Conservative Management of Acoustic Neuromas

What is the Required Frequency of MRI Scanning in the Wait and Scan Management?

The wait and scan policy is being increasingly used as the first measure after the diagnosis of a vestibular schwannoma (VS) using magnetic resonance imaging (MRI). As part of the European Academy of Otology and Neuro-Otology (EAONO) position statement on VS, the frequency of imaging has been studied in the literature. Among 163 studies, 29 fulfilled the inclusion criteria and were scored using the Grading of Recommendations, Assessment, Development, and Evaluation system. Because tumor growth rate during the first 5 years of follow-up is predictive of further growth during the upcoming years, a protocol for wait and scan is useful for centers dealing with this condition. The EAONO proposal is that after the initial diagnosis by MRI, a first new MRI would take place after 6 months, annually for 5 years, and then every other year for 4 years, followed by a lifelong MRI follow-up every 5 years. The first early MRI is to screen for fast-growing tumors, and the lifelong follow-up with tapered intervals is to detect late repeated growth.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

Growth of untreated vestibular schwannoma: a prospective study

Object

Small vestibular schwannomas (VSs) are often conservatively managed and treated only upon growth. Growth is usually reported in mm/year, but describing the growth of a 3D structure by a single diameter has been questioned. As a result, VS growth dynamics should be further investigated. In addition, baseline clinical parameters that could predict growth would be helpful. In this prospective study the authors aimed to describe growth dynamics in a cohort of conservatively managed VSs. They also compared different growth models and evaluated the ability of baseline parameters to predict future growth.

Methods

Between 2000 and 2006, 178 consecutive patients with unilateral de novo small-sized VSs identified among the Norwegian population of 4.8 million persons were referred to a tertiary care center and were included in a study protocol of conservative management. Tumor size was defined by MR imaging–based volume estimates and was recorded along with clinical data at regular visits. Mixed-effects models were used to analyze the relationships between observations. Three growth models were compared using statistical diagnostic tests: a mm/year–based model, a cm3/year–based model, and a volume doubling time (VDT)-based model. A receiver operating characteristic curve analysis was used to determine a cutoff for the VDT-based model for distinguishing growing and nongrowing tumors.

Results

A mean growth rate corresponding to a VDT of 4.40 years (95% CI 3.49–5.95) was found. Other growth models in this study revealed mean growth rates of 0.66 mm/year (95% CI 0.47–0.86) and 0.19 cm3/year (95% CI 0.12–0.26). Volume doubling time was found to be the most realistic growth model. All baseline variables had p values > 0.09 for predicting growth.

Conclusions

Based on the actual measurements, VDT was the most correct way to describe VS growth. The authors found that a cutoff of 5.22 years provided the best value to distinguish growing from nongrowing tumors. None of the investigated baseline predictors were usable as predictors of growth.

Epidemiology and natural history of vestibular schwannomas

This article describes various epidemiologic trends for vestibular schwannomas over the last 35 years, including a brief note on terminology. Additionally, it provides information on the natural history of tumor growth and hearing level following the diagnosis of a vestibular schwannoma. A treatment strategy based on the natural history of tumor growth and hearing also is discussed.