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Biomedical subjects

T Zahnert

Publications and source records attributed to T Zahnert.

At least 19 recordsLinked to original sources
PubMed2007

[A new model for training in tympanoplasty].

BACKGROUND: Functional simulation of middle ear reconstruction is a valuable tools for training in otosurgery. We introduce a new experimental model which provides a direct acoustic feedback of the functional quality of ossicular chain reconstruction. METHOD: In this model the tympanic membrane and the ossicular chain have to be reconstructed for proper sound transmission to an artificial inner ear receptor. The received signal is converted into acoustic information and consecutively provided via headphone. RESULTS: Any changes in the reconstruction (e. g. tilting the prosthesis) can be experienced online and immediately optimized by the surgeon or a trainee. CONCLUSION: The experimental model can be used for demonstration and training in otosurgery. This model is also suitable for comparing measurements of transfer functions in a calibrated version and can be applied to development and critical evaluation of middle ear prostheses.

Acoustic Stimulation↗
PubMed2007

[Conventional tomographic investigations of the reconstructed middle ear in temporal bone specimen].

BACKGROUND: In modern reconstructive middle ear surgery imaging plays an essential role as a diagnostic tool, especially in pre-operative planning. Nowadays imaging of surgical results as a matter of quality control in post-operative follow-up becomes more important. MATERIAL AND METHODS: Conventional tomography was performed in 10 temporal bone specimen using the CommCat IS 2000-system in order to evaluate anatomical structures and inserted middle ear prostheses (PORP/TORP). This imaging technique has not been used in middle ear surgery beforehand. RESULTS: Using conventional tomography characterization of anatomical structures of the temporal bone as e. g. the semicircular canals appeared to be of superior quality to comparable conventional radiographic imaging. Concerning imaging quality (contrast; resolution) conventional tomography allowed similar findings like computed tomography (CT)-scans in some of the investigated specimen while showing inferior sharpness quality due to technical reasons. Further advantages of conventional tomography in contrast to CT were the requirement of just 2.5 % of the CT's irradiation exposure, lack of metallic artefacts caused by implanted prostheses and the feasibility of distance- and angle-measurement of inserted prostheses towards the tympanic membrane which coincided extensively with the temporal bone preparation. CONCLUSIONS: Conventional tomography enables detailed anatomical imaging of the temporal bone region which outperforms conventional radiographic imaging, requires less irradiation dose than CT and helps avoid problems like metallic artefacts. This technique enhances immediate quality-control and seems to be therefore a promising tool for postoperative evaluation after reconstructive middle ear surgery.

Contrast Media↗
PubMed2007

[High duplication of an internal jugular vein].

The internal jugular vein is an important landmark in most cervical operations. The surgeon should know the exact position and possible variations to prevent complications. We report on a duplicated internal jugular vein, which is a rare anatomic anomaly and discuss aetiology and appearance of this malformation and the possible affecting of the accessory nerve.

Accessory Nerve↗
PubMed2007

[Multiple endocrine neoplasia type 1].

Owing to the growing use of ultrasound in the head and neck and to technical progress, the number of tumours diagnosed in the thyroid region is increasing. The rare differential diagnosis of multiple endocrine neoplasm type 1 in a case with a unilateral intrathyroidal lump and two lumps located dorsal to the contralateral thyroid is discussed.

Adenoma↗
PubMed2006

[Impact of TORP diameter on fracture of the footplate].

BACKGROUND: A columella-prosthesis is the typical reconstruction procedure of the ossicular chain in cases with a destroyed stapedial arch. Lightweight titanium prostheses are commonly used for this type of surgery. The smaller the prosthesis foot the lower the risk of dislocation and friction of the prosthesis with the bony rim of the oval niche. However, using a smaller prosthesis foot, fracture of the footplate and penetration of the prosthesis into the inner ear are conceivable. METHODS: Using fresh temporal bone preparations, lacking the stapedial arch, in conjunction with a load cell, the force needed to fracture the footplate was measured. Different prostheses with different foot diameters (0.2 - 0.8 mm) were used in these experiments. Furthermore, a human stapes was evaluated morphologically by scanning electron microscopy. RESULTS: The forces leading to fracture of the footplate were measured to be between 250 mN and 980 mN. Statistical analysis showed no significant difference between 0.2 mm and 0.8 mm prosthesis foots. Moreover, different forces were attributed to varying thickness of the stapes footplate. In scanning electron microscopy the rough and uneven bony surface of the footplate could be demonstrated. CONCLUSION: Due to the uneven footplate, only punctual contact of the prosthesis foot can be achieved. Hence, the risk of footplate fracture is not considerably higher by using smaller diameters. However, the use of smaller feet in upcoming generations of TORPs seems to be appropriate.

