Elevation of Internal Auditory Canal Pressure by Vestibular Schwannomas

Abstract

Pressure on the cochlear nerve as a result of tumor growth in the internal auditory canal may be responsible for hearing loss in patients with vestibular schwannomas. Modification of surgical techniques to address the elevated intracanalicular pressure may be beneficial in improving hearing preservation in these patients.

Hearing in Patients with Intracanalicular Vestibular Schwannomas

“…This assumption is supported by a study of 20 patients with both an intra-and extrameatal tumor component, as the wave V latency in measuring auditory evoked potentials correlated with the pressure in the IAC, as measured during surgery through the retrosigmoid approach [Lapsiwala et al, 2002]. However, Badie et al [2001] found that the IAC pressure correlated with the amount of tumor in the IAC in 15 patients, but could not document a significant relation between the pressure and hearing function , and Nadol et al [1996], observed no correlation between lateral extent of IAC invasion and PTA/SRT scores in 75 patients. In addition, Odabassi et al [2002] showed that the extent of IAC involvement was not related to the negative effects of the tumor on cochlear function as represented by DPOAEs.…”

Radiological factors related to pre-operative hearing levels in patients with vestibular schwannomas

“…The mean period of time between diagnosis and treatment was 37.11 ± 4.4 months. About 69% of patients reported their initial symptom as being a hearing deficit, followed by 25.3% with tinnitus, 16 …”

The role of the trigeminocardiac reflex in postoperative hearing function in non-vestibular schwannoma cerebellopontine angle tumors

“…However, mechanical injury to the cochlear nerve, increased IAC pressure and/or vascular injury to the auditory apparatus have been proposed for tumorinduced hearing loss. 18,19 Elevation of intrameatal pressure has also been directly correlated to the extent of VS invasion into the IAC. 18,19 However, non-VS tumors usually do not arise within the IAC but spread into the IAC secondarily.…”

“…18,19 Elevation of intrameatal pressure has also been directly correlated to the extent of VS invasion into the IAC. 18,19 However, non-VS tumors usually do not arise within the IAC but spread into the IAC secondarily. More specifically, CPA meningiomas that arise from the dural margin of the IAC are associated with a reduced quality of postoperative auditory function compared to other CPA meningiomas that spread secondarily into the IAC.…”