The influence of post-meningitic obliteration and ossification of the cochlea on cochlear microphonics.

Cochlear microphonics are electrical stimulus responses of the inner ear. They are generated by mechanical displacement of the hair cells caused by acoustic stimulation and can be recorded from the cochlear promontory via a needle electrode. In individuals with post-meningitic deafness, fibrous obliteration or ossification of the cochlea may occur. The aim of the present investigation was to establish whether obliteration or ossification leads to any alteration in the extent to which cochlear microphonics can be recorded (as compared with that in patients with a fluid-filled cochlea whose deafness was not post-meningitic), as an indication of changes in the mechanical displacement of the remaining hair cells. Cochlear microphonics in 15 individuals with proven obliteration or ossification of the cochlea were compared with those in 15 control subjects (deaf individuals whose hearing loss was not post-meningitic, and who had a fluid-filled cochlea). Our findings reveal no statistically significant differences between the two groups in the degree to which cochlear microphonics can be recorded. This study does not demonstrate evidence of a change in this property due to ossification or obliteration of the cochlea.

Experimental middle ear surgery in rabbits: a new approach for reconstructing the ossicular chain.

This experimental animal study aimed at evaluating a new prosthesis to replace the ossicular chain; we developed a new technique for surgical implantation into the middle ear of rabbits. The rabbit middle ear is, owing to the relative anatomical dimensions involved, an ideal environment for implantation procedures involving the ossicles, as the surgical conditions are similar to those of the human middle ear. This study included a total of 34 approximately six-month-old female white rabbits (New Zealand) weighing between 3.2 and 4.4 kg. The implants used were constructed of ceramic materials (titania, TiO(2)) of various pore sizes. Directly prior to implanting the total ossicular reconstruction prostheses (TORPs), as well as at 28, 84 and 300 days after implantation, electric response audiometry was used to determine the hearing thresholds of the animals (bone conduction; click stimulus nHL). An erbium:YAG laser was used to excise the original ossicular chain. Following implantation, we were unable to detect any stenosis of the outer ear canal or perforation of the tympanic membrane. The conductive hearing threshold was in the range of 4.21 +/- 6.68 dB nHL (n = 131). The hearing level showed no significant difference before and after surgery (P < 0.05).

Intraoperative computed tomography in otorhinolaryngology.

CONCLUSIONS: Intraoperative CT surgery provides the surgeon with additional information about the altered surgical site in difficult anatomical situations. The skull base and lamina papyracea may be revealed by means of intraoperative CT, which may be beneficial in endonasal sinus surgery involving difficult surgical sites, although individual ethmoid cells cannot be assessed owing to blood artefacts. This provides the surgeon with valuable information that may facilitate the procedure considerably. In soft-tissue surgery it is advisable to apply a contrast agent in order to achieve good soft-tissue contrast, thus allowing the tumour to be adequately distinguished from benign tissue. The intraoperative application of CT is a fairly time-consuming procedure, partly owing to the preparation time (set-up of the appliance; 10-min warming-up phase) and partly due to the length of time required to calculate each image (15 s). OBJECTIVE: CT is a well-established imaging method for the assessment of osseous and soft-tissue structures in the head and neck region. Saving information and transferring it to the intraoperative site may, however, be problematic. Computer-assisted navigation systems are now able to assist difficult surgical procedures in the field of otolaryngology. To investigate the indications for intraoperative CT, we used it in various surgical procedures in the head and neck region. MATERIAL AND METHODS: Intraoperative CT was applied using the Tomoscan M in 46 cases in order to demonstrate the surgical benefit of the following procedures: endonasal surgical procedures on the paranasal sinuses (maxillary and ethmoidal sinusitis, anterior fracture of the sphenoidal sinus); tumour removal by means of laser surgery (carcinomas of the hypopharynx and larynx); and cochlear implantation (to verify the electrode position). After positioning the patient on the CT table, the workstation was set up in the operating theatre. If necessary, the gantry could be moved over the patient's head without repositioning the patient. RESULTS: Intraoperative CT was used to assist in the exposure of the skull base and lamina papyracea in endonasal surgery of the paranasal sinuses. Individual ethmoidal sinuses could not be evaluated owing to blood artefacts. Intraoperative imaging proved particularly helpful in revision surgery for chronic sinusitis in cases with missing anatomical landmarks owing to previous surgeries, where there is an increased risk of inflicting damage to the skull base or orbita. The resection margins can be determined in craniofacial resections. In soft-tissue procedures, such as tumour removal by means of laser surgery, it proved possible to visualize the resection borders of malignant tumours. Assessment of the electrode position in cochlear implantation is particularly useful in revision cases and in cases of cochlear obliteration.