Biomechanical Phenomena↗
PubMed2006

A study on the prognostic significance of qualitative olfactory dysfunction.

We investigated the frequency and prognostic significance of qualitative olfactory dysfunction (parosmia, phantosmia) in a retrospective patient based study. A total of 392 patients with impairment of olfaction were tested at least two times for their olfactory function using the "Sniffin' Sticks". The mean interval between the first and the last test was 11 months. At the first visit 34% of all patients reported parosmia. Parosmia was most frequent in patients with postinfectious olfactory loss (56%), and less frequent in idiopathic, posttraumatic, sinunasal disease with frequencies of 10, 14, and 28%, respectively. In contrast, only 12% of all patients had phantosmias, with no significant differences between the patient groups. Improvement of olfactory function was found in 23% of all patients (n = 90). Pre-existing parosmia or phantosmia had no significant effect on recovery rate. Regarding qualitative olfactory dysfunction, 29% of those patients reporting parosmia reported relief of this symptom after an average of 12 months, whereas 53% of phantosmic patients lost phantosmia during the observation period. Although it has been suggested that olfactory distortion s could be regarded as an indicator of early recovery of decreased olfactory sensitivity, the current data indicate that occurrence of parosmia or phantosmia has little prognostic value. Phantosmia disappears at a faster rate than parosmia. These insights into qualitative olfactory dysfunction are regarded to be significant in the counseling of patients with olfactory loss.

Adolescent↗
PubMed2006

Chemosensory specific reduction of trigeminal sensitivity in subjects with olfactory dysfunction.

Humans with olfactory loss have been found to exhibit a decreased sensitivity of the chemosensory trigeminal system. It is not clear, whether the reduced trigeminal sensitivity is restricted to the chemosensitive properties of the trigeminal nerve, or whether it reflects a general decrease of trigeminal sensitivity which is also found for cutaneous afferents. To investigate the relationship between cutaneous somatosensory and intranasal chemosensory trigeminal sensitivity, 91 subjects were investigated. Forty-five of them were considered healthy controls, whereas 46 subjects had olfactory dysfunction. Subjects with olfactory dysfunction were found to have higher thresholds for CO2 than controls indicating lower trigeminal chemosensory sensitivity in subjects with olfactory dysfunction. Both etiology and degree of olfactory dysfunction appeared to have an impact on CO2 thresholds. In contrast, no such differences were found with regard to detection thresholds for electrical cutaneous stimulation. These results indicate that the decrease of trigeminal sensitivity in subjects with olfactory dysfunction is specific for chemosensory sensations.

Adult↗
PubMed2006

Chemosensory event-related potentials in relation to side of stimulation, age, sex, and stimulus concentration.

OBJECTIVE: For chemosensory event-related potentials (ERP) significant effects of age and sex have been demonstrated. The aim of the present study was to assess the effects of stimulus concentration, side of stimulation, and sex on the topographical distribution of chemosensory ERP in a large group of subjects stratified for different age groups. In addition, psychophysical measures of both olfactory and trigeminal function should be assessed in greater detail compared to previous work. METHODS: A total of 95 healthy subjects participated in the study. Olfactory functions were tested using the 'Sniffin' Sticks' comprising tests of odor identification, odor discrimination, and odor threshold. Trigeminal sensitivity was assessed on a psychophysical level using a lateralization paradigm. ERP to the olfactory stimulant H2S and the trigeminal irritant CO2 were recorded; stimuli were presented in different concentrations to the left and right nostril. RESULTS: Olfactory thresholds exhibited an age-related increase while the outcome of psychophysical trigeminal tests was not significantly affected by age. In contrast, there was no significant main effect of the factor 'sex' for olfactory tests, while women scored higher than men in the trigeminal task. ERP to olfactory and trigeminal stimuli exhibited a relationship to stimulus concentration, age, and sex with youngest women showing largest amplitudes and shortest latencies. There was no significant main effect of left- or right-sided stimulation on ERP. Measures of olfactory function were found to correlate with parameters of olfactory ERP even when controlling for the subject's age. In addition, correlations between scores in the lateralization task and parameters of the trigeminal ERP were found. CONCLUSIONS: Based on electrophysiological data obtained in a large sample size the present results established an age-related loss of olfactory and trigeminal function, which appears to be almost linear. Further, the present results emphasize that responses to chemosensory stimuli are related to sex, while the side of stimulation does not play a major role in the presently used paradigm. Finally, these data establish the lateralization paradigm as a psychophysical tool to investigate intranasal trigeminal function. SIGNIFICANCE: The present results obtained in a representative group of healthy subjects establishes a comprehensive set of data, which will serve as reference for future work in this area of research.

