The jugular dural fold-a helpful skull base landmark to the cranial nerves

During a retrosigmoid (or combined retrolabyrinthine-retrosigmoid) approach to the posterior fossa for vestibular neurectomy or removal of small acoustic neuromas, a white dural fold is a consistent landmark to cranial nerves VII through XII. This fold of dura appears as a white linear structure extending from the foramen magnum across the sigmoid sinus, attaching to the posterior aspect of the temporal bone, anterior to the vestibular aqueduct. The name "jugular dural fold" is suggested for this landmark. The jugular dural fold overlies the junction of the sigmoid sinus and the jugular foramen. As measured in formalin-fixed cadaver heads, the overall length of the jugular dural fold is 20.8 mm (+/- 2.9 mm). The cochleovestibular nerve lies 9.9 mm (+/- 1.5 mm) anterior to the superior aspect of the jugular dural fold, the glossopharyngeal nerve lies 9.5 mm (+/- 1.6 mm) anterior to the midpoint of the jugular dural fold, and the operculum of the vestibular aqueduct lies 6.6 mm (+/- 0.7 mm) posterior to the jugular dural fold. Intraoperative measurements in patients undergoing combined retrolabyrinthine-retrosigmoid vestibular neurectomy show an overall length of the jugular dural fold of 16.3 mm (+/- 1.9 mm). The cochleovestibular nerve lies 8.6 mm (+/- 1.3 mm) anterior to the superior aspect of the jugular dural fold, the glossopharyngeal nerve lies 8.6 mm (+/- 1.3 mm) anterior to the midpoint of the jugular dural fold, and the operculum lies 7.5 mm (+/- 0.8 mm) posterior to the jugular dural fold. The jugular dural fold can be used as a reliable landmark for rapidly locating cranial nerves in the posterior fossa.

Pneumolabyrinth: a late complication of stapes surgery

As temporal bone imaging techniques continue to improve, it is likely that we will see an increase in the detection of pneumolabyrinth. Several mechanisms have been proposed to explain how air enters the labyrinth. A small number of authors has reported an association between pneumolabyrinth and temporal bone fractures, perilymphatic fistulae, and displaced stapes prostheses. In this article, we describe a new case of pneumolabyrinth that was seen as a late complication of stapes surgery, and we summarize what is known about this rare condition.

Xanthoma of the temporal bone: a unique case of this rare condition

Xanthoma of the temporal bone is extremely rare; we describe only the fourteenth reported case. Our case is further remarkable because it is the first report of such an occurrence in a patient with familial type III hyperlipoproteinemia. Moreover, while otalgia, infection, hearing loss, and tinnitus were the most common initial symptoms in the previous 13 cases, our patient reported only diplopia, vertigo, and unstable gait. The patient underwent a simple mastoidectomy and debulking, and his diplopia, vertigo, and unstable gait resolved.

Endoscopic repair of cerebrospinal fluid rhinorrhea

Endoscopic repair of cerebrospinal fluid rhinorrhea is a promising alternative to traditional repair techniques. This article reports our experience with 21 cases (10 spontaneous, 8 iatrogenic, and 3 traumatic). Various diagnostic radiographic modalities were used, including computer-aided techniques. Most repairs were accomplished with a free fascial graft positioned in the epidural space. Postoperative lumbar drainage was used in 15 cases. Initial repair was successful in 18 cases (85.7%). In all 3 failures, the surgeon had difficulty with proper graft placement. Additionally, 2 of these cases were confounded by early inadvertent removal of the lumbar drain. All patients in whom the procedure failed underwent a second successful endoscopic repair. There were no major complications. In our experience endoscopic repair of cerebrospinal fluid rhinorrhea is a safe and effective approach that can be improved with computer-aided localization devices. Proper graft placement is critical, and lumbar drainage is an important adjunct in selected cases.

Intraoperative facial nerve monitoring: a comparison between electromyography and mechanical-pressure monitoring techniques

OBJECTIVES

To examine the hypothesis that for intraoperative facial nerve monitoring, an EMG monitor is more sensitive than a mechanical-pressure monitor. To compare the threshold sensitivity of the two facial nerve monitoring methods-mechanical-pressure versus EMG--by using them simultaneously during surgery. To assess and compare their true- and false-positive responses in otologic and neurotologic procedures.

SETTING

A tertiary referral private otology/neurotology practice.

