≈ length of the upper lip (ratio 1:1).

• Draw a vertical from the nasion to the alar groove.
• Draw a perpendicular from the alar groove to the nasal tip.
• Ratio of (alar groove to tip) : (nasion to tip) = 0.55 to 0.60
• When this ratio is maintained, the NFcA approximates 36°.

• Uses a 3-4-5 right triangle: hypotenuse = nasal length; projection = smallest arm.

• Ala-to-tip / lobular complex ratio: optimal 1:1
• Columellar show on lateral view: 3-5 mm is acceptable

---

Ethnic Variations (Dermatology 2-Vol Set, 5e)

---

PART 2: SLAD-R PROCEDURE

What is SLAD-R?

Important clarification: SLAD-R is a laryngology/voice procedure, entirely separate from rhinoplasty or facial aesthetics. It is covered in ENT textbooks under laryngeal dystonia and phonosurgery.

---

Background and Rationale

• In ADSD, the thyroarytenoid (TA) and lateral cricoarytenoid (LCA) muscles (adductors) fire involuntarily during speech via the recurrent laryngeal nerve (RLN).
• Standard of care had been repeated botulinum toxin (Botox) injections into the TA muscle - effective but temporary (3-4 months), requiring ongoing injections.
• The Dedo operation (RLN section alone) provided initial relief but had high recurrence rates because the proximal RLN stump re-innervated the adductors over time with dystonic impulses.
• SLAD-R was designed to overcome this failure by combining denervation with reinnervation using the ansa cervicalis, which provides tonic non-dystonic neural input, preventing pathological re-innervation.

---

Indications

• Adductor Spasmodic Dysphonia confirmed by laryngoscopy and EMG
• Inadequate response to, or patient dissatisfaction with, Botox injections
• Patient willingness to accept 3-6 months of post-operative breathiness
• Confirmed intact distal RLN stumps and intact ansa cervicalis bilaterally
• Normal glottic airway (not compromised)

Contraindications

• Glottic airway compromise
• Absent distal RLN stump
• Absent ansa cervicalis bilaterally
• Poor prognosis (insufficient life expectancy to benefit from reinnervation)

---

Surgical Technique (Chhetri and Berke, UCLA)

• EMG-equipped endotracheal tube (NIM-Response System, Medtronic Xomed) to monitor RLN integrity intraoperatively
• Operating table rotated 90° from anesthesiologist; surgeon stands at the head
• Shoulder roll placed to extend the neck
• IV dexamethasone 10 mg and prophylactic antibiotics before incision

• A horizontal cervical incision is made (similar to thyroid/parathyroid approach)
• Subplatysmal flaps elevated
• The strap muscles are divided or retracted to expose the larynx

• The recurrent laryngeal nerve is traced to its entry into the larynx
• The anterior (adductor) branch of the RLN - supplying the TA and LCA - is identified
• Intraoperative EMG confirms nerve identity

• A laryngotomy window is opened to expose the TA muscle insertion
• A 3-0 silk suture ties the anterior RLN branch close to its TA insertion
• The nerve is divided distal to the suture, leaving an adequate distal stump for anastomosis
• The nerve is retracted posteriorly and freed to the posterior border of the laryngotomy window
• The branch to the LCA is identified during this maneuver and divided

• A partial LCA myotomy is performed at the midbelly using microscissors
• This prevents LCA re-innervation from the proximal adductor nerve stump
• Initially full LCA myotomy was done; now partial myotomy is preferred to avoid permanent breathiness (especially in males)
• The distal RLN stump is sutured to the posterior lamina of the thyroid cartilage via the French-eye needle technique

• A branch of the ansa cervicalis nerve (C1-C3, normally supplying infrahyoid strap muscles) is harvested
• Microsurgical neurorrhaphy (7-0 or 8-0 nylon, epineural anastomosis x3 locations) is performed connecting the ansa cervicalis branch to the severed adductor nerve stump
• This provides tonic, non-dystonic reinnervation
• Microsurgical magnification (loupe or operating microscope) is mandatory

• The procedure is repeated on the other side of the neck

---

Post-operative Course and Outcomes

• 83% had significantly improved Vocal Handicap Index-10 (VHI-10) scores
• 91% rated post-surgery voice as more fluent than after Botox
• Majority achieved fluent voice with absent-to-minimal breathiness

---

Comparison with Botulinum Toxin

---

Key Nerves Involved

---

• Cummings Otolaryngology Head and Neck Surgery - Nasofacial Relationships, Nasal Rotation and Projection (Ch. 16)
• KJ Lee's Essential Otolaryngology - Facial Angles (Figure 54-2), p. 1057
• Chhetri DK & Berke GS. "Treatment of Adductor Spasmodic Dysphonia with Selective Laryngeal Adductor Denervation-Reinnervation Surgery." UCLA Health/Ann Otol Rhinol Laryngol 1999;108(3):227-31.
• Laryngopedia - SLAD-R overview