Rehabilitation of facial paresis due to a lesion of the facial nerve in clinical practice

Summary

Facial nerve lesions lead to a variety of functional, motor, and psychological limitations in all stages of the disease. Acute therapy in neurology and neurosurgery has long defined procedures based on evidence-based medicine. However, in follow-up, rehabilitation therapy procedures are inconsistent, with therapies applied according to empirical experience with little support from the evidence. Currently, some procedures are already being validated, but still either in a small sample of patients or only in individual areas. For example, in the field of electrotherapy, methodologies are inconsistent, without clearly defined recommendations. There are also no conclusive data on the effect of relaxation methods, massage, and manual lymphatic drainage. The use of mirror therapy and virtual therapy with biofeedback is positive, but here too, there appears a need for standardization of practice and the addition of evidence.

Keywords:

Facial nerve – therapy – evidence – palsy

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

 

 

Introduction

Nervus facialis (VIIth cranial nerve) is a mixed nerve. It has somatomotor, sensory, sensory and visceromotor components. The central motor neurons are located in the lower third of the gyrus praecentralis of the frontal cortex. They pass through the capsule interna to the caudal pontus, cross there and end in the motor nucleus of the facial nerve. From the nucleus of the brainstem it then ascends in the angulus pontocerebellaris and divides into the branches of the n. facialis and n. intermedius, then continues to the canalis n. facialis and ascends from the base of the skull in the foramen stylomastoideum. It passes beneath the external auditory canal to the region of the glandula parotis, and there it branches several times. From the anterior margin of the parotid gland the terminal branches arise, which supply the mimic muscles. About 60% of the fibers of the n. facialis are motor [1,2].

 

Peripheral lesions of the facial nerve

Idiopathic facial paresis accounts for 75-80% of all cases. The most common cause of paresis is exacerbation of herpes simplex virus (HSV) infection in the ganglion area. It can also be caused by inflammatory diseases (e.g. neuroborreliosis), trauma, metabolic disorders and others. In the case of peripheral involvement of the n. facialis, in contrast to central involvement of the facial nerve, ipsilateral eye closure and frowning are impaired. This type of paresis can be caused by both peripheral involvement of the n. facialis and lesions of the nerve nucleus in the brainstem.

 

Central lesion of the facial nerve

A common symptom of CMP is a central lesion of the n. facialis. The cause is damage to the first motoneuron of the contralateral center of the facial nerve. The lesion may occur throughout the first motoneuron from the nucleus through the brainstem subcortically or diffusely anywhere in the cerebral cortex [3,4]. Two-thirds of patients are affected by a central lesion of the facial nerve as a result of CMP, whereas neoplasia or inflammatory brain diseases lead to paresis less frequently [3].

The activation of the muscles in the forehead and eyelids originates from both cerebral hemispheres, therefore the cerebral hemispheres are not affected in unilateral damage [5].

A large proportion of human communication is nonverbal -⁠ using facial expressions. The social environment in which a person moves is sensitive to the aesthetic and functional consequences of facial paresis, regardless of the aetiology of the disability [6]. In particular, patients after stroke often suffer from depression, which prognostically impairs neuroplasticity and outcome of therapy. In this sense, functional quality of life is usually more important than the degree of disability [7]. Monitoring the degree of paresis with emphasis on social relationships and psychosocial attachments allows for improved communication between patient, physician and therapists [8]. In this regard, peripheral lesions of the facial nerve with implications for quality of life have been studied the most. However, as the average age of the human population increases, the number of patients with a central lesion of the n. facialis associated mainly with stroke is also increasing.

The psychosocial impact of the facial nerve lesion has been demonstrated, but only by questionnaire; no further solutions are proposed [8-12].

It is because of the severity of the psychosocial impact of persons with facial nerve lesions that it is appropriate to recommend to patients the intervention of a clinical psychologist and possibly group therapy with people with similar facial expressions.

 

Evaluation of paresis due to lesion of the facial nerve

Worldwide, a number of classification systems are used to assess the degree of facial nerve involvement [13,14], but none of them has been fully established for central facial paresis because all of them have been developed only for peripheral lesions of the n. facialis.

The clinical severity of peripheral facial nerve lesions is assessed by clinical tests such as the Stennert index or the House-Brackmann and Sunnybrook scales.

These tests do not take into account the functional and psychosocial perception of the consequences of the disease. Therefore, specific instruments have been developed that focus on the patient's subjective feelings and quality of life. In particular, the Facial Disability Index (FDI) and the Facial Clinimetric Evaluation Scale (FaCE). These contain questions that aim to clarify not only the patient's psychological attachments and feelings, but also the social standard of living in relation to his/her physical, psychological, functional and organic limitations [5].

