Authors of section

Authors

Damir Matic, John Yoo

General Editors

Daniel Buchbinder

Open all credits

Contralateral depressor angularis muscle excision

1. Introduction

With long standing unilateral facial paralysis hyperactivity of the contralateral depressor muscles of the lower lip result in significant asymmetry during function and rest.

Resection of the depressor angularis muscle can be a permanent solution.

irreversible paralysis mouth lower lip

2. Planning and surgical preparation

The location of the depressor angularis muscle can be determined by observing the vector of pull of the lower lip when the patient is asked to smile and show their lower teeth.

contralateral depressor angularis muscle excision

The location of the muscle is marked on the lower lip and chin, prior to the operation.

contralateral depressor angularis muscle excision

3. Technique

This procedure can be performed either under local or general anesthesia.

Incision

An intraoral incision is performed in the vestibule of the lower lip corresponding to the location of the skin markings.

contralateral depressor angularis muscle excision

Muscle resection

The muscle is identified intraorally and resected entirely from the mandible to the orbicularis oris muscle.

irreversible paralysis mouth lower lip

Note: care should be taken to avoid injury to the branches of the mental nerve during muscle excision.

contralateral depressor angularis muscle excision

Closure

The oral mucosa is closed with resorbable sutures.

contralateral depressor angularis muscle excision

4. Alternative 1 – Botulinum toxin injection

Lower lip asymmetry can be managed non-surgically with botulinum toxin injections into the muscle every 3-4 months.

Advantages of botulinum toxin injection:

  • Non-surgical
  • Reversible if patient not happy with result
  • Can be used as a test prior to muscle resection

Disadvantage of botulinum toxin injection:

  • Non-permanent
contralateral depressor angularis muscle excision

Case example: botulinum toxin injection

a) Patient presented with irreversible paralysis of the left marginal mandibular branch of the facial nerve.
b) Botulinum toxin was injected into the contralateral depressor angularis oris muscle (patient's right side) in order to give symmetry during function.

contralateral depressor angularis muscle excision

5. Alternative 2 – Marginal nerve division

This procedure is rarely indicated.

Advantages of marginal nerve division:

  • Permanent
  • Relatively simple

Disadvantages of marginal nerve division:

  • External scar
  • May paralyze adjacent muscles causing worsening asymmetry and function

Incision

A 2-3 cm incision is made below the border of the mandible, centered over the facial vessels.

contralateral depressor angularis muscle excision

Marginal nerve identification

The marginal branch of the facial nerve is predictably found deep to the platysma muscle and superficial to the facial vessels at the jaw.

contralateral depressor angularis muscle excision

A nerve stimulator can be used to identify the branches of the nerve and assess muscle function.

contralateral depressor angularis muscle excision

Nerve division

The branches that stimulate the depressors of the lip can be divided. This may require division of the entire marginal branch of the facial nerve.

contralateral depressor angularis muscle excision

6. Aftercare

Routine wound care is all that is necessary for the majority of the procedures.