Biomedical subjects

M M Maassen

Publications and source records attributed to M M Maassen.

32 records · Page 2Linked to original sources

PubMed1998

[First implantation of a totally implantable electronic hearing aid in patients with inner ear hearing loss].

For the majority of patients with sensorineural hearing loss (SNHL) many available hearing aids often do not achieve satisfactory results. For these patients partially implantable hearing devices have been developed, allowing distortion-free hearing and speech intelligibility that may be superior to conventional hearing aids. The external parts of partial implants, however, may result in a patient's stigmatization. Furthermore, they do not use the acoustic properties of the external auditory canal. Recently, we published the successful development of the first totally implantable hearing device for the treatment of SNHL (HNO 46 [1998] 853-863). Here we report the first implantations of this unique, totally implantable electronic hearing system in patients with SNHL: Implex TICA LZ 3001. The implant microphone is implanted subcutaneously in the outer ear canal near the ear drum. The signal is processed by a digitally programmable multichannel audioprocessor located subcutaneously on the bony skull behind the ear. A piezoelectric transducer is coupled to the body of the incus and drives the ossicular chain by vibratory actions. Energy is provided by an implantable battery. Implanted patients describe hearing as being distortion-free and transparent. Speech intelligibility and the hearing of music are improved. Patients may achieve better speech discrimination, especially in the presence of background noise. The aid can be used during sports, including swimming. To our knowledge, this is the first report of the implantation of a totally implantable electronic hearing system in patients. These results encourage further implantations of the totally implantable hearing system in the course of an ongoing clinical study.

Audiometry, Speech↗

PubMed1998

[Functional long-term results after open cholesteatoma surgery and ossiculoplasty with allogenic ossicles in adulthood].

BACKGROUND: Characteristic features of cholesteatoma of the middle ear are destruction of the bone and a high tendency for recurrent disease. The choice of surgical procedure is determined by audiological results and the rate of recurrent cholesteatoma. PATIENTS: One hundred fifty patients who underwent primary cholesteatoma surgery were investigated 3-5 years postoperatively. Preoperative and postoperative audiological results and rate of revision surgery were compared for the respective surgical procedures. All cholesteatomas were treated with an open surgical technique. The lateral attic walls and cholesteatomas were removed. RESULTS: Cholesteotoma recurred in 15 patients (10%). Primary reconstruction of the ossicular chain with a tympanoplasty (type III) was performed in 98 patients in the first operation. Approximately 80% of patients treated with a type III tympanoplasty had a maximum postoperative air-bone gap of 20 dB in the main speech range, depending on the frequency. In about 50% of patients, this value was 10 dB or less. Comparison of preoperative and postoperative conductive hearing loss between 250 Hz and 8000 Hz revealed an improvement (p < 0.05) of 10 dB (500 Hz, 3000 Hz, 4000 Hz) and 15 dB (250 Hz, 1500 Hz, 2000 Hz, 8000 Hz). CONCLUSIONS: In our opinion, a second look operation should be performed in cases where a large cholesteatoma cannot be removed with sufficient reliability. This applies especially to a cholesteatoma in the oval window. Here, we suggest second-look surgery after one year.

Adolescent↗

PubMed1998

Tympanoplasty type II with ionomeric cement and titanium-gold-angle prostheses.