J. House and D. Brackmann developed their rating scale in 1985 and it was introduced by the American Academy of Otolaryngology -⁠ Head and Neck Surgery as a standard system for assessing function and the extent of functional impairment [15]. Because of its simplicity and rapid applicability, the House-Brackmann scale became one of the most common means of classifying facial disability in everyday clinical practice only a few years ago [16]. This instrument allows the classification of paresis due to a facial nerve lesion into six grades according to severity [15].

In Germany, the Strennert index is widespread. Resting muscle tone and muscle mobility are assessed separately. The active movement of facial facial mimicry muscles is included in the assessment of 60% and resting muscle tone in 40% [17].

The Sunnybrook scale is popular especially in the USA. Recently, it has been increasingly adopted in Europe. It has been shown to be the most reliable test of inter -⁠ and intrarater reliability [18]. In addition to static symmetry, it assesses dynamic symmetry during free movements and forms of regional synkinesis [19].

The limitation of these classification systems and methods lies in the subjectivity of the assessment. They only assess visible muscle laxity and asymmetries [20]. This leads to a reduction in the validity of the examination because it does not take into account the non-motor impairments associated with the facial nerve lesion from the patient's subjective viewpoint, as confirmed by studies [21,22].

Another option is the Facial Disability Index (FDI), which is divided into two parts. The first has five questions and six possible answers for each question [21]. The questions in the first part deal with the physics of functions, and the answers are chosen on a scale ranging from 0-5. The second part explores social function and patient well-being. Answers are chosen on a scale of 1-6. A maximum of 100 points can be scored on a point scale. Higher scores correspond to less functional impairment, lower scores to greater functional limitation (Appendix 1).

The Facial Clinimetric Evaluation (FaCE) questionnaire contains 15 questions, each with five possible answers (Kahn et al. 2001 [18]). The individual questions are summarized into six different domains in the assessment and transformed using a predefined formula into a scale from 0 to 100. A high score reflects a low physical assessment and a high quality of life. A low score indicates severe physical impairment and low quality of life (not validated in the Czech version).

Comparing the studies published so far, it can be said that both types of paresis improve similarly over time, although the group of patients with peripheral paresis according to Volk et al. [23] shows a higher degree of impairment at the beginning of therapy (House-Brackmann initially 4.0 ± 1.3), since peripheral damage to the facial nerve, unlike central damage, almost always manifests as severe/complete paresis. Interestingly, using the FDI questionnaire testing, patients with central facial nerve lesions showed a more severe deficit in their quality of life than those with peripheral paresis [23].

It is important that for future practice the assessment is standardised and chosen to be usable and understandable by the general professional public. For the time being, the FDI and FaCE appear to be the most feasible to use in interdisciplinary collaboration in the rehabilitation of facial nerve lesions.

 

Traditional forms of facial nerve lesion rehabilitation

The lesion of the n. facialis brings many other complications than just impaired mobility of the facial muscles. For example, speech impairment, eating disorder with food residues in the cheek pockets, fluid intake (anterior drooling), saliva and fluid leakage from the mouth, visual disturbances associated with corneal drying, lack of tears with impaired eye cleaning, or impaired expression of emotions occur simultaneously. Patients are also at risk for depression and activation of mental illness due to significantly reduced quality of life [24]. In patients in whom complete restoration of facial nerve function cannot be achieved, exercise with nonspecific movement patterns without targeted therapeutic support is not beneficial. If the patient trains in the paralytic phase, for example, to smile or whistle only independently, without guidance and instruction from the therapist in front of a mirror, facial asymmetries and synkinesis may fully develop, even in cases with a good prognosis due to hyperactivity of the healthy half of the face [25]. The moment the first minimal movement appears, patients should be instructed to practice specific movements aimed at maintaining facial symmetry and preventing unwanted synchrony. Many studies, such as the review by Perier et al [26] or Cardoso et al [27], have shown that early treatment of a peripheral lesion after catching the onset has positive results even in patients with a negative prognosis. In patients after stroke with a central lesion of the n. facialis, functional motor and sensory therapy is started as early as 24 h after the onset of acute disease. This rehabilitation is a team effort involving speech therapists, physiotherapists and occupational therapists. The goal here is also the successful restoration of all facial movements and symmetry [25].

Other well-known therapeutic procedures are e.g. MimeTherapy according to Beurskens or neuromuscular training according to Diels, PNF, neuromuscular stimulation according to Kenny, also biofeedback with mirror or surface EMG show favourable results in clinical studies [25,27]. Electrical stimulation of mimic muscles should be used only in selected cases of peripheral lesions of the facial nerve with complete denervation of mimic muscles. Nonspecific use of electrical stimulation may increase the risk of secondary damage in the chronic phase [25].

