Electrophoretic separation and identification of perilymph proteins in cases of acoustic neuroma

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.

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.

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.

The relationship between pure tone thresholds and the radiological dimensions of acoustic neuromas

A retrospective analysis of 109 consecutive patients presenting with acoustic neuromas between 1986 and 1997 were undertaken. Sufficient data were available in 104 cases for comparison. In 65 cases patients had undergone surgery and the radiological diagnosis of acoustic neuroma was confirmed histologically. In this group there were 25 large and 40 small tumors when a maximal radiological diameter of 2.5 cm was used to subdivide the groups. When pure tone thresholds were compared at specific frequencies, in those with hearing ears, there was no significant difference between the two groups. Our results are compared with recent series and the causes of hearing loss associated with acoustic neuroma are discussed.

Predictors of volumetric growth and auditory deterioration in vestibular schwannomas followed in a wait and scan policy

OBJECTIVE

The purpose of this study was to identify factors predicting growth and audiologic deterioration during follow-up (FU) in a wait and scan (W&S) policy of vestibular schwannomas (VSs) using a novel volumetric measuring tool. So far, only consecutive magnetic resonance imaging (MRI) is able to show growth objectively, and growth, combined with hearing function, generally dictates further intervention. Other factors predicting growth or hearing deterioration would be invaluable and might ease clinical decision making.

STUDY DESIGN

Retrospective case study.

SETTING

Tertiary referral center.

PATIENTS

Sixty-three patients diagnosed with VS at Maastricht University Medical Center between 2003 and 2008, with FU data available from 36 patients.

INTERVENTION(S)

A W&S policy for unilateral VS with sequential contrast-enhanced T1- and T2-weighted MRI and audiograms during FU.

MAIN OUTCOME MEASURE(S)

1. Patient and radiologic VS features potentially related to growth and auditory function during a W&S policy. 2. The correlation between increase in VS volume and audiologic deterioration during FU.

RESULTS

Labyrinthine hypointensity on T2-weighted magnetic resonance images and complaints of hearing loss at presentation are predictive of a faster deterioration of hearing (p < 0.05). Growth during the first FU year predicts further growth. Vestibular schwannoma volume does not correlate with audiologic deterioration significantly.

CONCLUSION

Hypointensity on T2-weighted image of the affected labyrinth will result in a significant faster deterioration of hearing. Hearing loss was more profound, and hearing will deteriorate significantly faster in patients presenting with complaints of hearing loss. Significant growth during the first year of FU predicts further growth during FU. Sequential MRI cannot be substituted by audiologic examinations solely because increase in VS volume does not correlate with audiologic deterioration significantly.

Fundal fluid as a predictor of hearing preservation in the middle cranial fossa approach for vestibular schwannoma

OBJECTIVES

Determine if the presence of cerebrospinal fluid in the fundal region of the internal auditory canal on preoperative magnetic resonance imaging (MRI) scans is predictive of improved hearing preservation after removal of vestibular schwannoma through the middle cranial fossa approach. Relationships between fundal fluid, tumor nerve of origin, tumor size, and hearing preservation also are examined.

STUDY DESIGN

Retrospective review.

SETTING

Private practice tertiary neurotology referral center.

PATIENTS

One hundred one patients with preoperative MRI, complete preoperative and postoperative audiologic data, and histopathologically confirmed vestibular schwannoma treated with a middle cranial fossa approach between January 1, 2006, and June 30, 2009.

INTERVENTIONS

Primary middle cranial fossa approach for removal of vestibular schwannoma.

MAIN OUTCOME MEASURES

Fundal fluid status (presence or absence), preoperative and postoperative pure-tone average, and speech discrimination scores and tumor nerve of origin.

RESULTS

Fundal fluid was present in 75% of cases. Those with fluid had a higher rate of postoperative measurable hearing (77.6%) compared with those without fundal fluid (52%) (p <or= 0.014). Tumors arising from the superior vestibular nerve also were associated with a higher rate of preserved, serviceable, and measurable hearing, whereas the combination of the presence of fundal fluid and superior nerve tumor had a significantly better chance of hearing preservation than either factor alone.

CONCLUSION

The presence of fundal fluid on preoperative MRI is predictive of hearing outcomes and should be used in counseling patients who are considering hearing preservation surgery via a middle cranial fossa approach for the treatment of isolated vestibular schwannoma.

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.

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

BACKGROUND AND PURPOSE

Elevated protein levels have been reported in perilymph of patients with vestibular schwannoma. Fluid-attenuated inversion recovery (FLAIR) imaging is sensitive to high protein contents in fluids. The purpose of this study was to investigate if in patients with unilateral vestibular schwannoma, cochlear FLAIR signal intensity on the affected side is increased compared with the unaffected side and control subjects.

