Three-dimensional x-ray computed tomography of the temporal bone as an aid to surgical planning

Effects of middle ear lesions on pre and postoperative hearing outcomes in patients with chronic otitis media

Background and Objectives

The purpose of this study was to evaluate the effects of middle ear lesions on pre and postoperative hearing in patients with chronic otitis media (COM) and to assess the relationship between various prognostic factors and pre and postoperative hearing using more than 2000 COM surgery records retrieved from a computerized database released by the Korean Otologic Society in 2005.

Subjects and Methods

Data of 2312 COM surgeries, which had been conducted by a single surgeon from 1989 to 2009, were reviewed retrospectively. Mean preoperative and postoperative air-bone gap (ABG) was analyzed using a four-frequency (500, 1000, 2000, and 3000 Hz) pure tone average (PTA). Pre and postoperative ABGs were compared with regard to several prognostic factors, including disease duration, age, Eustachian tube function, existence of otorrhea, size of tympanic membrane perforation, degree of ossicular destruction, presence of cholesteatoma, and its type.

Results

Mean pre and postoperative ABGs of PTA in the 2079 cases studied were 27.88±13.33 dB and 17.38±15.64 dB, respectively, with a hearing success rate of 69%. The results suggested that preoperative ABGs were affected by Eustachian tube function, Griffin grade, presence of cholesteatoma and its type, and the degree of ossicular destruction. Hearing gains differed significantly among the groups when compared with factors of Griffin grade, presence or type of cholesteatoma, and the degree of ossicular destruction.

Conclusions

Many factors affected pre and postoperative ABGs and postoperative hearing outcomes. These results will be useful for designing future clinical studies on COM surgery, as well as for surgical planning and patient counseling in clinical practice.

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.

[Chronic otitis media as an introduction to intracranial otogenic complications]

INTRODUCTION

Otogenic intracranial complications are rare. Misdiagnosed and untreated can be dangerous for health and life. They should be always kept in mind.

AIM

We discuss patients in whom defects of skull base were observed during operation. These defects can lead to serious intracranial complications.

MATERIAL AND METHODS

We analyse patients with chronic otitis media operated in our department between 2004-2006. 250 operations on ears were performed in that period of time. We discuss patients with intracranial otogenic complications and patients in whom defects of skull base were noticed by chance during operations.

RESULTS

Defects of skull base were observed in 24 cases. Intracranial complications were in 3 patients. 1 patiens died because of abscess of cerebellum, others were treated with good distant effect. Used methods of reconstruction were effective, we observed no discharge of cerebro-spinal fluid and no other intracranial complications.

CONCLUSIONS

It exists group of patients with chronic otitis media that have asymptomastic defects of cranial fossa. These defects can be responsible for intracranial complications. MRI and TC are very important in preoperative diagnostics.

Quantitative morphology of facial nerve based on three-dimensional reconstruction of temporal bone

Objective

To investigate an effective method of quantitative analysis of the facial nerve and its adjacent structures on the basis of three-dimensional (3D) CT image reconstruction of the temporal bone.

Methods

The inner structures of the temporal bone from CT images of 34 healthy adults were reconstructed. Precise measurement of the facial nerve and its adjacent structures were accomplished by using Able Software 3D-DOCTOR.

Results

3D images of temporal bone structures, including facial nerve, tympanic annulus, cochleariform process, cochlea, semicircular canals, jugular fossa, and carotid artery, were reconstructed. Quantitative data of the facial nerve and its adjacent structures were analyzed, especially the detailed spatial relationships between the facial nerve and the surface of the mastoid process or tympanomastoid fissure.

Conclusion

3D reconstruction of CT images clearly displayed the detailed structures of the temporal bone. Quantitative data of the facial nerve and its adjacent structures are very useful for temporal bone surgery.

Do We Need Three-Dimensional Computed Tomography in Maxillofacial Surgery?

In a retrospective clinical study (2000-2003), 121 patients' radiographs and computed tomography scans were reviewed to establish the clinical value of three-dimensional computed tomography. Eighty patients had computed tomography scans; 48 had three-dimensional computed tomography scans for diagnosing facial fractures, 3 for diagnosing temporomandibular joint ankylosis, 1 for tumor with bone destruction, and 1 for a mandibular cyst. It is concluded that axial, coronal, and three-dimensional computed tomography is of crucial importance and should be mandatory for all suspected comminuted and displaced midface fractures instead of plain radiographs. Three-dimensional computed tomography is also recommended for comminuted mandibular fractures and temporomandibular joint ankylosis. Three-dimensional computed tomography is not recommended for the diagnosis of minimally displaced fractures.

Magnetic resonance imaging-based virtual endoscopy of inner ear pathology

OBJECTIVE

To study the feasibility of high-resolution magnetic resonance imaging (MRI)-based virtual endoscopy of the labyrinth to assess subtle inner ear pathology.

STUDY DESIGN

A retrospective case review of patient with known inner ear pathology to determine the feasibility and clinical value of MRI-based virtual labyrinthoscopy.

SETTING

Tertiary referral center.

PATIENTS

Ten patients with symptoms of sensorineural hearing loss or vertigo who underwent high-resolution MRI between 1996 and 1999.

INTERVENTION

Diagnostic image modality with three-dimensional (3-D) postprocessing to assess inner ear pathology.

MAIN OUTCOME MEASURES

To evaluate how 3-D rendering with virtual labyrinthoscopy can depict subtle labyrinthine pathology.

RESULTS

Cases with typical 3-D models and virtual labyrinthoscopic views are presented to illustrate this new image processing approach.

