Increased cochlear fluid-attenuated inversion recovery signal in patients with vestibular schwannoma

The use of cochlear-enhancement imaging to predict hearing preservation following vestibular schwannoma removal

BACKGROUND

Hearing preservation is challenging for patients after the removal of large vestibular schwannomas (VSs). Here, using preoperative magnetic resonance (MR) imaging, we investigated the significance of cochlear enhancement (CE) for predicting postoperative hearing preservation.

METHODS

Between January 2014 and December 2019, 34 VS-patients with serviceable hearing underwent tumor-removal surgery using a retrosigmoid approach. The presence or absence of CE using both T2-weighted and gadolinium-enhanced T1-weighted MR images was assessed in VS patients using the pixel-analysis method. Segmented volumetric analyses were also performed using GrowCut 3D slicer software.

RESULTS

There were 17 patients (50%) without CE and 17 (50%) with CE. Ten of the 17 non-CE patients (58.8%) had postoperative hearing preservation. In contrast, only 3 of the 17 patients with CE (17.6%) had postoperative hearing preservation. There were no significant tumor-characteristic differences between the two groups. The presence of CE on both the T2-weighted and the gadolinium-enhanced T1-weighted MR images correlated significantly with postoperative hearing outcomes (P=0.032). Only pure-tone averages were significantly different between the two groups (P=0.049).

CONCLUSIONS

Preoperative serviceable hearing is likely to be preserved after surgery in non-CE VS patients. Preoperative CE assessment using MR imaging may be a useful predictor for postoperative hearing outcomes in VS patients.

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.

Presbycusis and Hearing Preservation in Observed Vestibular Schwannomas

OBJECTIVE

We reviewed a cohort of patients with untreated sporadic vestibular schwannoma (VS) and examined the relationship between high-frequency hearing loss (HFHL) in the non-VS ear and long-term hearing outcomes in the VS-affected ear. We hypothesized that the progression of HFHL is associated with accelerated hearing decline in sporadic VS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary center.

PATIENTS

We studied 102 patients with sporadic VS diagnosed from 1999 to 2015 with ≥5 years of observation (median, 6.92; interquartile range, 5.85-9.29). Sixty-six patients had AAO-HNS class A/B hearing at presentation and were included in analysis.

INTERVENTIONS

Audiometry, serial magnetic resonance imaging for observation of VS.

MAIN OUTCOME MEASURES

Four-frequency pure tone average (PTA) and word recognition scores (WRS) in the VS-affected ear. Decline in high-frequency PTA (average of thresholds at 4000, 6000, and 8,000 Hz) was defined as ≥10 dB during the study period. Decline in WRS was defined as ≥10%.

RESULTS

Compared with those without, patients with progressive HFHL in the non-VS ear were more likely to experience a decline in WRS in the VS ear (80% vs. 54%, p = 0.031). However, the same group showed no difference (52% vs. 41%, p = 0.40) in decline in PTA of the VS ear.

CONCLUSIONS

Patients with observed VS who experience progressive HFHL in the non-VS ear are more likely to experience significant declines in speech understanding in the VS-affected ear over time. Patients with a history of presbycusis may have an increased risk of losing serviceable hearing because of sporadic VS.

Cochlear Ossification After Vestibular Schwannoma Surgery: A Temporal Bone Study

OBJECTIVE

This study aims to investigate patterns of cochlear ossification (CO) in cadaveric temporal bones of patients who underwent vestibular schwannoma (VS) surgery via the translabyrinthine (TL), middle cranial fossa (MF), or retrosigmoid (RS) approaches.

STUDY DESIGN

Histopathologic analysis of cadaveric temporal bones.

SETTING

Multi-institutional national temporal bone repository.

METHODS

The National Institute of Deafness and Communication Disorders and House Temporal Bone Laboratory at the University of California, Los Angeles and the Massachusetts Eye and Ear Otopathology Laboratory were searched for cadaveric temporal bones with a history of VS for which microsurgery was performed. Exclusion criteria included non-VS and perioperative death within 30 days of surgery. Temporal bones were analyzed histologically for CO of the basal, middle, and apical turns.

RESULTS

Of 92 temporal bones with a history of schwannoma from both databases, 12 of these cases met the inclusion criteria. The approaches for tumor excision included 2 MF, 4 RS, and 6 TL approaches. CO was observed in all temporal bones that had undergone TL surgery. Among temporal bones that had undergone MF or RS surgeries, 5/6 had no CO, and 1/6 had partial ossification. This single case was noted to have intraoperative vestibular violation after RS surgery upon histopathologic and chart review.

CONCLUSION

In this temporal bone series, all temporal bones that had undergone TL demonstrated varying degrees of CO on histological analysis. MF and RS cases did not exhibit CO except in the case of vestibular violation. When cochlear implantation is planned or possible after VS surgery, surgeons may consider using a surgical approach that does not violate the labyrinth.

Automated Whole Cochlear T2 Signal Demonstrates Weak Correlation with Hearing Loss in Observed Vestibular Schwannoma

INTRODUCTION

We sought to evaluate the correlation between whole cochlear T2 signal changes obtained with a novel automated segmentation method and hearing levels, both at diagnosis and over time, in patients with observed vestibular schwannoma.

METHODS

This retrospective correlation study within an academic medical center neurotology practice evaluated 127 patients with vestibular schwannoma observed over time, each with ≥2 MRI scans (367 total) and ≥2 audiograms (472 total). 86 patients had T2-weighted sequences with sufficient resolution for cochlear signal analysis, yielding 348 unique timepoint intervals. The main outcome measure was correlation of the ipsilateral-to-contralateral ratio of whole cochlear T2 signal with hearing outcomes as measured by pure tone average (PTA) and word recognition score (WRS).

RESULTS

Whole cochlear T2 signal ratios did not show a correlation with hearing levels at diagnosis. Change in signal ratio over time showed weak correlation with changes in PTA, but not WRS, over time. Cochlear signal ratio did not precede changes in hearing but did follow changes in both PTA and WRS.

CONCLUSION

Whole cochlear T2 signal ratios were weakly correlated with changes in hearing in patients with observed vestibular schwannoma. The technology of automated segmentation and signal processing holds promise for future evaluation of clinical entities causing cochlear signal changes.