Management of choanal atresia in cases of craniofacial malformation.

OBJECTIVE: To report the method and results of endonasal endoscopic approach in congenital choanal atresia in cases of craniofacial malformation. PATIENTS: The pathology of unilateral and bilateral choanal atresia and the treatment results in seven children treated between 1999 and 2006 are presented. 5 infants suffering from bilateral atresia also had severe malformations (Charge syndrome [2 patients], trisomy 18, microcephalus, central cranioschisis, cleft lip and anophthalmia 9). The surgical intervention was carried out immediately after birth. 2 patients with unilateral atresia were treated in their second and sixth year of life respectively. CT scan was the diagnostic procedure of choice. Intraoperative endoscopy showed both membraneous and osseous atresia. SURGICAL PROCEDURE: Trocars of different sizes were used to open the atresia plate, while the osseous parts were removed with diamond drills. Silicone tubes were inserted transnasally and remained in place for several months to improve the infants'ability to breath and drink. RESULTS: In all cases of bilateral atresia the tubes either had to be changed repeatedly or replaced with larger tubes due to dislocation and head growth. The septum was perforated in one case. No further stenoses were detected following the removal of the tubes (after 3-6 months). CONCLUSION: The transnasal access is particularly suited to newborns and infants because it induces a minor surgical trauma and carries a low risk of bleeding if endoscopes are used. The results show that the risk of restenoses can be minimised with sufficient fixating and in-patient care.

The influence of the coupling of actuation drivers of implantable hearing systems on the mechanics of the middle ear.

We used multifrequency tympanometry to provide middle ear mechanics after implantation of different implantable hearing aids. A total of 34 patients were included in the investigation; 19 of them were fitted with the Otologics system and 15 with the MED-EL Vibrant Soundbridge system. With the Otologics recipients, measurements were made preoperatively and both two months and at least 12 months postoperatively. Measurements involving the MED-EL patients were taken at least 12 months postoperatively. For all measurements, the non-implanted contralateral side was used as a control. Preoperatively, the resonance frequency of the Otologics patients was 904.3 +/- 218.2 Hz for the implanted side and 907.1 +/- 161.8 Hz for the non-implanted side. Postoperatively, a significant increase (p < 0.01) compared with the preoperative value and the control side was observed after two months: 1111.3 +/- 234.7 Hz, as opposed to 823.8 +/- 274.5 Hz on the contralateral side. After 12 months, the resonance point was restored to approximately the preoperatively measured values: 975 +/- 55.3 Hz (implanted side) and 901.3 +/- 207.1 (control side). The resonance frequency in the Symphonix patients, as measured after at least 12 months (on average, 35 months), was 1006.3 +/- 269.5 Hz on the non-implanted side and 900.1 +/- 249.3 Hz on the implanted side. It is apparent that the resonance frequency on the implanted side was higher than on the control side, although the difference was not significant (p = 0.496). Monitoring following the implantation of active hearing systems is therefore recommended in order that conclusions can be drawn regarding the adequacy of the coupling of the actuation driver to the ossicular chain.

[Image-guided minimal-invasive cochlear implantation--experiments on cadavers]. / Navigationsgeführte minimal-invasive Cochlea-Implantation--Untersuchungen am humanen Felsenbein.

