MR imaging of the inner ear and cerebellopontine angle: comparison of three-dimensional and two-dimensional sequences

The anatomical classification of AICA/PICA branching and configurations in the cerebellopontine angle area on 3D-drive thin slice T2WI MRI

BACKGROUND

With the technical advance of magnetic resonance imaging (MRI), we have been able to observe not only the small cranial nerves arising from the brain stem but also the branches of vertebrobasilar artery in the cerebellopontine angle (CPA) cistern.

PURPOSE

The purpose was to demonstrate the courses and configurations of the anterior inferior cerebellar artery (AICA) or posterior inferior cerebellar artery (PICA) branch including the internal auditory artery in the CPA cistern and evaluate the relationship between the facial-vestibulocochlear (VIIth-VIIIth) nerves and AICA/PICA on high-resolution, thin-slice, three-dimensional T2-weighted MRI using driven equilibrium pulse.

MATERIAL AND METHODS

Thirty-three men and 27 women aged 8-85 years old with sensory hearing loss or vertigo, and/or tinnitus were evaluated by thin-slice (0.75 mm) T2-weighted MRI. Five subjects (3 men, 2 women) without any auditory symptoms were also examined.

RESULTS

Thin-slice T2WI drive MRI revealed several variations of the AICA/PICA coursing, such as a loop formation (n=30, 48 sides) or the IAC extension (n=19, 30 sides). Contact with the vestibulocochlear nerve was seen in 31.7% subjects (n=19, 27 sides). The AICA/PICA branching and shape patterns relative to the CPA and IAC were classified into four major types: type 1A, nonloop AICA/PICA in the CPA cistern; type 1 B, nonloop AICA/PICA (internal auditory artery) entering the IAC; type 2A, loop-type AICA/PICA in the CPA cistern; and type 2B, loop-type AICA/PICA entering the IAC.

CONCLUSION

There was statistically significant association between types 1A and 2A (P<.01) regarding the existence of any auditory 3 symptoms. The results of our study suggest that this classification is simple and very useful for the elucidation of the mechanism of auditory symptoms and deciding the therapeutic strategies.

3D T2-weighted turbo spin-echo MR sequence for identifying cerebrospinal fluid leak after endoscopic endonasal pituitary surgery

BACKGROUND

This study aimed to assess the efficacy of MR images with 3D T2-weighted turbo spin-echo (3D T2-TSE) sequences for early identification of postoperative cerebrospinal fluid (CSF) leaks.

METHODS

We analyzed the medical records and radiological reports for 72 consecutive patients who underwent an endoscopic endonasal approach for sellar and parasellar lesions between April 2009 and December 2010. Patients were 38 men and 34 women with a mean age of 46.4 years. All underwent MR scanning within 2 postoperative days, which included 3D T2-TSE sequences as well as a conventional T2-weighted (T2W) protocol. Sequence accuracy in predicting postoperative CSF leaks was assessed for sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).

RESULTS

A postoperative CSF leak was confirmed in 6 of 72 patients (8.3 %). On immediate postoperative MR images, 39 patients were suspicious for CSF leaks on conventional T2W sequences, while 18 patients on 3D T2-TSE. The 3D T2-TSE imaging had superior specificity and PPV (50 % vs. 81.8 %, 15.4 % vs. 33.3 %), while there was no difference in sensitivity and NPV compared with conventional T2W sequences.

CONCLUSION

Compared to the conventional T2W protocol, MR imaging with the 3D T2-TSE protocol provides differential images around the sellar area with improved specificity and PPV for the detection of postoperative CSF leaks.

Cochlear implantation update: contemporary preoperative imaging and future prospects - the dual modality approach as a standard of care

The selection of cochlear implant (CI) candidates requires consideration of a variety of clinical and radiographic factors. The present article reviews the current knowledge regarding the preoperative imaging of CI candidates and explores emerging developments in different imaging modalities. Preoperative radiologic assessment should evaluate the status of the middle/inner ear, auditory nerve and central acoustic pathways. Preoperative computed tomography displays anatomic middle ear variations of surgical importance. MRI can demonstrate fluid/obliteration in the inner ear and depict the retrocochlear auditory pathways. Dual modality imaging with high-resolution computed tomography and MRI of the petrous bone and brain can provide the maximum information regarding surgical landmarks and detect deafness-related abnormalities. Cost-effectiveness issues also justify its use. New systems are now becoming available, offering improved soft-tissue delineation, sophisticated segmentation techniques, volumetric measurements, semitransparent views and superior surface resolution, thus significantly advancing our diagnostic acumen and making the preoperative evaluation of CI candidates more accurate and reliable.

