Paralysis of facial nerve emerges as a result of inflammation, surgery, infection, trauma and tumors. As a result, the patient has several cosmetic and functional defects. The patient is unable to use the facial muscles properly leading to inability to give proper expressions and may have defects such as twisted lips or dropping face etc. This leads to psychological and social distress, regardless of the condition being temporary or permanent, because the face and its expressions play a very important role in identifying one’s identity and persona.
Facial Nerve Decompression is recommended for patients having permanent facial palsy during which the facial nerve though intact but is compressed between the bones of the face and may be inflamed. This surgery helps in improving the cosmetic defect and maximizing functional recovery. Facial Nerve decompression is usually recommended after initial less invasive treatments have not yielded results.
Decompression is needed when the facial nerve is compressed anywhere along its way through the skull. This may occur due to injury, any kind of infection or Bell’s palsy. Decompressing the facial nerve might be done through one of three methodologies or a mix, where appropriate. These include the trans-mastoid, center fossa and trans-labyrinthine approaches.
Indications for Facial Nerve Decompression
Facial nerve Decompression is recommended when the patient has the following issues:
- Bell's palsy: This is a partial weakness or complete paralysis of the muscles of the face. There may be edema (swelling) of the facial nerve and marked vascular congestion. However, the exact cause behind the facial nerve compression is not known, and hence it is also called idiopathic Bell's palsy.
- Herpes zoster oticus: This is caused by viral infection. It is usually associated with herpetic eruption of the meatus and cavum conchae. During this infection, vertigo and deafness may also be seen. It is also called Ramsay Hunt Syndrome.
- Melkersson–Rosenthal syndrome: This syndrome is associated with recurring facial palsy and edema and usually occurs before 18 years of age.
- Skull fractures: More commonly longitudinal fracture of petrous bone and fracture of temporal bone can cause facial nerve compression.
- Birth injury: Use of forceps during the delivery can cause trauma to facial nerve. Compression of the diploic bone of the infant’s rudimentary mastoid process can compress facial nerve.
- Supportive otitis media: Edema and inflammation caused by this condition affect the facial canal and causes compression of facial nerve
- Parotid swelling: Abscess and tumors of parotid gland can cause compression of motor part of the facial nerve resulting in facial palsy.
- Tumors: Tumor of facial nerve like schwannomas and perineuromas. Other tumors which can compress facial nerve along its course like congenital cholesteatomas, parotid gland neoplasms, hemangiomas, acoustic neuromas, or metastases of other tumors.
- Other causes like viral, bacterial or fungal infections like chicken pox, streptococcal infection or candidiasis etc.
There are several medical tests to know that if the decompression surgery is needed or not and tests also shows the degree of injury.
- Nerve excitability test: In this test electrodes are situated over the main trunk and nerve is stimulated until the visual response is seen from the normal side and same is done for the diseased side. Then difference between the current required to produce response is measured. If it is more than 3.5mA then it suggests axonal degeneration. If it is more than 20 mA then it suggests immediate decompression surgery.
- Maximal stimulation test: In this test increasing electric stimulation to nerve is given until the facial twitch is seen then it is repeated to affected side. Difference between both sides are measured as equal, lesser or no response. It is very painful exam.
- Electroneurography: In this test electrodes are placed over the main trunk then supra threshold stimulus is given and muscle action potential is measured over the both side.
- Electromyography: In this test electrodes are directly placed in muscles and compound action potential of muscles is measured.
- Voluntary EMG: Useful in identifying a false positive Electroneurography. Presence of compound muscle action potential on voluntary EMG is a sign of good prognosis.
Transmastois Facial Nerve Decompression
In case the harm to the facial nerve is localized closer to the mastoid or tympanic segments of the nerve, then the trans-mastoid approach may additionally be used. The decompression is completed over 180 degrees of the nerve’s circumference. Essential surgical landmarks for this procedure are the digastric ridge (i.e. a ridge of bone, which is posterior to the facial nerve and medial to the tip of the mastoid), the fossa incudis and also the lateral semicircular canal. Throughout the method, the incus is also replaced by an interposition graft. This enables in-depth decompression of the nerve.
Middle Fossa And Trans-Labyrinthine Facial Nerve Decompression
The middle fossa approach is applied when the facial nerve injury extends to the labyrinthine segment of the nerve. In this process, the semicircular canal, bigger superficial petrosal nerve and also the vertical crest that separates the superior vestibular and facial nerves from one another, are all utilized as crucial surgical landmarks. The Middle fossa facial nerve decompression may be done alone or sometimes it may be combined with the trans-mastoid procedure when the temporal bone is involved. This mixture is especially useful in cases of trauma to the temporal bone. When there is intra-temporal facial nerve injury along with eventful impairment or loss of cochlea-vestibular function then a trans-labyrinthine decompression may be done.
As with any surgical treatment, there are few risks involved with the decompression of the facial nerve. These risks include and are not restricted to:
- Post-operative conductive and sensory hearing disorder
- Epidural bleeding
- Edema within the temporal lobe
- Dizziness may occur lasting for few weeks to some months
- Numbness of the ears
- Uncontrolled bleeding
- Temporary disturbance in taste
- Headaches and inadvertent injury to alternative cranial nerves.
Cost of Treatment Facial Nerve Decompression
The following are the primary factors that determine the cost involved in facial nerve decompression
- Hospital that patient chooses for his/her treatment
- Fees for the doctor/physician
- Cost of medicines and injections
- Cost of tests and diagnostic procedures
- Cost of surgery (if required)
- Cost of follow-up care