OBJECTIVE: The pronounced isolated erosion of the long incus process is a challenging situation during tympanoplasty. Here, we report two methods for reconstruction of the ossicular chain as tympanoplasty type II with the incus remaining in situ. (1) lonomeric cement is used, resulting in two characteristics: a direct link between stapes head and the long incus process is achieved. At the stapes head the link possesses a joint allowing physiological movements between incus and stapes. (2) Titanium-gold-angle prosthesis according to Plester were crimped to the long process of the incus and positioned onto the head of the stapes forming an articulation. STUDY DESIGN: Forty-five patients with missing long incus process underwent ossiculoplasty among which 41 patients were operated within a randomized, prospective clinical trial. For myringoplasty, the underlay technique with tragus perichondrium was used in all patients. SETTING: We investigated hospitalized patients. INTERVENTION: In 26 patients ossiculoplasty was performed as tympanoplasty type II, in 19 patients with incus interposition. MAIN OUTCOME MEASURE: The essential criterion was the postoperative air-bone-gap (dB). RESULTS: Incus interposition achieved less satisfactory results with an average remaining air-bone gap of 10-20 dB. By contrast, the two tympanoplasty type II procedures yielded average postoperative air-bone-gaps of 0-10 dB (p=0.0003 at 1 kHz; p=0.0028 at 4 kHz), thus reaching the "gold standard" of stapedotomy. The two type II procedures, however, were not equal. The angle prosthesis was restricted to cases with a sufficiently long incus process, whereas the cement-technique is also applicable, when only a short part of the long incus process remained. CONCLUSION: In the present study we show that in the case of a missing crus longum of the incus, a tympanoplasty type II achieved a statistically significant better hearing gain than an autograft interposition.

Audiometry↗

PubMed1997

[New methods of type II tympanoplasty in erosion of the long incus process].

Reliable methods of reconstruction of the ossicular chain in the situation of an isolated errosion of the long process of the incus using a tympanoplasty type II have not been available until recently. Instead, the tympanoplasty type III has been generally performed with the interposition of an autologous incus. In this presentation, we are describing two methods for reconstruction of the ossicular chain between the in-situ residing incus and the stapes on the other side so that the direct connection eventually will result in a tympanoplasty type II. In the first case, we used ionomeric cement in a way that features two characteristics: the direct connection between the stapes and the long process of the incus could be achieved as well as an articulation that was created on the head of the stapes. Hence, a too stiff connection between the head of the stapes and the long process of the incus could be avoided. In addition, a new method for precise microapplication of cooled bone cement (IONOCAP LV) with a syringe will be presented. In the second method titanium-gold-angle prostheses have been crimped to the long process of the incus and positioned onto the head of the stapes in the way of an articulation. So far, comparison of the audiological results of those two methods of a tympanoplasty type II reveal in average better results than postoperative conductive hearing thresholds of the conventional tympanoplasty type III. If the achieved results can be reproduced on a larger number of patients, the expected audiological results are likely to resemble those of stapes surgery.

Auditory Threshold↗

PubMed1997

[First comparisons with laser vibrometry measurements and computer simulation of ear ossicle movements].

The dynamic behavior of the ossicular chain is very complex and is frequency-dependent. To date, this has still not been fully investigated or understood. There remains a lack of measurement procedures to pick up the motion of the ossicles and ear drum simultaneously with sufficient resolution. The presented paper reports simultaneous measurements with laser-Doppler vibrometry at two points of the ossicular chain of cadaver specimens. Motions not observed were derived using mechanical simulation models on a computer and then evaluating appropriate mathematical equations. Using a sound stimulus, the displacement velocities of the umbo and stapes footplate were measured, and the corresponding transfer functions were derived by Fourier transform. Results were used for verification of the computer models. In the current investigations these models were refined and allow for the detailed investigation of the dynamic behavior of the ossicular chain, facilitating the optimal design of passive and active middle-ear implants.

Computer Simulation↗

PubMed1997

[Adjusting the geometry of implantable hearing aid components to human temporal bone. I: Electromechanical transducer].

Prerequisite to implantation of a piezoelectrical transducer of an implantable hearing aid is a shape allowing its implantation into human mastoid and middle ear. To approach this problem, a consecutive series of six transducer prototypes was created in an iterative process. Their functional geometry was evaluated in 50 human temporal bones. A shape for a functioning transducer was found which will enable implantation in 78% of the cases examined (confidence interval: 61.5%-89.2%). It will allow simultaneous implantation of the transducer into the mastoid and microphone, which is situated transmastoidal in the posterior wall of the ear canal. Furthermore, the transducer may be coupled to the ossicular chain or the perilymph.

