Are acoustic neuromas encapsulated tumors?

Peritumoral Signal on Postcontrast FLAIR Images: Description and Proposed Biomechanism in Vestibular Schwannomas

BACKGROUND AND PURPOSE

Anecdotally, postcontrast FLAIR images of vestibular schwannomas can show peritumoral hyperintense signal, hypothesized to represent gadolinium extravasation. This study assessed the incidence of this phenomenon in a cohort of patients with treatment-naïve sporadic vestibular schwannomas.

MATERIALS AND METHODS

A retrospective review of 20 patients with presumed vestibular schwannoma based on characteristic imaging findings and with dedicated internal auditory canal imaging, including postcontrast T1W1 and postcontrast FLAIR, was performed. Tumor size and location were recorded, as was the presence or absence of a fundal fluid cleft. Images were reviewed for the presence of peritumoral hyperintense signal on FLAIR images (a "halo") and for both subjectively and objectively elevated signal in the ipsilateral cochlea and fundus.

RESULTS

Patients were randomly selected from an institutional vestibular schwannoma registry. Eleven (55.0%) were women. A peritumoral halo was present in 90% of patients, averaging 1.0 (SD, 0.2) mm in thickness. The maximum mean FLAIR signal in the ipsilateral fundus (205.9 [SD, 110.2]) was significantly greater than on the contralateral side (121.6 [SD, 27.8]) (P = .02). Maximum mean ipsilateral intracochlear signal (167.8 [SD, 104.5]) was also significantly greater than on the contralateral side (113.4 [SD, 40.1]) (P = .04).

CONCLUSIONS

A peritumoral halo on postcontrast FLAIR images was present in 90% of our cohort with randomly selected, treatment-naïve sporadic vestibular schwannomas. Although its mechanism is unknown, this signal is hypothesized to represent gadolinium extravasation, given an ipsilateral increased signal in the adjacent internal auditory canal fundus and cochlea.

Application of Subperineural Resection Technique in Vestibular Schwannomas: Surgical Efficacy and Outcomes in 124 patients

Objective

We aimed to explore the application and prospects of the subperineural resection technique for tumor separation and removal under the perineurium during surgery for vestibular schwannomas (VSs).

Methods

This study retrospectively analyzed 124 patients with VSs who underwent surgery via a retrosigmoid approach from July 2015 to October 2020 in the Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University. The data will be discussed with regard to the following aspects: clinical features, surgical strategies, tumor resection extent, facial–acoustic function preservation, and postoperative complications.

Results

Gross total resection (GTR) of the tumor was achieved in 104 patients, with a GTR rate of 83.9%, and subtotal resection (STR) of the tumor was achieved in 20 patients. There was no significant difference in facial and acoustic nerve functional preservation between GTR and STR, as well as in tumor resection between solid and cystic tumors. The retention rate reached 97.6% in terms of complete anatomical facial nerve preservation. Facial nerve function was assessed using the House–Brackmann (HB) grading score. Consequently, HB grades of I–II, III–IV, and V–VI were determined for 96 (77.4%), 25 (20.2%), and 3 (2.4%) cases, respectively, 1 week postoperatively and accounted for 110 cases (88.7%), 13 cases (10.5%), and 1 case (0.8%), respectively, at 6 months. Fifteen of 35 (42.9%) patients with serviceable hearing before the operation still had serviceable hearing at 6 months postoperatively. There were 5 cases of cerebellar or brainstem bleeding after the operation, and one patient died. Multivariate logistic regression analysis showed that older age (≥60 years, p = 0.011), large tumor (>3 cm, p = 0.004), and cystic tumor (p = 0.046) were independent risk factors associated with the extent of adhesion between the tumor and the brainstem and facial–acoustic nerve.

Conclusion

We successfully applied the subperineural resection technique to a large series of patients with VSs and achieved satisfactory results. Accurate identification of the perineurium and subperineural resection of the tumor can effectively reduce the disturbance of the facial–acoustic nerve during the operation and provide an intuitive basis for judging the tumor boundary. The subperineural resection technique may be conducive to improving the rate of total tumor resection and facial–acoustic nerve functional preservation in the surgical treatment of VSs.

Risk factors for recurrence and regrowth of spinal schwannoma

BACKGROUND

Spinal schwannoma recurs after initial surgery at a rate of 4%-6%, with known risk factors including subtotal resection, multilevel involvement, large tumor size, and malignant histopathology. This study examined risk factors for schwannoma recurrence and residual tumor regrowth.

