Tumors can affect the facial nerve in a number of ways. Brain tumors in the posterior fossa of the skull, such as medulloblastomas, arise very close to the nucleus, or the origin, of the facial nerve in the brainstem. Compression in this area by such a tumor can cause complete facial paralysis. More commonly, surgery to remove such a brain tumor can result in collateral damage. For many patients, the need to obtain negative tumor margins must outweigh the need to preserve facial nerve activity.
Tumors can also arise anywhere along the path of the facial nerve. An acoustic neuroma is a benign tumor that arises from the lining of nerves, most often the eighth cranial nerve, or the vestibulocochlear nerve. The supportive cells that line all nerves (Schwann cells) are responsible for nourishing the underlying nerve and provide it with the proper chemical balance to transmit signals. When these cells overgrow in a tumor-like fashion, they can compress the adjacent facial nerve and brainstem. Also, in the process of removing the tumor, damage can be sustained to the facial nerve, thereby manifesting as complete facial paralysis.
The parotid gland is the largest salivary gland in the face. It sits in front of the ear as a heart-shaped structure and passes down and around the earlobe region. The facial nerve is intimately associated with the parotid gland. As the nerve exits the skull behind the ear and in front of the mastoid bone, it begins to pass through the parotid gland. It will then arborize within the gland and exit as the main branches of the facial nerve as they move towards their target muscles. The parotid gland can be a source of tumors that can, in turn, have an impact on the facial nerve. Pleomorphic adenoma is the most common parotid tumor and typically presents as a painless swelling near the border of the jaw and in front of the ear. The differential diagnosis can include malignancies such as adenoid cystic carcinoma or adenocarcinoma and inflammation of the gland, called parotitis. Surgical excision is the treatment of choice for all tumors of the parotid gland. This is known as a parotidectomy and is typically performed by an otolaryngologist. However, in a small percentage of cases, removal of the tumor can result in damage to the facial nerve or its branches. This is typically evident immediately at the end of surgery.
Vascular birthmarks or anomalies consist of mostly benign tumors and malformations. Vascular tumors such as infiltrative hemangiomas and Kaposiform hemangioendotheliomas (KHE) can also produce facial nerve problems, most frequently in relation to surgical excision. In many cases, vascular tumors will naturally or with medication go on to involute or disappear with time. Although not technically classified as tumors, vascular malformations can be present at birth and continue to expand over a lifetime. Lymphatic malformations (lymphangioma or cystic hygroma), venous malformations, and arteriovenous malformations (AVM) can cause facial nerve dysfunction through inflammation. Although this can be temporary and frequently resolves with non-steroidal anti-inflammatory medications such as ibuprofen, permanent damage can occur with attempts at surgical excision.
Neurofibromatosis is a unique genetic disorder that can affect any nerve tissue in the body. Tumors form on nerves and can be quite large in some cases. Although the majority of neurofibromas are benign, they can grow large and create significant disfigurement or life-threatening symptoms such as brain compression. Treatment is aimed at controlling the symptoms of growth. Surgical excision is still the preferred option for addressing these tumors. However, when they occur in the face, they can result in significant deformity and a risk of damage to the facial nerve. The Facial Paralysis Center’s neurologists are leaders in the treatment of neurofibromatosis. Contouring procedures are combined with facial nerve exploration. In the event of tumor involvement of the facial nerve, the team is ready to address the resulting facial paralysis in an early fashion.
Dr. Panossian is an expert in the surgical exploration and repair of the facial nerve and is often requested for management of facial nerve injuries resulting from removal of tumors. He is also an expert in vascular anomalies and neurofibromatosis. Contact the Facial Paralysis Center today to discuss your options.