A meta-analysis by Cardoso et al. (2008) investigating the benefits of mirror-less and mirror-front exercise using EMG biofeedback, although positive, was not reliable due to the small number of probands [28]. This was followed by Teixeira et al. with a large meta-analysis of physical therapy -⁠ electrostimulation of the fascial muscles in combination with other methods, with no significant effect demonstrated [24]. Thus, according to the studies, combined procedures did not provide evidence of superiority of one type of treatment over another.

In another study on early rehabilitation of Bell's palsy in 2013 [29], its benefit was demonstrated, with a significantly positive effect of therapy according to the degree of disability and duration. The timeliness of the therapy setting had a significantly positive effect on the subsequent severity of the patient's disability.

In research by Pourmomeny et al. using biofeedback therapy (2014), patients had a reduced risk of disruptive synkinesis. However, only 16 patients were included in the study group [30]. Clinical trials of acupuncture and other traditional Chinese medicine methods for n. facialis lesions do not meet today's scientific criteria [31].

In summary, a number of studies have described the positive effect of training in combination with biofeedback therapy [30,32,33]. However, the level of these studies is low; for example, there has been insufficient evidence to date that electrical stimulation, a common tool used in physiotherapy, improves the course of functional recovery, and there is no evidence of a negative effect. There are no relevant data for massage and manual lymphatic drainage.

In a study by Martinez et al. with mirror therapy on the Mirror Effect PLUS computer system [32], the group using this system had better results. Similarly, in a study with mirror therapy where the effect was verified using EMG, this group performed better [33].

This suggests that an early individual therapeutic programme in the form of mime muscle training with biofeedback promotes improved facial function and reduces the risk of adverse consequences. In contrast to early treatment of central paresis, active attempts at movement are prohibited during the paralytic phase in peripheral facial paresis. Here, passive measures (mobilisation, tactile stimulation, mental training, relaxation) are preferred. In most cases, electrical stimulation is not indicated in both types of paresis.

 

Innovative forms of facial nerve lesion rehabilitation using new technologies

In recent years, with the use of modern technologies, telerehabilitation has been developed, which can reduce time and financial costs and increase the efficiency of the rehabilitation process. Telerehabilitation uses a wide range of devices from conventional video calls and wearable electronics to robust rehabilitation systems. In a 2023 meta-analysis, Hao et al. reported that combining telerehabilitation with virtual reality can be an effective alternative to traditional rehabilitation for patients after stroke in terms of improving motor and cognitive function and overall quality of life [34]. Telerehabilitation has also been used, for example, in patients with aphasia [35], Parkinson's disease [36], MS [37] and to promote physical activity in neurological patients [38]. So far, only isolated pilot studies have appeared in the literature in the area of telerehabilitation of facial nerve lesions [39,40].

In cooperation between the Clinic of Rehabilitation Medicine of the 3rd Faculty of Medicine of Charles University and the Centre for Support of Application Outcomes and Spin-off Companies of the 1st Faculty of Medicine of Charles University, research and experimental development of the Rehamime telerehabilitation system, which enables virtual mirror therapy in the patients' home environment, is underway (Figure 1). This system combines methods of tactile stimulation, mental training, video therapy and mirror therapy with the possibility of online monitoring and individualised adjustment of therapy according to the patient's current condition (Fig. 2). A positive effect of this intervention has been observed in case studies (Figure 3). A randomized controlled trial is currently underway to objectively evaluate the efficacy.

 

Conclusion

The results of the studies published so far lean towards the use of mirroring and biofeedback therapies that work cortically and subcortically rather than peripherally.

For central paresis, it is important to start therapy 24 h after the onset of damage. In interdisciplinary therapy, we target facial symmetry, reduction of speech and swallowing disorders, drooling, and the ability to specifically control isolated muscle movements. With the help of coordination exercises, it is necessary to promote muscle function to prevent unwanted synkinesias. Targeted exercises guided by a therapist using biofeedback (mirror or EMG) not only improve facial expressive function but also reduce the risk of secondary impairment and restore quality of life in the psychosocial domain.

During the paralytic phase in peripheral facial paresis, we do not recommend active attempts at movement. On the contrary, passive exercises such as mobilisation, tactile stimulation and relaxation are fully indicated during this phase.

Even in the chronic phase, targeted therapy in both forms can alleviate consequences such as synkinesis, contractures or painful spasms. In addition to traditional treatments, modern technologies allow to improve the accessibility, intensity and effect of therapies with the possibility of remote control by a specialist. Further studies, preferably multicentre studies with a sufficient number of patients, are needed to improve the evidence base for therapeutic procedures.

Furthermore, we wanted to point out the inconsistency of approaches that are implemented without an evidence-based basis and the need to develop general recommendations for the rehabilitation of people with impaired facial muscle mobility, unifying assessment within interdisciplinary collaboration. These general recommendations, despite the significant epidemiology of this disorder, are still inconsistent and therapy is provided in a rather empirical manner.

 

Conflict of interest

The authors declare that they have no conflict of interest in relation to the subject of the study.