Masseteric Nerve Transfer Surgery for Facial Nerve Reanimation

What Is the Masseteric Nerve Transfer?

Masseteric nerve transfer is a nerve transfer surgery performed to restore facial expressions in patients with long-term or permanent facial paralysis. In this procedure, the masseteric nerve, which controls the chewing muscle and contains strong motor fibers, is micro-surgically connected to the branches of the facial nerve that have lost their function. The goal of the procedure is to transmit electrical impulses from a healthy nerve source to the paralyzed facial muscles, thereby restoring smiling movements and facial symmetry. For this reason, the method is generally preferred in cases of unilateral facial paralysis and can provide a faster muscle response compared to other nerve transfers. As a result, masseteric nerve transfer offers an effective and permanent solution for facial paralysis treatment, both functionally and aesthetically, when the right patient selection is made.

Who is a Good Candidate for Masseteric Nerve Transfer?

We can say that suitable candidates for masseteric nerve grafting are generally patients with the following characteristics:

• Individuals with early-stage facial paralysis
• Individuals with facial nerve damage
• Patients with viable muscle tissue
• Individuals with healthy chewing function
• Individuals experiencing unilateral paralysis
• Individuals in good general health

How is Masseter Nerve Transfer Performed?

Masseter nerve transfer (masseteric-facial nerve transfer) is a microsurgical reinnervation technique used to restore active facial movement, particularly in cases of long-term peripheral facial paralysis. In this technique, the masseteric nerve, which innervates the chewing muscle (m. masseter) and has a high motor axon density, is surgically coapted to the appropriate branch of the dysfunctional facial nerve (most often the zygomatic or buccal branches responsible for smiling).

The procedure is performed under general anesthesia through a limited incision made in front of the ear or on the side of the face; first, the distal branches of the facial nerve are dissected and their viability is assessed, then the masseteric nerve emerging from the mandibular branch of the trigeminal nerve is carefully located, and an end-to-end anastomosis is performed under a microscope using epineural or perineural sutures, ensuring sufficient length. Thus, while the patient's smile is triggered by teeth clenching, a more spontaneous mimic pattern may develop over time due to central adaptation.

Masseteric Nerve Transfer Recovery Process

Masseteric nerve transfer is a functional reinnervation procedure applied particularly in cases of long-term peripheral facial paralysis, and the recovery process is evaluated in two main phases: surgical recovery and nerve regeneration.

1. Early Stage (First 1–3 Weeks)

In the first few days after surgery, mild swelling, bruising, and sensitivity along the incision line may be observed. This period is the phase where wound healing is the primary focus. Generally:

• Discharge occurs within 1–2 days.
• Sutures are removed within 7–10 days (if non-absorbable sutures were not used).
• Mild pain or fatigue may be felt during chewing; this is temporary.

Facial movements are not yet expected at this stage, as it takes time for the nerve fibers to reach the muscles.

2. Nerve Regeneration Period (1–6 Months)

After microsurgical coaptation between the masseteric nerve and facial nerve branches, axonal growth begins. Nerve healing progresses at an average rate of 0.5–1 mm per day. In most patients:

• The first muscle contractions may be seen from the third month onwards.
• Between 4 and 6 months, teeth clenching and smiling begin to develop.

Physical therapy and neuromuscular rehabilitation are critically important during this period. Initially, the patient triggers the smile by clenching their teeth; over time, a more natural facial expression pattern may develop thanks to brain adaptation.

3. Functional Maturation Period (6–18 Months)

Muscle strength and coordination improve during this process. As reinnervation is completed:

• Smile symmetry becomes more pronounced.
• Muscle tone increases.
• Voluntary movements become more controlled.

In some patients, a full spontaneous smile may not develop; however, it is usually possible to achieve a strong and symmetrical voluntary smile.

Masseteric Transfer vs. Other Nerve Transfers

Masseteric nerve transfer used in facial paralysis surgery has certain advantages and disadvantages compared to traditional methods. These differences generally relate to the speed of recovery, quality of smile, and degree of surgical difficulty. In this context, the differences can be listed as follows:

1. Masseteric Nerve Transplantation vs. Cross Facial Nerve Graft (CFNG)

A cross-face nerve graft involves transferring a nerve from the healthy side of the face to the paralyzed side. In this context, the differences between masseteric nerve transfer and cross-face nerve graft are as follows:

• Recovery Time: Masseteric transfer yields much faster results (average 4-6 months). It may take 12-18 months for the cross graft to reach the paralyzed side.
• Spontaneity (Naturalness): Because the cross graft is attached to the unaffected side, the paralyzed side moves spontaneously when the person smiles. With masseteric grafting, however, the person must initially learn to “clench their teeth” in order to smile.
• Nerve Strength: The masseteric nerve provides a very strong motor stimulus, which allows the corner of the mouth to lift more powerfully.

2. Masseteric Nerve Transplantation vs. Hypoglossal Nerve Transplantation

Hypoglossal nerve transfer involves connecting the nerve that controls tongue movement to the facial nerve. The differences between masseteric nerve transfer and hypoglossal nerve transfer are as follows:

• Side Effects: In hypoglossal nerve transfer, tongue weakness, speech and swallowing difficulties may occur. In masseteric nerve transfer, the unilateral chewing muscle is sacrificed; however, since the other chewing muscles compensate for this, no significant loss of function occurs.
• Muscle Tone: The hypoglossal nerve is very successful in maintaining the symmetry (tone) of the face at rest; however, the masseteric nerve is superior in providing active smiling function.

The Effect of Masseteric Transfer Surgery on Facial Paralysis

Masseteric transfer surgery is a powerful reinnervation method that aims to restore active facial expression, particularly in cases of long-term peripheral facial paralysis. In this technique, the masseteric nerve, which innervates the chewing muscle and has a high motor axon density, is micro-surgically coapted to the branches of the facial nerve that have lost their function. Thus, motor impulses from a healthy nerve source are transmitted to the paralyzed facial muscles, and the smile function in particular is attempted to be reactivated. In this context, the most important advantage of the masseteric facial nerve transfer method is that it provides a strong and rapid muscle response; in most patients, the first muscle contractions can be observed within 3–6 months. Therefore, when the right patient selection is made, masseteric transfer offers an effective and permanent solution in facial paralysis treatment, both functionally and aesthetically.

If you would like detailed information about masseteric nerve transfer, you can contact Dr. Berke Özücer and his team, who specialize in facial paralysis.