Vestibular tumor
Template:Vestibular tumor
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
Vestibular tumors are growths that tend to develop underneath the serous tissue of the sublinguinal region. They may be found anywhere between the chin and the larynx (or voicebox) and are not more inclined to one side of the body than the other. They are predominantly present in adolescent females though they are not directly related to any hygienal issues. While surgery is the most often cure, deaths rarely occur due to the existence of vestibular tumors.
Historical Perspective
The first reported case of a vestibular tumor was in 1898 in Lancaster, Pennsylvania. Though there have been stories of growths of the like of vestibular tumors, this was the first medically reported case. At the time, surgery was too dangerous, so Emilia Walfen was forced to live with the tumor, which eventually grew to the size of a Concord grape.
Pathogenesis
Recent studies in NF2 patients led to the identification of the neurofibromin 2 gene, which is located on chromosome 22. The NF2 gene produces merlin, also known as schwannomin, a cell membrane-related protein that acts as a tumor suppressor. Biallelic inactivation of the NF2 gene is found in most sporadic vestibular schwannomas.
Microscopic pathology
- Vestibular schwannomas arise from perineural elements of the Schwann cell.
- They occur with equal frequency on the superior and inferior branches of the vestibular nerve.
- Microscopically, zones of alternately dense and sparse cellularity, called Antoni A and B areas, respectively, are characteristic of vestibular schwannomas.
- Malignant degeneration is extremely rare, with only six cases having been reported.
- Immunohistochemical staining for S100 protein is usually positive in both the benign and the rare malignant forms of this tumor.
Risk Factors
Common risk factors for the development of vestibular schwaomas include:
- Childhood exposure to low-dose radiation for benign conditions of the head and neck
- Radiofrequency radiation from the use of mobile phones
- Noise exposure
Epidemiology and Demographics
Incidence
- The overall incidence of vestibular schwannomas is approximately 1 per 100,000 person-years in the United States.
- Bilateral vestibular schwannomas are primarily observed in patients with neurofibromatosis type 2 (NF2).
- The tumors are unilateral in more than 90 percent of cases, affecting the right and left sides with equal frequency.
Age
- The median age at diagnosis is approximately 50 years.
Gender
- Vestibular schwannomas occur equally in both genders.
Natural History, Complications, and Prognosis
Vestibular schwanama pose a major health impediment if left untreated as they might cause pressure on adjacent posterior fossa structures such as cerebellum or brainstem and result in ataxia Brainstem compression, cerebellar tonsil herniation, hydrocephalus, and death can occur in untreated cases. Common complication include seizures and paralysis difficulty swallowing due to the pressure on the tongue or pharynx. The functions of the lower cranial nerves can also become impaired, leading to dysarthria, dysphagia, aspiration, and hoarseness.
Diagnosis
History and Symptoms
- Symptoms associated with vestibular schwannoma can be due to cranial nerve involvement, cerebellar compression, or tumor progression. Clinical manifestations in this series included the following:
| Never involvement | Incidence | Symtpoms |
|---|---|---|
| Cochlear nerve | 95 percent |
|
| Vestibular nerve | 61 percent |
|
| Trigeminal nerve | 17 percent |
|
| Facial nerve | 6 percent |
|
| Tumor progression |
|
Physical Examination
- Hearing tests are typically abnormal due to involvement of the acoustic nerve.
- The Weber and Rinne tests may be useful in suggesting asymmetric sensorineural hearing impairment.
- Neurologic examination may reveal other cranial nerve deficits
- A decreased or absent ipsilateral corneal reflex and facial twitching or hypesthesia may occur as cranial nerves V and VII become affected.
- Romberg, Hall-Pike, and other common office balance tests are typically normal.
Treatment
Surgery and Device Based Therapy
Surgery is most often the decision made by the patients and it is rather affordable though if not treated may lead to life-long problems.