Reanimation from the paralyzed face: Causes of facial paralysis

Causes of Facial Paralysis

The etiologies of facial paralysis are very varied. Intracranial causes include congenital abnormalities, malignancies, degenerative diseases, trauma, vascular conditions along with other rare causes. Intratemporal causes include malignancy, trauma, infections, Bell's palsy, osteopetrosis and iatrogenic causes.

Extracranial causes include malignancies (parotid gland as well as tumors of adjacent structures), trauma and iatrogenic injury. Bell's palsy, or idiopathic facial nerve palsy, is the most common cause of facial nerve paralysis despite the fact that 85% of people with Bell's palsy will recover spontaneously.

Several important physical finding can help to tell apart intracranial (upper motor neuron) from extracranial causes of facial paralysis. Both supranuclear areas provide contributions to the frontal and upper orbicularis occuli muscles. Therefore, these muscles might be partially spared if the etiology is intracranial, creating an ipsilateral "lower face" paralysis.

In addition, during periods of intense emotion, facial movements can happen on the affected side. You should remember that the extracranial facial nerve is really a purely motor nerve; therefore extracranial paralysis shouldn't involve decreased lacrimation (superficial petrosal nerve), changes in hearing (nerve to stapedius) or changes in taste (chorda tympani).

Preoperative Planning

It is important to evaluate the patient carefully, in order to look for the cause and extent of paralysis and the status of the muscles involved. A history is obtained, focusing on the onset and duration of weakness. A complete physical exam of the neck and head including a cranial nerve exam is performed. The muscles of facial expression are evaluated for bulk, symmetry and function-both statically and dynamically.

In addition, electrical testing is conducted to determine the physiologic status from the facial nerve branches and also the muscles from the face. Such tests, however, aren't entirely accurate and tend to overestimate the extent of functional loss. High res helical CT is of value in localizing the precise site of pathology.

Long-standing paralysis (greater than 2-3 years) will result in atrophy and fibrosis of the facial muscles and the inability to regain function purely by reinnervation. In these cases a muscle transposition or transplant procedure is required. The goal of the individual is essential to consider. Older patients might be content with achieving static facial symmetry resting, whereas younger patients usually desire a dynamic repair that will allow them to smile.

Direct Nerve Repair

This is actually the most effective process of reanimating the paralyzed face. It is contingent on the adequate function from the target muscles. One should not attempt to restore function to some muscle that continues to be paralyzed for over 3 years solely by reinnervating it. In the past, many surgeons advocated waiting a minimum of 3 weeks just before nerve repair. It's now known that immediate repair of the injured facial nerve yields the best results. In direct nerve repair, an attempt is built to align the fascicles.

Once proper orientation of these two stumps is achieved, the perineurium is sewn together followed by the epineurium using 9-0 silk. Smaller nerves in the distal branches can be repaired having a single full-thickness suture. If the stumps from the nerve have a neuroma or appear crushed, the nerve ends should be "freshened" until normal appearing nerve can be seen. Direct repair should be undertaken only when a tension free repair can be done. Outcomes are directly correlated to the age of the individual, with younger patients faring far better than older ones.

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