Studies of MEMS Acoustic Sensors as Implantable Microphones for Totally Implantable Hearing-Aid Systems.

There is a need for high-quality implantable microphones for existing semiimplantable middle-ear hearing systems and cochlear prosthesis to make them totally implantable, thus overcoming discomfort, inconvenience, and social stigma. This paper summarizes and compares the results of an in-vitro study on three design approaches and the feasibility of using microelectromechanical system acoustic sensors as implantable microphones to convert the umbo vibration directly into a high-quality sound signal. The requirements of sensors were selected including the ability to withstand large body shocks or sudden changes of air pressure. Umbo vibration characteristics were extracted from literature and laboratory measurement data. A piezoelectric vibration source was built and calibrated to simulate the umbo vibration. Two laboratory models of the acoustic sensor were studied. The model-A device, using electrets-microphone as the sensor, was designed and tested in the laboratory and on temporal bones. The results verify that the laboratory measurement is consistent with the temporal bone characterization and achieves a near flat frequency response with a minimum detectable signal of a 65-dB sound-pressure-level (SPL) at 1 kHz. The model-B sensor was then designed to increase the sensitivity and provide an easy mounting on umbo. The model-B device can detect 40-dB SPL sound in the 1-2 kHz region, with 100-Hz channel bandwidth. The results of model-A and model-B displacement sensors and the acceleration sensor are summarized and compared. A preliminary design of the implantable displacement sensor for totally implantable hearing-aid systems is also presented.

Diagnosis and management of spontaneous cerebrospinal fluid-middle ear effusion and otorrhea.

OBJECTIVES/HYPOTHESIS: Spontaneous leak of cerebrospinal fluid (CSF) into the middle ear can occur in adults without a history of temporal bone trauma or fracture, meningitis, or any obvious cause. Therefore, clues may be lacking that would alert the otolaryngologist that fluid medial to an intact eardrum, or fluid emanating from an eardrum perforation, is likely to be CSF fluid. A review of relevant medical literature reveals that herniation of the arachnoid membrane through a tegmen defect may be congenital, or CSF leak may occur when dynamic factors (i.e., brain pulsations or increases in intracranial pressure) produce a rent in the arachnoid membrane. Because tegmen defects may be multiple rather than single, identifying only one defect may not be sufficient for achieving definitive repair. Data on nine cases of spontaneous CSF leak to the ear in adult patients from four medical centers are presented and analyzed to provide collective information about a disorder that can be difficult to diagnose and manage. STUDY DESIGN: Retrospective review of nine cases of spontaneous CSF middle ear effusion/otorrhea. RESULTS: The majority of patients presented with symptoms of aural fullness and middle ear effusion. Many developed suspicious clear otorrhea only after insertion of a tympanostomy tube. Two patients had multiple defects in the tegmen and dura, and five patients had meningoencephaloceles confirmed intraoperatively. Five patients underwent combined middle cranial fossa/transmastoid repair. Materials used in repair included temporalis fascia, free muscle graft, Oxycel cotton, calvarial bone, pericranium, bone wax, and fibrin glue. CONCLUSIONS: CSF middle ear effusion/otorrhea can develop in adults without a prior history of meningitis or head trauma or any apparent proximate cause. Although presenting symptoms can be subtle, early suspicion and confirmatory imaging aid in establishing the diagnosis. Because surgical repair by way of a mastoid approach alone can be inadequate if there are multiple tegmen defects, a middle fossa approach alone, or in combination with a transmastoid approach, should be considered in most cases.

Hearing rehabilitation using the BAHA bone-anchored hearing aid: results in 40 patients.