Suppression of inner ear signal intensity on fluid-attenuated inversion recovery magnetic resonance imaging in cats with vestibular disease

OBJECTIVES

Otitis media/interna (OMI) is the most common cause of peripheral vestibular disease in cats. The inner ear contains endolymph and perilymph, with perilymph being very similar in composition to cerebrospinal fluid (CSF). As a very-low-protein fluid, it would be expected that normal perilymph should suppress on fluid-attenuated inversion recovery (FLAIR) MRI sequences. Based on this, we hypothesized that MRI FLAIR sequences should provide a non-invasive way of diagnosing inflammatory/infectious diseases such as OMI in cats, something that has previously been demonstrated in humans and, more recently, in dogs.

METHODS

This was a retrospective cohort study in which 41 cats met the inclusion criteria. They were placed into one of four groups, based on presenting complaint: clinical OMI (group A); inflammatory central nervous system (CNS) disease (group B); non-inflammatory structural disease (group C); and normal brain MRI (control group; group D). Transverse T2-weighted and FLAIR MRI sequences at the level of the inner ears bilaterally were compared in each group. The inner ear was selected as a region of interest using Horos, with a FLAIR suppression ratio calculated to account for variability in signal intensity between MRIs. This FLAIR suppression ratio was then compared between groups. Statistical analyses were performed by an experienced statistician, with a general linear model used to compare mean FLAIR suppression ratio, CSF nucleated cell count and CSF protein concentration between groups.

RESULTS

The OMI group (group A) had significantly lower FLAIR suppression scores compared with all other groups. The CSF cell count was also significantly increased in the OMI (group A) and inflammatory CNS disease (group B) groups compared with the control group (group D).

CONCLUSIONS AND RELEVANCE

This study demonstrates the utility of MRI FLAIR sequences in diagnosing presumptive OMI in cats, similarly to in humans and dogs. This study is relevant to practicing veterinary neurologists and radiologists in interpreting MRI findings in cats with suspected OMI.

Increased Labyrinthine T1 Postgadolinium Signal Intensity Is Associated with the Degree of Ipsilateral Sensorineural Hearing Loss in Patients with Sporadic Vestibular Schwannoma

BACKGROUND AND PURPOSE

Vestibular schwannomas are benign, generally slow-growing tumors, commonly presenting with hearing loss. Alterations in the labyrinthine signal are seen in patients with vestibular schwannoma; however, the association between imaging abnormalities and hearing function remains poorly defined. The purpose of this study was to determine whether labyrinthine signal intensity is associated with hearing in patients with sporadic vestibular schwannoma.

MATERIALS AND METHODS

This was an institutional review board-approved retrospective review of patients from a prospectively maintained vestibular schwannoma registry imaged in 2003-2017. Signal-intensity ratios of the ipsilateral labyrinth were obtained using T1, T2-FLAIR, and postgadolinium T1 sequences. Signal-intensity ratios were compared with tumor volume and audiometric hearing threshold data including pure tone average, word recognition score, and American Academy of Otolaryngology-Head and Neck Surgery hearing class.

RESULTS

One hundred ninety-five patients were analyzed. Ipsilateral labyrinthine signal intensity including postgadolinium T1 images was positively correlated with tumor volume (correlation coefficient = 0.17, P  = .02). Among signal-intensity ratios, postgadolinium T1 was significantly positively associated with pure tone average (correlation coefficient = 0.28, P  < .001) and negatively associated with the word recognition score (correlation coefficient = -0.21, P  = .003). Overall, this result correlated with impaired American Academy of Otolaryngology-Head and Neck Surgery hearing class (P  = .04). Multivariable analysis suggested persistent associations independent of tumor volume with pure tone average (correlation coefficient = 0.25, P  < .001) and the word recognition score (correlation coefficient = -0.17, P  = .02) but not hearing class (P  = .14). No consistent significant associations were noted between noncontrast T1 and T2-FLAIR signal intensities and audiometric testing.

CONCLUSIONS

Increased ipsilateral labyrinthine postgadolinium signal intensity is associated with hearing loss in patients with vestibular schwannoma.

Labyrinthine Fluid Signal Intensity on T2-Weighted MR Imaging in Patients With Vestibular Schwannomas Undergoing Proton Radiotherapy: A Longitudinal Assessment

OBJECTIVE

In vestibular schwannoma patients, a loss of signal intensity (SI) on T2-weighted magnetic resonance imaging (MRI) has been reported within the ipsilateral labyrinth. The purpose of this study was to quantitatively evaluate the occurrence and course of this intensity loss in relation to proton radiotherapy and its possible association with hearing loss.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Patients who received proton therapy for a vestibular schwannoma and underwent at least two high-resolution T2-weighted cisternographic sequence (constructive interference in steady state/fast imaging employing steady-state acquisition/DRIVE) MRIs and audiometry assessments.

MAIN OUTCOME MEASURES

Relative T2 SIs from the vestibules and basal/apical cochlear turns of the labyrinth, bilaterally.

RESULTS

Ninety-five MRI scans from 34 patients were included. The apical turn of the ipsilateral cochlea showed a lower mean cochlear SI than on the contralateral side (±3.5 versus 5.0). The mean relative cochlear SI did not significantly change after proton radiotherapy. The ipsilateral vestibule showed a higher SI than the cochlea. The relative mean cochlear SI was not directly correlated to (the degree of) hearing loss before or after proton radiotherapy, nor did it predict future hearing loss.

CONCLUSION

The relative mean cochlear SI on cisternographic T2-MRI in vestibular schwannoma patients is diminished on the treated side, when compared with the ipsilateral vestibule and the contralateral cochlea/vestibule. The SI of the ipsilateral cochlea does not further decrease after proton radiotherapy and seems to be related to the tumor rather than the therapy. The diminished cochlear SI does not correlate with subsequent loss of hearing.

Intracochlear signal in FIESTA-C and hearings of patients with cerebellopontine angle schwannoma

BACKGROUND

Hearing loss in patients with cerebellopontine angle (CPA) schwannoma, is thought to be caused by the damage to the cochlea and the cochlear nerve.

AIM

This study aimed to examine the relationships between the intracochlear signal in magnetic resonance imaging (MRI) and hearing in patients with CPA schwannoma.

MATERIAL AND METHOD

In 79 patients with CPA schwannoma, we retrospectively examined the signal in the cochlea on the affected side was compared with that on the unaffected side to determine signal degradation in fast imaging reagents steady-state acquisition with cycle phases (FIESTA-C) MRI. For hearing evaluation, pure tone audiometry (PTA), speech audiometry, distortion product otoacoustic emissions (DPOAE), and auditory brainstem response (ABR) were used. For each parameter, we examined the differences between the groups with and without signal degradation.