STUDY DESIGN

Prospective case-controlled study.

PATIENTS AND METHODS

The facial nerve of 46 consecutive patients undergoing various otologic and neurotologic procedures was stimulated intraoperatively using a pulsed constant-current. Facial responses were monitored using the Silverstein WR-S8 Monitor/Stimulator and the Brackmann EMG System simultaneously. The threshold (i.e., minimal) current level required to elicit a response from each monitor was recorded. Monitor responses to facial nerve manipulation (including false-positive responses) were assessed by continuous recording of all responses, using the Wiegand Monitoring System, and noting the causative event for each response.

RESULTS

The EMG monitor responded to lower current threshold (p < 0.001) in every surgical procedure and for every nerve segment studied. However, the average threshold difference was <0.05 mAmps and in clinical practice, when using above threshold stimulation, becomes negligible. In posterior fossa surgery, the EMG monitor showed higher sensitivity by responding earlier to various manipulations of the bare facial nerve. The EMG had more false-positive responses than the mechanical-pressure monitor.

CONCLUSIONS

In otologic surgery, if monitoring is required, the mechanical-pressure monitor is used. In neurotologic surgery, both monitors are used simultaneously.

A reevaluation of the 512-Hz Rinne tuning fork test as a patient selection criterion for laser stapedotomy

OBJECTIVE

This study aimed to challenge the classical hypothesis that a negative preoperative 512-Hz Rinne tuning fork test (bone conduction greater than air conduction) is a necessary condition to allow consistent objective and subjective hearing improvement with surgery for otosclerosis.

STUDY DESIGN

The study design was retrospective (chart review and questionnaire).

SETTING

The study was conducted at a Florida Ear and Sinus Center at Sarasota, Florida, a tertiary otology-neurotology referral center.

PATIENTS

Patients who underwent primary laser stapedotomy with equivocal (air=bone) preoperative 512-Hz Rinne test results participated.

INTERVENTION

KTP laser stapedotomy was performed.

MAIN OUTCOME MEASURES

Audiologic measurements of air-bone gap closure and patient assessment of hearing improvement and satisfaction were conducted.

RESULTS

The air-bone gap was closed to within 10 dB in all cases. There were no complications. Eighteen patients were questioned about their results. Hearing improvement was subjectively described as "excellent" or "good" by 17 (94%), and 16 (89%) thought the surgery was "absolutely" worthwhile.

CONCLUSIONS

The preoperative 512-Hz Rinne test results need not be negative to achieve significant air-bone gap closure and subjective appreciation of improved hearing.

Lightning injury of the tympanic membrane

Lightning injury to the ear is known, but specific reports are lacking. Four patients with tympanic membrane perforations who were managed surgically are reported. Their presentations, evaluations, intraoperative findings, and outcomes are discussed as they relate to the proposed pathogenic mechanisms. The authors' standard wide exposure tympanoplasty approach with two layer tympanic membrane repair is described. The added steps in performing this procedure may be necessary to ensure a good result in this unique group of patients.

Prediction of facial nerve function following acoustic neuroma resection using intraoperative facial nerve stimulation

Methods of monitoring the facial nerve during posterior fossa surgery continue to evolve. In an effort to predict acute and final facial nerve function following acoustic neuroma resection, the lowest current applied to the facial nerve at the brainstem necessary to elicit facial muscle response was measured using strain gauge and electromyographic facial nerve monitors. A retrospective analysis of 121 patients who had undergone acoustic neuroma surgery was performed. Sixty-five patients had intraoperative facial nerve monitoring and 44 had sufficient data for inclusion in this study. The acute and final facial nerve functions, according to the House-Brackmann classification, were assessed with regard to intraoperative stimulation-current thresholds. Nineteen of 20 patients who required 0.10 mA or less to elicit a facial muscle response had a House-Brackmann grade I facial nerve outcome. The upper limit of the 95% confidence interval of stimulation threshold for patients with a final grade I facial nerve function is 0.17 mA. All of the patients in this study, with stimulation thresholds ranging up to 0.84 mA, had a final grade III or better result. A poor outcome in our series, a final grade III facial nerve function, is best predicted by a poor acute result, specifically an acute grade VIA facial nerve function. We suggest that it is possible to predict the facial nerve function based on intraoperative threshold testing.

