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New details about the role of proinflammatory pathways in the molecular pathogenesis of vestibular schwannoma have inspired the researchers to experiment aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) in the treatment of the tumor. Encouraging evidences have been reported in clinical studies. However, a double-blind, placebo-controlled, randomized trial is still missing and needed to ultimately address the efficacy of aspirin as a cytostatic on vestibular schwannoma and its correct posology. Second and even more ambitious target would be application of aspirin as a cytostatic for secondary prevention of tumor growth. In the personal experience, nine patients have undergone subtotal tumor resection and have been prescribed postoperative aspirin off-label with the purpose of avoiding recurrences. The maximum follow-up period has been 47 months, and only the first patient needed reoperation due to tumor regrowth; the remaining eight patients are being followed up and show stable tumors.

Hydroxyapatite cement (HAC) is an osteoconductive material that serves as a scaffold over and inside which bone can grow without intervening fibrous tissue. With micropore diameters of 2–5 nm, HAC is highly resistant to infection. Whether it should be used as the sole bone substitute during cranioplasty or as an adjunct to other materials, it is still a matter of debate, and no direct answer really exists. At our institution, bone flap is always repositioned and fixed with titanium screws prior to layering the HAC. As reconstructive retrosigmoid cranioplasty was combined with an underlay hourglass-shaped autologous pericranium duraplasty, no postoperative wound infections or meningitis were observed nor were clinically significant cerebrospinal fluid (CSF) leaks reported. In the perspective of reducing the postoperative CSF leak rate as much as possible, it is advisable to focus the upcoming research not only on cranioplasty but also on the combination duraplasty-cranioplasty, which yielded very good results in our experience.

CSF fistulas into the soft tissues of the skull base can cause wound breakdown and/or pseudomeningocele, which often becomes very painful and debilitating. In addition, drainage of spinal fluid from the skin increases the risk for surgical site infections and meningitis. Diverse techniques for posterior cranial fossa dural reconstruction and closure have been reported: application of synthetic dural patches, incorporation of autologous tissues, and augmentation with “muscle plugs.” Even if a variety of dural substitutes is currently available, many articles in the literature suggest that autologous materials are preferable compared to nonautologous substitutes. Our group reported the use of autologous pericranium harvested during the opening step of retrosigmoid approach, inserted and stitched as an underlay hourglass-shaped plug for dural closure. We did not observe any surgical site infections, meningitis, CSF leaks, or new neurological symptoms using properly this dural closure technique.

One hundred sixty consecutive patients (mean age, 49.9 years) were operated at San Filippo Neri Hospital, Rome, between September 2010 and April 2018. Mean tumor size was 23.3 mm. One hundred thirty-five patients (84.4%) had completely preserved facial nerve function (HB 1) before surgery; 56 (35%) patients had preoperative serviceable hearing (AAO-HNS classes A/B). Retrosigmoid approach was performed in all the cases except for one, wherein the patient underwent a translabyrinthine approach. The total or near-total (thin capsule residue left on the brainstem) resection rate was obtained in majority of cases. In the last 14 surgical procedures, a flexible endoscope was employed for final check in the IAC. At 6 months after surgery, 149 (93.7%) patients had HB 1 or facial nerve function. Among 56 patients who had serviceable hearing before surgery, 35 retained it, thus yielding a hearing preservation rate of 62.5%. In 63 procedures, diluted topical papaverine was used for improving the blood flow in microvasculature of cranial nerves.

The current strategy in vestibular schwannoma surgery dictates early intraoperative identification of the facial nerve by means of intraoperative monitoring. Imaging studies designed to trace the course of the facial nerve preoperatively should theoretically enhance surgical safety. The use of diffusion tensor tractography (DTT) for nerve tracking has evolved as a reliable technique in this regard. The latest systematic review available in the literature showed that complete tracking of the nerve’s course was obtained in 96.6% of cases and that surgical concordance with the preoperative DTT findings was obtained in 90.7%. The authors deemed preoperative DTT for facial nerve identification a useful adjunct in the surgical planning for large tumors (>2.5 cm). The application of tractography to detailed morphological reconstruction of the cranial nerves is a recent technology; therefore, it has potential limitations. These include a limited ability to distinguish the fibers of VII and VIII nerves, which could be overcome by combining DTT with specific MRI sequences.

Using a retrosigmoid approach, the internal auditory meatus cannot be completely opened to expose the fundus in order to preserve the superior and posterior semicircular canals. Therefore, a straight microscopic view cannot provide an adequate visualization of the most lateral part of the internal auditory canal (IAC). Endoscope assistance provides optimal exposure of the fundus of the IAC and improves the ability to evaluate the extent of resection intraoperatively. Our group reported the successful surgical treatment (total resection) of three cases of intracanalicular vestibular schwannomas operated on with an endoscopic-assisted retrosigmoid approach by means of a flexible endoscope (4-mm × 65-cm, Karl Storz, Inc.). The main advantage of the flexible endoscope is the possibility to orient the endoscopic tip directly into the IAC to obtain an optimal visualization of the fundus. As opposed to rigid devices, the flexible endoscope has to be manipulated with two hands. However, this limitation can be easily overcome through good cooperation and synchronicity between the operator and the assistant.

