Facial Reanimation

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Introduction

Facial paralysis presents a complex challenge to the reconstructive surgeon. Since Sir Charles Bell first described the course of the facial nerve in 1821, our understanding has led to the development of the vast array of surgical options used to treat patients with facial paralysis.

Sir Harold Gillies stated in 1919 that the aim of surgical reconstruction is to restore the normal form; this primarily aims to preserve function and then subsequently address the esthetics. The fundamental problem when considering facial paralysis is that there is currently no conceivable way to restore the 17 muscles of facial expression successfully. The second challenge facing the surgeon is that no patient is the same as another. Not only the etiology behind facial paralysis dictates which operations are available, the age group, the anatomy available and, most importantly, what the patient wants all make the decision-making process vital.

The presentation of facial nerve paralysis also adds to the conundrum, ranging from an isolated marginal branch palsy to a complete bilateral palsy. The approach to the management of any patient with facial paralysis should be to break the face down into three units: the forehead, the eyes, and the mid- and lower face. In a young child, the skin quality is far superior to that of an elderly patient and thus problems encountered are different to the adult population. Frequently, there is minimal asymmetry at rest and therefore focus needs to be directed at restoring dynamic function. In the elderly patient, skin elasticity is poorer and asymmetry at rest may be strikingly obvious and static treatment options may yield the desired outcome.

What is the importance of facial palsy reconstruction? This is not cancer surgery and patient survival is not the main outcome being measured. The impact facial paralysis has on an individual can be devastating and can be broken down into functional and psychological factors. If a patient is unable to close their eye and the cornea is insensate, the globe will dry leading to ulceration and ultimately blindness. Diminished oral continence and poor speech are other functional problems encountered. A child who is unable to smile or convey emotion effectively may be subject to bullying and psychological trauma and an adult with profound asymmetry at rest make be mistaken for being angry by another individual, causing the patient to become socially reclusive. ^,

The aim of this chapter is to give the reader a strategy on how to tackle facial paralysis. The anatomy of the facial nerve and other important structures of the face will be reviewed as this provides the foundation on which the evolution of surgical techniques have been based. The information provided should enable a surgeon to have a methodical approach to patient management; however, it must be stressed that the information should be used as a guideline and that each patient will require a customized approach to a greater or lesser extent. This makes facial palsy surgery one of the most fascinating and challenging aspects of reconstructive surgery; not only are the technical aspects pushing the limits of modern surgery but the decision-making process is equally as difficult and one must select the correct tools from the surgeon’s vast armamentarium to complete the task at hand. To the reconstructive surgeon it combines the epitome of what we seek to achieve: a functional outcome in which one has to consider the esthetic result, as the face is the center of human interaction.

Anatomy of the Facial Nerve

The facial nerve develops embryologically from the second pharyngeal branchial arch, the hyoid arch. The motor division derives from the basal plate of the embryonic pons whilst the sensory division arises from the cranial neural crest. The sensory portion, known as the intermediate nerve, is responsible for supplying taste to the anterior two-thirds of the tongue, secretory and vasomotor fibres to the lacrimal, submandibular, and sublingual glands, the mucous membranes of the nose and mouth, and finally, sensation over the external auditory meatus and posterior skin of the ear. The cortical fibers of the facial nerve arise from the lower third of the motor cortex, passing through the internal capsule and the middle third of the cerebral peduncle to supply the seventh nucleus in the lower pons and is closely related to the abducens and vestobulocochlear nerves. Of clinical importance, the supranuclear innervation is bilateral to the muscles of the forehead and eyes, but only contralateral to the muscles of the lower face; this accounts for the sparing of the forehead muscles in cases of supranuclear lesions in comparison to nuclear or infranuclear lesions. The course of the nerve can be simply divided as follows.

Anatomy of Potential Donor Nerves for Facial Reanimation

Whilst discussing the anatomy of the facial nerve it is worth spending some time to consider other local nerves of the face. Frequently, another donor nerve is required when either there is absence of a functioning facial nerve or if it is inappropriate to consider its use. Here, three other potential donor nerves will be considered.

Vascular Supply of the Face

The arterial supply of the face is predominantly via branches of the external carotid artery and the ophthalmic artery. The ophthalmic artery branches to give rise to the supraorbital and supratrochlear arteries to supply the forehead. Consideration here will be given to the branches that arise from the external carotid artery as these are of more practical use when free muscle transfer is proposed. The three main facial arteries most suitable for arterial anastomosis are the facial artery, the superficial temporal artery, and the transverse facial artery.

The facial artery arises in the carotid triangle just distally to the lingual artery behind the ramus of the mandible. It passes deep to the digastric and stylohyoid muscles and along the posterior border of the submandibular gland, superficial to the hypoglossal nerve. At the point of the anteroinferior angle of the masseter it crosses over the body of the mandible and proceeds tortuously towards the angle of the mouth. In the face it branches to give rise to the inferior and superior labial arteries and terminates as the angular artery and the lateral nasal artery.

The superficial temporal artery arises from the external carotid artery when it bifurcates to also give rise to the maxillary artery. The superficial temporal artery originates at the level of the parotid gland behind the neck of the mandible. It then courses cranially just anterior to the tragus, crossing superficially to the zygomatic process, and is covered by the auricularis anterior muscle and a dense fascia. The temporal and zygomatic branches of the facial nerve cross the artery and it is accompanied closely by the auriculotemporal nerve, which lies immediately posteriorly. It terminates by branching to form the parietal and frontal arteries.

The transverse facial artery arises from the superficial temporal artery before it emerges from the parotid gland. It travels transversely across the face, running between the zygomatic arch superiorly and the parotid duct inferiorly superficial to the masseter muscle.

When planning free functional muscle transfer good knowledge of the vascular supply is critical. Facial anatomy is by no means consistent and frequently secondary options are required ; in some cases even direct end-to-side anastomosis to the external carotid artery may have to be considered to prevent flap failure. Preoperative assessment with a Doppler can offer the surgeon some reassurance.

Etiology of Facial Paralysis