Single Vertical Incision for BAHA: Preliminary Results

Objective

A single vertical skin incision with subcutaneous tissue undermining is a cosmetic alternative to standard dermatome skin graft elevation for bone anchored hearing aid (BAHA) placement. A vertical incision minimizes alopecia and simplifies wound closure, while maintaining thin skin flaps. We aimed to determine the preliminary complication rate using a 4cm skin inicsion with 4⋉4 cm of subcutaneous tissue removal.

Methods

A retrospective chart review of patients undergoing BAHA placement from January 2006 to August 2007 was performed. This search was filtered to include only vertical incision BAHA patients. Complications including skin irritation or infection, skin overgrowth, and implant extrusion were tallied. Pertinent patient risk factors were identified. 71 patients underwent vertical incision surgery, with a mean followup time of 6.8 months. 50 patients had sensorineural hearing losses and 21 had conductive hearing losses.

Results

No patient had spontaneous extrusion of the titanium abutment. There were 5 minor complications (skin irritation 3, wound infection requiring oral antibiotics 1, postoperative hematoma 1) and 7 major complications (irritation requiring abutment removal 1, skin overgrowth or infection requiring flap revision 6). Total complication rate was 16% and major complication rate was 9.8%.

Conclusions

A single vertical incision for BAHA placement has a similar complication rate to traditional dermatome use in this preliminary study, though more follow-up is necessary to identify cases of late skin overgrowth. Patients with thick scalps or risk factors for hypertrophic scarring may require placement of longer abutments.

Distribution of low-frequency nerve fibers in the auditory nerve: Temporal bone findings and clinical implications

HYPOTHESIS

Low-frequency cochlear fibers are on the outer surface of the auditory nerve adjacent to the vestibular nerve in the distal part of the internal auditory canal.

BACKGROUND

There is a misconception that low-frequency cochlear fibers are in the core of the cochlear nerve and are surrounded by high-frequency fibers.

METHODS

We analyzed temporal bones with a loss of upper spiral ganglion cells caused by different etiologies (n = 6) and traced the corresponding fibers into the distal internal auditory canal. Spiral ganglion cells for each segment (I-IV) of the cochlea were counted, and we defined the location of nerve fibers from the various segments.

RESULTS

There was total or near-total degeneration of the upper spiral ganglion cells in these bones. Corresponding low-frequency fibers were on the outer surface of the cochlear nerve adjacent to the vestibular nerve in the distal segment of the internal auditory canal.

CONCLUSION

Low-frequency fibers seem to be located at the periphery of the cochlear nerve. These findings provide one possible explanation for the low-frequency sensorineural hearing loss found in 10% of patients with vestibular nerve schwannomas and may have clinical relevance in the diagnosis of these lesions.

Prevention and Treatment of Cerebrospinal Fluid Leak After Translabyrinthine Acoustic Tumor Removal

OBJECTIVE

To determine the incidence rate of cerebrospinal fluid (CSF) leak after translabyrinthine acoustic tumor removal using titanium mesh cranioplasty and to compare with previous series and historical controls.

STUDY DESIGN

Database analysis with historical controls.

SETTING

Tertiary referral neurotologic private practice.

PATIENTS

The series of 389 patients who underwent titanium mesh cranioplasty after translabyrinthine tumor removal between March 2003 and July 2005. The results were compared with those in a group of 1,195 translabyrinthine tumor removal patients from our previously published series and with those in a group of 324 patients from the immediately preceding two-year period.

INTERVENTION

Cranioplasty using titanium mesh after acoustic tumor removal.

MAIN OUTCOME MEASURES

Rates of CSF leak for this method and previous methods of closure.

RESULTS

Thirteen patients (3.3%) had CSF leaks when using the new method of titanium mesh closure. This compares with rates of 10.9% and 8.7% in series in which other methods of closure were used (p < 0.001 and 0.003). The rates of CSF leak requiring reoperation were 0.5%, 2.5%, and 1.9% for the new and the two older series, respectively.

CONCLUSION

In our hands, titanium mesh cranioplasty seems to reduce the rate of CSF leaks after the translabyrinthine removal of acoustic tumors.

Auditory brainstem implants: surgical aspects

Patients with neurofibromatosis type 2 often develop bilateral life-threatening vestibular schwannoma necessitating tumor removal, which results in deafness. We developed the auditory brainstem implant (ABI) in order to be able to electrically stimulate the cochlear nucleus complex in patients with bilateral cochlear nerve injury from bilateral schwannoma. After tumor removal, the electrode array of the ABI is inserted into the lateral recess of the fourth ventricle and placed over the surface of the ventral and dorsal cochlear nuclei. The ABI is designed to stimulate auditory neural structures within the cochlear nucleus in order to convey salient cues about the frequency, amplitude, and temporal characteristics of sounds. To date, more than 200 patients have received an ABI device at our institution. Recently, penetrating ABIs were introduced, and preliminary results of penetrating ABIs are discussed in this paper. The surgical anatomy of the nucleus and surgical placement of the ABI in patients with neurofibromatosis type 2 are described, and surgical considerations in this group of challenging patients are detailed.

