Local muscle flaps may enable dynamic movements of the oral commissure.
The two muscles that can be used for this are the masseter and the temporalis.
Clinical assessment prior to surgery is necessary to determine that the muscles of mastication are functioning.
Traditionally, the temporalis muscle flap requires detaching its origin from the temporal fossa. This may involve either the entire muscle or a portion of it. The muscle is then turned over the zygomatic arch and anchored to the commissure. When the muscle origin is used as the dynamic component, it is termed "antidromic".
The limitation of this technique is the small excursion despite the correct vector. In addition, excessive bulk over the zygomatic arch and significant hollowing in the temporal fossa will occur.
The temporalis mini muscle sling technique can be used as a dynamic reconstruction of the upper portion of the nasolabial fold. This technique achieves only minimal excursion (1-2 mm) and is best used in combination with other dynamic techniques.
Several modifications have been described using the temporalis muscle transposition for facial paralysis. Recently, the orthodromic temporalis muscle transposition has gained popularity. The term "orthodromic" refers to the insertion point (coronoid process) of the temporalis muscle being used as the dynamic component.
Orthodromic temporalis muscle transposition involves releasing the muscle at its insertion on the coronoid and attaching it either directly or with the use of tendon graft to the oral commissure. The temporalis muscle origin can also be released either completely or partially, in order to increase muscle reach.
This allows dissection onto the deep temporal fascia which covers the temporalis muscle.
A portion of the muscle origin is detached and mobilized off of the temporal fossa. Classically, this has been described with the posterior part of the muscle, but it can be performed detaching the entire origin, to increase the reach of the muscle.
A coronoidectomy is performed to enable muscle release and mobilization.
The temporalis muscle is reattached to the oral commissure either directly or with the use of tendon graft.
The skin incision is closed in layers.
The need for aftercare is to reduce the chance of inadvertent release of the suspension procedure. This can include maintaining soft diet 2-3 weeks postoperatively and minimizing exertion and trauma to the area during this period.
Generally, 4-6 weeks postoperatively patients are encouraged to return to normal activities without restrictions.
Infrequently, some patients may need formal mouth opening exercise if they develop trismus.
Specific physiotherapy exercises are started after this time. The goals are to improve symmetry both at rest and during function, through biofeedback and patient practice (in front of a mirror).