Gale Gardner

Hearing preservation in unilateral acoustic neuroma surgery.

This paper reviews the principal English literature on hearing preservation in unilateral acoustic neuroma surgery. Seventeen case reports and 13 surgical series are included. In addition, we report ten cases of our own, two with successful hearing preservation. The purpose of this report is to study feasibility, success rate, and associated problems. Previous reports have been compared in terms of criteria that we have selected. A classification system similar to Silversteins is used. The total number of cases under review is 621, with 221 reported successes. Cases limited to those having a unilateral acoustic neuroma, with valid supportive audiometry, were 394, with 131 successes. The approximate overall rate of success is 33%. There are five cases of hearing preservation with unilateral acoustic neuromas 3 cm or larger when supporting audiometric data are available, the largest being “4–5 centimeters.” Problems included mixing of unilateral acoustic neuromas with other types of tumors and failure to include comprehensive data, particularly audiometry. We conclude 1) that hearing preservation is a reasonable goal in unilateral acoustic neuroma surgery, although the number of available candidates is relatively small and 2) that intelligent selection of patients and high quality surgical technique are the keys to success.

Nonsurgical management of small and intracanalicular acoustic tumors.

It is generally accepted that the proper treatment for acoustic tumors is surgical removal. In fact, there is little, If any, reference to nonsurgical treatment of these tumors in the recent medical literature. We would like to report on the nonsurgical management of six patients with cerebellopontine angle tumors based upon CT examination. The diagnostic findings, follow-up data, and the rationale upon which the decision was made to treat the patients nonsurgically will be presented, as will a review of the pertinent literature.

105 patients operated upon for cerebellopontine angle tumors - experience using combined approach and CO2 laser.

In Memphis, TN, we have treated surgically 105 patients with cerebellopontine angle tumors. In reporting that experience here, we place major emphasis on the use of two surgical aids: a combined surgical approach and the CO2 laser. Diagnostic techniques are also discussed, along with data management, postoperative results, and complications.

High resolution computed tomographic scanning in the detection of intratemporal neuromas of the facial nerve.

Continued refinements in the technique of high resolution computed tomographic scanning now allow the study of the pathology of intratemporal tumors of the facial nerve. The normal anatomy of this area and a selected case of facial nerve neuroma diagnosed with high resolution computed tomography are presented.

Image-Interactive Orientation in the Middle Cranial Fossa Approach to the Internal Auditory Canal: An Experimental Study

Approaches through the middle cranial fossa directed at reaching the internal auditory canal (IAC) invariably employ exposure of the geniculate ganglion, the superior semicircular canal (SSC) or the epitympanum. This involves risk to the facial nerve and hearing apparatus. To minimize this risk, we conducted a laboratory study on 9 cadaver temporal bones by using an image-interactive guidance system (StealthStation) to provide topographic orientation in the middle fossa approach. Surface anatomic fiducials such as the umbo of the tympanic membrane, Henles spine, the root of the zygoma and various sutures were used as fiducials for registration of CT-images of the temporal bone. Accurate localization of the IAC was achieved in every specimen. Mean target localization error varied from 1.20 to 1.38 mm for critical structures in the temporal bone such as the apex of the cochlea, crus commune, ampula of the SSC and facial hiatus. Our results suggest that frameless stereotaxy may be used as an alternative to current methods in localizing the IAC in patients with small vestibular schwannomas or intractable vertigo undergoing middle fossa surgery.

Selective absorption and control of thermal effects: a comparison of the laser systems used in otology and neurotology.

The surgical lasers available for use by the otologist and neurosurgeon include the CO2, argon, and neodymium:yittrium-aluminum-garnet (Nd:YAG). Selection of a laser should be based on the principles of power density, radiant exposure, and selective absorption, with a particular application in mind. The history of and relevant literature on lasers in otology are reviewed, and basic research findings are presented. Our conclusions are that (1) lasers are viable for many neurotologic applications; (2) the effect of the CO2 laser is purely thermal at the tissue surface; (3) the argon and Nd:YAG lasers, both pigment-dependent, may penetrate tissues to variable levels before absorption and conversion to thermal energy; (4) the CO2 laser can achieve much higher power densities than the argon or Nd:YAG lasers; (5) since there is a discrepancy between focused spot size and actual lesion size, with the argon effect being approximately 5× and the CO2 effect about 2×, the resulting lesions are essentially equal in size; and (6) no laser is best for all neurotologic procedures and should be evaluated based on the lasers basic physical principles to exploit the advantages and minimize the disadvantages.

Neuroradiological detection of small and intracanalicular acoustic tumors: an emphasis on CO2 contrast-enhanced computed tomographic cisternography.

Seventy patients suspected clinically of having an acoustic tumor were evaluated using the computed tomographic (CT) scan as the initial neuroradiological procedure, followed by CO2 contrast CT cisternography in cases where the intravenous contrast-enhanced scan did not reveal any lesion. Forty-eight gas CT cisternograms revealed 10 small acoustic tumors, 2 of which were totally intracanalicular. The authors present a review of the basic CT anatomy of the temporal bone as it relates to acoustic tumors. Based upon the ease of performance of the procedure, the low postexamination morbidity, and the excellent diagnostic results, CO2 CT cisternography is recommended as the procedure of choice in the diagnosis of small and intracanalicular acoustic tumors.