CONCLUSION

The virtual endoscopic view of the labyrinth revealed subtle inner ear pathology. This 3-D postprocessing technique is able to render inner surface changes of tiny structures within the inner ear. It can be performed within a very short time using dedicated hybrid rendering techniques. It allows visualization of pathology in a comprehensive way for clinicians and is able to add 3-D information for troubleshooting in doubtful two-dimensional findings. We suggest the term virtual labyrinthoscopy for virtual intraluminal visualization of the labyrinth.

Microsurgery without a microscope: laboratory evaluation of a three-dimensional on-screen microsurgery system

In microvascular surgery, procedures may be both technically and physically demanding. Precise movements sustained over long hours in addition to typically compromised surgeon and assistant positioning lead quickly to physical and mental fatigue. Many of the positioning problems encountered are related to the fact that the eyes of the surgeon must be continually fixed to the microscope eyepieces. This study explores a possible solution: a microscope system that eliminates the need to view the operative field through the microscope eyepieces. A Three-dimensional On-screen Microsurgical System (TOMS) was used and contrasted with conventional operative microvascular surgery in the laboratory setting. The surgeon's comfort, his ability to instruct microsurgical technique, pertinent technological performance, and the procedure itself were evaluated using a standardized questionnaire. Based on data collected in this study, we conclude that divorcing the surgeon's eyes from the microscope eyepieces using the TOMS may make prolonged microvascular procedures less physically demanding and may increase the comfort level of both the surgeon and his assistant, although refinements to the technology are required.

Temporal bone fractures

High-resolution technique is essential to the evolution of temporal bone fractures. Axial and coronal scan planes are optimal but may not be possible in acutely traumatized patients. A knowledge of normal temporal bone anatomy is important and can be obtained from standard texts, so it will not be considered in detail in this article. Classically, petrous temporal bone fractures have been classified as longitudinal, transverse, or mixed. Recent publications have emphasized the importance of describing fractures in terms of planes rather than lines. According to this concept, most temporal bone fractures are actually oblique, and true longitudinal fractures are rare. Petrous temporal bone fractures may be associated with cranial nerve or vascular injuries when the fracture extends to the skull base. This is particularly true of the oblique fracture, which characteristically extends anteromedially to the skull base through weak places in that area, thus avoiding the compact bone of the otic capsule surrounding the labyrinth. The most common associated injury is to the facial nerve in its geniculate or proximal tympanic segment. Transverse fractures frequently involve the labyrinth. A careful search for various types of ossicular dislocation should be performed in association with temporal bone fractures, because this may result in conductive hearing loss. The site of cerebrospinal fluid otorhinorrhea resulting from temporal bone fractures can usually be defined on plain high-resolution temporal bone images, but intrathecal contrast may be helpful. Temporal bone fractures caused by gunshot wounds are frequently complex and may be limited by metallic streak artifacts. Pediatric patients have different proportions of facial nerve injury and types of hearing loss as compared with adults.

Petrosectomies for invasive tumours: surgery and reconstruction

Tumours involving the temporal bone have historically carried a bad prognosis. The only prospect of cure is radical en bloc resection. Temporal bone resection for malignancies is, however, such a formidable undertaking that many centres label such tumours as unresectable. Additionally, the enormity of the surgical defect poses a major reconstructive challenge. A review of 14 petrosectomies (in 12 males and 2 females) performed for extensively invasive neoplasms in and around the ear is presented. All underwent immediate reconstruction, the majority (12/14) with free tissue transfers. 9 of the 14 patients (64%) are still alive after a mean follow-up of 70 months (range 4-8 years). With the use of free tissue transfers, an aggressive approach with regard to the resection margins can safely be adopted in the full knowledge that the eventual size of the defect need not compromise tumour clearance. Additionally, free flaps provided a reliable dural seal. This approach of radical en bloc resection with free flap reconstruction has decreased the mortality (compared to the literature), while largely reducing the morbidity to that of unavoidable cranial nerve resection.

Clinical usefulness of three-dimensional reconstruction of the temporal bone from CT scans in cholesteatoma cases

The importance of computed tomography (CT) in analyzing temporal bone diseases has increased, and the ability to reconstruct the temporal bone structures in three dimensions from multiple CT films has been required. In order to facilitate the visualization of temporal bone structures, we tried reconstructing temporal bone CT images three-dimensionally using a personal computer, and evaluated the possibility of using three-dimensional CT images clinically. Temporal bone CT scan films from five cases of cholesteatoma and a case of otosclerosis as control were examined. Four temporal bone structures (temporal bone contour, middle ear, mastoid, and inner ear) and cholesteatoma, extracted from enlarged black and white CT films, were inputted to the personal computer. Data import and image reconstruction procedures were performed using commercially available software. Our results indicate that three-dimensional reconstructions contribute to visualizing temporal bone structures spatially, and to choosing surgical approaches in difficult cases, such as petrous bone cholesteatoma. In conclusion, three-dimensional reconstructions using a personal computer is useful in the diagnosis and treatment of cholesteatoma.

Three-dimensional CT of the middle ear and adjacent structures

Three-dimensional (3D) computed tomography of the middle ear and adjacent structures has been carried out in two cadaveric heads from axial and coronal high-resolution images. The structures shown on the images of the walls of the tympanic cavity are illustrated. The usefulness and limitations of the technique, in this region, are discussed: use of grey level volumes at the surface of the slices and the inclusion of structural landmarks is emphasized. The 3D representations show the anatomical spacial relationships of the small structures in and around the middle ear to advantage. The information may be of use in surgical orientation.