A vestibular schwannoma—historically referred to as an acoustic neuroma—is a benign, typically slow-growing neoplasm arising from Schwann cells of the vestibular division of the eighth cranial nerve (vestibulocochlear nerve). The term “acoustic neuroma” remains widely used, although it is anatomically imprecise: the tumor originates from the vestibular rather than the cochlear component of cranial nerve VIII.
Vestibular schwannomas are the most common tumors of the internal auditory canal and cerebellopontine angle, accounting for approximately 80% of neoplasms in this region. Histologically, they are classified as WHO grade 1 tumors and are therefore benign, without malignant transformation in the usual clinical course.
The reported incidence is approximately 1–1.5 cases per 100,000 population per year, with peak presentation between the fourth and sixth decades of life. Men and women are affected with approximately equal frequency. Tumor growth is generally slow, averaging 1–2 mm per year; in approximately 40% of patients, no measurable growth is observed during follow-up.
Most vestibular schwannomas occur sporadically. Bilateral vestibular schwannomas are characteristic of neurofibromatosis type 2 (NF2), a hereditary tumor-predisposition syndrome in which tumors frequently present at a younger age.
The clinically established Koos classification stratifies vestibular schwannomas into four stages according to tumor size and their anatomical relationship to adjacent structures:
Symptoms result primarily from progressive compression or impairment of cranial nerves and adjacent structures within the internal auditory canal and cerebellopontine angle. The severity of clinical symptoms often, although not invariably, correlates with tumor size.
The diagnosis of vestibular schwannoma is primarily imaging-based. High-resolution MRI combined with comprehensive audiological assessment enables accurate tumor characterization and staging and provides the basis for individualized treatment planning. Contrast Enhanced MRI of the Brain and Internal Auditory Canals – Imaging
Particularly important when bilateral disease is suspected, including evaluation for NF2-associated vestibular schwannomas.
Stereotactic radiosurgery is an established treatment modality for appropriately selected Koos I–III vestibular schwannomas, supported by more than three decades of clinical experience and extensive long-term outcome data. At ERCM, two complementary radiosurgical platforms are used to enable highly individualized, high-precision treatment planning and delivery.
ZAP-X was specifically developed for intracranial stereotactic radiosurgery. Its gyroscopic architecture enables irradiation from a broad range of non-coplanar beam angles distributed around the patient’s head without conventional gantry rotation. This permits highly conformal dose delivery to the target with a steep dose gradient toward adjacent critical structures, including the facial nerve, cochlea/cochlear nerve region, and brainstem.
A recent comparative study evaluating stereotactic radiosurgery versus active surveillance demonstrated superior tumor control with comparable hearing-preservation outcomes and a lower risk of neurological or functional deterioration. These findings further support the safety and efficacy of radiosurgery in appropriately selected patients with vestibular schwannoma.
In the clinical example shown on the original ERCM webpage, CyberKnife radiosurgery not only achieved cessation of tumor growth but was followed by a marked reduction in tumor volume over time. On subsequent follow-up imaging, the residual mass became barely discernible.
Further information on radiosurgery and patient experiences is available through the German patient organization Vereinigung Akustikus Neurinom e.V.
In the case shown, the CyberKnife treatment (image on the left) not only stopped the tumor's growth, but the acoustic neuroma also became noticeably smaller over time (middle image).
In the further course (image on the right), the mass is barely visible anymore.
The two terms refer to the same tumor. “Acoustic neuroma” is the traditional and widely recognized term, whereas “vestibular schwannoma” is anatomically and histopathologically more precise. The tumor arises from Schwann cells of the vestibular division of cranial nerve VIII rather than from the cochlear nerve.
Large clinical series report long-term tumor control rates of approximately 93–97% at 10 years. Facial nerve function is preserved in more than 97% of patients. In patients with useful hearing before treatment, serviceable hearing can be maintained in approximately 50–70% of cases. Outcomes depend on tumor size, baseline hearing, radiation dose, follow-up duration and
patient-specific factors.
A transient increase in tumor volume—often termed pseudoprogression or transient post-treatment swelling—is a recognized radiological response during the first 1–2 years after radiosurgery and has been reported in approximately 30–50% of patients. It may reflect treatment-related edema, intratumoral change and necrosis and does not, by itself, indicate treatment failure. Persistent serial growth beyond the expected post-treatment interval requires careful multidisciplinary reassessment.
NF2 is a rare hereditary tumor-predisposition syndrome associated with pathogenic alterations involving the NF2 gene on chromosome 22. Bilateral vestibular schwannomas are a hallmark of the disorder. Management is particularly challenging because preservation of hearing and cranial nerve function is crucial. Radiosurgery may be considered in selected patients to achieve tumor control while minimizing treatment-related neurological morbidity.
Serious treatment-related complications are uncommon. Potential effects include:
The availability of several effective treatment strategies means that management should always be individualized, taking into account tumor characteristics, hearing status, age, comorbidities, symptoms, and the patient’s personal circumstances and preferences.
We are pleased to provide individual, non-binding advice regarding your treatment options.