OBJECTIVE: This study evaluates the U.S. experience with the first 40 patients who have undergone audiologic rehabilitation using the BAHA bone-anchored hearing aid. STUDY DESIGN: This study is a multicenter, nonblinded, retrospective case series. SETTING: Twelve tertiary referral medical centers in the United States. PATIENTS: Eligibility for BAHA implantation included patients with a hearing loss and an inability to tolerate a conventional hearing aid, with bone-conduction pure tone average levels at 60 dB or less at 0.5, 1, 2, and 4 kHz. INTERVENTION: Patients who met audiologic and clinical criteria were implanted with the Bone-Anchored Hearing Aid (BAHA, Entific Corp., Gothenburg, Sweden). MAIN OUTCOME MEASURES: Preoperative air- and bone-conduction thresholds and air-bone gap; postoperative BAHA-aided thresholds; hearing improvement as a result of implantation; implantation complications; and patient satisfaction. RESULTS: The most common indications for implantation included chronic otitis media or draining ears (18 patients) and external auditory canal stenosis or aural atresia (7 patients). Overall, each patient had an average improvement of 32+/-19 dB with the use of the BAHA. Closure of the air-bone gap to within 10 dB of the preoperative bone-conduction thresholds (postoperative BAHA-aided threshold vs. preoperative bone-conduction threshold) occurred in 32 patients (80%), whereas closure to within 5 dB occurred in 24 patients (60%). Twelve patients (30%) demonstrated 'overclosure' of the preoperative bone-conduction threshold of the better hearing ear. Complications were limited to local infection and inflammation at the implant site in three patients, and failure to osseointegrate in one patient. Patient response to the implant was uniformly satisfactory. Only one patient reported dissatisfaction with the device. CONCLUSIONS: The BAHA bone-anchored hearing aid provides a reliable and predictable adjunct for auditory rehabilitation in appropriately selected patients, offering a means of dramatically improving hearing thresholds in patients with conductive or mixed hearing loss who are otherwise unable to benefit from traditional hearing aids.

Patients' perceived outcomes after stapedectomy for otosclerosis.

We conducted a retrospective study of 29 patients who had undergone stapedectomy for otosclerosis to determine how well their subjective perceptions of hearing improvement correlated with objective audiometric measurements. Patients expressed their assessments of hearing function by completing two versions of the Hearing Disability and Handicap Scale (HDHS). One version of the HDHS was based on patients' retrospective recollections of their hearing impairment prior to surgery, and the other reflected their assessment of their current function. We evaluated these HDHS data both separately and in conjunction with pre- and postoperative audiometric findings. Following surgery, the group's mean pure-tone average improved significantly, from 58 to 27 dB--that is, the average patient had a moderately severe hearing loss preoperatively and only a mild hearing loss postoperatively. Significant improvement was also reflected in the difference between the mean pre- and postoperative HDHS scores, although some patients indicated that they experienced almost no improvement. Overall, our findings indicated that there was a relationship between objective and subjective assessments of hearing improvement following surgery, but that it was weak. Although most patients perceived significant improvement, the degree of that perceived improvement cannot be predicted from the pure-tone audiogram. We conclude, therefore, that a significant difference between audiometric findings and HDHS self-assessments is useful in identifying patients who might benefit from additional counseling and/or aural rehabilitation.

Outpatient tympanomastoidectomy: factors affecting hospital admission.

BACKGROUND: Outpatient tympanomastoidectomy is common in many medical centers. However, failure of same-day discharge is often the result of postoperative nausea and vomiting (PONV). Many times this leads to hospital admission after tympanomastoidectomy, and it is often difficult to predict before surgery whether PONV will be an issue that impedes same-day discharge. OBJECTIVE: To determine the clinical factors correlated with the incidence of PONV requiring hospital admission after chronic ear surgery by hypothesizing that the complexity of a particular case, as measured using a 10-point scale, is predictive of surgical time or failure of same-day hospital discharge. STUDY DESIGN: Retrospective medical chart review of 103 patients having mastoidectomy with tympanoplasty for chronic otitis media over a 2-year period. METHODS: We recorded patient age, clinical data, surgical times, types of agents used for induction and maintenance of anesthesia, use of prophylactic antiemetic drugs, types and doses of analgesic agents, and PONV. Univariate and multivariate logistic regression analyses were performed to determine which variables were associated with PONV that required hospital admission. RESULTS: One third of patients studied were safely discharged from the hospital the day of surgery, and 92% were discharged within 23 hours. The most common cause for observation admission to the hospital was PONV. The only variable in multivariate analysis that significantly correlated with PONV mandating hospital admission after tympanomastoid surgery was a history of motion sickness or PONV (odds ratio, 5.21; P =.02). Although severity of disease did not correlate with length of hospital stay, it directly correlated with length of surgery. CONCLUSIONS: A history of PONV or motion sickness is predictive of PONV and length of hospital stay. Routine planning for a 23-hour overnight observation stay seems warranted for all patients undergoing tympanomastoidectomy, despite severity of disease.