METHODS

Sixty-five patients who underwent resection of spinal schwannoma in our department between July 2010 and December 2018 and were followed up for more than 1 year were retrospectively analyzed for age, sex, follow-up duration, imaging and surgical data, recurrence, reoperation, and Japanese Orthopaedic Association scores before and 1 year after surgery. Patients with postoperative recurrence or residual tumor regrowth of >10% at the final visit (R+ group) were compared with patients without recurrence or regrowth (R- group). Multivariate logistic regression analysis was performed to analyze concurrent effects of risk factors on recurrence and regrowth.

RESULTS

The 65 patients (mean age 52.4 years at surgery) had schwannomas involving cervical (n = 14), thoracic (n = 25), and lumbar (n = 26) spinal levels. Mean follow-up duration was 58 months. Location was intradural in 65%, extradural in 17%, and both intradural and extradural in 18%. There were 4 recurrences (6.2%), and the mean interval between surgery and recurrence was 18.8 months. Seven patients (10.8%) experienced regrowth. Comparing group R+ (n = 11) and group R- (n = 54), univariate analysis showed significant differences in Sridhar tumor classification, giant tumor (Sridhar classification II, IVb, and V), left-right and cranial-caudal tumor size, largest diameter, operative time, blood loss, subtotal resection, reoperation, fusion surgery, and follow-up duration. Multivariate logistic regression analysis revealed giant tumor (Sridhar classification types II, IVb, and V) as an independent risk factor for recurrence and regrowth.

CONCLUSIONS

This retrospective review of 65 consecutive patients with spinal schwannoma in a single institution demonstrated that 16.9% had recurrence or regrowth, demonstrating that this potential risk should be kept in mind.

Long-term risk of recurrence and regrowth after gross-total and subtotal resection of sporadic vestibular schwannoma

OBJECTIVE

The management of vestibular schwannoma (VS) remains controversial. One commonly cited advantage of microsurgery over other treatment modalities is that tumor removal provides the greatest chance of long-term cure. However, there are very few publications with long-term follow-up to support this assertion. The purpose of the current study is to report the very long-term risk of recurrence among a large historical cohort of patients who underwent microsurgical resection.

METHODS

The authors retrospectively reviewed the medical records of patients who had undergone primary microsurgical resection of unilateral VS via a retrosigmoid approach performed by a single neurosurgeon-neurotologist team between January 1980 and December 1999. Complete tumor removal was designated gross-total resection (GTR), and anything less than complete removal was designated subtotal resection (STR). The primary end point was radiological recurrence-free survival. Time-to-event analyses were performed to identify factors associated with recurrence.

RESULTS

Four hundred fourteen patients met the study inclusion criteria and were analyzed. Overall, 67 patients experienced recurrence at a median of 6.9 years following resection (IQR 3.9-12.1, range 1.2-22.5 years). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following resection were 93% (95% CI 91-96, 248 patients still at risk), 78% (72-85, 88), 68% (60-77, 47), and 51% (41-64, 22), respectively. The strongest predictor of recurrence was extent of resection, with patients who underwent STR having a nearly 11-fold greater risk of recurrence than the patients treated with GTR (HR 10.55, p < 0.001). Among the 18 patients treated with STR, 15 experienced recurrence at a median of 2.7 years following resection (IQR 1.9-8.9, range 1.2-18.7). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following GTR were 96% (95% CI 93-98, 241 patients still at risk), 82% (77-89, 86), 73% (65-81, 46), and 56% (45-70, 22), respectively. Estimated recurrence-free survival rates at 5, 10, and 15 years following STR were 47% (95% CI 28-78, 7 patients still at risk), 17% (5-55, 2), and 8% (1-52, 1), respectively.

CONCLUSIONS

Long-term surveillance is required following microsurgical resection of VS even after GTR. Subtotal resection alone should not be considered a definitive long-term cure. These data emphasize the importance of long-term follow-up when reporting tumor control outcomes for VS.

