Cochlear implant and congenital cholesteatoma.

BACKGROUND: The occurence of cholesteatoma and cochlear implant is rare. Secondary cholesteatomas may develop as a result of cochlear implant surgery. Primarily acquired cholesteatoma is not typically associated with congenital sensorineural hearing loss or cochlear implant in children. The occurrence of congenital cholesteatoma during cochlear implant surgery has never been reported before, partly because all patients are preoperatively submitted to imaging studies which can theoretically exclude the disease. CASE PRESENTATION: We have reported a rare case of congenital cholesteatoma, found during sequential second side cochlear implantation in a 3-year-old child. The child underwent a computed tomography (CT) scan and magnetic resonance imaging (MRI) at 12 months of age, before the first cochlear implant surgery, which excluded middle ear pathology. The mass was removed as an intact pearl, without visible or microscopic violation of the cholesteatoma capsule. All the areas where middle ear structures were touching the cholesteatoma were vaporized with a laser and the cochlear implant was inserted uneventfully. Further follow-up excluded residual disease. CONCLUSION: We believe that primary, single stage placement of a cochlear implant (CI) with simultaneous removal of the congenital cholesteatoma can be performed safely. However, to prevent recurrence, the capsule of the cholesteatoma must not be damaged and complete laser ablation of the surface, where suspicious epithelial cells could remain, is recommended. In our opinion, cholesteatoma removal and cochlear implantation should be staged if these conditions are not met, and/or the disease is at a more advanced stage. It is suspected, that the incidence of congenital cholesteatoma in pediatric CI candidates is much higher that in average pediatric population.

Functional and physical outcomes following use of a flexible CO2 laser fiber and bipolar electrocautery in close proximity to the rat sciatic nerve with correlation to an in vitro thermal profile model.

This study compared functional and physical collateral damage to a nerve when operating a Codman MALIS Bipolar Electrosurgical System CMC-III or a CO2 laser coupled to a laser, with correlation to an in vitro model of heating profiles created by the devices in thermochromic ink agarose. Functional damage of the rat sciatic nerve after operating the MALIS or CO2 laser at various power settings and proximities to the nerve was measured by electrically evoked nerve action potentials, and histology of the nerve was used to assess physical damage. Thermochromic ink dissolved in agarose was used to model the spatial and temporal profile of the collateral heating zone of the electrosurgical system and the laser ablation cone. We found that this laser can be operated at 2 W directly above the nerve with minimal damage, while power settings of 5 W and 10 W resulted in acute functional and physical nerve damage, correlating with the maximal heating cone in the thermochromic ink model. MALIS settings up to 40 (11 W) did not result in major functional or physical nerve damage until the nerve was between the forceps tips, correlating with the hottest zone, localized discretely between the tips.

Spread of cochlear excitation during stimulation with pulsed infrared radiation: inferior colliculus measurements.

Infrared neural stimulation (INS) has received considerable attention over the last few years. It provides an alternative method to artificially stimulate neurons without electrical current or the introduction of exogenous chromophores. One of the primary benefits of INS could be the improved spatial selectivity when compared with electrical stimulation. In the present study, we have evaluated the spatial selectivity of INS in the acutely damaged cochlea of guinea pigs and compared it to stimulation with acoustic tone pips in normal-hearing animals. The radiation was delivered via a 200 µm diameter optical fiber, which was inserted through a cochleostomy into the scala tympani of the basal cochlear turn. The stimulated section along the cochlear spiral ganglion was estimated from the neural responses recorded from the central nucleus of the inferior colliculus (ICC). ICC responses were recorded in response to cochlear INS using a multichannel penetrating electrode array. Spatial tuning curves (STCs) were constructed from the responses. For INS, approximately 55% of the activation profiles showed a single maximum, ∼22% had two maxima and ∼13% had multiple maxima. The remaining 10% of the profiles occurred at the limits of the electrode array and could not be classified. The majority of ICC STCs indicated that the spread of activation evoked by optical stimuli is comparable to that produced by acoustic tone pips.

