Causes of vestibular schwannoma
Vestibular schwannoma (VS), also known as acoustic neuroma, is a benign tumour that develops on the vestibulocochlear nerve, which is responsible for transmitting sound and balance information from the inner ear to the brain. The exact cause of vestibular schwannomas is poorly understood but is believed to be linked to a genetic mutation or environmental factors.
Chromosome 22
In most cases, vestibular schwannomas are sporadic, occurring randomly without a clear cause. However, recent research has shown that a small percentage of cases are associated with a mutation in the tumour suppressor gene on chromosome 22.
The tumour suppressor gene on chromosome 22, also known as NF2 (neurofibromatosis type 2), is crucial in regulating cell growth and division. When a mutation occurs in this gene, it can lead to uncontrolled cell growth and the formation of tumours, including vestibular schwannomas (1).
Family history
While 95% of vestibular schwannomas occurs sporadically without any known cause, some rare genetic conditions have been linked to an increased risk of developing these tumours. One of these conditions is neurofibromatosis type 2 (NF2), a genetic disorder that causes the growth of tumours on nerves throughout the body, including the vestibular nerve.
NF2 is an inherited condition, meaning that it runs in families. Individuals with a family history of NF2 are at higher risk of developing vestibular schwannomas and other nerve tumours. Genetic testing and counselling may be recommended in these cases to assess the risk of developing vestibular schwannoma and other associated conditions (2).
Cell phones
Numerous studies have investigated the potential connection between cell phones and VS, but the results have been inconclusive. The World Health Organization’s International Agency for Research on Cancer conducted a comprehensive study on this topic. It concluded that there is no clear evidence to suggest that cell phone use causes vestibular schwannomas.
In the COSMOS prospective cohort multinational study, 264,574 participants were followed, accruing to 1,836,479 person-years (3). The findings suggest that the cumulative amount of mobile phone use is not associated with the risk of vestibular schwannoma.
On the contrary, cell phones make it easy for individuals to recognize issues with their hearing and seek proper medical attention, ultimately leading to early diagnosis and treatment of hearing loss.
Prolonged noise exposure
While exposure to loud noises can cause damage to the inner ear and potentially lead to hearing loss, there is no scientific evidence to support the claim that it can cause vestibular schwannoma.
In the most extensive case-control study in Norway using 1913 vestibular schwannoma patients and 9566 age and sex-matched control, no association between loud noise exposure and the development of vestibular schwannoma was found (4).
In another case-control study from Denmark, no association between traffic noise exposure and the development of vestibular schwannoma was found (5).
Childhood exposure to low-dose radiation of the head and neck
There has been ongoing concern regarding the potential link between childhood exposure to low-dose radiation of the head and neck and the development of VS.
Studies have shown that the majority of VS occur sporadically, with only a tiny percentage being associated with a genetic predisposition or exposure to high-dose radiation, such as that used in specific medical treatments. Low-dose radiation, such as that received during routine medical imaging or from environmental sources, is not believed to impact VS development significantly (6).
The current scientific consensus suggests that childhood exposure to low-dose radiation is not a significant risk factor for the development of VS.
Benign tumours of the parathyroid gland
Benign tumours of the parathyroid gland in the neck, known as parathyroid adenomas, are commonly associated with an overproduction of parathyroid hormone (PTH), leading to hyperparathyroidism. Some studies have suggested a possible association between hyperparathyroidism and an increased risk of developing VS, but further research is needed to confirm this link(7). There is limited evidence linking parathyroid adenomas to the development of VS.
Smoking
Several studies have suggested that cigarette smoking may have a protective effect against the development of VS(8).However, the increased risk of developing other malignancies associated with smoking, such as lung cancer and heart disease, far outweighs any potential benefits for VS. Therefore, it is not advisable to encourage smoking as a means of protection against this specific type of tumour due to the myriad of other health risks associated with smoking. It is important to prioritize overall health and well-being when making lifestyle choices.
Aspirin
Aspirin has been suggested to have a potential protective effect against the development of VS. While there is not enough evidence to recommend aspirin as a therapy for patients with VS currently, studies have shown that aspirin may act as a negative risk factor for the development of sporadic VS. This suggests that aspirin could potentially help prevent the formation of these tumors. Further research is needed to fully understand the mechanisms behind this potential protective benefit and to determine if aspirin could be used as a preventive measure for VS(9).
Viruses
While viruses have been shown to be a cause of approximately 15% of all cancers, no direct relationship has been established between viruses and VS. Research on the possible viral involvement in VS is limited, and further studies are needed to determine any potential links between viruses and this type of tumour. (10).
Pregnancy and hormonal contraceptives in vestibular schwannoma
There is currently not enough evidence to support pregnancy and hormonal contraceptives as a cause of the formation of vestibular schwannoma.
Hormones may play a role in the growth of vestibular schwannoma, especially in patients with Neurofibromatosis type 2 (NF2).
References
3.M, Schüz J, Toledano MB, Vermeulen R, Auvinen A, Harbo Poulsen A, Deltour I, Smith RB, Heller J, Kromhout H, Huss A, Johansen C, Tettamanti G, Elliott P. Mobile phone use and brain tumour risk – COSMOS, a prospective cohort study. Environ Int. 2024 Mar;185:108552. doi: 10.1016/j.envint.2024.108552. Epub 2024 Mar 2. PMID: 38458118.