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.
V2 receptors maintain plasma osmolality and are coupled to aquaporin channels in the collecting ducts of kidneys where they regulate AVP levels. Conivaptan hydrochloride functions by antagonizing V2 receptors in the renal collecting ducts and thus causing aquaresis or water secretion. Typical pharmacodynamic effects of the drug are an increase in  net fluid loss, increase in  urine output, and decrease in the osmolality of urine. Conivaptan inhibits its own metabolism in the body, displaying non-linear pharmacokinetics. About 99% of conivaptan found is bound to human plasma proteins over the range of 10 ng/mL to 1000 ng/mL. The mean half-life of the drug is 5 hours and mean clearance is 15.2 L/hr. Adverse effects
Most adverse reactions to conivaptan are found at the site of infusion. Other complications include blood and lymphatic system disorders, gastrointestinal disorders, metabolism and nutrition disorders, psychiatric disorders as well as vascular disorders. There is risk of too rapid correction of hyponatremia causing fatal osmotic demyelination syndrome. Chemistry
Conivaptan hydrochloride is an off-white or a pale yellow power with a solubility of 0.25 mg/mL in water at 23 °C. The injectable formulation consists of 20 mg conivaptan hydrochloride, 0.4 g ethanol, 1.2 g propylene glycol and water. Development and commercialization
Conivaptan hydrochloride was discovered by Yamanouchi Pharmaceuticals and marketed by Astellas. Yamanouchi Pharmaceuticals filed a new drug application to the FDA for conivaptan hydrochloride to treat hyponatremia on 2 February 2004. On 1 December, Yamanouchi received approval for investigational hyponatremia treatment using conivaptan hydrochloride.