Cochlear reimplantation: surgical techniques and functional results.

OBJECTIVES/HYPOTHESIS: The most common indication for cochlear reimplantation is device failure. Other, less frequent indications consist of "upgrades" (e.g., single to multichannel), infection, and flap breakdown. Although the percentage of failures has decreased over time, an occasional patient requires reimplantation because of device malfunction. The varying designs of internal receiver/stimulators and electrode arrays mandate an examination of the nature and effects of reimplantation for the individual designs. The purpose of the current study was to investigate the reimplantation of several implant designs and to determine whether differences in surgical technique, anatomical findings, and postoperative performance exist. STUDY DESIGN: Retrospective chart review. METHODS: The subjects were 33 of 618 severely to profoundly deaf adults and children who had implantation at the New York University Medical Center (New York, NY) between February 1984 and December 2000. The subjects had previously had implantation with either a single-channel 3M/House (House Ear Institute, Los Angeles, CA) or 3M/Vienna (Technical University of Vienna, Vienna, Austria) device or with one of the multichannel Clarion (Advanced Bionics, Sylmar, CA), Ineraid (Smith & Nephew Richards, TN), or Nucleus (including the Contour) devices (Cochlear Corp., Englewood, CO) before reimplantation. RESULTS: Length of use before reimplantation ranged from 1 month to 13 years and included traumatic and atraumatic (electronic) failures, as well as device extrusion or infection. Results indicated that postoperative performance was either equal to or better than scores before failure. None of the devices explanted caused damage that precluded the implantation of the same or an upgraded device. These findings support the efficacy and safety of internal implant designs as related to the maintenance of a functional cochlea for the purpose of reimplantation. CONCLUSIONS: Cochlear reimplantation can be performed safely and without decrement to performance. The number of implanted electrodes at reinsertion were either the same or greater in all cases.

Electrode to modiolus proximity: a fluoroscopic and histologic analysis.

HYPOTHESIS: This study was conducted to evaluate the electrode to modiolus proximity of two commonly used electrodes (Nucleus and Clarion) and a new prototype electrode. BACKGROUND: Theoretical advantages of modiolus-hugging cochlear implant electrodes include reduced stimulus energy requirements, more efficient power management and longer battery life, more discreet ganglion cell population stimulation, and reduced facial nerve stimulation. METHODS: Fluoroscopic analysis and histologic surface preparation analysis of electrode position and trauma. RESULTS: The Nucleus straight electrode occupied an outer wall position in the scala tympani. The Clarion electrode occupied a more intermediate position. The actively coiling prototype electrode was modiolus hugging but caused more trauma than the other two electrodes tested. CONCLUSIONS: The optimal modiolus-hugging atraumatic intracochlear electrode does not currently exist.

Shaw scalpel in revision cochlear implant surgery.

The use of traditional electrocautery is prohibited in revision or replacement cochlear implant surgery because of the concern for end organ tissue damage. Additionally, electrical current spread to the malfunctioning device could interfere with an accurate cause-of-failure analysis. Clinical reports have confirmed the utility of the Shaw scalpel for dermatologic, ophthalmic, and head and neck surgery. The Shaw scalpel is a thermally activated cutting blade that provides a bloodless field through immediate capillary and small vessel hemostasis. Avoidance of wound and flap complications is of primary concern in cochlear implant surgery. The long-term wound healing compared favorably to that of other surgical cutting instruments in several experimental reports. We have routinely used the Shaw scalpel in revision cochlear implant surgery and in primary surgery whenever electrocautery was contraindicated. We have retrospectively evaluated 22 cases in which the Shaw scalpel was used for cochlear implant revision and primary surgery. The chart review included patient demographics, the indication for surgery, the contraindication for electrocautery, intraoperative surgical notes, the wound healing evaluation, the evaluation for alopecia, and postoperative speech understanding. No significant complications occurred intraoperatively, and the long-term wound healing results were no different from those obtained with conventional surgical techniques. The explanted devices were undamaged, and valuable diagnostic information could be obtained. All patients performed at or better than their preoperative levels on speech recognition testing. Our results indicate that the Shaw scalpel is a relatively safe, easy-to-use, and effective instrument.