MATERIALS AND METHODS

Fifteen patients with unilateral vestibular schwannoma and 25 age-matched control subjects (without a history of hearing loss) were retrospectively evaluated. All patients and controls had routine 5-mm FLAIR and T1- and T2-weighted imaging of the brain. The signal intensity of both cochleae was evaluated by placing a small region of interest on FLAIR images. The signal intensity of the brain stem was also determined by placing a second region of interest. A ratio of cochlear signal intensity to brain stem signal intensity (CIBI ratio) was determined. A t test was used to compare the CIBI ratios.

RESULTS

In patients, the mean CIBI ratio of the affected side was 0.89 +/- 0.18, and that of the unaffected side was 0.57 +/- 0.12. In control subjects, it was 0.51 +/- 0.07. The CIBI ratio of the affected side was significantly higher compared with the unaffected side (P < .001) and compared with control subjects (P < .001).

CONCLUSION

Patients with vestibular schwannoma have increased cochlear FLAIR signal intensity on the affected side compared with the unaffected side and healthy subjects.

Rebuilding lost hearing using cell transplantation

OBJECTIVE

The peripheral auditory nervous system (cochlea and auditory nerve) has a complex anatomy, and it has traditionally been thought that once the sensorineural structures are damaged, restoration of hearing is impossible. In the past decade, however, the potential to restore lost hearing has been intensively investigated using molecular and cell biological techniques, and we can now part with such a pessimistic view. In this review, we examine an important field in hearing restoration research: cell transplantation.

METHODS

Most efforts in this field have been directed to the replacement of hair cells by transplantation to the cochlea. Here, we focus on transplantation to the auditory nerve, from the side of the cerebellopontine angle rather than the cochlea.

RESULTS

Delivery of cells to the cochlea is potentially damaging, and nerve cells transplanted distally to the Schwann-glial transitional zone (cochlear side) may become inhibited when they reach the transitional zone. The auditory nerve is probably the most suitable route for cell transplantation.

CONCLUSION

The auditory nerve occupies an important position not only in neurosurgery but also in various diseases in other disciplines, and several lines of recent evidence indicate that it is a key target for hearing restoration. It is familiar to most neurosurgeons, and the recent advances in the molecular and cell biology of inner-ear development are of direct importance to neurorestorative medicine. In this article, we review the anatomy, development, and molecular biology of the auditory nerve and cochlea, with emphasis on the advances in cell transplantation.

Histopathology of the inner ear in unoperated acoustic neuroma

Although hearing loss is the most common presenting symptom in patients with acoustic neuroma, the pathophysiology of hearing loss associated with acoustic neuroma is unknown. Although primary dysfunction of the auditory nerve is intuitively logical, available histopathologic and clinical data suggest that although neural degeneration is common, it alone does not adequately account for hearing loss in many cases. The purpose of this study was to evaluate 11 cases of unoperated unilateral acoustic neuromas. Temporal bones were identified by means of a search mechanism provided by the National Temporal Bone, Hearing, and Balance Pathology Resource Registry and were prepared for light microscopy by standard techniques. Quantification of spiral ganglion cells, hair cells, stria vascularis, and spiral ligament was accomplished for each specimen. In addition, the maximum diameter and volume of each tumor were calculated from histopathologic sections. Increasing tumor size did predict a reduced spiral ganglion count. However, although there was a tendency for decreasing spiral ganglion cell count and for increasing tumor size to predict a higher pure tone average and lower speech discrimination score, these correlations did not reach statistical significance. In tumor ears in which the speech discrimination score was 50% or less, there was always significant degeneration of other structures of the inner ear in addition to neurons, including hair cells, the stria vascularis, and the spiral ligament. Endolymphatic hydrops and eosinophilic precipitate in the perilymphatic spaces were found in 2 of 3 such cases. It is concluded that acoustic neuromas appear to cause hearing loss, not only by causing degeneration of the auditory nerve, but also by inducing degenerative changes in the inner ear. It is hypothesized that the proteinaceous material seen histologically may represent the products of up-regulated genes in acoustic neuroma, some of which may interfere with normal cochlear function.

Prognostic value of magnetic resonance imaging findings in hearing preservation surgery for vestibular schwannoma

OBJECTIVE

The purpose of this study was to determine whether three magnetic resonance imaging (MRI) findings (tumor size, extension to the fundus, intralabyrinthine signal intensity) have a predictive value to hearing preservation in vestibular schwannoma surgery.

STUDY DESIGN

A retrospective study was conducted of preoperative high-resolution MR images in a series of consecutive hearing preservation attempts for vestibular schwannomas.

PATIENTS

Twenty-six consecutive records of patients with an acoustic tumor removed via a retrosigmoid transcanal approach were analyzed, and the MR images were reviewed blindly and compared with postoperative hearing.

SETTING

The study took place in a tertiary referral center. Imaging Techniques: The MR sequences used in this study were unenhanced and gadolinium-enhanced T1-weighted spin-echo images and gradient echo images (3DFT-CISS).