Minimally invasive technique of auricular cartilage harvest for tissue engineering.

Tissue engineered human cartilage is presently being utilized in clinical research programs in a variety of medical disciplines including otolaryngology, urology, and orthopedics. In this study, we present a new methodology for auricular cartilage harvest that can be applied to tissue engineering. Eight 16-week-old pigs were subjected to a traditional open cartilage harvest technique involving suture closure, while the other ear was subjected to the closed stitchless cartilage harvest, using a 12-gauge core biopsy needle. Surgical time was significantly (p < 0.0001) shorter (3.5 +/- 2.8 min for closed vs. 14.4 +/- 5 min for open), and no sutures where utilized in the closed technique. Sample weights were significantly (p < 0.00001) greater (0.115 +/- 0.028 g vs. 0.045 +/- 0.005 g) for the closed techniques. However, the minimally invasive closed technique had fewer incidents of bruising, hematoma, long-term stitch abscess, and scarring. Cell culture data shows no disadvantage to either technique with regards to cell growth characteristics. Final histological data from donor ears indicates favorable results with the minimally invasive technique. This technique preserves cell viability and isolation efficiency while decreasing surgical time and lessening postoperative complications.

Spondyloepiphyseal dysplasia congenita associated with conductive hearing loss.

Spondyloepiphyseal dysplasia is a disorder characterized by abnormalities of growth. Previous studies of this disorder have identified a significant incidence of associated hearing loss. Hearing loss has been reported to occur in 25 to 30% of affected patients. To date, all reports of associated hearing loss have indicated the presence of a sensorineural component. In this article, we report the case of a child who was diagnosed with spondyloepiphyseal dysplasia congenita and who was found to have a significant conductive hearing loss with a Carhart's notch, indicating the likely presence of stapes footplate fixation. We also review the diagnosis of this condition and the literature associated with hearing loss as it occurs with this disorder.

Temporal bone fractures: otic capsule sparing versus otic capsule violating clinical and radiographic considerations.

OBJECTIVE: To assess the practicality and utility of the traditional classification system for temporal bone fracture (transverse vs. longitudinal) in the modern Level I trauma setting and to determine whether a newer system of designation (otic capsule sparing vs. otic capsule violating fracture) is practical from a clinical and radiographic standpoint. METHODS: The University of Massachusetts Medical Center Trauma Registry was reviewed for the years 1995 to 1997. Patients identified as sustaining closed head injury were reviewed for basilar skull fracture and temporal bone fracture. Clinical and radiographic records were evaluated by using the two classification schemes. RESULTS: A total of 2,977 patients were treated at the trauma center during this time. Ninety (3%) patients sustained a temporal bone fracture. The classic characterization of transverse versus longitudinal fracture (20% vs. 80%, respectively) was unable to be determined in this group; therefore, clinical correlation to complications using that paradigm was not possible. By using the otic capsule violating versus sparing designation, an important difference in clinical sequelae and intracranial complications became apparent. Compared with otic capsule sparing fractures, patients with otic capsule violating fractures were approximately two times more likely to develop facial paralysis, four times more likely to develop CSF leak, and seven times more likely to experience profound hearing loss, as well as more likely to sustain intracranial complications including epidural hematoma and subarachnoid hemorrhage. CONCLUSION: The use of a classification system for temporal bone fractures that emphasizes violation or lack of violation of the otic capsule seems to offer the advantage of radiographic utility and stratification of clinical severity, including severity of Glasgow Coma Scale scores and intracranial complications such as subarachnoid hemorrhage and epidural hematoma.

Facial canal decompression leads to recovery of combined facial nerve paresis and trigeminal sensory neuropathy: case report.