RESULTS

In the hearing test results, the I-wave latency of ABR was significantly longer in the group with signal degradation in FIESTA-C (1.84 ± 0.35 msec vs. 2.04 ± 0.37 msec, p = 0.048). There was no statistically significant difference in other tests.

CONCLUSION

The MRI signal changes in the cochlear were related to the I-wave latency of ABR and reflected cochlear function.

SIGNIFICANCE

We suggested the cochlear signal changes in CPA schwannoma patients related the hearing.

Relationship between Signal Intensity of the Labyrinth and Cochleovestibular Testing and Morphologic Features of Vestibular Schwannoma

Objectives The aim of this article was to evaluate the relationship between signal intensity of the labyrinth and vestibulocochlear function and morphologic features of vestibular schwannoma (VS).

Design Cross-sectional Study.

Setting Tertiary referral center.

Participants Fifty-four patients with sporadic, untreated VS.

Main Outcome Measure Signal intensity of the cochlea and vestibule (SIRc and SIRv: signal intensity of cochlea/vestibule compared with cerebellar signal intensity; AURc and AURv: SIRc/SIRv of the affected side compared with the unaffected side) in 1.5T T2-weighted images was correlated with size (Hannover classification), cystic status, distance from the fundus of the internal auditory canal, video head impulse test (vHIT), and audiometry.

Results Signal intensity of the vestibule was higher than that of the cochlea (p < 0.01). Large tumors had lower SIRc than smaller tumors (p = 0.03); Hannover T1 tumors had higher SIRc (p < 0.01), SIRv (p < 0.01), AURc (p < 0.01) and AURv (p < 0.01) than the rest; heterogenous and cystic tumors had higher SIRv than solid large tumors (p = 0.02); superior vestibular nerve pattern on vHIT had higher SIRv and AURv than inferior vestibular nerve and mixed patterns (p = 0.03 and 0.004, respectively); and there was a weak correlation between AURv and speech discrimination (r = 0.33, p = 0.04).

Conclusion A more abnormal signal intensity of the labyrinth is associated with larger size and solid status of VS. There was a positive relationship between signal intensity of the labyrinth and speech discrimination scores on audiogram.

Cochlear T2 Signal May Predict Hearing Outcomes After Resection of Acoustic Neuroma

OBJECTIVE

Examine the impact of preoperative cochlear Fast Imaging Employing Steady-state Acquisition (FIESTA) and Constructive Interference in Steady State (CISS) signal intensity on hearing outcomes after middle cranial fossa (MCF) resection of acoustic neuroma (AN).

METHODS

Adult patients (≥18 years) who underwent MCF AN resection for hearing preservation (HP) between November 2017 and September 2019 were retrospectively reviewed. All patients had preoperative word recognition score (WRS) ≥50%. HP was defined as postoperative WRS ≥50%. A neuroradiologist blinded to patients' clinical and audiometric outcomes reviewed patients' preoperative magnetic resonance images. Ipsilateral-to-contralateral cochlear FIESTA/CISS signal intensity ratios were determined using hand-drawn regions of interest focused on the cochlear fluid. Preoperative and postoperative pure tone average (PTA) and WRS were reviewed.

RESULTS

Fifty-one patients were reviewed (60.8% female). Mean age was 47 years and mean tumor size 9.2 mm (±3.8). Hearing was preserved in 56.9% (n = 29). FIESTA/CISS signal ratios did not significantly differ between patients with and without HP. Lower FIESTA/CISS signal ratios correlated with greater declines in hearing (r = 0.322, p = 0.011 for PTA; and r = 0.384, p = 0.004 for WRS). On multivariate analysis accounting for tumor size and preoperative PTA/WRS, decreases in FIESTA/CISS signal ratios independently predicted greater declines in hearing by PTA (b = -100.9, p = 0.012) and WRS (b = 76.208), although the latter result was not statistically significant (p = 0.078).

CONCLUSIONS

Cochlear FIESTA/CISS signal intensity may be a predictor of postoperative hearing loss after MCF AN resection. In this cohort, degraded preoperative cochlear FIESTA/CISS signal strongly predicted postoperative hearing loss.Level of Evidence: IV.

Signal and morphological changes in the endolymph of patients with vestibular schwannoma on non-contrast 3D FLAIR at 3 Tesla

Background

Non-contrast FLAIR revealed increased signal within the inner ear in patients with vestibular schwannoma, which is generally assumed to occur in the perilymph; however, the majority of previous studies did not differentiate between the endolymph and perilymph. Therefore, endolymph signal changes have not yet been investigated in detail. The purpose of the present study was three-fold: (1) to assess perilymph signal changes in patients with vestibular schwannoma on heavily T2-weighted (T2W) 3D FLAIR, also termed positive perilymphatic images (PPI), (2) to evaluate signal and morphological changes in the endolymph on PPI, and (3) to establish whether vertigo correlates with the signal intensity ratios (SIR) of the vestibular perilymph or vestibular endolymphatic hydrops.

Methods

Forty-two patients with unilateral vestibular schwannoma were retrospectively recruited. We semi-quantitatively and qualitatively evaluated the perilymph signal intensity on the affected and unaffected sides. We also quantitatively examined the signal intensity of the vestibular perilymph and assessed the relationship between vertigo and the SIR of the vestibular perilymph on the affected side. We semi-quantitatively or qualitatively evaluated the endolymph, and investigated whether vestibular hydrops correlated with vertigo.

Results

The perilymph on the affected side showed abnormal signal more frequently (signal intensity grade: overall mean 1.45 vs. 0.02; comparison of signal intensity: overall mean 36 vs. 0 cases) and in more parts (the entire inner ear vs. the basal turn of the cochlea and vestibule) than that on the unaffected side. No significant difference was observed in the SIR of the vestibular perilymph with and without vertigo (5.54 vs. 5.51, p = 0.18). The endolymph of the vestibule and semicircular canals showed the following characteristic features: no visualization (n = 4), signal change (n = 1), or vestibular hydrops (n = 10). A correlation was not observed between vestibular hydrops and vertigo (p = 1.000).

Conclusions

PPI may provide useful information on signal and morphological changes in the endolymph of patients with vestibular schwannoma. Further research is warranted to clarify the relationship between vertigo and the MR features of the inner ear.

Brainstem hyperintensity in patients with vestibular schwannoma is associated with labyrinth signal on magnetic resonance imaging but not vestibulocochlear tests

OBJECTIVES

Focal hyperintensity in the dorsal brainstem (HDB) has been described in large cerebellopontine angle tumours and is thought to represent vestibular nuclei degeneration, but its functional significance has not been thoroughly investigated. Our aim was to analyse its relationship to imaging characteristics of the tumour and inner-ear structures and to vestibulocochlear functional tests.