MAIN OUTCOME MEASURES

The predictive value of three MRI signs was analyzed: tumor size, lateral extension of the tumor (with and without obliteration of the fundus), and the maintenance of, or decrease in, the intralabyrinthine signal intensity on the affected side in comparison with the signal intensity on the opposite normal side as seen on 3DFT-CISS images.

RESULTS

The tumor size in ears in which hearing was preserved averaged 15 mm and was 17 mm in those cases where hearing was not preserved. Hearing was preserved in 50% of ears when the tumor did not extend to the fundus but in only 33% when the fundus was obliterated by tumor. A "normal" intralabyrinthine signal on CISS images (being an isointense signal when compared with the contralateral unaffected ear) was followed by hearing preservation in 82% of ears, whereas in cases where the intralabyrinthine signal was low, hearing was preserved in only 20%. This correlation was statistically significant (p < 0.05).

CONCLUSION

The intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images is a valuable additional tool for determining candidacy for hearing preservation surgery. In two cases with preoperative decrease in signal intensity of the intralabyrinthine fluids, control MRI after surgery showed spontaneous recovery of normal intralabyrinthine signal intensity. The authors hypothesize that vascular compression in the internal auditory canal by the tumor is responsible for the observed intralabyrinthine signal decrease.

Use of protein electrophoresis in the diagnosis of cerebrospinal fluid rhinorrhoea

The diagnosis of CSF rhinorrhoea on clinical grounds alone can be difficult. We describe how the use of non-invasive electrophoretic analysis of nasal secretions for tau protein (asialotransferrin) helped in the management of cases where the existence of a CSF leak was in doubt. Patients were thus saved unnecessary invasive investigations or surgery. A modification of the method of analysis, which improves diagnostic accuracy, is described.

Immunoblotting of transferrin in the identification of cerebrospinal fluid otorrhoea and rhinorrhoea

Cerebrospinal rhinorrhoea is potentially serious due to the risk from infection. In patients presenting with a nasal discharge of clear fluid it is important to identify the nature of the fluid. Cerebrospinal fluid is readily identified by the presence of asialo-transferrin (tau protein). A method is presented for the identification of tau protein based upon agarose electrophoresis, followed by transfer onto cellulose nitrate membrane and immunochemical detection of transferrin. The method is reliable, sensitive and simple, and requires only basic electrophoresis apparatus.

Perilymphatic fistula: analysis of free amino acids in middle ear microaspirates

High-performance liquid chromatography was used to determine 19 free amino acid concentrations in perilymph, serum/plasma, and red blood cell intracellular fluid. Significant differences were found between perilymph and these fluids. Free amino acid analysis was then used to quantitatively analyze middle ear microaspirates in order to test the hypothesis that perilymph is a potential source of clear fluid in perilymphatic fistulas (PLF). Fourteen unknown samples from patients with visually identified PLF, including patients with no identifiable otic capsule defect, were studied. Six samples on amino acid pattern analysis were correlated most similarly with perilymph (rrho greater than 0.95). Four of these six samples were scored on the basis of quantitative amino acid values as similar to perilymph. However, three samples of clear fluid were more similar to serum/plasma than to perilymph on both amino acid pattern and quantitative amino acid score analysis. These results objectively suggest perilymph as a potential source of clear fluid in some patients with a diagnosis of PLF. Not all clear fluid observed in the middle ear, however, is potentially perilymph.

MRI in acoustic neuroma: a review of 35 patients

This retrospective study is aimed to assess the diagnostic efficacy of MRI in relation to contrast enhanced CT and air-CT-cisternography. MRI examinations were performed in 35 patients with suspected neurosensorial damage and suggestive of acoustic neuroma: 27 presented on MRI with unilateral tumors, 3 patients had a bilateral tumor and 5 patients were negative on all imaging modalities. The total number of acoustic neuromas detected was therefore 33. To date microscopic analysis has been performed on 12 tumors and histological data based on type Antoni A and Antoni B classification is available. Contrast enhanced CT detected 19 tumors, yielding an overall sensitivity rate of 58%. Air-CT cisternography identified an additional 5 tumors with a sensitivity rate of 100%. MRI identified 33 acoustic neuromas in 30 patients and was negative in 5 patients (sensitivity and accuracy 100%). Considering sensitivity in relation to location, MRI was much better than contrast enhanced CT for internal auditory canal (IAC) tumors (100% versus 36%) and better for cerebello-pontine angle tumors (CPA) tumors (100% versus 68%). The evolution of MRI technique, the various pulse sequences used and their actual selection is discussed. Seven patients received a paramagnetic contrast agent (Gadolinium-DTPA) with the additional benefit of a better demonstration of the tumor. The results suggest that MRI is the best non invasive technique for demonstrating acoustic neuromas.