Multichannel cochlear implants: relation of histopathology to performance

OBJECTIVES

To determine the relationship of surviving neural elements to auditory function in multichannel cochlear implant temporal bones.

STUDY DESIGN

Case series of all 14 existing multichannel cochlear implants in our temporal bone collection.

METHODS

Devices included Nucleus 22 (n = 11), Nucleus 24 (n = 1), Ineraid (n = 1), and Clarion (n = 1). Morphologic evaluation of structural elements including spiral ligament, stria vascularis, hair cells, peripheral processes, and spiral ganglion cells was performed. Clinical performance data were obtained from patient charts. For eight patients, nonimplanted contralateral temporal bones were available and paired comparisons were made.

RESULTS

Despite frequent absence of hair cells and peripheral processes, all bones had at least some remaining spiral ganglion cells. Percent of normal remaining structures were unrelated to auditory performance with the implant for any of the structural elements. Ganglion cell count in segment III showed significant negative correlations to speech discrimination scores for words and sentences (Rhos = -.687 and -.661, P < or = .03 and .04) as did segment IV and total ganglion cell count with word score (Rhos = -.632 and -.638; P < or = .05). Spiral ganglion cell survival did not differ between implanted and nonimplanted ears, with the exception of segment I, which had fewer cells in the implanted ear (P < or = .028).

CONCLUSIONS

Performance variability of cochlear implants cannot be explained on the basis of cochlear neuronal survival. Although hair cells and peripheral processes were frequently absent or greatly diminished from normal, all subjects had at least some spiral ganglion cells. And, in this series, there was an inverse relationship between survival of ganglion cells and performance.

Multichannel cochlear implants: relation of histopathology to performance

OBJECTIVES

To determine the relationship of surviving neural elements to auditory function in multichannel cochlear implant temporal bones.

STUDY DESIGN

Case series of all 14 existing multichannel cochlear implants in our temporal bone collection.

METHODS

Devices included Nucleus 22 (n = 11), Nucleus 24 (n = 1), Ineraid (n = 1), and Clarion (n = 1). Morphologic evaluation of structural elements including spiral ligament, stria vascularis, hair cells, peripheral processes, and spiral ganglion cells was performed. Clinical performance data were obtained from patient charts. For eight patients, nonimplanted contralateral temporal bones were available and paired comparisons were made.

RESULTS

Despite frequent absence of hair cells and peripheral processes, all bones had at least some remaining spiral ganglion cells. Percent of normal remaining structures were unrelated to auditory performance with the implant for any of the structural elements. Ganglion cell count in segment III showed significant negative correlations to speech discrimination scores for words and sentences (Rhos = -.687 and -.661, P < or = .03 and .04) as did segment IV and total ganglion cell count with word score (Rhos = -.632 and -.638; P < or = .05). Spiral ganglion cell survival did not differ between implanted and nonimplanted ears, with the exception of segment I, which had fewer cells in the implanted ear (P < or = .028).

CONCLUSIONS

Performance variability of cochlear implants cannot be explained on the basis of cochlear neuronal survival. Although hair cells and peripheral processes were frequently absent or greatly diminished from normal, all subjects had at least some spiral ganglion cells. And, in this series, there was an inverse relationship between survival of ganglion cells and performance.

Human Cochleae With Three Turns: An Unreported Malformation

OBJECTIVE

The objective of this histologic study of archival temporal bone sections was to describe the morphology of human cochleae found with three turns, a previously unreported anomaly, found in three pairs of temporal bones.

METHODS

The authors conducted histopathologic processing and measurement of basilar membrane length. Basilar membrane length was compared with that found in six normal control bones.

RESULTS

Cochleae with three complete turns, rather than the usual two and a half turns, are described for the first time. All had longer than normal basilar membranes, with a mean length of 40.6 mm compared with a mean of 33.8 mm in the normal bones.

CONCLUSIONS

Human cochleae with three turns exist as an unreported anomaly. This is a new category of anomaly, not likely based on interruption of development.

Understanding drug ototoxicity: molecular insights for prevention and clinical management

Ototoxicity is a trait shared by aminoglycoside and macrolide antibiotics, loop diuretics, platinum-based chemotherapeutic agents, some NSAIDs and antimalarial medications. Because their benefits in combating certain life-threatening diseases often outweigh the risks, the use of these ototoxic drugs cannot simply be avoided. In this review, the authors discuss some of the most frequently used ototoxic drugs and what is currently known about the cell and molecular mechanisms underlying their noxious effects. The authors also provide suggestions for the clinical management of ototoxic medications, including ototoxic detection and drug monitoring. Understanding the mechanisms of drug ototoxicity may lead to new strategies for preventing and curing drug-induced hearing loss, as well as developing new pharmacological drugs with less toxic side effects.