Vestibular nerve section

In the nearly 90 years since Frazier first performed an eighth nerve section through the posterior fossa for the treatment of Ménières's disease, the surgical management of Ménière's disease has come full circle. With refinements in surgical technique and advancements in instrumentation, optics, illumination, and neuromonitoring, a procedure that was once resoundingly condemned by the otologic community is now regarded as the procedure of choice in patients with serviceable hearing. The vestibular nerve section has experienced a renaissance. The posterior fossa vestibular nerve section has undergone an evolution, and the combined retrolabyrinthine-retrosigmoid vestibular nerve section represents the highest form. It is a significant improvement over its predecessors and our procedure of choice in properly selected patients.

Endoscopy in otology and neurotology

Since the early 1980s rigid endoscopes have been used by otorhinolaryngologists in the United States primarily for sinus surgery. Recently rigid endoscopes have been used as an adjunct to standard otologic and neurotologic procedures. Diagnostic inspection of the middle ear can be performed through a myringotomy incision to rule out perilymphatic fistula, for identification of cholesteatoma, or for evaluation of the status of the ossicular chain. During chronic ear surgery endoscopes can be used to locate hidden cholesteatoma in difficult to visualize areas such as the eustachian tube, attic, sinus tympani, and beneath an intact posterior canal wall. In acoustic neuroma surgery in which hearing preservation is an objective endoscopes are used to inspect the lateral aspect of the internal auditory canal (IAC) for residual tumor. During vestibular neurectomy endoscopes are used to view the IAC and to help identify the cochleovestibular cleavage plane. The applications, techniques, and limitations of rigid endoscopy in otology and neurotology are discussed.

Laryngeal involvement in neurofibromatosis

Neurofibromas of the larynx are an uncommon component of neurofibromatosis, but should be considered in the differential diagnosis of patients with a submucosal supraglottic mass. Complete surgical excision is the treatment of choice; however, incomplete excision may be preferable to aggressive debilitating surgery. Plexiform neurofibroma differs from non-plexiform neurofibroma in that it is poorly circumscribed and highly infiltrative. Tracheostomy may be necessary. Sarcomatous degeneration is reported and carries a poor prognosis.

A comparison of growth rates of acoustic neuromas: nonsurgical patients vs. subtotal resection

A conservative approach to the management of acoustic neuromas in elderly patients has been used since 1971. Elderly patients without symptoms of brain stem compression are initially treated by observation and yearly radiographic imaging. A translabyrinthine radical-subtotal resection is performed if brain stem compression is present or if tumor is growing rapidly. Twenty-three patients, ages 65 to 86 years, had initial nonsurgical management of their tumors. Growth rates could be determined for 16 patients. Thirteen patients not requiring surgery had an average tumor growth rate of 0.6 mm/yr. Three patients with an average growth rate of 6.8 mm/yr eventually required surgery. No patient whose tumor was < 15 mm at initial evaluation has experienced brain stem symptoms or demonstrated rapid tumor growth. Twenty-four patients ages 65 to 86 years underwent planned subtotal tumor excision. Eighteen patients followed postoperatively for more than 1 year demonstrated an average rate of regrowth of tumor of 0.7 mm/yr.

Middle ear air injection after chronic ear surgery

In the early period after chronic ear surgery, the reasons for conductive hearing loss may be difficult to determine. Patients who cannot autoinflate the middle ear after 3 weeks, or who have a negative Rinne test result with the 512 Hz tuning fork, are treated with a transtympanic injection of 0.5 cc of air with a 27-gauge needle and tuberculin syringe. This represents 20% of patients who had chronic ear surgery. Results show that hearing may be immediately improved, the sensation of pressure in the ear may be reduced, and fluid may be cleared from the middle ear. Other benefits may include the release of adhesions. The surgeon is better able to assess the thickness of the graft, and the status of the ossicular chain reconstruction can be determined. There have been no complications of middle ear infection or failure of the micropuncture site to heal. In our practice, middle ear air injection is a routine procedure in patients with inadequate eustachian tube function after chronic ear surgery. This report describes the results of 100 patients over 14 years who received middle ear air injections after chronic ear surgery compared with a control group of 100 patients who did not meet the criteria for requiring air injection. Hearing was immediately improved in 74% of patients as determined by Rinne testing. Audiograms were performed in 25 of these patients, documenting a mean improvement in pure-tone average of 16 dB. The long-term hearing results in patients undergoing air injection, who by definition had evidence of poor eustachian tube function, are similar to the results in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)