The auditory brainstem response test (ABR) is a cost-effective test to see if a VS has perhaps compromised the cochlear nerve.Computed tomography (CT scan) of the head will detect moderate to large sized VS but can miss small sized VS. VS appears as isodense to surrounding brain parenchyma on CT. VS does not have calcifications in it. Large VS will expand the size of internal acoustic meatus (IAC), thus associated with poor hearing function because the nerves within the IAC are compressed, particularly the cochlear nerve. However, facial nerve is less commonly affected. The main advantage of CT scan is to assess the extent of bony involvement by VS. VS enhances when iodinated contrast is given. Contrasted CT scan of temporal bone can done if the subject is unsuitable to undergo MRI scan.MRI scan is the imaging of choice because it can more accurately differentiate the mass from other tumours such as meningioma, facial nerve schwannoma, epidermoid cyst, arachnoid cyst, aneurysm, and brain metastasis. MRI scan also helps in surgical planning and follow-up of the tumour after surgery. VC is usually isointense on T1 weighted images, hyperintense on T2 weighted images, and enhances after given gadolinium contrast. Management
Microsurgery for Sporadic VS
The Guidelines on the Treatment of Adults with Vestibular Schwannoma issued in 2018 by the Congress of Neurological Surgeons in the U.S. looked at the long-term evolution of treatments for VS.
Radiation dosages overall were reduced over the years as experience showed that excellent tumor control rates could be maintained even as dosages were lowered to benefit hearing preservation and facial nerve function. Generally, single-session Gamma Knife radiosurgery is limited in use to VSs less than 3 cm in diameter to avoid possible complications with facial nerves, brainstem and the cochlea apparatus. The risk of radiation-induced secondary tumors is very small, in the range of 0.01-0.02%. The risk for NF2 patients appears to be slightly higher. Medical and gene therapies
The 1991 NIH Consensus Statement recommended attention to "the development of pharmaceutical and other alternative medical treatments, such as tumor suppressing agents." Ideally, a drug could be found to permanently shrink or eradicate VSs, with minimal side effects. A key step forward in 1993 was the identification of the NF2 gene and its protein product Merlin, which modulates the complex molecular signaling pathways that control cell proliferation. These pathways that drive VS formation (tumorigenesis) and growth are currently under investigation. A second important field of study in molecular biology investigates ways to stop the formation (angiogenesis) of the new blood vessels that are needed to support tumor growth by supplying nutrients and oxygen. In 1998, the glycoprotein named VEGF (vascular endothelial growth factor) that initiates proliferation was discovered. An anti-VEGF drug named bevacizumab (Avastin) was developed and showed promise in stopping this vascular proliferation. Unfortunately, when tested for NF2 tumors, the therapy required prolonged treatment resulting in hypertension and impaired wound healing.