Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study

Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge®) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT’s irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen’s reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.     

Patient quality of life after vestibular schwannoma removal: possibilities and limits to measuring different domains of patients' wellbeing

European Archives of Oto-Rhino-Laryngology - Since the 1980s, health-related quality of life (HRQOL) has been recognized in the assessment of medical treatment. To determine the health-related...     

Guided surgery in a subtemporal approach in CPA tumors?

BACKGROUND: Computer assisted surgery (CAS) permits the visualization of hidden bony covered structures invisible for the human eye with radiological 3d data sets. The surgeon might be able to orientate anatomically during surgery without having to prepare the according landmarks. This would mean less surgical traumatization and a shorter and smaller operation corridor. METHOD: We determined the use of CAS in a quality assurance analysis with the subtemporal approach in 8 patients with supra-meatal tumors type A of the cerebellopontine angle. Various navigation systems and methods for referencing for the registration of the patients' heads were used. The question was whether it is possible intraoperatively without preparation of known anatomical landmarks to define the borders of an optimal positioned temporary bone cap and to identify the bony covered inner auditory canal and its neuronal structures without orienting neurostimulation. RESULT: It was possible with CAS to assess intraoperatively the borders of a temporary bone cap above the cranially positioned mastoid cell. However, the objective inaccuracy of 2 to 28 mm observed during surgery did not allow a secure identification of the inner auditory canal. CONCLUSIONS: CAS with the subtemporal approach cannot replace the conventional preparation of known anatomical landmarks nor neurostimulation to identify neural structures, due to the expected high inaccuracy with the non-invasive referencing systems that are available today.     

Electrophysiologic examinations in low frequency hearing impairment: clinical and prognostic aspects

INTRODUCTION: Low-frequency hearing impairment (LFHI) is mainly associated to endolymphatic hydrops and shows a high variety of possible outcomes. Electrophysiologic examinations are widely recommended in diagnostics of LFHI, wheras up to now no data exist about the prognostic value of these examinations in a conservative therapeutic regimen. METHODS: In a quality assessment, we retrospectively evaluated the records of 90 patients, and performed an audiometric follow-up for analysis of long-time hearing data. All patients had undergone diagnostic electrocochleographic examination (ECochG) and then had been treated with rheologic infusions, followed by dehydrating infusions in patients lacking complete remission. The results of both therapeutic strategies and of long-time results were correlated to electrophysiologic findings. RESULTS: The prognosis of LFHI is significantly reflected by pretherapeutic electrocochleographic data. All significant parameters were associated to compound action potential (CAP) whereas parameters associated to cochlear microphonics (CM) did not include any utilizable prognostic value. In patients with a good outcome, the latency of CAP complex was significantly shorter, and the width of CAP complex significantly smaller than in patients with poor hearing outcome after rheologic and after dehydrating therapy and in long time assessment. The relation of summating potential (SP) und CAP was significantly smaller when the outcome was sufficient or good for either therapy and in long time analysis. Steep CAP-input-output-curves were associated to insufficient outcome after rheologic therapy and in long time assessment, but not for dehydrating therapy. CONCLUSIONS: The results indicate that ECochG is of significant prognostic value concerning hearing outcome after conservative therapy in patients suffering from LFHI. It can help the physician to counsel the patient and perform an effective management of the disease. We conclude that ECochG should be performed before the onset of therapy, including collection of SP and CAP data whereas CM parameters may be omitted.     

Evaluation of the HiFocus electrode array with positioner in human temporal bones

The aim of the study presented was to assess the insertion mode and possible intracochlear trauma after implantation of the HiFocus electrode with positioner in human temporal bones. The study was performed in five freshly frozen temporal bones. The position of electrodes was evaluated using conventional X-ray analysis, rotational tomography and histomorphological analysis. Insertion of the HiFocus electrode with positioner resulted in considerable trauma to fine cochlear structures including fracture of the osseous spiral lamina, dislocation of the electrode array from the scala tympani into the scala vestibuli and fracture of the modiolus close to the cochleostomy. The implication of the results regarding clinical outcome will be discussed.     

Evidence of a novel gene for the LAV-syndrome

BACKGROUND: Both LAV- (large or enlarged vestibular aqueduct) and Pendred-syndrome are autosomal recessive diseases. In contrast to Pendred-syndrome, LAV-syndrome is characterised only by an enlarged vestibular aqueduct. Pendred-syndrome is a more complex disease. Classically it is characterised by sensorineural hearing loss and enlargement of the thyroid gland. Up to now, only mutations in SLC26A4 gene are known as being responsible for both syndromes. The gene for Pendred-syndrome (SLC26A4) has been localised by linkage analysis of chromosome 7q31. This protein is expressed in the inner ear, thyroid gland, kidney, and placenta. Functional analysis of the gene product (pendrin) in Xenopus laevis oocytes revealed that pendrin acts as an iodide/chloride and chloride/formate exchanger. METHOD: Each of the exons and flanking splice regions of the SLC26A4 gene were analysed by direct sequencing. Haplotype analysis was undertaken with microsatellite markers spanning a 5 Mbp area around the localisation of the SLC26A4 gene. RESULTS: In sequence analysis of 42 patients with bilateral enlargement of the vestibular aqueduct, no mutation could be identified in 30 % of cases. In some of these cases, a linkage to the gene localisation on chromosome 7q31 could not be detected. CONCLUSION: Our results indicate evidence for a second gene involved in the development of LAV-syndrome.     

Planning and simulation of microsurgical laser bone ablation

Purpose  

Laser ablation of hard tissue is not completely understood until now and not modeled for computer-assisted microsurgery. A precise planning and simulation is an essential step toward the usage of microsurgical laser bone ablation in the operating room.     

Tinnitus in Cochlear Implant Users: The Freiburg Experience

Cochlear implantation is a well-accepted method of aural rehabilitation in deaf or severely hearing-impaired adults and children. A majority of patients not only suffer from hearing impairment but from tinnitus. The high rate of preoperative tinnitus in adults (68.1%) stands in contrast to assumed lower rates in children. Unknown are such factors as how tinnitus develops in children, how they realize what tinnitus is, and whether the mechanism of development of tinnitus differs from that in adults, respectively. Electrical stimulation of the auditory pathway is followed by loss, or at least reduction, of tinnitus in most cases (75%). Also, the insertional trauma alone is able to stop tinnitus in some patients. Attention must be paid to the low risk of developing tinnitus postoperatively. No reports are available regarding tinnitus in children. Though younger children may not be able to report, some adolescent patients report preoperative or postoperative tinnitus (or both) that is reduced by electrical stimulation at the rates seen in adults. Further investigations are needed to define the mechanism of tinnitus development in children and to define optimal stimulation modes and rates for tinnitus reduction with best auditory performance.