Abstract
Objective
To date, the majority of the vestibular schwannoma (VS) literature has focused on tumor control rates, facial nerve function and hearing preservation. Other factors that have been shown to significantly affect quality-of-life (QOL), such as dizziness, remain understudied. The primary objective of the current study is to investigate the association between radiation dose to the vestibule and post-treatment changes in vestibular function and patient reported dizziness handicap.
Materials and methods
This is a prospective observational pilot study at a tertiary academic referral center including all subjects that underwent linear accelerator-based stereotactic radiotherapy (SRS) for sporadic VS and completed pre-treatment and post-treatment vestibular testing and Dizziness Handicap Inventory (DHI) questionnaires. Associations between objective vestibular test results, patient-reported DHI scores and radiation dose parameters were investigated.
Results
Ten patients met inclusion criteria. Tumor control was achieved in all individuals. There were no statistically significant associations or identifiable trends between radiation dose and change in vestibular function or DHI scores. Notably, the four ears receiving the highest vestibular dose had minimal changes in vestibular function tests and DHI scores.
Conclusions
To the best of our knowledge, no previous reports have described the association between radiation dose to the vestibule and post-treatment changes in vestibular function and patient reported DHI. Based on these preliminary data, radiation dose to the vestibule does not reliably predict change in objective or subjective vestibular outcome measures.
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Introduction
Vestibular schwannomas (VS), also known as acoustic neuromas, are slow growing benign tumor arising from the vestibular component of the eighth cranial nerve. Collectively they account for 8% of all intracranial tumors and approximately 90% of cerebellopontine angle (CPA) lesions . The majority of patients present with gradual unilateral hearing loss, tinnitus, and imbalance; with progressive growth, trigeminal neuropathy, facial palsy and hydrocephalus may ensue. Given the increased availability of high-resolution computed tomography (CT) and magnetic resonance imaging (MRI), over the last several decades we have witnessed a significant increase in disease prevalence with a greater proportion of patients presenting with small tumors and less severe symptoms .
Current management options include microsurgery, radiation therapy in the form of fractionated stereotactic radiotherapy (FSRT) and single fraction stereotactic radiosurgery (SRS), and observation with serial imaging . Over the past 20 years we have seen a significant evolution of SRS/FSRT treatment strategies aimed at minimizing collateral radiation injury and optimizing tumor control . In particular, there has been a growing interest in improving dosimetric parameters in order to reduce treatment associated facial neuropathy and hearing loss . Several reports have demonstrated a strong inverse association between cochlear dose and early post-treatment hearing preservation .
To date, the overwhelming majority of the VS literature has focused on tumor control, facial nerve function and hearing preservation, while other factors that have been shown to significantly affect quality-of-life (QOL), such as dizziness, remain understudied . As we continue to optimize radiation treatment planning techniques in order to improve functional outcomes, it may be important to consider specific dose parameters to the vestibule. The primary aim of the current study is to determine the influence of radiation dose to the vestibule on change in balance function and patient reported dizziness handicap following treatment.
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