The extracisternal approach in vestibular schwannoma surgery and facial nerve preservation

The classical surgical technique for the resection of vestibular schwannomas (VS) has emphasized the microsurgical anatomy of cranial nerves. We believe that the focus on preservation of the arachnoid membrane may serve as a safe guide for tumor removal. Method The extracisternal approach is described in detail. We reviewed charts from 120 patients treated with this technique between 2006 and 2012. Surgical results were evaluated based on the extension of resection, tumor relapse, and facial nerve function. Results Overall gross total resection was achieved in 81% of the patients. The overall postoperative facial nerve function House-Brackmann grades I-II at one year was 93%. There was no recurrence in 4.2 years mean follow up. Conclusion The extracisternal technique differs from other surgical descriptions on the treatment of VS by not requiring the identification of the facial nerve, as long as we preserve the arachnoid envelope in the total circumference of the tumor.

Magnetic resonance imaging surveillance following vestibular schwannoma resection

OBJECTIVES/HYPOTHESIS

To describe the incidence, pattern, and course of postoperative enhancement within the operative bed using serial gadolinium-enhanced magnetic resonance imaging (MRI) following vestibular schwannoma (VS) resection and to identify clinical and radiologic variables associated with recurrence.

STUDY DESIGN

Retrospective cohort study.

METHODS

All patients who underwent microsurgical resection of VS between January 2000 and January 2010 at a single tertiary referral center were reviewed. Postoperative enhancement patterns were characterized on serial MRI studies. Clinical follow-up and outcomes were recorded.

RESULTS

During the last 10 years, 350 patients underwent microsurgical VS resection, and of these, 203 patients met study criteria (mean radiologic follow-up, 3.5 years). A total of 144 patients underwent gross total resection (GTR), 32 received near-total resection (NTR), and the remaining 27 underwent subtotal resection (STR); 98.5% of patients demonstrated enhancement within the operative bed following resection (58.5% linear, 41.5% nodular). Stable enhancement patterns were seen in 24.5% of patients, regression in 66.0%, and resolution in only 3.5% of patients on the most recent postoperative MRI. Twelve patients recurred a mean of 3.0 years following surgery. The average maximum linear diameter growth rate among recurrent tumors was 2.3 mm per year. Those receiving STR were more than nine times more likely to experience recurrence compared to those undergoing NTR or GTR (P < .001). Nodular enhancement on the initial postoperative MRI was associated with a 16-fold increased risk for future recurrence compared to those with linear patterns (P = .008). Among those with nodular enhancement on baseline postoperative MRI, a maximum linear diameter of ≥ 15 mm or volume of ≥ 0.4 cm(3) was associated with an approximate five-fold increased risk for future growth (P < .02).

CONCLUSIONS

Persistent nonspecific radiologic enhancement within the postoperative field is common, making the diagnosis of tumor recurrence challenging. Factors including completeness of resection and baseline postoperative MRI findings provide valuable information regarding risk for recurrence, which may assist the clinician in determining an appropriate postoperative MRI surveillance schedule. Future studies using standardized terminology and consistent study metrics are needed to further refine surveillance recommendations.

Is an Acoustic Neuroma an Epiarachnoid or Subarachnoid Tumor?

BACKGROUND:

There are arguments about whether acoustic neuromas are epiarachnoid or subarachnoid tumors.

OBJECTIVE:

To retrospectively examine 118 consecutively operated-on patients with acoustic neuromas to clarify this point.

METHODS:

Epiarachnoid tumors are defined by the absence of an arachnoid membrane on the tumor surface after moving the arachnoid fold (double layers of the arachnoid membrane) toward the brainstem. In contrast, subarachnoid tumors are characterized by the arachnoid membrane remaining on the tumor surface after moving the arachnoid fold. Based on this hypothesis, we used intraoperative views and light and electron microscopy to confirm the existence of an arachnoid membrane after the arachnoid fold had been moved.

RESULTS:

The tumors were clearly judged to be subarachnoid tumors in 86 of 118 patients (73%), an epiarachnoid tumor in 2 patients (2%), whereas a clear judgment was difficult to make in the remaining 30 patients (25%).

CONCLUSION:

The majority of acoustic neuromas are subarachnoid tumors, with epiarachnoid tumors being considerably less common.

Do facial nerve displacement pattern and tumor adhesion influence the facial nerve outcome in vestibular schwannoma surgery?

OBJECTIVE

To assess the nerve facial displacement by a vestibular schwannoma and nerve adhesion to tumor as predictive factors of facial function outcome.

STUDY DESIGN

A prospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

Ninety-six patients undergoing a solitary vestibular schwannoma surgery during 2005 were included. Data concerning tumor size (Stage 1, intracanalicular; Stage 2, < or =15 mm in the cerebellopontine angle [CPA]; Stage 3, 15-30 mm in the CPA; and Stage 4, >30 mm in the CPA), intraoperative facial nerve displacement (Type 1, anterior to the tumor; Type 2, anterior and superior to the tumor and separated from the cochlear nerve; Type 3, superior to the tumor; and Type 4, posterior to the tumor), degree of tumor adhesion (weak, intermediate, and strong) and postoperative facial function according to the House and Brackmann classification at days 10, 30, 90 and 180 were collected.

RESULTS

A good facial function (Grade 1 or 2) was reported in 73% at postoperative Day 180. Univariate analysis showed that facial outcome was better in small tumors, in displacement Types 1 and 2 (Type 1, 46%; Type 2, 34%; and Type 3, 20%), and in tumors with weak and intermediate adhesion (weak, 10%; intermediate, 38%; and strong, 52%). Facial nerve displacement and adhesion were related to tumor stage. The combination of tumor stage, adhesion, and nerve displacement in a logistic regression model was highly predictive of postoperative facial function.

CONCLUSION

Facial nerve displacement and nerve adhesion to tumor are significant predictive factors of facial function outcome after vestibular schwannoma surgery in addition to tumor size.

Histological considerations of the cleavage plane for preservation of facial and cochlear nerve functions in vestibular schwannoma surgery

Object

The authors analyzed the tumor capsule and the tumor–nerve interface in vestibular schwannomas (VSs) to define the ideal cleavage plane for maximal tumor removal with preservation of facial and cochlear nerve functions.

Methods

Surgical specimens from 21 unilateral VSs were studied using classical H & E, Masson trichrome, and immunohistochemical staining against myelin basic protein.

Results

The authors observed a continuous thin connective tissue layer enveloping the surfaces of the tumors. Some nerve fibers, which were immunopositive to myelin basic protein and considered to be remnants of vestibular nerve fibers, were also identified widely beneath the connective tissue layer. These findings indicated that the socalled “tumor capsule” in VSs is the residual vestibular nerve tissue itself, consisting of the perineurium and underlying nerve fibers. There was no structure bordering the tumor parenchyma and the vestibular nerve fibers. In specimens of tumors removed en bloc with the cochlear nerves, the authors found that the connective tissue layer, corresponding to the perineurium of the cochlear nerve, clearly bordered the nerve fibers and tumor tissue.

Conclusions

Based on these histological observations, complete tumor resection can be achieved by removal of both tumor parenchyma and tumor capsule when a clear border between the tumor capsule and facial or cochlear nerve fibers can be identified intraoperatively. Conversely, when a severe adhesion between the tumor and facial or cochlear nerve fibers is observed, dissection of the vestibular nerve–tumor interface (the subcapsular or subperineurial dissection) is recommended for preservation of the functions of these cranial nerves.

Expression of HIF-1, galectin-3, cox-2 and Wilms tumor-1 protein in multiple schwannomas of the conus medullaris

Schwannomatosis is a clinical syndrome that requires thorough clinical and radiological assessments before the diagnosis is made. Although schwannomatosis has been reported before, all were in multiple organ sites. The authors report a case of multiple intra-dural schwannomas of the conus medullaris expressing HIF-1, galectin-3, cox-2 and Wilms tumor-1 protein; which to the best of our knowledge has not been previously reported in schwanomatosis.

Microdebrider decompression of schwannoma: a novel method of excising a neck mass

OBJECTIVE

This case report describes the excision of a large neck neurofibroma causing compression of the esophagus and airway in a young patient with neurofibromatosis type 2 (NF2). At the conclusion of this article, readers should be able to describe a novel method of excising large encapsulated neck masses using microdebridement for decompression. The safety and efficacy of this method is discussed.

STUDY DESIGN

The subject of this report was a 26-year-old woman with NF2. She presented with an enlarging right neck mass extending from the mandible to the clavicle that was compressing both her airway and esophagus. Given her auditory brainstem implant, unipolar cautery was contraindicated. Therefore, it was planned to decompress the patient's neck mass using a microdebrider before attempting to fully dissect out the mass.