BACKGROUND: The accuracy of navigation systems can be improved significantly by using high-resolution flat panel-based Volume Computed Tomography (fpVCT) so that new surgical therapeutic concepts become feasible. A navigation-guided minimally-invasive cochleostomy places highest requirements on the accuracy of intraoperative navigation. METHODS: A flat-panel Volume Computed Tomograph (fpVCT) was used to scan four human temporal bones. The isometric voxel size was 200 microm. The preoperative planning was used to define an optimized drilling channel from the mastoid surface to the round window niche and the scala tympani providing a safety margin to critical anatomical structures such as facial nerve, chorda tympani, sigmoid sinus and posterior wall of auditory canal. The canal was drilled hand-operated with a navigated drill following the previously planned trajectory. Afterwards the drilled canal was imaged by fpVCT. Conventional dissection including mastoidectomy and posterior tympanotomy assured correct localization of the cochleostomy. RESULTS: Path planning took an average of 54 minutes (range 35-85 minutes). Installation took an average of 16 minutes (range 14-19 minutes). The drilling procedure itself took an average of 7.75 min (range 5-12 minutes.) The RMSE-values varied between 0.1 and 0.2 mm (Table 1). All four specimens showed a cochleostomy located at the scala tympani anterior inferior to the round window. The chorda tympani was damaged in one specimen--this was preoperatively planned as a narrow facial recess was encountered. The time needed for planning and system-installation could be reduced continuously. CONCLUSIONS: This feasibility study demonstrates that using current image-guided surgery technology in combination with fpVCT allows drilling of a minimally invasive channel to the cochlea with loco typico cochleostomy. The necessary accuracy of intraoperative navigation can be achieved by use of fpVCT (technical accuracy between 0.1 and 0.2 mm). Our results demonstrate the feasibility of a navigation-guided minimally-invasive cochleostomy loco typico. While we are enthused by this preliminary work, we recognize the barriers which exist in translation to clinical application. These include surgical issues (e.g. control of unexpected bleeding) and electrode issues (e.g. development of insertion tools).

[Tuberculous Otitis media - a rare differential diagnosis in Germany]. / Tuberkulöse Otitis media -Eine seltene Differenzialdiagnose in Deutschland.

A 28-year-old female patient with a migrant background presented for surgery with a suspected cholesteatoma in the left ear. The patient reported having had an aural discharge for several months; otoscopic examination revealed a runny ear, and discrete granulation tissue was seen. Pure-tone audiometry showed conduction hearing loss of 30-40 dB across all frequencies in the left ear; high-resolution computed tomography of the temporal bone revealed that the mastoid and tympanic cavity were completely obscured. The intraoperative finding showed a caseous space-occupying mass that completely filled the tympanic cavity. The suspected diagnosis of tuberculosis was corroborated by pathohistological, microbiological and molecular biological tests. Tuberculostatic therapy was initiated at a different location. Although tuberculosis of the middle ear is a rare condition in Germany, it should nevertheless be considered when making a differential diagnosis, especially in high-risk patients where cholesteatoma is suspected on clinical and radiological evidence or in patients with a chronic middle ear process.

Four years' experience with the minimally invasive surgical approach in cochlear implant surgery.

This is a prospective study on 808 profoundly or totally deaf patients who underwent either unilateral or bilateral cochlear implantation, involving a minimally invasive surgical approach, at the Medical University of Hannover's Department of Otolaryngology between May 2001 and May 2005. Advanced Bionics, Cochlear and MED-EL devices were used, the latter having been in use at our department since the beginning of 2003. The aim of our investigation was to determine the optimal surgical technique, evaluate safety aspects and gauge patient satisfaction with this minimally invasive surgical approach during cochlear implantation. Surgical technique is analysed. Complications such as skin flap problems did not occur. The use of this minimally invasive surgical technique did not increase the surgical risk. This procedure proved both cosmetically and psychologically beneficial for patients, especially for children and their parents.

[Use of the round window micro cath for inner ear therapy - results of a placebo-controlled, prospective study on chronic tinnitus]. / Der Round-Window micro Cath zur Lokaltherapie des Innenohres - Ergebnisse einer plazebokontrollierten, prospektiven Studie bei chronischem Tinnitus.