Adolescent↗
PubMed2006

[Documentation of endonasal changes in blood volume using optical rhinometry].

BACKGROUND: In optical rhinometry, the nose is transilluminated with light and the light absorption by the nasal tissue is measured continuously. Using this method, a real time documentation of changes in nasal blood volume is possible. The method has been evaluated using the nasal allergen provocation test. In this study, the ability of optical rhinometry to detect changes in the nasal blood volume due to various posture changes is examined. METHODS: Optical rhinometry was tested on ten healthy probands, with several examinations being performed on each. RESULTS: By bending the neck, lying down or stopping breathing, stronger light extinction was found. Standing up quickly caused a sudden but short decrease in light extinction. A small amount of exercise, such as making a fist several times, decreased light extinction. Harder exercise on an ergometer led to a stronger decrease in light extinction. In the Valsalva maneuver, an increase in light extinction for the duration of the maneuver was observed. Changes in breathing through the nose or mouth or counting from 1 to 100 had no influence. CONCLUSIONS: Using the new method of optical rhinometry, it is possible to detect changes in endonasal blood volume caused by changes of intrathoracic pressure, changes in posture or physical exercise, non-invasively and in real time. This technique can therefore be used for further research on the regulation of the nasal blood flow.

Adult↗
PubMed2005

[Endocranial complications in otitis media: what you need to remember].

Thanks to the potency of antibiotics, life-threatening complications of otitis media are rare. In many cases, however, the symptomatology is veiled, and the course of the disease tends to be protracted. Secondary symptoms may preponderate and often mask those associated with the ear itself. If a case of otitis media fails to clear up, or mastoiditis develops, or sensorineural deafness, vertigo, headaches, seizures, or meningism occur, the possibility of an otogenous complication must immediately be considered and the patient submitted to diagnostic imaging without delay, so as to ensure early surgical treatment of a possible lesion in the ear.

Acute Disease↗
PubMed2005

[Pitfalls in ossicular chain reconstruction].

Today, the reconstruction of the ossicular chain is standard in middle ear surgery. It is performed as a one step procedure in cases of non-inflamed middle ears, as well as in cases of chronic ear diseases. In contrast to the past, a large tympanic cavity is today regularly reconstructed, which contributes to a normally ventilated middle ear. Reconstruction of the ossicular chain is necessary to keep the tympanic membrane in its normal position.However, many modern prostheses are available with different designs and material properties. This article aims to give an overview of the acusto-mechanical and surgical aspects of ossicular chain reconstruction. After a description of normal middle ear vibration, the biomechanical background of the reconstructed middle ear (incus reconstruction, stapes reconstruction) is discussed.

Ear Diseases↗
PubMed2004

[The cartilage guide: a solution for anchoring a columella-prosthesis on footplate].

BACKGROUND: A torp (columella-prosthesis) is the typical ossicular reconstruction in cases of a destroyed stapedial arch. Yet, many unsatisfactory hearing results are due to the lack of a stable, reliable anchoring of the base of the prosthesis on the footplate. Some solutions have been postulated, amongst them the perforation of the footplate with a tiny spike at the lower end of the prosthesis, which, however, many otosurgeons regard as too dangerous for the inner ear. Specially designed silicone sheets cannot guarantee a permanent guide of the columella. METHODS: From our good experience with cartilage in different reconstruction procedures, we therefore developed a cartilage guide for the oval window niche. An oval 2,5 x 3,5 mm cartilage with a central hole is cut out of a thin (0,2 - 0,3 mm) cartilage plate with a help of a cartilage punch, which we had designed in collaboration with Heinz Kurz manufacture. The cartilage is placed into the oval niche and its hole guides the prosthesis onto the centre of the footplate. RESULTS: Temporal bone experiments demonstrated a reliable sound transport through this guide. Revision surgery revealed a stable ingrowth of the cartilage plate into the oval niche, its perforation securely guiding the prosthesis similar to a piston on to the footplate. The first short time hearing results (max. 1 year) in 22 patients confirmed the acoustic quality of this stabilisation of a columella on the footplate as compared to a matched control group. CONCLUSIONS: The stabilization of the columella with a cartilage-guide might solve one of the many problems with unsatisfactory hearing results after the reconstruction of a completely destroyed ossicular chain.

