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

Investigating the Efficacy of Botox Injections in Non-Cranial Nerve VII Innervated Muscles for Facial Synkinesis Management

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Synkinesis
• Intervention / Treatment: Drug: Botulinum Toxin Type A Injection [Botox]

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.

• Study Type: Interventional
• Enrollment (Estimated): 50
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Christine Little, MD; Phone Number: 6504555258; Email: christine.little@vumc.org
• Study Contact Backup: Name: Amy Wang; Phone Number: 2818859243; Email: amy.wang@vumc.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: 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.	Drug: 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.
Other: 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).	Drug: 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Headache Impact Test (HIT-6)	This 6-item questionnaire seeks to understand the severity of headaches and impact on every-day quality of life. The survey is widely validated for assessing headache symptom and burden. We plan to add in 3 additional questions to this survey including 1) how often do you experience headaches (1 = never or rarely, 2 = 1-2 days a week, 3 = 3-4 days a week, 4 = nearly every day), 2) on a scale of 1-10 (10 = most severe) how severe are your headaches, and 3) I feel as if my Botox injections improved my headaches (Y/N). HIT-6 Scale: 1 = Never 2 = Rarely 3 = Sometimes 4 = Very often 5 = Always	Pre-treatment and repeated 5 weeks post-treatment
Synkinesis Assessment Questionnaire (SAQ)	This 9-item questionnaire assesses functional status (hyperactive and/or inappropriately active facial muscles) related to facial synkinesis and is already given at each clinic visit as a routine part of clinical practice. The survey is well validated for evaluating synkinesis symptoms in patients with facial nerve injury. SAQ scale: 1 = seldom or not at all, 2 = occasionally, or very mildly, 3 = sometimes, or mildly, 4 = most of the time, or moderately, 5 = all the time, or severely	Pre-treatment and repeated 5 weeks post-treatment
Temporomandibular Disorder Questionnare (TMD-7)	This 7-item questionnaire assesses symptoms related to temporomandibular mandibular joint (TMJ) disorder. It asks about jaw pain, tightness, clicking and difficulty eating, among other things. We plan to add in 3 additional questions to this survey including 1) how often do you experience jaw pain/tightness (1 = never or rarely, 2 = 1-2 days a week, 3 = 3-4 days a week, 4 = nearly every day), 2) on a scale of 1-10 (10 = most severe) how severe is your jaw pain/tightness, and 3) I feel as if my Botox injections improved my jaw pain/tightness (Y/N). TMD-7 Scale: 1 = Rarely or Never 2 = A few times a month 3 = Once or Twice a Week 4 = Nearly Every Day	Pre-treatment and repeated 5 weeks post-treatment

Collaborators and Investigators

• Sponsor: Vanderbilt University Medical Center
• Investigators: Principal Investigator: Priyesh Patel, MD, VUmc

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): June 30, 2027
• Study Completion (Estimated): June 30, 2027

Study Registration Dates

• First Submitted: December 7, 2025
• First Submitted That Met QC Criteria: December 7, 2025
• First Posted (Actual): December 19, 2025

Study Record Updates

• Last Update Posted (Actual): April 15, 2026
• Last Update Submitted That Met QC Criteria: April 12, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: botulinum toxin
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Dyskinesias; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Synkinesis; Amino Acids, Peptides, and Proteins; Proteins; Biological Factors; Hydrolases; Enzymes; Enzymes and Coenzymes; Botulinum Toxins; Metalloendopeptidases; Endopeptidases; Peptide Hydrolases; Metalloproteases; Bacterial Proteins; Bacterial Toxins; Toxins, Biological; Botulinum Toxins, Type A
• Other Study ID Numbers: 251490

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes