Magnetic resonance imaging after translabyrinthine complete excision of vestibular schwannomas

Translabyrinthine Excision of a Transmodiolar Intralabyrinthine Schwannoma Mimicking Meniere's Disease: A Case Report

Intralabyrinthine schwannomas (ILSs) are rare tumors involving the otic capsule. Notably, they are often misdiagnosed because their symptoms mimic those of other, more common inner ear pathologies. Diagnosis requires high-resolution contrast-enhanced magnetic resonance imaging (MRI), which reveals filling defects (using a T2-weighted MRI sequence) or focal enhancement (using a T1-weighted MRI sequence with gadolinium enhancement) in the inner ear. A 52-year-old male patient with intractable vertigo or single-sided deafness should raise suspicion of this clinical entity as a differential diagnosis. Translabyrinthine excision of the tumor along with auditory rehabilitation using a cochlear implant can provide good outcomes with minimal morbidity in carefully selected cases. Here, we present an interesting case of a transmodiolar ILS mimicking Meniere's disease, wherein surgery using the translabyrinthine approach and an extended cochleostomy yielded favorable outcomes.

Evaluating growth trends of residual sporadic vestibular schwannomas: a systematic review and meta-analysis

BACKGROUND

Gross total resection remains the gold-standard approach for vestibular schwannomas (VS) when surgery is indicated. In select cases, incomplete resection (IR) becomes a desired alternative to preserve the facial nerve function and the patient's quality of life. While a lot of earlier studies described incompletely resected sporadic VSs as dormant, more recent studies reported a higher growth rate following IR, therefore an evaluation of the residual VS growth rates could have important implications for the follow-up treatment protocols and provide relevant information for neurosurgeons, neuro-otologists, neuropathologists, and radiologists. Although prognostic factors predicting preoperative VS growth have been previously investigated, these factors have not been investigated following IR. Our review aims to examine the growth rate of residual sporadic VS following IR and to examine variables associated with the regrowth of residual VS.

METHODS

The review was conducted in accordance with the PRISMA guidelines. Six databases (MEDLINE (Ovid), Embase (Ovid), CINAHL Plus (EBSCO), Cochrane Central Register of Controlled Trials (CENTRAL), WHO International Clinical Trials Registry Platform and UK Clinical Trials Gateway (WHO ICTRP) were searched. Full-text articles analysing growth rates in at least ten patients who had residual VS after IR were assessed. We conducted a meta-analysis using a random-effects model via RevMan.

RESULTS

14 studies totalling 849 patients were included in the analysis. The mean planimetric growth rate was 1.57 mm/year (range 0.16-3.81 mm/year). The mean volumetric growth rate was 281.725 mm³/year (range 17.9-530.0 mm³/year). Age, sex, pre-operative tumour size/volume, cystic tumour sub-type, MIB-1 index, and intracanalicular tumour location were not associated with residual growth. Residual tumour size/volume was statistically significant to growth (OR = 0.65, 95% CI 0.47-0.90, p = 0.01). Radiological re-growth occurred in an average of 26.6% of cases (range 0-54.5%).

CONCLUSION

From our analysis, only the residual tumour volume/size was associated with residual VS growth. Therefore, close postoperative surveillance for the first year, followed by an annual MRI scan for at least 5 years, and subsequently extended interval surveillance remains of utmost importance to monitor disease progression and provide timely surgical and adjuvant interventions. Our study shows that future work should be aimed at molecular and histological characteristics of residual VSs to aid prognostic understanding of growth.

Facial Nerve Function Outcome and Risk Factors in Resection of Large Cystic Vestibular Schwannomas

Objective Cystic vestibular schwannomas (VS) in contrast to solid VS tend to have accelerated growth, larger volume, rapid/atypical presentation, lobulated/adherent surface, and unpredictable course of the cranial nerves. Cystic VS are surgically challenging, with worse clinical outcomes and higher rate of subtotal resection (STR).

Methods We retrospectively analyzed postoperative outcomes of 125 patients with cystic VS, operated between years 2005 and 2019 in our center. We confronted the extent of the resection and House-Brackmann (HB) grade of facial palsy with the results of comparable cohort of patients with solid VS operated in our center and literature review by Thakur et al.1

Results Translabyrinthine approach was preferred for resection of large, cystic VS (97.6%). Gross-total resection (GTR) was achieved in 78 patients (62.4%), near-total resection (NTR) with remnant (<4 × 4 × 2 mm) in 43 patients (34.4%), and STR in 4 patients (3.2%). NTR/STR were significantly associated with higher age, tumor volume >5 cm3, retrosigmoid approach, high-riding jugular bulb, tumor adherence to the brain stem, and facial nerve (p = 0.016; 0.003; 0.005; 0.025; 0.001; and <0.00001, respectively).