METHODS

The neck mass was exposed and then entered. Using a Xomed XPS microdebrider (Medtronic Inc., Minneapolis, MN), the mass was debrided and debulked in all directions taking care not to violate the capsule. After this, the entire capsule was dissected out using only bipolar cautery and suture ligatures for hemostasis.

RESULTS

Microdebrider decompression of the neck neurofibroma allowed for preservation of the capsule without injuring vital structures in the neck. Postoperatively, the patient's swallowing and laryngeal function improved markedly.

CONCLUSION

Microdebrider debulking before dissection of the patient's large neck mass safely relieved compression of the airway and esophagus. This method may be applied to other large benign masses in the neck as well.

Postoperative imaging and follow-up of vestibular schwannomas

OBJECTIVE

No standards exist regarding patient follow-up after complete vestibular schwannoma resection. We surveyed neurotologists and neurosurgeons to determine practice patterns.

STUDY DESIGN

A nonrandomized sample of American Neurotology Society and North American Skull Base Society members was surveyed. Questions concerned years in practice, experience with vestibular schwannoma surgery, and postoperative follow-up algorithms given the scenario of complete gross tumor removal. Data were collected, tallied, and statistically analyzed.

SETTING

Academic and private practice neurotologists and neurosurgeons.

SUBJECTS

Nonrandom sample of American Neurotology Society and North American Skull Base Society members.

MAIN OUTCOME MEASURES

Number of postoperative magnetic resonance imaging scans, timing of magnetic resonance imaging scans, timing of final magnetic resonance imaging scan, timing of final visit, and variability between specialties.

RESULTS

Four hundred ninety-eight surveys were sent and 135 were returned (27.1%). The average number of postoperative magnetic resonance imaging scans was 3.6 for neurotologists (range, 1-11) and 5.6 for neurosurgeons (range, 1-13). This was statistically significant (p >0.001). There was no correlation between number of magnetic resonance imaging scans and either years in practice or tumor experience. Average length of follow-up varied greatly (1 year to lifetime) but was most commonly 5 years. Eight percent of neurotologists varied their postoperative routine on the basis of surgical approach, whereas none of the neurosurgeons did.

CONCLUSION

There remains no standard postoperative imaging algorithm for patients after complete vestibular schwannoma resection.

Surgical pathology of spinal schwannomas: a light and electron microscopic analysis of tumor capsules

OBJECTIVE

Although spinal schwannomas are often encountered, the pathology of the tumor capsule has not been reported. In this study, we describe the ultrastructural pathology of the tumor capsule of spinal schwannomas.

METHODS

In 18 patients who underwent total removal of spinal schwannomas (C2-conus), the tumor capsule was collected and examined by light and electron microscopy.

RESULTS

The thickness of the tumor capsule ranged from 15 to 800 microm (mostly 30-100 microm) and was composed of three layers from the surface to the center: 1) a thinly stretched nerve tissue layer; 2) a fibrous layer of fibrocytes, abundant collagen fibers, and tumor vessels; and 3) a thin transitional layer intermingled with fibrous components and tumor cells. The thickness of each layer varied in different regions of the surface. There was no clear separation between the tumor capsule and the neoplastic tissue, even on the electron microscopic level. A number of nerve fibers ran through the fibrous layer and beneath the capsule as well as in the nerve tissue layer.

CONCLUSION

Compared with vestibular schwannomas, which have been reported to be covered by an extremely thin layer (3-5 microm) of connective tissue, spinal schwannomas were well encapsulated. The capsule was composed of three distinct components; however, the cleavage between thin capsule and tumor cells was indistinct, and the thickness of the axon-containing capsule varied from site to site. Therefore, resection of the nerve of tumor origin, rather than enucleation, would be justified to avoid tumor recurrence. Surgeons should be aware of this pathology when performing the procedure.

[Diagnosis of cerebellum-pontine angle tumors using artificial intelligence techniques]

We are concerned in this paper with learning classification procedures from known cases. More precisely, we provide a diagnostic model that discriminate between cerebellum-pontine angle (CPA) tumors and otorhinolaryngological (ENT) disorders. Usually, in order to distinguish between CPA tumors and ENT disorders one must perform clinical-neurological examination together with expensive radiological imagery (CT and MRI). The proposed model was obtained through artificial intelligence methods and presented a good accuracy level (88.4%) when tested against new cases, considering only clinical examination without radiological imagery results.