Adolescent↗
PubMed2001

[Intraoperative measurement of stapes mobility using a hand-guided electromagnetic probe].

BACKGROUND: The hearing results of otosurgery are still unsatisfactory. Even after successful implantation of middle ear prostheses there often remains an air bone gap of 30 dB or more. As possible reasons dislocation of the prostheses due to scar growth, changes in prostheses' attachment or ventilation disorders are being discussed. Decreased stapes mobility, which has been judged only manually up to now, is supposed to be a further reason. METHOD: We are introducing a new electromagnetic probe. The output signal of this device is proportional to the impedance of the stapes-annular ligament cochlear fluid system at the sensor's resonance frequency (2.4 kHz). The advantage of this system is characterised by its hand-guidance. Injury of the sensitive stapes-annular ligament due to tremor movements of the surgeon can be excluded using a special construction of the sensor head. The maximum force of the sensor's tip onto the stapes during measurement is limited to below 5 mN. RESULTS: Preliminary measurement results of 20 patients are presented with normal and abnormal stapes mobility. These results are compared to the subjective impression of the surgeon, who usually tested the stapes mobility by hand. As a result of our investigations probe measurements can detect more exactly decreased mobility of the stapes than the surgeon. CONCLUSIONS: Our device may help to detect latent stapes fixation caused by chronic inflammation of the middle ear. The intraoperative measurement of stapes mobility may influence the strategy of the surgeon. Furthermore it would be helpful in patient consulting prior to a revision-tympanoplasty with predicting the potential hearing improvement.

Cholesteatoma, Middle Ear↗
PubMed2001

[Visualization of cochlear implant electrode movements in the cochlea by using x-ray microscopy].

BACKGROUND: The movements of the electrode cable of a cochlear implant inside the cochlea during the insertion procedure generally are invisible, even in temporal bone experiments. Yet, the development of new designs of electrodes, their positioning near to the modiolus etc. requires an exact knowledge on the dynamic behaviour of the electrodes inside the cochlea. The exclusive method for looking through the undamaged cochlea walls is by x-ray technique. METHODS: A specific x-ray tube with a focal spot size of barely 5 microns allows useful direct magnifications of more than 20-30 times. We performed temporal bone experiments with this tube and studied the behaviour of conventional and perimodiolar electrode cables of a MedEl-Cl during the insertion procedure under fluoroscopic viewing. RESULTS: The high resolution imaging revealed the influence of stiffness of the electrode cable on the insertion depth of a conventional electrode. If the angle of the direction of insertion was too steep, the resulting kinking of the cable at the medial wall of the basal turn was instantly visible. The direct visualisation of the movements of the cable was useful in optimizing the design and stiffness of various prototypes of perimodiolar electrodes for a deep insertion. CONCLUSIONS: The dynamic examination technique disclosed that the stiffness of actual electrode cables is not optimally adapted to the form of the cochlear cavity for deep insertion. The non-destructive visualisation technique will facilitate the development of advanced electrode design, especially for various concepts of perimodiolar electrodes.

Cochlea↗
PubMed2001

Tremor in otosurgery: influence of physical strain on hand steadiness.

BACKGROUND: The microscopically small middle ear structures require the otosurgeon to have a steady hand because instrument stability is a critical factor for a successful microsurgical procedure. Hand steadiness is mainly influenced by the tremor movements of the hand. The aim of this study was to measure hand tremor under simulated microsurgical conditions and to estimate the influence of different kinds of physical strain (e.g., physical exertion and hand exercise), as well as food abstinence and coffee consumption. Further, the effect of one-or two-handed manipulation and microsurgical experience was investigated. METHODS: The hand movements of 16 adult subjects were assessed during a defined manual manipulation using a stapes model to simulate microsurgical procedures. A laserinterferometric-based displacement technique was developed to measure tremor amplitude and frequency, as well as maximum displacement, to evaluate the subjects' fine motor skills. RESULTS: The mean tremor frequency across all measurements was 8.1 Hz and did not show any dependence on different kinds of physical strain. Two-handed manipulations showed significantly lower tremor amplitudes than one-handed performances. Tremor amplitude and maximum displacement did not change after hand exercise, food abstinence, and coffee consumption. However, after physical exertion, a significant increase in the tremor amplitude was found. Subjects with advanced microsurgical experience showed smaller tremor amplitudes for one-handed runs. CONCLUSION: The tremor data are interpreted as a recommendation to avoid physical exertion before microsurgery. In cases of absolute necessity for hand steadiness, two-handed manipulations are preferable. Further, hand steadiness might be improved by microsurgical training and experience.

Adult↗