METHODS

We retrospectively reviewed 54 patients with a histological diagnosis of vestibular schwannoma (VS). Magnetic resonance imaging tumour characteristics (size, cystic composition and distance from the cochlear aperture), signal intensity ratio of the cochlea and vestibule in fluid-attenuated inversion recovery (FLAIR) and fast imaging employing steady-state acquisition (FIESTA)/fast spin-echo imaging with variable flip angles (CUBE) and vestibulocochlear function tests (audiometry, auditory brainstem response (ABR) and video head impulse testing (vHIT)) were obtained. Statistical analyses were performed to evaluate their relation to focal HDB.

RESULTS

Focal HDB was found in 22% of VS. It was significantly associated with large (p < 0.001) and cystic (p = 0.004) tumours and also with tumours located further from the cochlear aperture (p = 0.039). The signal intensity ratio of the cochlea on FLAIR was higher in patients with HDB (p < 0.014), but this difference was not observed in FIESTA/CUBE (p = 0.981). Audiometry, ABR and vHIT results did not significantly differ in patients with HDB, but ABR results were worse in patients with higher cochlear signal intensity on FLAIR sequences (p = 0.026).

CONCLUSIONS

Focal HDB in patients with VS was associated with increased signal intensity ratio of the cochlea on FLAIR in patients with VS but not directly to the results of vestibulocochlear function tests.

Inner Ear Enhancement With Delayed 3D-FLAIR MRI Imaging in Vestibular Schwannoma

OBJECTIVES

To evaluate blood-labyrinth barrier permeability using delayed gadolinium enhanced three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) in patients with untreated sporadic vestibular schwannoma (VS) to interrogate the etiopathogenesis of progressive sensorineural hearing loss.

DESIGN

Prospective case series.

SETTING

Single institution tertiary care center.

PARTICIPANTS

Patients with previously untreated small to medium-sized unilateral VS undergoing 3D-FLAIR imaging 10 minutes (immediate) and 5 to 8 hours (delayed) after administration of intravenous gadolinium.

MAIN OUTCOME MEASURES

Comparison of cochlear and vestibular signal intensity ratios (SIRs) across immediate and delayed images and across the tumor and nontumor ear.

RESULTS

Six of eight (75%) patients demonstrated asymmetric enhancement of inner ear structures on delayed contrast-enhanced imaging. Delayed mean cochlea and vestibule SIRs were significantly greater than immediate SIRs (cochlea: 1.91 versus 1.21 [p = 0.02]; vestibule 1.74 versus 1.15 [p = 0.02]). A higher vestibule SIR was statistically significantly associated with poorer pure-tone average and word recognition scores (p = 0.001).

CONCLUSION

Ears with VS exhibited increased enhancement on delayed 3D FLAIR imaging. These findings suggest that alterations in blood-labyrinth barrier permeability may explain progressive sensorineural hearing loss in a subset of patients with untreated VS.

T2 relaxation time shortening in the cochlea of patients with sudden sensory neuronal hearing loss: a retrospective study using quantitative synthetic magnetic resonance imaging

OBJECTIVES

High cochlear signal intensity on three-dimensional (3D) T2 fluid-attenuated inversion recovery (FLAIR) sequences in patients with sudden sensorineural hearing loss (SSNHL) has been reported. Here, we evaluated the cochlear T2 relaxation time differences in patients with idiopathic SSNHL using quantitative synthetic MRI (SyMRI).

METHODS

Twenty-four patients with unilateral SSNHL who underwent precontrast conventional 3D FLAIR and SyMRI were retrospectively included. T1 and T2 relaxation times and the proton density (PD) of the bilateral ears were measured by manually drawn regions of interest. Wilcoxon signed-rank tests and intra- and interobserver correlation analyses were performed. Qualitative analysis was also performed to determine the presence and laterality of the asymmetric high signal intensity on synthetic FLAIR (SyFLAIR) images.

RESULTS

The T2 relaxation time was significantly lower in the affected (basal and apico-middle turns) than in the unaffected cochlea (basal turn: 519 ± 181.3 vs. 608.8 ± 203.6, p = 0.042; apico-middle turn: 410.8 ± 163.8 vs. 514.5 ± 186.3, p = 0.037). There were no significant differences in the T1 relaxation time and PD between the affected and unaffected ears (p > 0.05). Additionally, three patients without asymmetric signal intensity on conventional MRI showed asymmetric increased signal intensity in the affected ear on SyFLAIR.

CONCLUSIONS

The T2 relaxation time was significantly shorter in the affected than in the unaffected cochlea of patients with idiopathic SSNHL. The SyMRI-derived T2 relaxation time may be a promising imaging marker, suggesting that the changes in inner ear fluid composition are implicated in the idiopathic SSNHL development.

KEY POINTS

• T2 relaxation time was significantly lower in the affected than in the unaffected cochlea. • SyFLAIR showed increased lesion conspicuity compared to conventional 3D-FLAIR in detecting asymmetric high signal intensity of the affected side. • SyMRI-derived T2 relaxation time may be a promising imaging marker of the affected ear in patients with idiopathic SSNHL.

Predicting Hearing Outcomes in Conservatively Managed Vestibular Schwannoma Patients Utilizing Magnetic Resonance Imaging

OBJECTIVE

Management of small vestibular schwannomas has evolved to where observation with interval imaging is an accepted treatment strategy. Loss of residual hearing is a known complication of observation. Magnetic resonance imaging (MRI) may provide critical information to assist in determining which tumors are at highest risk of hearing loss. We wished to determine what effect fundal cap size and cochlear fluid-attenuated inversion recovery (FLAIR) signal had on the progression of hearing loss in a large cohort of observed subjects.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary academic referral center.

PATIENTS

Three hundred ninety-three adults with a vestibular schwannoma who underwent expectant management with serial audiograms and MRI.

INTERVENTIONS

Audiogram and MRI.

MAIN OUTCOME MEASURES

Hearing outcomes included pure-tone average and word discrimination score (WRS). Cochlear FLAIR signal was measured as a ratio between the affected and nonaffected cochlea. Cerebrospinal fluid fundal cap was measured from the most lateral aspect of the tumor to the fundus of the internal auditory canal.