Stability of the cochlear implant array in children.

OBJECTIVE: To determine cochlear implant electrode stability in the young patient. Electrode migration due to future skull growth was a concern that led to prohibiting implantation in children less than 2 years of age. Recently, the high level of performance achieved by young implantees has led to a re-evaluation of this lower age limit, requiring an assessment of the effects of skull growth over time. STUDY DESIGN: Prospective radiographic analysis of electrode position of cochlear implants in young children. METHODS: Twenty-seven children implanted with the Nucleus (Cochlear Corp., Denver, CO) or Clarion (Advanced Bionics Inc., Sylmar, CA) multi-channel cochlear prostheses were subjects for this study. Follow-up radiographic studies were obtained for a period of 1 month to 5 years after implantation. The age at time of implantation ranged from 14 months to 5 years. An intraoperative modified Stenver's view plain radiograph was obtained as a baseline. After implantation, on a yearly basis transorbital Stenver's and base views were obtained for comparative purposes. Additional radiographs were obtained whenever a change in performance or electrode map caused suspicion for extrusion. Electrode position was determined using a computer graphics enhancement technique whereby image contrast filters enhanced the visibility of the electrode array and surrounding bony structures. RESULTS: An analysis of the data revealed no migration of the electrode array over time. CONCLUSIONS: The confirmation of the stability of the electrode array alleviates the concern of the effects of skull growth on cochlear implantation in young children.

Cerebrospinal fluid drainage in the management of CSF leak following acoustic neuroma surgery.

A retrospective analysis was performed on 174 patients operated on from 1992 to 1995 to evaluate the safety and efficacy of continuous lumbar cerebrospinal fluid drainage (CLCFD) in the management of cerebrospinal fluid (CSF) leaks following acoustic neuroma surgery. There was a 17% incidence of CSF leak. CLCFD stopped the leak in 87% of cases. There were no cases of meningitis associated with CLCFD. One deep vein thrombosis was treated without sequelae. It is concluded that CLCFD is safe and efficacious. The authors recommend that CLCFD be implemented immediately when indicated, foregoing a trial of conservative therapy. Indications and precautions are discussed.

Database for sensorineural hearing loss.

We are creating a bank of EBV immortalized lymphoblast cells and extracted DNA taken from the blood of deaf children and their relatives, in order to study the molecular basis of hereditary deafness. We have established a corresponding database for sensorineural hearing loss that records clinical data for each entered specimen. The purpose of this paper is to present the content and design of the computerized relational database. The data model is designed first to identify known etiologies of deafness, either acquired or syndromic, and then to characterize the clinical features of the deaf individual, and both their affected and non-affected family members. The application operates in a graphical environment of visual prompts and message panels. The database is organized by sections which record demographic data, presenting complaints, otologic history, birth and perinatal history, developmental history, symptoms of chronic airway obstruction, family history, neurologic history, congenital infections, hospitalizations and surgical history, medication history, vestibular findings, audiometry, radiology, medical conditions and syndromes and physical examination. The database was developed on a commercially available software product. Our database is presented as a model for use by other clinicians and investigators.

Comparison of technetium-99m-glucarate and thallium-201 for the identification of acute myocardial infarction in rats.