Inner-ear obliteration in ulcerative colitis patients with sensorineural hearing loss

Objective:

Systemic autoimmune diseases, including ulcerative colitis, may involve the inner ear. Several ulcerative colitis cases presenting with sensorineural hearing loss have been reported. We report the T2-weighted, three-dimensional, inner-ear magnetic resonance imaging findings in the inner ears of two such patients.

Methods:

Case reports and a review of the literature concerning autoimmune disease and sensorineural hearing loss are presented.

Results:

We describe two cases of ulcerative colitis with sensorineural hearing loss in which three-dimensional magnetic resonance imaging revealed obliteration of the inner ear. Those inner ears with obliteration had severe hearing loss, and responded poorly to steroid therapy.

Conclusion:

To our knowledge, there has been no previous published report of the T2-weighted, inner-ear magnetic resonance imaging findings of cases of ulcerative colitis with sensorineural hearing loss. This paper represents the first published report in the world literature of inner-ear obliteration in such patients. Three-dimensional magnetic resonance imaging is beneficial in elucidating the pathophysiology of the inner-ear involvement seen in ulcerative colitis.

CT–MR image data fusion for computer assisted navigated neurosurgery of temporal bone tumors

PURPOSE

To demonstrate the value of multi detector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative work up of temporal bone tumors and to present, especially, CT and MR image fusion for surgical planning and performance in computer assisted navigated neurosurgery of temporal bone tumors.

MATERIALS AND METHODS

Fifteen patients with temporal bone tumors underwent MDCT and MRI. MDCT was performed in high-resolution bone window level setting in axial plane. The reconstructed MDCT slice thickness was 0.8 mm. MRI was performed in axial and coronal plane with T2-weighted fast spin-echo (FSE) sequences, un-enhanced and contrast-enhanced T1-weighted spin-echo (SE) sequences, and coronal T1-weighted SE sequences with fat suppression and with 3D T1-weighted gradient-echo (GE) contrast-enhanced sequences in axial plane. The 3D T1-weighted GE sequence had a slice thickness of 1mm. Image data sets of CT and 3D T1-weighted GE sequences were merged utilizing a workstation to create CT-MR fusion images. MDCT and MR images were separately used to depict and characterize lesions. The fusion images were utilized for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient.

RESULTS

Tumorous lesions of bone and soft tissue were well delineated and characterized by CT and MR images. The images played a crucial role in the differentiation of benign and malignant pathologies, which consisted of 13 benign and 2 malignant tumors. The CT-MR fusion images supported the surgeon in preoperative planning and improved surgical performance. The mean intraoperative accuracy of the navigation system was 1.25 mm.

CONCLUSION

CT and MRI are essential in the preoperative work up of temporal bone tumors. CT-MR image data fusion presents an accurate tool for planning the correct surgical procedure and is a benefit for the operational results in computer assisted navigated neurosurgery of temporal bone tumors.

[Benign and malignant lesions in the region of the inner ear and cerebellopontine angle]

Tumorous lesions in the region of the inner ear and cerebellopontine angle are very rare and can be classified into benign and malignant disease forms. This contribution presents and explains the CT and MRI characteristics of these tumors.High-resolution computed tomography (HRCT) in the axial projection is applied for evaluation in the high-resolution bone window. The coronary slices can be reconstructed from the axial datasets or in individual cases examined in the coronary plane.HRCT excellently demonstrates osseous lesions and in individual cases - e.g., exostoses - it can simply suffice to perform HRCT of the temporal bone, while HRCT is also excellent for detecting osseous lesions to determine whether the tumor is benign or malignant.MRI, on the other hand, excellently shows the extent of tumor spread because of its superb soft tissue contrast. Consequently, HRCT and MRI images of the inner ear and cerebellopontine angle provide meaningful information for visualization and classification of tumorous lesions. The two methods should not be considered as competing but rather as complementary and among other aspects exert considerable influence on the therapeutic approach.

