Intralabyrinthine schwannoma

Intralabyrinthine schwannoma

Intralabyrinthine schwannoma or primary inner ear schwannoma (PIES) is a tumour that originates in the inner ear. The importance is that this tumour has up till now been underdiagnosed, even missed in some cases, in South Africa. Although it is considered benign it causes a lot of problems.

Intralabyrinthine schwannoma
A magnetic resonance image (MRI) of a cochlear schwannoma (yellow arrow).

Hearing loss is very common and occurs in nearly all patients with intralabyrinthine schwannoma.  In 2013, a large literature review of 234 patients reported a 99% rate of hearing loss. Hearing loss may be progressive or sudden.

Disequilibrium and balance disorders are more common than vertigo (a sensation of motion) which occurs in 60% of patients. Tinnitus is nearly universally present and it is therefore not strange for PIES to mimic Meniere’s Disease (MD).

Vestibular schwannomas (VS) are the most common observed abnormality seen on magnetic resonance imaging (MRI) in patients who present with sudden sensori neural hearing loss (SSNHL). It is found that 4,5% of patients with SSNHL has a vestibular schwannoma and that an intralabyrinthine schwannoma represent 10% of all temporal bone schwannomas. 50% of these tumours will actually grow. They can originate in different parts of the inner ear and may spread outside the inner ear.

Primary inner ear schwannoma
Intraoperative image of a intralabyrinthine  schwannoma  a) Lateral semicircular canal. b) Superior semicircular canal

MRI of the inner ear is the examination of choice and administration of gadolinium (intravenous contrast injection) is obligatory, otherwise it may be missed.
Regarding the management of these tumours they may be observed or removed with microsurgery, depending on the circumstances. Radiotherapy is indicated to a lesser degree than microsurgery.

Cochlear implantation (CI) can restore hearing in some cases if the cochlear nerve is intact. For those patients with no hearing a CI can often be performed at the same time that the tumour is removed.

It should be emphasized that MRI with gadolinium contrast administration is indicated in all patients with unexplained sensorineural hearing loss (SNHL) and asymmetrical mixed hearing loss.