Patients with a vestibular schwannoma and good hearing are often advised to observe the tumour. A strategy of watchful waiting with follow-up magnetic resonance imaging (MRI) is then suggested.

Hearing loss in non-growing vestibular schwannoma

A vestibular schwannoma may present with normal hearing

This option is considered in the light that a number of vestibular schwannomas, when discovered, may not grow.

An intervention at this stage, especially with larger tumours, whether surgery or radiation may cause hearing loss and even total deafness. Another consideration is that functional hearing may be retained for some time in patients with growing tumours. Those with partial hearing loss may benefit with a hearing aid.

Research however have shown that if the natural course of hearing in patients with non-growing vestibular schwannomas are investigated it seems that the hearing declines more rapidly in the vestibular schwannoma ear than in the non-affected ear. The exact mechanism for this phenomenon is not known but it is believed that the non- growing vestibular schwannoma may secrete proteins that acts as toxins to the inner ear, causing hearing loss. This is true for pure tone averages as well as speech discrimination scores.

Speech discrimination

Normal (100%) speech discrimination in the right (red) and left (blue) ear

It is really important that a speech discrimination test is always done as part of the hearing assessment. Even the slightest deterioration in speech discrimination may be a significant indicator for the development of significant hearing loss.

On the other hand, a pre-operative speech discrimination score of 100% may indicate a good outcome regarding hearing preservation with middle cranial fossa surgical removal of the tumour. It is generally easier to preserve hearing during surgery if the tumour is smaller. If a vestibular schwannoma is allowed to reach a larger size in the attempt to retain some hearing, the final outcome and possibility of a cochlear implantation may be compromised.

If you are diagnosed with a suspected vestibular schwannoma make sure that speech discrimination is performed as part of your hearing assessment, before any decisions regarding management are taken. Hearing can still deteriorate even if the tumour does not grow.