RESULTS

An increased cochlear FLAIR ratio was associated with a worse initial WRS (p = 0.0001, β=-0.25). A multivariate regression analysis demonstrated the variables fundal cap and initial WRS to significantly predict change in WRS over time. The larger the fundal cap size, the smaller the change in the WRS (p = 0.047, β=-0.35).

CONCLUSIONS

Cerebrospinal fluid fundal cap size predicts the natural history of hearing in vestibular schwannoma patients. The presence of a smaller fundal cap is correlated with a greater risk of progression of hearing loss and should be a variable considered in the management of small vestibular schwannomas.

MRI of the Internal Auditory Canal, Labyrinth, and Middle Ear: How We Do It

MRI is firmly established as an essential modality in the imaging of the temporal bone and lateral skull base. It is used to evaluate normal anatomic structures, evaluate for vestibular schwannomas, assess for inflammatory and/or infectious processes, and detect residual and/or recurrent cholesteatoma. It is also extensively used in pre- and postoperative evaluations, particularly in patients with vestibular schwannomas and candidates for cochlear implantation. Nevertheless, despite the widespread use of MRI for these purposes, many radiologists remain unfamiliar with the complex anatomy and expected imaging findings with such examinations. The purpose of this review is to provide an overview of the most useful MRI sequences for internal auditory canal and labyrinthine imaging, review the relevant anatomy, and discuss the expected appearances of the most commonly encountered pathologic entities. In addition, the features at pre- and postprocedural MRI will be discussed to help ensure that diagnostic radiologists may be of greatest use to the ordering physicians. © RSNA, 2020.

Inner ear fluid-attenuated inversion recovery MRI signal intensity in dogs with vestibular disease

The inner ear contains endolymph and perilymph. The second is comparable and in continuity with the cerebrospinal fluid (CSF) so it is expected to suppress in fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) if normal. Even though inner ear FLAIR abnormalities have been extensively described in humans with inner ear disease, its diagnostic value in dogs is yet to be proven. The goal of this retrospective cohort study was to investigate the diagnostic utility of FLAIR MRI in dogs with vestibular disease. A review of medical records identified 101 dogs that had brain MRI performed because of vestibular signs. Based on the final diagnosis, patients were allocated to three groups: otitis media/interna, idiopathic vestibular disease, and central vestibular disease. Additionally, a control group (n = 73) included dogs with normal MRI and without vestibular signs. Inner ears were delineated using a region of interest, and signal intensity was measured in FLAIR and T2-weighted images. The percentages of suppression in FLAIR were calculated and compared between affected and unaffected sides of each individual and between groups using a general linear mixed model. Correlation between suppression and CSF cell count and protein concentration was assessed. Affected inner ears in dogs with otitis media/interna had decreased suppression in FLAIR compared to the unaffected side (P < .001), and all other groups (P < .01). No significant correlation was detected between CSF results and suppression. These results show the diagnostic value of FLAIR in otitis media/interna due to lack of suppression in the affected inner ear.

Biomarkers in Vestibular Schwannoma-Associated Hearing Loss

Vestibular schwannomas (VSs) are benign tumors composed of differentiated neoplastic Schwann cells. They can be classified into two groups: sporadic VS and those associated with neurofibromatosis type 2 (NF2). VSs usually grow slowly, initially causing unilateral sensorineural hearing loss (HL) and tinnitus. These tumors cause HL both due to compression of the auditory nerve or the labyrinthine artery and due to the secretion of different substances potentially toxic to the inner ear or the cochlear nerve. As more and more patients are diagnosed and need to be managed, we are more than ever in need of searching for biomarkers associated with these tumors. Owing to an unknown toxic substance generated by the tumor, HL in VS may be linked to a high protein amount of perilymph. Previous studies have identified perilymph proteins correlated with tumor-associated HL, including μ-Crystallin (CRYM), low density lipoprotein receptor-related protein 2 (LRP2), immunoglobulin (Ig) γ-4 chain C region, Ig κ-chain C region, complement C3, and immunoglobulin heavy constant γ 3. Besides, the presence of specific subtypes of heat shock protein 70 has been suggested to be associated with preservation of residual hearing. It has been recently demonstrated that chemokine receptor-4 (CXCR4) is overexpressed in sporadic VS as well as in NF2 tumors and that hearing disability and CXCR4 expression may be correlated. Further, the genetic profile of VS and its relationship with poor hearing has also been studied, including DNA methylation, deregulated genes, growth factors, and NF2 gene mutations. The knowledge of biomarkers associated with VS would be of significant value to maximize outcomes of hearing preservation in these patients.

Utility of Magnetic Resonance Imaging in Differentiating Cerebrospinal Fluid Leak from Middle Ear Effusion

Objective

To demonstrate the clinical utility, sensitivity, and specificity of standard magnetic resonance imaging (MRI) sequences in differentiating temporal bone cerebrospinal fluid leaks from all other middle ear effusions.

Study Design

Retrospective imaging review.

Setting

Academic medical center.

Subjects

Patients with cerebrospinal fluid leaks or other middle ear effusions who also underwent MRI.

Methods

Patients were assigned to cerebrospinal fluid leak and other effusion cohorts based on clinical course, findings at surgery/myringotomy, and beta-2 transferrin fluid analysis. Reviewers blinded to the clinical outcome examined T1-weighted, T2-weighted, diffusion-weighted, fluid-attenuated inversion recovery (FLAIR), and 3-dimensional (3D) acquired T2-weighted MRI sequences. For each sequence, fluid imaged in the temporal bone was graded as either similar or dissimilar in signal intensity to cerebrospinal fluid in the adjacent subarachnoid space. Signal similarity was interpreted as being diagnostic of a leak. Test characteristics in predicting the presence of a leak were calculated for each series.

Results

Eighty patients met criteria (41 leaks, 39 other effusions). The 3D T2 series was 76% sensitive and 100% specific in diagnosing a leak, and FLAIR was 44% sensitive and 100% specific. The T1-weighted (73% sensitive, 69% specific), T2-weighted (98% sensitive, 5.1% specific), and diffusion-weighted (63% sensitive, 66% specific) series were less useful.

Conclusions

MRI, with attention to 3D T2 and FLAIR series, is a noninvasive and highly specific test for diagnosing cerebrospinal fluid leak in the setting of an indeterminate middle ear effusion.