One year after the surgery, 76% of patients had HB grades 1 to 2, 16% had HB grades 3 to 4, and 8% had HB grades 5 to 6 palsy. Worse outcome (HB grades 3 to 6) was associated with preoperative facial palsy, tumor volume >25 cm3, and cyst over the brain stem (p = 0.045; 0.014; and 0.05, respectively). Comparable solid VS operated in our center had significantly higher HB grades 1 to 2 rate than our cystic VS (94% versus 76%; p = 0.03). Comparing our results with literature review, our HB grades 1 to 2 rate was significantly higher (76% versus 39%; p = 0.0001). Tumor control rate 5 years after surgery was 95.8%.

Conclusion Our study confirmed that microsurgery of cystic VS has worse outcomes of facial nerve preservation and extent of resection compared with solid VS. Greater attention should be paid to the above-mentioned risk factors.

Imaging of the Vestibular Schwannoma: Diagnosis, Monitoring, and Treatment Planning

Appropriate imaging strategies for the detection, treatment planning, and posttreatment monitoring of vestibular schwannomas will be discussed. The typical and variant imaging appearances of vestibular schwannomas, as well as the imaging features that should prompt consideration of differential diagnoses, will be illustrated. Understanding the natural history of vestibular schwannomas, optimal measurement and definition of tumour growth helps the radiologist evaluate for the failure of conservative management and requirement for surgery or radiotherapy. In order to determine the success of conservative management, the radiologist is required to understand the natural history of vestibular schwannomas and how tumour growth is defined. Finally, the imaging features which help guide appropriate treatment with surgery or radiotherapy will be highlighted, and the expected posttreatment imaging changes will be described.

Magnetic Resonance Imaging Surveillance for Vestibular Schwannoma After Microsurgical Resection Using a Retrosigmoid Transmeatal Approach

BACKGROUND

Vestibular schwannoma (VS) is a benign, usually slow-growing tumor. The drawback of radical microsurgical VS resection is the increased likelihood of neurologic injury, forcing surgeons to leave a tumor remnant in some cases. We evaluated the prognostic value of magnetic resonance imaging (MRI) enhancement patterns to determine the risk of tumor regrowth.

METHODS

This clinical study included 30 patients (20 women and 10 men) with VS who underwent surgery via a retrosigmoid transmeatal approach. The extent of resection was assessed by MRI 6 months after surgery. Two subtypes of intracanalicular linear enhancement were defined: linear enhancement of the walls of the internal auditory canal (IAC) or in the cerebellopontine angle (CPA) and linear enhancement covering the end of the IAC. All patients included in the study underwent follow-up MRI every year for at least 6 years.

RESULTS

Intracanalicular nodular enhancement suggestive of a tumor remnant was seen in the IAC in 11 patients (36.7%). Volume of nodular enhancements was <0.5 cm³ when measurable. The enhancement remained stable throughout follow-up except in 2 cases that showed a slight decrease in size and in 1 case with an initial tumor remnant of 0.5 cm³ showing a slight increase over the years. Eighteen patients (60%) had linear enhancement in the IAC or in the CPA. No patients with linear enhancement showed nodular enhancement.

CONCLUSIONS

Although specific monitoring protocols can be designed based on MRI findings 6 months after microsurgical VS resection, follow-up should be maintained indefinitely given the slight possibility of very late regrowth.

MIB Index as Predictor of Recurrence in Sporadic Vestibular Schwannomas

OBJECTIVE

Nearly 9.2% of vestibular schwannomas (VS) recur. We evaluate the association of cell proliferative markers like MIB with recurrence in VS.

METHODS

Retrospective data of 144 consecutive patients who underwent surgical excision for sporadic VS between January 2010 and July 2015 were collected. Comparison between groups based on recurrence of VS was done.

RESULTS

The average age of the study population was 43.95 ± 12.86 years with 77 (53.5%) men. The average maximal diameter of VS was 40.25 ± 7.23 mm. Gross total resection was done in 52 (36.1%) patients. While near total resection was performed in 81 (56.3%) patients, the remaining 11 (7.6%) patients underwent a subtotal resection. The mean follow-up period was 37.99 ± 10.09 months (24-60). Recurrence of VS was observed in 18 (12.5%) patients. There was no difference between the groups for diameter of the tumor (42.22 ± 8.04 vs. 39.64 ± 7.00 mm; P = 0.191). The average MIB index value was higher in patients with recurrence of tumor at follow-up (4.78 ± 5.77 vs. 1.89 ± 1.48 mm; P < 0.001). There was no difference between the groups for extent of resection or postoperative complications. MIB was the only significant predictor for recurrence (β = 1.355 (1.07-1.78; confidence interval 95%); P = 0.031). On receiver operating characteristic curves, a cutoff value of 3.5% for MIB showed a specificity of 84.1%.

CONCLUSIONS

MIB index ≥3.5% is associated with recurrence in VS. Maximal diameter of the tumor and extent of resection are perhaps not associated with recurrence of VS.

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 dilemma of early postoperative magnetic resonance imaging: when efficiency compromises accuracy: case report

BACKGROUND AND IMPORTANCE

Postoperative magnetic resonance imaging (MRI) is critical to the clinical decision-making process for patients undergoing resection of intracranial tumors. The accuracy of immediate postoperative MRI in determining the presence of residual disease following intracranial tumor resection, however, has not been studied.

CLINICAL PRESENTATION

A 57-year-old man underwent an uncomplicated retrosigmoid craniotomy for the resection of a cystic vestibular schwannoma. Immediate gadolinium-enhanced postoperative MRI, performed within 1.5 hours of surgery, was notable for a plaquelike, lobular, avidly enhancing collection with MRI characteristics consistent with fluid density extending from the porus acusticus into the cerebellopontine angle. This anomalous lesion disappeared upon repeat imaging 48 hours later, and the patient had no attributable clinical sequelae. He was discharged home without issues within 12 hours of repeat imaging.

CONCLUSION

We demonstrate here that immediate postoperative, gadolinium-enhanced MRI scans after tumor resection may result in avid enhancement in the region of surgical manipulation, likely due to leakage of gadolinium chelates into the subarachnoid space from residual compromise of the blood-brain barrier immediately following surgical manipulation. Early imaging is no longer routinely performed at our institution unless otherwise clinically indicated.

ABBREVIATIONS

FLAIR, fluid-attenuated inversion recoveryIAC, internal auditory canal.

Congenital Peripheral Vestibular Syndrome in a Domestic Ferret (Mustela putorius furo)

A 3-month-old intact female ferret (Mustela putorius furo) was presented with a 2-month history of ataxia. On physical examination, the ferret had difficulty standing upright. During the neurologic examination, the patient had a left head tilt and positional strabismus, circled to the left, and was ataxic. Results of the complete blood count were consistent with a mild normocytic normochromic anemia. Initial treatment was supportive. Magnetic resonance imaging was performed and revealed an asymmetry of the inner ears. A brainstem auditory evoked response test was also performed. History, clinical signs, and diagnostic test results indicated that the ferret was suffering from congenital peripheral vestibular syndrome and left-sided deafness. Congenital disease should be considered in the differential diagnosis of young ferrets with peripheral vestibular syndrome. Supportive care and physiotherapy can improve balance and motor function, leading to an acceptable quality of life.

Clinical impact of early CT scans after lateral skull-base surgery

OBJECTIVE

To determine the frequency and clinical significance of abnormalities on postoperative computerized tomography (CT) scans performed within 24 hours after lateral skull base surgery.

STUDY DESIGN

Case series with chart review. Setting Inpatient tertiary care hospital.

METHODS

Adult patients undergoing lateral skull base surgery were identified using CPT code search from January 2010 to January 2013. Patient demographics, type of skull base lesion, surgical approach, length of operation, time between end of the surgery and CT scan, CT scan findings, and patients' postsurgical neurologic status were collected.

RESULTS

One hundred and seventy-two patients were identified who had a postoperative CT scan after lateral skull base surgery. Diagnoses included schwannoma (95), cerebrospinal fluid fistula (29), middle fossa encephaloceles (9), meningioma (13), superior semicircular canal dehiscence (12), and other disease processes (14). The approaches were middle fossa (64), translabyrinthine (70), suboccipital (17), infratemporal (8), and combined/other (13). Mild pneumocephalus was almost always found, along with mild extra-axial blood. Twenty-four patients had significant mass effect found on CT scan, but this was present preoperatively. Three patients had a mild subdural without neurological decline. No patient suffered any clinically significant neurological decline, although 5 patients reported finger numbness that resolved spontaneously and 2 patients had confusion in the immediate postoperative period.

CONCLUSION

Clinically significant abnormalities on immediate postoperative CT scans were rare, as were cases of neurological decline. Further prospective studies could determine a more cost-effective algorithm for routine use of postoperative imaging.