Effects of Photobiomodulation and Electrical Stimulation Among Bell's Palsy Patients

Overview

Despite promising evidence supporting both photobiomodulation (PBM) and electrical stimulation (ES) in Bell's palsy rehabilitation, key gaps remain in the literature. Few studies have directly compared these modalities under standardized conditions, especially while keeping facial exercises constant across groups. Inconsistent treatment parameters such as variations in PBM wavelength or ES intensity limit the comparability and replication of existing findings. Additionally, many studies rely on subjective outcome measures and lack structured timelines for assessing facial symmetry, neuromuscular coordination, or long-term recovery, including complications like synkinesis. These limitations highlight the need for a well-controlled comparative study to determine the more effective modality when paired with consistent facial rehabilitation exercises.

Bell's palsy is the most common form of lower motor neuron facial paralysis, accounting for approximately 60-75% of such cases. Although the exact cause remains unknown, it is often linked to viral infections that trigger inflammation of the facial nerve, leading to localized swelling, loss of myelin sheath, and reduced blood flow. Several factors have been identified that may increase susceptibility to the condition, including elevated blood glucose levels, poorly managed hypertension, severe pre-eclampsia, migraines, and exposure to radiation. Patients experience either partial or complete facial weakness, often accompanied by numbness, discomfort, sensitivity to sound, and changes in taste. Bell's palsy is primarily diagnosed through clinical assessment, with other potential causes being ruled out. Among the various rehabilitative strategies, photobiomodulation (PBM) and electrical stimulation (ES) have gained significant attention. Both are non-invasive therapeutic modalities used to stimulate nerve regeneration, reduce inflammation, and promote muscle function. However, comparative studies evaluating their effectiveness in treating facial disability due to Bell's palsy remain limited. This study, therefore, aims to investigate the comparative effects of PBM and ES on facial disability in patients suffering from Bell's palsy, helping clinicians make evidence-informed decisions for optimal patient outcomes. Physiotherapy plays a crucial role in Bell's palsy rehabilitation by targeting neuromuscular facilitation, enhancing synaptic activity, and restoring functional facial expressions. Photobiomodulation therapy, previously referred to as low-level laser therapy (LLLT), employs low-intensity lasers or light-emitting diodes (LEDs) to deliver light energy into tissues. This energy is absorbed by chromophores in cells, especially cytochrome c oxidase, triggering a cascade of biochemical events that stimulate ATP production, modulate reactive oxygen species (ROS), and reduce inflammation. These effects create a favorable environment for nerve regeneration and tissue healing. Electrical stimulation involves applying controlled electrical currents through the skin to elicit muscle contractions. By stimulating the facial nerve or its motor endplates, ES is thought to maintain muscle tone, prevent atrophy, and potentially re-educate facial muscles through repetitive activation. Different protocols involve varying frequencies and waveforms, with surface electrodes most commonly used in clinical practice. The theoretical underpinning of both PBM and ES lies in the concept of neuroplasticity and tissue responsiveness to bioelectrical and biochemical signals. However, the optimal modality, timing, and dosage for facial nerve rehabilitation remain areas of ongoing research and debate, necessitating further empirical investigation.