Botox Injections in Non-Cranial Nerve VII Innervated Muscles for Facial Synkinesis

NCT ID: NCT07295288

Last Updated: 2025-12-29

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: PHASE4
• Total Enrollment: 50 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2026-02-01
• Study Completion Date: 2026-06-30

Brief Summary

Facial synkinesis is a condition that occurs following facial nerve (CN7) injury, typically secondary to Bell's palsy, trauma, surgery (e.g., acoustic neuroma resection), or malignancy. Synkinesis is due to aberrant regeneration of the facial nerve, where axons regrow improperly and result in misdirected innervation of facial muscles. This results in involuntary, uncoordinated muscle movements, where activation of one muscle group triggers unintended contractions in others. Standard treatment of facial synkinesis involves botulinum toxin (BT) injections into muscles controlled by CN7 to reduce these unwanted movements. However, patients often anecdotally report that adding BT injections into non-CN7 innervated muscle groups, such as the masseter and temporalis muscles, improve their synkinesis symptoms. This study therefore aims to assess whether adding BT injections to non-CN7 innervated muscle groups, specifically the masseter and temporalis muscle, can improve treatment outcomes for people with facial synkinesis. This study will use a crossover design, where each participant will serve as their own control to compare treatment effects. In the first treatment arm, patients will receive only their standard BT injections into muscle groups controlled by CN7 - no other muscles will be treated. In the second treatment arm, will receive the same standard BT injections in CN7 muscles, plus additional injections into masseter and temporalis muscles. Patients will be randomized to a specific treatment arm at their first visit. At their second visit, they will be randomized to the other treatment arm, in standard crossover study design. Pre- and post-treatment surveys will be collected to assess the benefit of adding non-CN7 muscle groups.

Detailed Description

Facial synkinesis is a debilitating condition that occurs following injury to the facial nerve (CN7). It results from misdirected nerve regrowth, leading to involuntary, often conflicting muscle movements (e.g., eye closure during smiling or neck muscle tightening). This causes functional impairments (e.g., cheek biting, eating difficulties, reduced visibility), cosmetic concerns, and increased rates of anxiety and depression. Facial synkinesis has been reported in the literature to affect up to 75% of patients with facial nerve injury.

Chemodenervation of facial muscle groups using targeted BT injections has become a mainstay treatment for facial synkinesis. Typically, BT is selectively injected into hyperfunctioning CN7-innervated muscles on the injured side to allow for relaxation and restoration of organized muscle contraction. BT may also be injected into CN7-innervated muscles on the contralateral non-affected side, to improve facial symmetry. These injections have been shown across numerous studies to be safe, improve facial symmetry, and decrease severity of synkinesis symptoms. Injections are typically preformed every 3-6 months, depending on the needs of the patient and duration of injection benefit.

While synkinesis is thought to predominantly affect CN7 innervated muscles, in our clinical experience many patients also experience painful contracture of non-CN7 innervated muscles, such as the temporalis or master muscles. We therefore routinely inject these muscle groups with BT during patients synkinesis treatments. While patients anecdotally report that injection of non-CN7 innervated muscles improve their synkinesis symptoms in our clinical practice, this has not been systematically studied in the literature. This study therefore aims to investigate whether extending BT injections to non-cranial nerve 7-innervated muscles, specifically the masseter and temporalis muscle, can enhance outcomes for facial synkinesis.

Since participants are already receiving BT as standard care, the study introduces no additional risks, focusing only on adjusting injection targets within their existing treatment. This research addresses a critical gap in managing synkinesis, where current treatments are limited, and could lead to refined protocols that enhance patient quality of life by reducing symptoms and improving facial symmetry. The potential benefits-improved function, aesthetics, and mental well-being-outweigh the minimal risks, as the intervention aligns with established, safe practices.

Conditions

Synkinesis

Keywords

botulinum toxin

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

Even MRN

Patients with MRNs ending in an even number will undergo their standard BT injections (CN7 muscle groups only) + non-CN7 muscle groups at their first treatment session, followed by standard BT injections alone at their second treatment session.

Group Type: OTHER

Botulinum Toxin Type A Injection [Botox]

Intervention Type: DRUG

Patients will receive standard of care synkinesis treatment. Depending on the treatment arm, they will receive additional botox injections to temporalis and masseter muscle groups which will only be injected on the ipsilateral side to the facial nerve injury. Decision to include the temporalis and/or masseter muscles will be based on each patients response to screening questions regarding jaw pain/tightness or headaches.

Odd MRN

Patients with MRNs that end in an odd number will undergo the reverse injection process (standard BT injections alone at first treatment session, followed by standard BT injections + non-CN7 muscle groups at their second treatment session).

Group Type: OTHER

Botulinum Toxin Type A Injection [Botox]

Intervention Type: DRUG

Patients will receive standard of care synkinesis treatment. Depending on the treatment arm, they will receive additional botox injections to temporalis and masseter muscle groups which will only be injected on the ipsilateral side to the facial nerve injury. Decision to include the temporalis and/or masseter muscles will be based on each patients response to screening questions regarding jaw pain/tightness or headaches.

Interventions

Botulinum Toxin Type A Injection [Botox]

Patients will receive standard of care synkinesis treatment. Depending on the treatment arm, they will receive additional botox injections to temporalis and masseter muscle groups which will only be injected on the ipsilateral side to the facial nerve injury. Decision to include the temporalis and/or masseter muscles will be based on each patients response to screening questions regarding jaw pain/tightness or headaches.

Intervention Type: DRUG

Eligibility Criteria

Inclusion Criteria

• Age > 18 years.
• Current diagnosis of facial synkinesis due to facial nerve paralysis/paresis.
• Scheduled to undergo BT injection for management of facial synkinesis.
• Have undergone > 3 prior BT injection sessions at VUMC for facial synkinesis.
• Able to read and understand English.
• Symptoms of neck tightness, jaw tightness, or headaches.

Exclusion Criteria

• Cognitive impairment that would preclude the ability to provide informed consent
• Unable to read text on a written survey or computer screen

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Vanderbilt University Medical Center

OTHER

Sponsor Role: lead

Responsible Party

Priyesh Patel

Assistant Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Priyesh Patel, MD

Role: PRINCIPAL_INVESTIGATOR

VUMC

Central Contacts

Christine Little, MD

Role: CONTACT

Phone: 6504555258

Email: christine.little@vumc.org

Amy Wang

Role: CONTACT

Phone: 2818859243

Email: amy.wang@vumc.org

Other Identifiers

251490

Identifier Type: -

Identifier Source: org_study_id