Dehiscence of the superior and/or posterior semicircular canal: delineation on T2-weighted axial three-dimensional turbo spin-echo images, maximum intensity projections and volume-rendered images

The purpose of this study was to compare the ability of T2-weighted three-dimensional turbo spin-echo (TSE) images, maximum intensity projections and three-dimensional volume-rendered images for delineation of semicircular canal dehiscence. In 26 patients with dehiscence of the superior and/or posterior semicircular canal and 26 control patients, TSE images were obtained with two different resolutions and maximum intensity projection (MIP) and 3D volume-rendered images reconstructed. All images were evaluated by two radiologists in consensus regarding the visualization of anatomical structures and dehiscence of the semicircular canals. Computed tomography was used to confirm or exclude dehiscence. Dehiscence of the semicircular canals was delineated on axial MR images and on 3D volume-rendered images, but not on MIP images. The number of false positive cases was reduced from 3 to 0 with an increase in matrix, rendering results similar to those obtained with CT. Dehiscence of the semicircular canals can be assessed on high resolution MR images. Volume-rendered 3D images allow for immediate perception of the location of defects in semicircular canal dehiscence. These images may facilitate understanding of the extent and location of the defects.

Imaging of the upper cranial nerves I, III–VIII, and the cavernous sinuses

This article discusses the upper cranial nerves (I, III-VIII) and their anatomy as it pertains to intra-axial nuclei and tracts, cisternal portions, and extracranial portions. In addition, the most common pathologic processes affecting the upper cranial nerves are discussed and illustrated. Because the evaluation of small structures requires imaging techniques that provide high resolution and contrast, MR imaging is the examination of choice. CT still plays a limited but important role in the evaluation of intraosseous portions of some cranial nerves.

Driven equilibrium (drive) MR imaging of the cranial nerves V–VIII: comparison with the T2-weighted 3D TSE sequence

PURPOSE

The aim of this study is to evaluate the efficacy of the driven equilibrium radio frequency reset pulse (DRIVE) on image quality and nerve detection when used in adjunction with T2-weighted 3D turbo spin-echo (TSE) sequence.

MATERIALS AND METHODS

Forty-five patients with cranial nerve symptoms referable to the cerebellopontine angle (CPA) were examined using a T2-weighted 3D TSE pulse sequence with and without DRIVE. MR imaging was performed on a 1.5-T MRI scanner. In addition to the axial resource images, reformatted oblique sagittal, oblique coronal and maximum intensity projection (MIP) images of the inner ear were evaluated. The nerve identification and image quality were graded for the cranial nerves V-VIII as well as inner ear structures. These structures were chosen because fluid-solid interfaces existed due to the CSF around (the cranial nerves V-VIII) or the endolymph within (the inner ear structures). Statistical analysis was performed using the Wilcoxon test. P < 0.05 was considered significant.

RESULTS

The addition of the DRIVE pulse shortens the scan time by 25%. T2-weighted 3D TSE sequence with DRIVE performed slightly better than the T2-weighted 3D TSE sequence without DRIVE in identifying the individual nerves. The image quality was also slightly better with DRIVE.

CONCLUSION

The addition of the DRIVE pulse to the T2-weighted 3D TSE sequence is preferable when imaging the cranial nerves surrounded by the CSF, or fluid-filled structures because of shorter scan time and better image quality due to reduced flow artifacts.

Common crus aplasia: diagnosis by 3D volume rendering imaging using 3DFT-CISS sequence

AIM

The purpose of this study was to evaluate the findings of three-dimensional (3D) volume rendering (VR) imaging in common crus aplasia (CCA) of the inner ear.

MATERIALS AND METHODS

Using 3D VR imaging of temporal bone constructive interference in steady state (CISS) magnetic resonance (MR) images, we retrospectively reviewed seven inner ears of six children who were candidates for cochlear implants and who had been diagnosed with CCA. As controls, we used the same method to examine 402 inner ears of 201 patients who had no clinical symptoms or signs of sensorineural hearing loss. Temporal bone MR imaging (MRI) was performed with a 1.5 T MR machine using a CISS sequence, and VR of the inner ear was performed on a work station. Morphological image analysis was performed on rotation views of 3D VR images.

