The purpose of the study was to assess the effects of a novel technique involving facial stretching of the unaffected side along with a structured exercise for the affected side on facial symmetry and facial functions as compared to conventional exercise. A hospital-based parallel-group randomized trial was completed among patients with acute Bell’s palsy in Mangalore, India. Participants were randomized to receive facial stretching and a structured exercise program (experimental group) or the conventional exercise regimen (conventional group). Primary outcomes were facial symmetry and voluntary movement; assessed by the Sunnybrook Facial Grading System (SFGS). Both regimens were given for 3 weeks, with baseline, 10th day, and 20th day assessments. Out of 31 participants screened, 24 were eligible and 12 participants each were assigned to experimental and conventional groups. Change scores revealed greater improvement in the SFGS score (p = 0.002) for the experimental group participants. Facial stretching and structured exercise program exhibited promising results in enhancing facial symmetry and function in acute Bell’s palsy when compared to conventional exercise regimen.
Introduction
Bell’s palsy (BP) is an acute primary idiopathic lower motor neuron disorder characterized by sudden unilateral facial weakness1, with an annual incidence ranging from 11.5 to 53.5 per 100,000 persons2,3. The symptoms of BP can range from mild weakness to severe paralysis and include, absence of forehead wrinkling, drooping of the mouth corner, eye dryness or excessive tearing, ear pain, difficulty eating, and impaired taste sensation4. While about two-thirds of patients recover fully within three months, a significant proportion continue to experience persistent symptoms, including facial asymmetry and involuntary movements (synkinesis) which impact their psychological and social quality of life4,5,6.
Current medical management of BP primarily involves antivirals and corticosteroids. A 2019 Cochrane review suggested limited effectiveness of these interventions in resolving BP symptoms7. However, a 2020 systematic review indicated potential benefits of this combination in reducing long-term sequelae8.
Physical therapy interventions for BP include facial muscle expression exercises, facial massage, electrotherapy, diathermy, kinesiotaping, and neuromuscular reeducation4,5,6,9,10. A recent systematic review demonstrated the clinical effectiveness of facial muscle exercises in enhancing early recovery of facial muscle strength, symmetry, and movement, as indicated by Sunnybrook Facial Grading System (SFGS) scores, and overall facial function, reflected in Facial Disability Index (FDI) scores. This study compared facial muscle exercises with various other interventions, including electrical stimulation, mirror biofeedback, acupuncture, mime therapy, Proprioceptive Neuromuscular Facilitation (Kabat), antiviral and corticosteroid drugs, hyperbaric oxygen therapy, facial re-training, surgical interventions, laser therapy, taping techniques, feedback training, and combination therapies11. Conversely, a prior systematic review examining diverse physical therapy interventions for BP suggested that while facial exercises may alleviate symptoms, particularly in acute cases, their efficacy for idiopathic facial paralysis lacks robust evidence and necessitates further high-quality research12.
Current physiotherapy interventions primarily target the primary impairment on the paretic side13,14. However, the muscle imbalance resulting from facial palsy, which places the non-paretic side muscles in a perpetually shortened state, is never addressed in previous studies. This shortened state can cause architectural changes at the functional unit and connective tissue levels including a reduction of sarcomeres in series, and passive stiffness and/or contracture development in intramuscular connective tissues15,16. Additionally, overactivity of the non-paretic side muscles perpetually elongates/stretches the paretic muscles beyond their optimal length, limiting their force generation capacity17. However, these changes can be prevented by passive stretching or active stimulation18. In particular, short, daily periods of stretch can prevent the loss of sarcomeres and muscle atrophy19.
Given the conflicting evidence and limitations of current physical therapy approaches, this study introduces a novel facial stretching technique combined with a structured exercise program. This combined stretching and strengthening exercise program, grounded in systematic review findings and previous studies12,20,21, highlights the importance of addressing facial muscle imbalances. Such an approach promotes facial symmetry by reducing overactive unaffected side muscles and strengthening the weaker side with structured exercises22. Muscle balance is essential for harmonious facial movements23 and the current study attempts to assess the efficacy of a novel stretching technique combined with a structured exercise program against conventional therapy for improving facial asymmetry, synkinesis, and facial neuromuscular function among acute BP patients.
Methods Study design
The parallel-group facility-based randomized clinical trial was conducted in the hospitals attached to Kasturba Medical College, Mangalore. Approval was obtained from the Institutional Ethics Committee (IEC KMC MLR-11-19/575). The trial was registered in the Clinical Trials Registry India (CTRI/2020/02/023,240) on 11/02/2020. The study adhered to the ethical principles of the Declaration of Helsinki for research involving human participants.