Cochlear Implantation↗

PubMed1997

[Adjusting the geometry of implantable hearing aid components to human temporal bone. II: Microphone].

Recently, an implantable hearing aid for rehabilitation of sensorineural hearing loss has been developed. One component of the device is the microphone for implantation into the posterior canal wall. The membrane of the microphone can be covered by skin, cartilage, or fascia, avoiding reduction in sound transmission at the same time. In the study presented here, the microphone was implanted into 50 cadaver specimens of human temporal bone. Localization of the microphone was determined by the anatomical situation of the facial nerve. The microphone and the piezoelectric transducer could be implanted in 78% of the temporal bones after total mastoidectomy. In the final version of the microphone, the size was 4.5 mm and total weight 400 mg.

Cochlear Implantation↗

PubMed1997

[Ossicular coupling of an implantable hearing aid transducer using an Er:YAG laser].

Special coupling devices made of pure gold or titanium have been developed to connect a new implantable hearing aid transducer (Tübingen implant) to the ossicular chain. They allow piezotransducer probe-tip connection to the long process of the incus or the stapedial head. Similar to the design of conventional PORPs (partial ossicular replacement prostheses), the coupling devices can be fixed at the ossicular chain, e.g., with the eye loop of stapedial piston prostheses or the bell element of golden wire PORPs. A crimp technique allows connection between coupling device and transducer probe tip [5]. The main disadvantage in connecting the long process of the incus or the stapes having is to drill a dorsal tympanotomy in the posterior wall of the ear canal during surgery. The short distance between tympanotomy and N. facialis contains serious surgical risks. To avoid the risk of facial paralysis, Fredrickson's alternative coupling technique for the body of the incus is investigated in this paper [2]. In this case, the transducer probe tip will be positioned to the incus body and placed on its surface with controlled elastic displacement of the ossicular chain. The simple direct attachment of the probe-tip end on the surface of the incus, however, will not guarantee a stable long-term connection. Thus, by creating a conical, 0.5-to 0.7-mm-deep hole in the incus, the probe tip will be fitted much better. With a novel surgical Erbium-YAG laser this can be done in a contactless procedure. In this paper, first results of microsurgical laser applications with human temporal bones will be shown.

Cochlear Implantation↗

PubMed1997

[An implantable hearing aid for inner ear hearing loss. Short-term implantation of microphone and transducer].

A microphone constructed for implantation in the posterior wall of the auditory canal and a piezoelectric transducer serving as the main components of an implantable hearing aid were temporally implanted in five patients during middle ear surgery under local anesthesia. The microphone was positioned beneath the skin of the auditory canal such that it completely covered the microphone membrane. The vibratory element of the transducer was coupled to the malleus in four patients with normal ossicular chains and directly to the stapes in one patient with missing incus. The microphone and transducer were electrically connected with an external battery-driven signal amplifier. Speech material and music were presented in the operation room at a sound level of 65 dB SPL under free-field conditions. The patients had to estimate the quality of speech, music, and their own voice as well as the effects of bone-conducting noises. All patients were able to hear with the system. An intraoperative talk without vision contact was possible without any problems, as was understanding of numerals ("Freiburger Zahlentest"). Perception of music was judged as "clear and undistorted with all broadband component." The estimation was also valid for one patient with a sensorineural hearing loss. One patient declared the music to be "a little of unnatural." Bone-conducted sound was estimated as normal in two patients, better than without an implant in one patient with sensorineural hearing loss, and "somewhat metallic" in another patient. Hearing the own voice was considered "normal" in two cases "monotonous" in one case, and "a little bit roaring" in another case. An amplification factor that can be technically realized in an implantable hearing aid was necessary for one of the patients with sensorineural hearing loss to perceive music at a pleasant volume. On the basis of this study, essential requirements for the construction of a fully implantable hearing aid are fulfilled.

Adult↗

PubMed1997

Preoperative assessment of the implantable middle ear pump system using CT scans and conventional X-rays of the temporal bone.

