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

Official title

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

Overview

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.

Interventions

• 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.

Primary outcome measures

• Synkinesis Assessment Questionnaire (SAQ) [Time frame: Pre-treatment and repeated 5 weeks post-treatment]
• Headache Impact Test (HIT-6) [Time frame: Pre-treatment and repeated 5 weeks post-treatment]
• Temporomandibular Disorder Questionnare (TMD-7) [Time frame: Pre-treatment and repeated 5 weeks post-treatment]

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Open label

Primary purpose

Treatment

Study locations

Center list to be confirmed — check the primary protocol.

Identifiers

NCT: NCT07295288 · 251490

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