The most important instruments for vestibular schwannoma surgery can be grouped as follows: standard microsurgical instruments, electronic microsurgical devices, endoscopes, and intraoperative neurophysiological monitoring (IONM) devices. Standard—i.e., mechanical—microsurgical instruments are used for tumor dissection, fragmentation, and piecemeal resection. Electronic microsurgical devices consist of bipolar forceps, used to achieve precise hemostasis; handheld 2μ-thulium flexible laser fiber, which can be used for hemostasis, capsule and dural incision and vaporization, and tumor debulking; and ultrasonic aspirator, mainly used for tumor debulking and internal auditory canal (IAC) opening. The endoscopes allow direct observation of the lateral extremity of the IAC and enable the surgeon to visualize and remove the deepest tumor remnants. IONM devices stimulate both facial and cochlear nerves and detect their responses so as to offer real-time monitoring of their functional state during surgery.

Silent cerebral vasospasm following surgical resection of vestibular schwannomas is much more common than previously thought. This might mean that the cerebral circulation shows a high reactivity to surgical trauma, and it can be hypothesized that this happens not only in elastic and muscular arteries but also in arterioles—and especially those within the cerebellopontine angle. From this perspective, prevention of vasospasm is useful for microvascular protection of the cranial nerves. Papaverine is known to be a potent vasodilator directly acting on smooth muscle and causing it to relax. Intra-arterial administration of papaverine has been used to treat arterial vasospasm after aneurysmal subarachnoid hemorrhage. When applied topically, it acts as a smooth muscle relaxant to break intraoperative vasospasm. The most important side effects of topical papaverine in vestibular schwannoma surgery are transient palsies of facial and cochlear nerves. It has been proposed that intracisternal papaverine at a concentration of 0.3% would be reasonably safe.

Vestibular schwannomas (also known as acoustic neuromas) are intracranial tumors arising from Schwann cells, which form the myelin sheath around the vestibulocochlear bundle. Vestibular schwannomas account for 5–10% of intracranial tumors and are the most common neoplastic lesions in the cerebellopontine angle. The main risk factor is the exposure to radiation and, as most recently ascertained, leisure noise. They are classified as WHO grade I tumors and have a locally compressing effect rather than an infiltrative tendency. The site of origin is the inferior vestibular nerve in 70% of cases and the superior vestibular nerve in 20%. The most common symptoms are hearing loss (95% of patients) and tinnitus (63%), usually with a chronic onset. The diagnostic workup requires audiometry and magnetic resonance imaging with gadolinium contrast to confirm the clinical suspicion. Different grading systems have been proposed to stage tumor progression, Samii’s classification being one of the most commonly used.

Eight video clips are commented, showing the surgical steps of a standard retrosigmoid approach to a case of right-sided vestibular schwannoma, grade T4a according to Samii’s classification. Keyhole craniotomy is performed and followed by dural incision. Facial nerve is then located, and the capsule is incised by means of thulium laser fiber. The internal auditory canal is opened, and the contents are dissected in order to preserve the facial nerve. Flexible endoscopy final check in the internal auditory canal is shown in the case of a left-sided intracanalicular vestibular schwannoma, grade T1.

The rationale for laser use in tumor resection is both to allow for “no-touch” cutting and for tissue debulking, with hemostatic benefit. Laser surgery, in general, has shown various advantages, such as reduction of mechanical trauma and intraoperative bleeding. Three types of laser have been successfully used in vestibular schwannoma surgery, potassium titanyl phosphate (KTP-532), CO2, and the novel 2μ-thulium lasers, which has been deemed safe especially in “difficult” conditions (e.g., highly vascularized and hard tumors).

Vestibular schwannomas (VS) mainly arise from either the superior (SVN) or the inferior vestibular nerve (IVN). Preoperative vestibular testing in patients affected by VS can be useful to predict which one of the vestibular nerves the tumor arises from. The relevance of identifying the nerve of origin lies in its prognostic factor for hearing preservation after surgery, with tumors arising from the (SVN) having a much higher hearing preservation rate. Diverse studies in the literature have tested the correlation between abnormal vestibular testing results and the nerve of origin of VSs; the techniques experimented in such context are posturography, vestibular evoked myogenic potentials (VEMPs), caloric test (always in combination with VEMPs), and video head impulse test (vHIT). vHIT has yielded promising results, with a positive predictive value ranging from 89.5 to 100%, so that the pattern of semicircular canal dysfunction on vHIT has been proposed to have a localizing value to identify the nerve of origin in VSs.