BACKGROUND: Trigeminal sensory neuropathy is often associated with facial idiopathic nerve paralysis (Bell's palsy). Although a cranial nerve viral polyneuropathy has been proposed as the usual cause, in many instances the etiology remains unclear. This case report of recovery of both trigeminal and facial neuropathy after surgical decompression of the facial nerve suggests an anatomic link. METHODS: A case of a 39-year-old woman presenting with recurrent unilateral facial paralysis is summarized. Her fifth episode, which did not spontaneously recover, was associated with retroorbital and maxillary pain as well as sensory loss in the trigeminal distribution. RESULTS: A middle cranial fossa approach for decompression of the lateral internal auditory canal, labyrinthine segment of the facial nerve and the geniculate ganglion was performed. The patient's pain and numbness resolved immediately postoperatively, and the facial paralysis improved markedly. CONCLUSION: This result implicates a trigeminal-facial reflex as hypothesized by others. It suggests that decompression of the facial nerve can lead to improvement in motor and sensory function as well as relief of pain in some patients with combined trigeminal and facial nerve dysfunction.

Merkel cell carcinoma of the external auditory canal invading the intracranial compartment.

PURPOSE: To report an unusual case of an intracranial extension of Merkel cell carcinoma originating in the external ear canal and causing neurological deficits. CASE REPORT: An 86-year-old woman, with a 16-month history of an external auditory canal mass, presented with hemiparesis, facial paralysis, and obtundation. Radiographic images showed an intracranial mass extending into the petrous bone. METHOD: The patient had a craniotomy for intracranial tumor resection with concurrent mastoidectomy for facial nerve decompression and obtundation and hemiparesis were resolved. Residual tumor was subsequently treated with adjuvant radiation therapy, and facial nerve function consequently improved. CONCLUSION: Merkel cell tumors rarely invade the intracranial compartments. Residual tumor and neurological deficits may respond to adjuvant radiation therapy.

Improved axon diameter and myelin sheath thickness in facial nerve cable grafts wrapped in temporoparietal fascial flaps.

Injury to the facial nerve in the temporal bone presents a challenge to the recovery of nerve function, in that the fallopian canal in which it lies is poorly vascularized. This study was designed to determine if wrapping an intratemporal facial nerve defect repaired with a cable graft with a well-vascularized temporoparietal fascial (TPF) flap would improve facial nerve regeneration. To evaluate this question, a defect was created in the intratemporal left facial nerve of 10 rabbits. All nerves were repaired using cable grafts. In 5 animals, the nerve graft was wrapped with temporoparietal fascia, whereas in the other 5 rabbits it was not. Three additional animals underwent exposure only. The contralateral nerve served as a control in all animals. Quantitative analysis of the nerve graft 12 weeks after repair revealed greater recovery of original fiber diameter and myelin sheath thickness in TPF flap-wrapped repairs. Histological evidence of improved neural regeneration and functional nerve recovery was also seen in the repairs where the TPF flap was utilized. Nerve conduction and electromyographic studies of the cable-grafted nerve at 6 and 12 weeks were equivocal, however.

Trigeminal neo-neurotization of the paralyzed face.

Sporadic reports throughout the literature have documented the spontaneous return of facial function following deliberate intraoperative sacrifice of the facial nerve. Trigeminal reinnervation of the facial muscles has been suggested as one possible mechanism for this occurrence. Evidence for the phenomenon of trigeminal neo-neurotization has been documented experimentally. The case of a 62-year-old woman who underwent total left parotidectomy with transection of a large facial nerve segment is presented in order to provide further clinical evidence supporting trigeminal neo-neurotization of the facial nerve. Despite the lack of any efforts to reinnervate the patient or graft the facial nerve defect, the patient spontaneously developed return of facial function. Postoperative clinical and electrical testing in this case supports trigeminal-facial reinnervation as the cause for return of facial function. The case report is summarized with a brief discussion, and the relevant literature is thoroughly reviewed.

Invisible culprit: intralabyrinthine schwannomas that do not appear on enhanced magnetic resonance imaging.