RESULTS

In all seven cases, CCA was diagnosed by the absence of the common crus. The remaining superior semicircular canal (SCC) was normal in five and hypoplastic in two inner ears, while the posterior SCC was normal in all seven. One patient showed bilateral symmetrical CCA. Complicated combined anomalies were seen in the cochlea, vestibule and lateral SCC.

CONCLUSION

3D VR imaging findings with MR CISS sequence can directly diagnose CCA. This technique may be useful in delineating detailed anomalies of SCCs.

Imaging of the upper cranial nerves I, III-VIII, and the cavernous sinuses

This article discusses the upper cranial nerves (I, III-VIII) and their anatomy as it pertains to intra-axial nuclei and tracts, cisternal portions, and extracranial portions. In addition, the most common pathologic processes affecting the upper cranial nerves are discussed and illustrated. Because the evaluation of small structures requires imaging techniques that provide high resolution and contrast, MR imaging is the examination of choice. CT still plays a limited but important role in the evaluation of intraosseous portions of some cranial nerves.

Cranial nerve XII: the hypoglossal nerve

The hypoglossal nerve, cranial nerve XII, is the motor supply of the tongue. An understanding of the intracranial and extracranial components is fundamental in the evaluation of hypoglossal pathology. The following discussion of the evaluation of the hypoglossal nerve will involve the embryology, anatomy, clinical basis, and imaging techniques with pathologic correlations.

CT and MR imaging of acquired abnormalities of the inner ear and cerebellopontine angle

INTRODUCTION

Several entities of acquired lesions may affect the inner ear and cerebellopontine angle. The imaging of these lesions depends on the clinical history, and should be adapted to the lesion searched for and suspected by the otolaryngologist. In this paper, the modality of CT and MR imaging which is suited to delineate the acquired lesions of this region will be presented.

MATERIALS AND METHODS

CT and/or MR imaging of the inner ear and cerebellopontine angle was performed in all cases in which an acquired lesion of this region was suspected by the otolaryngologist. CT was performed in the axial and coronal plane with the use of a high-resolution bone-window-level-setting. MRI was performed in the axial plane using high-resolution 3D T2-weighted fast spin echo sequences and 3D T1-weighted gradient echo sequences before and after the i.v. application of gadopentate dimeglumine. The obtained images were evaluated for the depiction of the acquired lesions.

RESULTS

CT best depicted osseous lesions such as traumatic affections or lesions leading to ossification of the inner ear. Tumorous lesions were delineated in those cases in which they yielded to bony changes. Inflammatory or tumorous lesions not yielding to bony changes or intralabyrintine calicifications were not depicted. MRI delineated very well all lesions leading to soft tissue changes, and moderately depicted traumatic changes yielding to less severe fractures affecting the investigated region.

CONCLUSION

CT and MR imaging are suited differently to delineate the acquired lesions of the inner ear and cerebellopontine angle. CT is excellently suited to depict osseous lesions, while MRI is excellently suited to delineate lesions affecting the soft tissue structures. These two imaging modalities should be used depending on the clinical question, and are supposed to be complementary methods.

MRI of the inner ear: comparison of axial T2-weighted, three-dimensional turbo spin-echo images, maximum-intensity projections, and volume rendering

RATIONALE AND OBJECTIVES

To compare the ability of axial T2-weighted, three-dimensional, turbo spin-echo (3D TSE) images, targeted maximum-intensity projections (MIPs), and 3D volume reconstructions to depict anatomic details of the labyrinth.

METHODS

In 24 volunteers, 3D TSE images were obtained. MIPs and 3D volume reconstructions were performed from the acquired data. All images were evaluated by three radiologists independently regarding the visualization of the different anatomic structures.

RESULTS

In the axial slices, most anatomic details were visible in comparison with observations by the other modalities. The 2.5 windings of the cochlea were best depicted on the MIPs. Volume reconstructions rendered excellent spatial information regarding the vestibule and semicircular canals and were the only technique that demonstrated all three ampullae in all cases.

CONCLUSIONS

Axial TSE images, MIPs, and 3D volume reconstructions are complementary modalities that provide different information. Our results suggest that improved diagnostic information can be obtained by applying these volume visualization reconstruction techniques.