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Audiovestibular Morbidity


Summary By: Lori Davila
Date: June 13, 2014


The 'Mechanisms of Hearing Loss in Neurofibromatosis Type 2' is a report which is part of the findings in the National Institute of Health's NF2 Natural History Study, was data reviewed to determine complete hearing loss for individuals with NF2 as a result of:

  • dramatically different Schwannomas tumor sizes along the Vestibulocochlear Nerve (CN8), these tumors are more commonly known as Vestibular Schwannoma (VS) but referred to in the report as Cochleovestibular Schwannomas (CSV)
  • a tumor so small it may not even show up on an MRI
  • or why hearing loss progression can be either sudden, gradual or can be lost and returned before finally complete loss
  • an attempt to understand why Avastin helped some individuals and not others

A theory of the cause was proposed and might help determine ears at risk for hearing loss as a result of VS for individuals with NF2 who still have some hearing.

In MRI's patient scans were reviewed, not just after Gadolinium contrast was injected but before as well. While Gadolinium was helpful to see the sizes of tumors, before contrast the flow of fluid in the Cochlear could be seen using an additional imaging method of Fluid Attenuated Inversion Recovery (FLAIR).

The conclusion was that it is definitely not just tumor size around the nerve alone that causes disrupt the communication of sound from the ear to the brain that causes hearing loss, but can be from smaller tumors in the Cochlear Nerve or Vestibulocochlear Nerve, however it can also be the result of an abnormal amount of fluid in the Cochlear. Additionally, in the case of Avastin, hearing returned is not always a result of tumor size but a change in the fluid in the Cochlear as well.

While the exact cause of the fluid obstruction was not identified or at least not mentioned, this reports identification of additional reasons is hearing loss can help to at least be used to identify potential hearing loss sooner and determine if an individual on Avastin has a chance at retaining hearing sooner so an individual can be suggested to try a different treatment that might save what is left of hearing quickly.

Source

Asthagiri, A. R., Vasquez, R. A., Butman, J. A., Wu, T., Morgan, K., Brewer, C. C., ... & Lonser, R. R. "Mechanisms of hearing loss in neurofibromatosis type 2." PloS one, 7(9), e46132. (2012)
Source: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0046132 | DOI: 10.1371/journal.pone.0046132