A completely implantable micropump system for drug delivery has recently been developed. After implantation in the temporal bone, this microdosage system enables application of drugs into the middle ear and round window area. Successful application of this new technology depends upon a suitable fit of the micropump within the patient's temporal bone. To obtain information about the fit before surgery, we analyzed 50 cadaver temporal bone specimens before total mastoidectomy, using conventional X-ray and spiral CT scans for water volume determination. Spiral CT is a feasible method for preoperative planning of the surgical implantation of the implantable middle ear micropump system (TI-DDS). The best parameter for a preoperative judgment is the volume of the mastoid cavity, as determined by CT. Implantation may be recommended when the mastoid volume, as measured by CT, is greater than 6.6 ml. To be certain that the implantable drug delivery system will be implantable, a cut-off value of 9.3 ml seems to be advisable. Spiral CT imaging is of great value as a tool for testing implantation preoperatively. The imaging is accomplished in approximately 30 seconds. Our preliminary results with cadaveric temporal bones are encouraging. Further studies are needed in order to transfer the results to a clinical implantation situation.

Ear, Middle↗

PubMed1997

A totally implantable drug delivery system for local therapy of the middle and inner ear.

Local therapy of middle and inner ear diseases is being used, but is restricted to cases of ear drum perforation or to repeated invasive intratympanic drug application by the physician. In accordance with the Medical Device Directive (class III), a bone-anchored, totally implantable drug delivery system (TI-DDS) has been developed. It includes a micropump for subcutaneous, patient-controlled activation, a drug reservoir and a septum port. A thin guide-wired catheter leads from the pump outlet to the point of application in the mastoid or middle ear cavities. Local inner ear therapy with suitable drugs is possible by positioning the catheter's end near the round window membrane. The system requires no battery and will offer a wide range of patient-controlled bolus applications (25 microliters per activation). We first analyzed the three-dimensional implantation geometry of the mastoid cavity. Basic micromechanical problems have been solved in order to create several prototypes. The TI-DDS has already undergone extensive in vitro testing. Recent results of pump rate precision and digital pressure force testing are promising. Local drug treatment for conditions such as lidocaine-sensitive tinnitus, secretory otitis media, Meniere's disease, localized pain and intralesional cancer is under discussion. Furthermore, local application of future biotechnological trophic factors for inner ear treatment is anticipated. The basic engineering is completed and initial animal tests are in preparation.

Animals↗

PubMed1993

[Jaffé-Lichtenstein fibrous dysplasia as a cause of progressive protrusio bulbi and temporary vision loss].

We report the rare clinical and morphological features found in a patient with fibrous dysplasia of the paranasal sinuses. In general, diagnosis of tumor sinuses can be made without difficulty and can be made on the basis of three criteria: clinical examination, radiographic findings and histologic examination of a biopsy. Nevertheless, if rare morphological findings occur, obtaining the correct diagnosis can be complicated. Therefore, we report our experiences in managing a 22 year old woman with fibrous dysplasia located in the paranasal sinuses that resulted in proptosis and temporary blindness. The diagnostic and therapeutic implications are elucidated.

Adult↗

PubMedDate not supplied

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment.

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

Cochlear Implants↗

PubMedDate not supplied

Cognitive and psychomotor function during hypoglycemia: a comparison between porcine and human insulin.

After an overnight euglycemic clamp, blood glucose levels were precisely lowered on two nonconsecutive mornings via a glucose-controlled insulin infusion system (GCIIS, Biostator) using either purified porcine insulin (PPI) or human insulin (HI). Two cognitive and psychomotor tests were significantly different in 8 type-I diabetic subjects and 8 healthy volunteers at four timepoints, when mean blood glucose concentrations (BGCs) were 100, 65, 50, and 40 mg/dl. Also, a significant difference (p = 0.005) could be found between the mean of all reaction time testing (RTT) values under HI as compared with the mean of all RTT values under PPI. Lowering the BGC resulted in a significant increase in the reaction time (p = 0.012). These effects were not dependent on the type of insulin being used nor were they typical of a particular study group.

Adolescent↗