BACKGROUND: The local therapy of inner ear diseases provides a means of directly applying pharmacological substances and delivering electrical stimulation to inner ear structures. Problems relating to dosage, systemic effects and the blood-cochlear barrier are thus avoided, which is not the case with systemic therapy. The preferred access point is the membrane of the round window. PATIENTS AND METHODS: An appropriately shaped catheter (DURECT Corporation, Cupertino, CA, USA), whose double-lumen passage system permits the variation of concentration and flow, is inserted into the round window niche. In a prospective, placebo-controlled clinical study, this application system was tested in 20 patients with chronic tinnitus. Following implantation the substances lidocaine, glutamate, glutamic acid and caroverine were applied via an attached external micropump. RESULTS: The values for tinnitus loudness, level of irritation caused by the tinnitus and subjective effectiveness of the therapy - measured by means of the visual analog scale (VAS) - showed no significant change, although the most marked improvement was indicated for caroverine. CONCLUSIONS: These results indicate that a positive effect was observable only in a proportion of the patients. Continuous therapy of tinnitus and inner ear diseases will only be possible once a totally implantable microdosage system has been developed.

[The interesting case -- case number 61]. / Der interessante Fall Nr. 61.

A 58-year-old patient presented after having undergone radiation therapy, afterloading therapy and chemotherapy of a T4 nasopharynx carcinoma. On the basis of the MRI findings, local tumour recurrence was suspected. The samples taken from the nasopharynx and the left maxillary sinus confirmed this diagnosis. Neuroradiological imaging showed that the tumour extended into the area around the left skull base and also revealed an irregular formation located in the left temporal flap. Therefore not only tumour resection (Fisch approach type C) but also a temporal craniotomy was indicated in order to determine the degree of intracerebral tumour extension. The dura mater, which had been intact, was intraoperatively opened and revealed vital brain tissue, i. e. tumour infiltration had not reached the brain. It was concluded that the radiological findings probably indicated a postradiogenic necrosis of the temporal flap. The presented case illustrates the rare differential diagnostic procedure carried out in a patient with radiogenic necrosis while taking into account the possibility of local tumour infiltration into the brain parenchyma.

[Bone ablation using ultrashort laser pulses. A new technique for middle ear surgery]. / Knochenablation mittels ultrakurzer Laserpulse. Eine neue Technik für die Mittelohrchirurgie.

OBJECTIVES: Laser applications within the tympanic cavity area are widely accepted. Commonly used systems are CO(2), argon, KTP and erbium devices. The disadvantages are heat development and/or acoustic load of the inner ear. A new laser with ultra short pulses was examined concerning its ablation characteristics and tested for possible applications in the tympanic cavity. METHODS: Investigations on human ossicles and porcine compacta were performed with a femtosecond laser in order to determine the ablation parameters. This included measurements of the dependency of the threshold energy on the pulse duration and the determination of the ablation ratio using different pulse energy levels. On the basis of histological slices the thermal damages of the bone were examined. Additionally, the processed samples were analyzed with an optical microscope and with a scanning electron microscope in order to evaluate the quality of the perforations. RESULTS: The measurements showed that the threshold energy has a lower level than the threshold energy of the conventional laser systems. At a pulse duration of 180 fs the smallest fluence, with which an erosion can be achieved, is below 1 J/cm(2). With increasing pulse duration the necessary threshold energy also rises. Due to the low energy level necessary for ablation and the extremely short pulse duration, less thermal damage is induced to the surrounding bone tissue as compared to conventional laser systems. The analysis of the scanning electron microscope demonstrates the extreme precision of this laser system. The achieved accuracy of the incisions and drillings ranges in the microm-area. CONCLUSIONS: The fs laser represents a new surgical tool for middle ear surgery. It works efficiently and in a touch-free procedure. Due to its high precision and the reduced side effects an advantage in the handling of bony structures is to be expected in relation to other laser systems. Apart from the perforation of the stapes footplate, in particular the handling and modelling of the incus, a further field of applications includes enhanced coupling, e. g. for implantable hearing aids and ossicular chain replacement prosthesis.