Radiosurgery of vestibular schwannoma: prognostic factors for hearing outcome using 3D-constructive interference in steady state (3D-CISS)

PURPOSE

Stereotactic radiosurgery (SRS) is an effective treatment for vestibular schwannoma (VS). Three-dimensional (3D) constructive interference in steady state (CISS) is the preferred magnetic resonance imaging (MRI) sequence for evaluating signal changes in the inner ear endolymph. Previous studies demonstrated a correlation between pretreatment cochlear signal intensity in 3D-CISS and posttherapeutic hearing outcomes. The purpose of our study was to compare 3D-CISS sequences before and after primary SRS of unilateral VSs to evaluate the effect of radiosurgery on the 3D-CISS signal intensities of cochlea and sacculus/utriculus.

METHODS

We retrospectively reviewed 47 patients with unilateral VS treated with SRS. The neuroradiological MRI datasets were analysed to evaluate the signal intensity of the inner ear structure, tumour size, Koos grade, tumour volume, and infiltration of the cochlear aperture before therapy and at follow-up. The differences in these signal intensities before SRS and at follow-up were correlated with clinical symptoms, cochlear radiation dose, tumour volume and infiltration of the cochlear aperture.

RESULTS

No differences were found between signal intensities in cochlea and utriculus/sacculus before and after SRS and no correlation with clinical symptoms, cochlear radiation dose, tumour volume, Koos grade or infiltration of the cochlear aperture (all p > 0.05).

CONCLUSION

Our study supports the theory of a complex interaction causing alteration of the endolymph protein concentration and not a direct dependency on the SRS. Use of modern dosing schemes will have a positive impact on clinical outcome with preservation of hearing in patients with VS.

Is an Intravenous Injection of Gadolinium Really Necessary for Intralabyrinthine Schwannomas MR Examination?

OBJECTIVES

Our aim was to confirm the usefulness of T2-weighted (T2W) gradient-echo sequence for detection and topographic diagnosis of intralabyrinthine schwannomas (ILS) compared with T1W contrast-enhanced sequence as gold standard, to evaluate the necessity of intravenous gadolinium injection for ILS follow-up imaging.

METHODS

Thirty patients with ILS were retrospectively enrolled and compared to a control group of 30 patients with no inner ear pathology. All patients underwent a T2W gradient-echo steady-state free precession (SSFP) acquisition at 3T, which was visually analyzed by two radiologists and compared to contrast-enhanced T1W sequence. A quantitative analysis was also performed, with the measurement of the tumor and inner ear signal on T2W images and the measurement of the tumor length in cochlear schwannomas.

RESULTS

T2W FIESTA-C sequence correctly diagnosed ILS with a sensitivity (Se) of 95% and a specificity (Sp) of 100%, with matching results for their topographic evaluation (Se 92%, Sp 98%) compared with the gold-standard. The difference between the two sequences was only 2.5%, with excellent interobserver agreement. The tumor signal on T2W images was significantly lower than the normal bright signal of the normal inner ear fluids (mean signal ratio = 0.42 vs 0.98).

CONCLUSION

The positive and topographic diagnostic accuracy of T2W FIESTA-C sequence was excellent compared with the T1W contrast-enhanced sequence, even though the latter remains easier and faster to analyze for an untrained radiologist. The performances of T2W gradient-echo sequence at 3T make it a reasonable alternative strategy for following ILS after they are diagnosed.

The 'full-blown' MRI of sudden hearing loss: 3D FLAIR in a patient with bilateral metastases in the internal auditory canals

We report a case of a 57-year-old man with bilateral masses in the internal auditory canal. The peculiar findings at magnetic resonance imaging with tridimensional fluid-attenuated inversion recovery sequence combined with clinical data provided new insights into understanding the pathophysiology of the hearing loss.

3D-constructive interference into steady state (3D-CISS) labyrinth signal alteration in patients with vestibular schwannoma

OBJECTIVE

To evaluate signal intensity of the inner ear using 3D-CISS imaging and correlated signal characteristics in patients with vestibular schwannoma to neuro-otological symptoms.

METHODS

Sixty patients with unilateral vestibular schwannoma were retrospectively reviewed. All patients had had initial and follow-up magnetic resonance imaging (MRI). Individual treatment strategies consisted of "wait-and-watch", surgical tumour resection, stereotactic radiosurgery or both surgery and stereotactic radiosurgery. For all patients a complete baseline and treatment course neuro-otological examination was re-studied.

RESULTS

On initial MRI, 3D-CISS sequence signal loss of the membranous labyrinth was present in 20 patients (33.3%); signal loss of cochlea in 20 (33.3%) and coincident signal loss of sacculus/utriculus in 17 (85%) of them. Sequential analysis of follow-up MRI series demonstrated slightly increased labyrinthine signal degradation, independently of the chosen therapy. Correlation of initial MRI results with initial neuro-otological symptoms showed significance only for cochlear obstruction versus vertigo (p=0.0397) and sacculus/utriculus obstruction versus vertigo (p=0.0336). No other statistically significant relationships were noted.

CONCLUSION

3D-constructive interference into steady state (3D-CISS) is appropriate for observing inner ear signal loss in patients with vestibular schwannoma. However, except for vertigo, no significant correlation was noted between initial neuro-otological symptomatology and signal loss of the inner ear.

Differentiation of vestibular schwannomas from meningiomas of the internal auditory canal using perilymphatic signal evaluation on T2-weighted gradient-echo fast imaging employing steady state acquisition at 3T

BACKGROUND

Our aim was to confirm the usefulness of the perilymphatic signal changes on T2-weighted (T2W) gradient-echo sequence to differentiate vestibular schwannomas from internal auditory canal (IAC) meningiomas, through a compartmental analysis of inner ear fluids signal intensity.

METHODS

A total of 203 patients with all criteria for typical vestibular schwannoma on T1-weighted contrast-enhanced sequences were retrospectively enrolled (190 schwannomas and 13 meningiomas). All patients underwent a T2W gradient-echo steady state free precession (SSFP) acquisition at 3T. Two radiologists analysed the signal intensity of the perilymph (cistern and cochlea) and endolymph (saccule and utricle) using a region of interest-based method for obtaining ratios between the analysed structures and the cerebrospinal fluid (CSF).

RESULTS

Obstructive vestibular schwannomas showed a markedly decreased perilymphatic signal in both cistern and cochlea; the cistern/CSF ratio (Ci/CSF) was 0.62. The decrease was more moderate in IAC meningiomas (Ci/CSF = 0.81). For Ci/CSF > 0.70, the tumour was more likely a meningioma, with a 92% sensitivity and 83% specificity. No endolymphatic signal changes were observed.