Participants
The study included participants with acute, primary unilateral idiopathic lower motor neuron facial palsy (Bell’s Palsy). The exclusion criteria comprised of secondary lower motor neuron facial palsy, temporomandibular joint dysfunction, prosthetic dentures or braces, facial dysmorphism, and severe ear pain potentially interfering with assessment or treatment.
The sample size was calculated using the below-mentioned formula with an assumption of a difference in the change score of 20 for facial symmetry and function across the two intervention arms, 90% power, a clinically accepted difference of 15, and a 10% non-response rate, resulting in 12 participants in each study arm.
where Z1 − α = 1.96, Z1 − β = 1.281.
Participants were enrolled from February 2020 to March 2021, following referrals from neurologists or physicians. Prior to enrollment, informed consent was obtained from each interested participant who met the eligibility criteria.
Medical management
All participants were treated according to the National Institutes of Health (NIH) guidelines for acute BP, as recommended in previous studies10,24. The medical regimen consisted of Prednisone at a dose of 60 mg daily for the initial 5 days, followed by a tapering dose of 10 mg per day over the subsequent 5 days. Additionally, participants received oral Acyclovir or Valacyclovir for the first 5 days, aligning with established protocols4.
Randomization and masking
Participants were randomly assigned to experimental group (facial stretching and structured exercise regimen) or the conventional group (conventional exercise regimen) using a permuted block randomization technique with varying block (4 and 6). Allocation concealment was maintained using the opaque envelop method with the sequence secured by one investigator (PM). Another investigator (AN) assigned participants to the study groups.
Interventions
Both groups received therapy 6 days a week for 3 weeks. Each session began with a faradic galvanic test to gauge facial muscle response irrespective of the intervention arm. Responsive participants received faradic current targeting facial muscles in two sets of 30 contractions while non-responsive participants received galvanic stimulation over the facial nerve trunk and motor branches. Both groups received only one session of faradic/galvanic stimulation per day.
The experimental group received four stretching techniques: three on the unaffected side and one on the affected side of face. During initial sessions, bystanders or family members were trained in three techniques through hands-on guidance from the therapist and were given printed instructional handouts. All four stretching techniques were repeated 10 times with a stretch hold of 10–15 s. The patient was directly taught the fourth technique for the affected side. They were instructed to perform the stretching technique four sessions daily at home. Follow-up assessments ensured that the correct technique was executed. Following each session’s stretching exercise, participants in the experimental group performed a specific set of exercises that focused on minimizing or avoiding overactivity of the facial muscles on the unaffected side.
Participants in the conventional group received exercise based on the Northeast London Foundation Trust (NELFT)-National Health Service (NHS) guidelines. Conventional group participants were instructed to perform these exercises four times daily at home, with follow-up assessments to ensure correct execution. Both groups were instructed to perform facial exercises in front of the mirror. Details of both experimental and conventional exercise protocols are appended and accessible at https://doi.org/10.17605/OSF.IO/UVW89. Models have provided informed consent for the publication of animated images included in the online open access appendix.
Outcome measures
The primary outcome measure was the Sunnybrook Facial Grading System (SFGS), a regional weighted system assessing resting symmetry, voluntary movement, and synkinesis. The total SFGS composite score ranges between 0 and 100, where 0 stands for total paralysis and 100 for normal facial function. The House Brackmann Scale (HBS), a widely accepted facial grading system, was included as a secondary measure to evaluate the severity of nerve damage in facial nerve palsy. Additionally, the Facial Disability Index (FDI), consisting of physical and social subscales, was included to assess the disability related to facial neuromuscular dysfunction. Using standard procedures, blinded independent assessors performed assessments at baseline, on the 10th day (mid-intervention), and on the 20th day (post-intervention).
Statistical analysis
Data analysis was performed using IBM SPSS Statistics Version 25.0. Demographic and clinical characteristics at baseline were compared between treatment groups to assess the effectiveness of the randomization procedure. Results were presented as proportions and summary measures. Group comparisons utilized the Kruskal–Wallis, Wilcoxon’s signed-rank, and Mann–Whitney U tests. Analyses of outcome data were performed by an experienced statistician blinded to group allocation. A p-value of < 0.05 was considered statistically significant.
Results
Thirty-one study participants underwent eligibility assessment, of which three were excluded based on inclusion and exclusion criteria and four due to difficulty commuting. The CONSORT flow chart is shown in Fig. 1. Of the 24 eligible patients, 12 were randomized to each group: facial stretching and exercise or conventional exercise. Following allocation to the conventional group, due to travel ban imposed during the COVID19 pandemic, data collection for one patient was incomplete and lost to follow-up. Demographic details and baseline characteristics for the remaining 23 participants are provided in Table 1. Treatment compliance rates were 100% for the experimental group and 91.6% for the conventional group.