Intralabyrinthine schwannoma (ILS) is an infrequent tumor that arises in isolation within the periphery of the temporal bone. Only 32 cases have been reported to date in the literature, of which 12 were discovered at autopsy. Prior to the advent of gadolinium-enhanced magnetic resonance imaging (Gd-MRI), only 1 ILS had been diagnosed preoperatively. However, after Gd-MRI became a common modality, 5 ILSs were imaged. Two additional cases are reported that were discovered during labyrinth-destructive surgery despite normal Gd-MRI findings. Possible explanations for and potential ramifications of nonenhancing ILS are discussed.

Ganglionic hamartoma of the intracanalicular acoustic nerve causing sensorineural hearing loss.

OBJECTIVE: This article highlights the clinical presentation and treatment issues of ganglionic hamartoma of the internal auditory canal and emphasizes the similarity of this lesion to acoustic neuroma regarding its audiologic and radiographic characteristics. STUDY DESIGN: This article is composed of case reports and a literature review. SETTING: The study was performed at a university hospital/tertiary referral center. PATIENT: A patient with biopsy-proven ganglionic hamartoma of the acoustic nerve was studied. INTERVENTION: Intervention consisted of surgical therapy. MAIN OUTCOME MEASURE: The main outcome measure was clinical evaluation. RESULTS: The result was successful removal of lesions with facial nerve preservation. CONCLUSIONS: An intracanalicular ganglionic hamartoma resulted in progressive sensorineural hearing loss and magnetic resonance imaging findings suggestive of small acoustic neuroma. This lesion, composed of an admixture of ganglion cells, fibroadipose-tissue, and normal myelinated axons, although rare, should be added to the differential diagnosis of internal auditory canal lesions.

Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients.

PURPOSE: To determine the computed tomographic (CT), magnetic resonance (MR) imaging, and angiographic findings of papillary endolymphatic sac tumors. MATERIALS AND METHODS: Clinical and imaging studies in 20 patients (aged 17-65 years) with histopathologically proved papillary endolymphatic sac tumors were retrospectively reviewed. Patients underwent CT (n = 18), MR imaging (n = 15), or angiography (n = 12). CT scans were evaluated for bone erosion and calcification; MR images, for signal intensity, enhancement patterns, and flow voids; and angiograms, for tumoral blood supply. RESULTS: All tumors were destructive and contained calcifications centered in the retrolabyrinthine region at CT. The MR imaging appearance varied with lesion size; 12 of 15 tumors showed increased signal intensity at T1-weighted imaging. The high-signal-intensity area was circumferential in lesions 3 cm or smaller and was scattered throughout the lesion in advanced tumors. Only tumors larger than 2 cm had flow voids. The blood supply arose predominantly from the external carotid artery. Large tumors had additional supply from the internal carotid and posterior circulation. CONCLUSION: Papillary endolymphatic sac tumors are destructive, hypervascular lesions that arise from the temporal bone retrolabyrinthine region. Increased signal intensity at unenhanced T1-weighted MR imaging is common and may help distinguish these lesions from more common, aggressive temporal bone tumors.

Differential expression of transthyretin in papillary tumors of the endolymphatic sac and choroid plexus.

Aggressive papillary tumors of the temporal bone, occurring sporadically or as part of von Hippel-Lindau disease, have been shown to originate within the endolymphatic sac or duct. Also implicated as a potential precursor from which some of these tumors may arise is ectopic choroid plexus epithelium. To aid in the differentiation between papillary tumors of endolymphatic sac and duct origin and those arising from choroid plexus, an immunohistochemical study using stains for transthyretin (TTR), cytokeratins, S-100 protein, epithelial membrane antigen (EMA), and glial fibrillary acidic protein (GFAP) was carried out on archival specimens of normal and neoplastic endolymphatic sac and duct and choroid plexus epithelium. Transthyretin, a marker for choroid plexus epithelium, was found to show differential expression between choroid plexus papillomas and aggressive papillary tumors of the endolymphatic sac or duct. Therefore the use of TTR in concert with other immunohistochemical stains appear to aid in the differentiation between intracranial and intratemporal papillary tumors arising from choroid plexus and endolymphatic sac or duct epithelium.