CONCLUSION

The pronounced decrease in perilymphatic signal on a T2W SSFP sequence in obstructive vestibular schwannoma provides a new tool to differentiate schwannomas from IAC meningiomas, which may be useful to overcome the insufficiencies of morphological analysis.

The Management and Imaging of Vestibular Schwannomas

Vestibular schwannomas are the most common cerebellopontine angle tumor. During the past century, the management goals of vestibular schwannomas have shifted from total resection to functional preservation. Current treatment options include surgical resection, stereotactic radiosurgery, and observation. Imaging has become a crucial part of the initial screening, evaluation, and follow-up assessment of vestibular schwannomas. Recognizing and understanding the management objectives, various treatment modalities, expected posttreatment findings, and complications allows the radiologist to play an essential role in a multidisciplinary team by providing key findings relevant to treatment planning and outcome assessment. The authors provide a comprehensive discussion of the surgical management, role of radiation therapy and observation, imaging differential, and pre- and posttreatment imaging findings of vestibular schwannomas.

Clinical significance of an increased cochlear 3D fluid-attenuated inversion recovery signal intensity on an MR imaging examination in patients with acoustic neuroma

BACKGROUND AND PURPOSE

The increased cochlear signal on FLAIR images in patients with acoustic neuroma is explained by an increased concentration of protein in the perilymphatic space. However, there is still debate whether there is a correlation between the increased cochlear FLAIR signal and the degree of hearing disturbance in patients with acoustic neuroma. Our aim was to investigate the clinical significance of an increased cochlear 3D FLAIR signal in patients with acoustic neuroma according to acoustic neuroma extent in a large patient cohort.

MATERIALS AND METHODS

This retrospective study enrolled 102 patients with acoustic neuroma, who were divided into 2 groups based on tumor location; 22 tumors were confined to the internal auditory canal and 80 extended to the cerebellopontine angle cistern. Pure tone audiometry results and hearing symptoms were obtained from medical records. The relative signal intensity of the entire cochlea to the corresponding brain stem was calculated by placing regions of interest on 3D FLAIR images. Statistical analysis was performed to compare the cochlear relative signal intensity between the internal auditory canal acoustic neuroma and the cerebellopontine angle acoustic neuroma. The correlation between the cochlear relative signal intensity and the presence of hearing symptoms or the pure tone audiometry results was investigated.

RESULTS

The internal auditory canal acoustic neuroma cochlea had a significantly lower relative signal intensity than the cerebellopontine angle acoustic neuroma cochlea (0.42±0.15 versus 0.60±0.17, P<.001). The relative signal intensity correlated with the audiometric findings in patients with internal auditory canal acoustic neuroma (r=0.471, P=.027) but not in patients with cerebellopontine angle acoustic neuroma (P=.427). Neither internal auditory canal acoustic neuroma nor cerebellopontine angle acoustic neuroma showed significant relative signal intensity differences, regardless of the presence of hearing symptoms (P>.5).

CONCLUSIONS

The cochlear signal on FLAIR images may be an additional parameter to use when monitoring the degree of functional impairment during follow-up of patients with small acoustic neuromas confined to the internal auditory canals.

Cochlear obliteration after translabyrinthine vestibular schwannoma surgery

The objective of the study was to determine the temporal occurrence of cochlear obliteration following translabyrinthine vestibular schwannoma resection. A retrospective chart review, cross-sectional study, and sequential analysis of the time series were performed. The retrospective study included patients undergoing translabyrinthine resection for stage T1-T2 vestibular schwannoma from 2007 to 2010 without prior therapy and postoperative follow-up including MRI of the brain and the cerebellopontine angle. Already 3 months after surgery a radiographic labyrinthine change was observed in 66.7 %, a partial obstruction in 50 %, and an obstruction limited to the saccule in 16.7 %. Only 33.3 % of the patients showed an unchanged inner ear. In consideration of early cochlear obstruction after translabyrinthine vestibular schwannoma resection, temporary follow-up is necessary. Since the indications for cochlear implantation (CI) have been extended, especially concerning patients with single-side deafness, a simultaneous or early second-stage CI after tumour removal should be discussed.

Decreased vestibular signal intensity on 3D-FIESTA in vestibular schwannomas differentiating from meningiomas

INTRODUCTION

With reported characteristic MR features, it is difficult to differentiate vestibular schwannomas (VSs) from cerebellopontine angle (CPA) meningiomas (CPAMs) in some cases. This study aimed to evaluate vestibular signal intensity changes in patients with VS and those with CPAM on three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA), and to test the effectiveness of the signal intensity change to differentiate these two common CPA tumors.

METHODS

We retrospectively reviewed 21 patients with unilateral VS, six patients with unilateral CPAM, and 25 control subjects. Setting regions of interest in the bilateral vestibules and cerebellar white matter on 3D-FIESTA, we compared the ratio of the signal intensity (SIR) of the vestibule to that of the cerebellar white matter (SIRv) among the VS, CPAM, and control subject groups. We also compared the ratio of SIRv on the affected side (a-SIRv) to that on the unaffected side (AURv) between the VS and CPAM.

RESULTS

The a-SIRv in the VS group was significantly lower than the overall SIRv in the control subjects (pre-contrast, P < 0.001; post-contrast, P < 0.001) and the a-SIRv in the CPAM group (pre-contrast, P = 0.001; post-contrast, P = 0.001). The AURv in the VS group was significantly lower than that in the CPAM groups (pre-contrast, P < 0.001; post-contrast, P < 0.001).

CONCLUSION

Decreased vestibular signal intensity on the affected side on 3D-FIESTA was observed in patients with VS, but not in those with CPAM or in normal subjects. The signal intensity change has the potential to be used in differentiating VS from CPAM.

Postoperative imaging of vestibular schwannomas

Symptomatic vestibular schwannomas can be treated with resection (translabyrinthine, retrosigmoid [suboccipital], or middle cranial fossa approaches) or stereotactic radiosurgery. When appropriate, auditory brainstem stimulators can also be implanted in patients with current or impending hearing loss due to bilateral vestibular schwannomas. Imaging plays a prominent role in determining management following these procedures. In this article, the expected postoperative imaging appearances are depicted. The radiological features of complications are also reviewed, including recurrent tumor, fat graft necrosis, CSF leakage, infection, hydrocephalus, cerebral infarction, venous sinus thrombosis, hemorrhage, and temporal lobe and cerebellar contusions.