The scintigraphic identification of acute severe ischemic myocardial injury requires a marker that localizes rapidly and specifically in zones of damaged myocardium. Technetium-99m-glucarate, a six-carbon dicarboxylic acid, which behaves in vivo somewhat like fructose, was recently described as a marker of severe acute ischemic injury with necrosis. This study was performed to determine the interval between the onset of myocardial ischemia and initial uptake and the duration of a positive scan in experimental animals. Serial injections and images were recorded over 10 days following ligation of the left anterior descending coronary artery of the rat. The distribution of 99mTc-glucarate was compared to that of regional myocardial perfusion monitored with 201TI. The findings on radionuclide imaging were compared to histologic changes in the myocardium. Sequential pinhole images of both radionuclides were collected at 3 hr, 24 hr, 72 hr and 7-10 days following ligation. Ten rats had normal 201TI distributions, no uptake of glucarate and no evidence of infarction by TTC staining at autopsy. Twenty-one rats had either 201TI lesions or evidence of infarction at autopsy. In 17 of these rats, significant acute 99mTc-glucarate uptake was noted, decreasing at 24 hr, and was not seen at 72 hr or 7-10 days. The extent of perfusion abnormality was greatest at 3 hr in most animals; the lesion decreased in four (33%), increased in one (8%) and remained stable in the remainder. These data suggest that 99mTc-glucarate may be a useful marker of acute myocardial injury.

Regional perfusion, oxygen metabolism, blood volume and immunoglobulin G accumulation at focal sites of infection in rabbits.

Infection causes remarkable changes in extracellular fluid volume, blood flow and oxygen consumption in the region of the lesion. To determine the sequence and magnitude of these changes, we performed serial scintigraphic measurements in 10 rabbits with experimental Escherichia coli abscesses. Positron emission tomography with C15O2, 15O2 and 11CO was used to measure regional blood flow, oxygen extraction (OEF) and blood volume; extracellular fluid volume was evaluated by single photon scintigraphy with indium-111 immunoglobulin G (IgG). Images were recorded following tracer administration at 1 and 7-10 days after infection. At the first imaging time, blood flow to infected muscle had increased by 40% compared with control sites (7.4 +/- 0.6 to 10.8 +/- 3.8 ml/min.100 g), OEF had decreased from 55% +/- 34% to 45% +/- 14%, and the infected-to-contralateral (I/C) ratio of IgG had increased to 3.34 +/- 1.85. At the later imaging time, flow had increased by almost threefold compared with day 1 (29.4 +/- 9.8 ml/min.100 g), OEF had decreased to 29% +/- 14%, and the I/C ratio for IgG had remained constant. Although OEF fell, oxygen delivery (OEF x flow) increased from 4.07 ml/min (control value) to 4.86 ml/min on day 1 and 8.64 ml/min on days 7-9. The infected-to-contralateral (IC) ratio of 15O2/C15O2 was 0.74 +/- 0.15 on day 1 and 0.77 +/- 0.10 at 7-9 days. These studies indicate that expansion of the extracellular fluid volume increases early in the evolution of the infection and exceeds changes in regional perfusion and oxygen delivery.

Perfusion lung scans vs pulmonary angiography in evaluation of suspected primary pulmonary hypertension.

A retrospective review of 15 patients with angiographically- or biopsy-documented primary pulmonary hypertension was performed to assess the value of pulmonary perfusion scanning in noninvasively differentiating these patients from those with potentially operable, chronic (large-vessel) thromboembolic pulmonary hypertension. None of the 15 patients with primary pulmonary hypertension demonstrated a segmental or larger perfusion defect whereas such defects have been uniformly present in previous reports of patients with large-vessel thromboembolic pulmonary hypertension. While perfusion scans in primary pulmonary hypertension may show certain abnormalities, the presence of segmental or larger perfusion defects should suggest the diagnosis of potentially correctable, large-vessel thromboembolic pulmonary hypertension rather than small-vessel, obliterative (primary, idiopathic) pulmonary hypertension.

Cornea plana: a case report.

A case of cornea plana with its typical clinical findings has been presented along with ultrasonographic documentation confirming the axial length of the globe to be normal in this condition. It is presented to draw attention to the clinician that although cornea plana is rare, it should be considered in the differential diagnosis of a patient with small eyes or suspected microcornea.