Frequency and diagnostic utility of intralabyrinthine FLAIR hyperintensity in the evaluation of internal auditory canal and inner ear pathology

RATIONALE AND OBJECTIVES

Fluid-attenuated inversion recovery (FLAIR) imaging can detect elevated protein levels in fluid that may be difficult or impossible to detect with T1- or T2-weighted imaging. The purpose of this study is to evaluate the frequency and asses the diagnostic utility of abnormal FLAIR signal in various types of inner ear and internal auditory canal (IAC) pathology.

MATERIALS AND METHODS

A retrospective review of medical records and magnetic resonance images from 187 consecutive patients who underwent imaging of the temporal bones for possible inner ear or IAC pathology over a 1-year period were reviewed for abnormal increased FLAIR signal, increased intrinsic T1 signal, abnormal enhancement after gadolinium administration, and the presence of a mass lesion within the cerebellopontine angle, IAC, or inner ear. Reviewers were blinded to clinical diagnosis.

RESULTS

Twenty-five of 32 (78%) patients with schwannomas restricted to the IAC and cerebellopontine angle demonstrated associated increased FLAIR signal within the ipsilateral inner ear structures. The sensitivity, specificity, positive predictive value, and negative predictive value of inner ear FLAIR hyperintensity for a schwannoma were 80%, 95%, 78%, and 95%, respectively. Inner ear FLAIR hyperintensity was also seen in cases of intracochlear hemorrhage, labyrinthitis, and labyrinthitis ossificans, but these conditions did not occur with sufficient frequency in our study population to determine statistical significance.

CONCLUSION

Identification of inner ear FLAIR hyperintensity can alert the radiologist to scrutinize pre- and post-gadolinium T1-weighted images and T2-weighted images for subtle IAC and inner ear abnormalities. Although enhancement after the administration of gadolinium contrast media is the gold standard for detection of schwannoma, inner ear FLAIR hyperintensity may be a helpful diagnostic adjunct for vestibular schwannoma. This may be particularly helpful when gadolinium was not administered and the T2-weighted images are equivocal, especially when dedicated thin-section imaging of the IACs and temporal bones was not performed.

Increased signal intensity of the cochlea on pre- and post-contrast enhanced 3D-FLAIR in patients with vestibular schwannoma

INTRODUCTION

In the vestibular schwannoma patients, the pathophysiologic mechanism of inner ear involvement is still unclear. We investigated the status of the cochleae in patients with vestibular schwannoma by evaluating the signal intensity of cochlear fluid on pre- and post-contrast enhanced thin section three-dimensional fluid-attenuated inversion recovery (3D-FLAIR).

METHODS

Twenty-eight patients were retrospectively analyzed. Post-contrast images were obtained in 18 patients, and 20 patients had the records of their pure-tone audiometry. Regions of interest of both cochleae (C) and of the medulla oblongata (M) were determined on 3D-FLAIR images by referring to 3D heavily T2-weighted images on a workstation. The signal intensity ratio between C and M on the 3D-FLAIR images (CM ratio) was then evaluated. In addition, correlation between the CM ratio and the hearing level was also evaluated.

RESULTS

The CM ratio of the affected side was significantly higher than that of the unaffected side (rho < 0.001). In the affected side, post-contrast signal elevation was observed (rho < 0.005). In 13 patients (26 cochleae) who underwent both gadolinium injection and the pure-tone audiometry, the post-contrast CM ratio correlated with hearing level (rho < 0.05).

CONCLUSION

The results of the present study suggest that alteration of cochlear fluid composition and increased permeability of the blood-labyrinthine barrier exist in the affected side in patients with vestibular schwannoma. Furthermore, although weak, positive correlation between post-contrast cochlear signal intensity on 3D-FLAIR and hearing level warrants further study to clarify the relationship between 3D-FLAIR findings and prognosis of hearing preservation surgery.

Signal intensity change of the labyrinth in patients with surgically confirmed or radiologically diagnosed vestibular schwannoma on isotropic 3D fluid-attenuated inversion recovery MR imaging at 3 T

OBJECTIVE

The purpose of this study was to evaluate the signal intensity (SI) change of the labyrinth in patients with vestibular schwannoma on isotropic 3D fluid-attenuated inversion recovery (FLAIR) imaging at 3 T.

METHODS

Thirty-four patients with surgically confirmed or radiologically diagnosed vestibular schwannoma were included in this study. Retrospectively, we visually and quantitatively compared the SIs of the cochlea and vestibule on the affected side with those on the unaffected side. We also investigated whether there was correlation between the SI ratios (SIRs) of the labyrinth and the audiometric findings.

RESULTS

On 3D FLAIR images, the SI of the cochlea and vestibule on the affected side was significantly increased in 97% (33/34) and 91% (31/34), respectively. While the SI of the cochlea was diffusely increased, that of the vestibule was only partially increased. Quantitative study also revealed statistically significantly higher SIRs of the cochlea (0.99 +/- 0.29) and vestibule (0.73 +/- 0.31) on the affected side, compared with the cochlea (0.47 +/- 0.20) and vestibule (0.19 +/- 0.10) on the unaffected side. There was no significant correlation of the SIRs of the labyrinth with the degree of hearing loss.

CONCLUSION

In patients with vestibular schwannoma, isotropic 3D FLAIR imaging is a useful method for the evaluation of the SI changes of the labyrinth.

Diagnosis and therapy of vestibular schwannoma

MRI studies are of paramount importance for diagnosis and follow-up measurements during conservative and postinterventional management of vestibular schwannomas (VS). MRI findings that convey important information for hearing-preservation VS surgery are: length of tumor-cochlear nerve contact, involvement of the internal auditory canal, incomplete filling of internal auditory canal, tumor size less than 15 mm and the intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images. Functional neuro-otologic studies of facial nerve function, hearing and vestibular/balance function provide a valuable means of assessment of the actual impairment of the functional status of the VS patient. Intraoperative monitoring of facial nerve function and hearing has been refined, resulting in improved final postoperative facial nerve and hearing outcomes in VS patients treated with microsurgery. Long-term results reported by teams practicing stereotactic radiosurgery or fractionated stereotactic radiotherapy have been very encouraging. On the other hand, conservative management appears to be a viable option for a select group of VS patients. The refinement of surgical technique has rendered surgery safer and less invasive, resulting in better functional outcomes. Steroid use is currently used postinterventionally to improve final hearing outcome, although with questionable effectiveness. Physical rehabilitation programs are applied to accelerate vestibular functional recovery postoperatively and there is weak evidence that early physical rehabilitation may improve the final facial nerve outcome. Quality-of-life measures have emerged as important determinants of final therapeutic decision-making. More studies with high levels of evidence are needed to support clinical decisions.