Transtemporal planned partial resection of bilateral acoustic neurinomas

Extended middle cranial fossa approach for acoustic neuroma surgery

The enlarged middle cranial fossa approach was used for removal of acoustic neuromas in 209 cases. Complete tumor removal was accomplished in 96% of cases. Hearing was preserved in 51% of cases, with better results in smaller tumors. Our experience with the enlarged middle fossa approach has led us to discard the translabyrinthine approach for removal of acoustic neuromas.

Management of the acoustic neuroma in an only hearing ear

Heightened physician awareness of the sociologic and psychologic trauma related to deafness coupled with an increased emphasis on early diagnosis has prompted the employment of sophisticated diagnostic studies in an attempt at identification of an acoustic neuroma as a cause of hearing loss. Because profound bilateral hearing impairment is a catastrophic event, the management and care of an individual with an eighth nerve lesion in an only hearing ear remains a significant challenge for both patient and physician. In this article we will summarize our experience with this unique patient population through case presentations that will include diagnostic testing and intraoperative and perioperative findings. The literature regarding diagnosis and management will be reviewed. Recommendations for options available in the care of these patients will be discussed.

Decision making in acoustic neuroma management: the only hearing ear

Patients with acoustic neuroma in their only hearing ear are not frequently seen in clinical practice. Managing this group of patients is a challenge to both patient and surgeon. In this study we report on five cases of acoustic neuroma in an only hearing ear. Our decision for nonsurgical management of those patients with regular follow-up using auditory brainstem responses and magnetic resonance imaging is discussed. Other management options currently available are considered as well.

Management of acoustic neuroma in the only hearing ear

Patients with acoustic neuroma in their only hearing ear are not frequently seen in clinical practice. Managing this group of patients is a challenge to both the patient and surgeon. In this study we report on five cases of acoustic neuroma in an only hearing ear. Our decision for conservative management of those patients with regular follow-up using auditory brain stem response and magnetic resonance imaging is discussed. Other management options currently available are reviewed as well.

Hearing preservation in solitary vestibular schwannoma surgery using the retrosigmoid approach

The results of 50 cases of vestibular schwannoma surgery with hearing preservation performed by the retrosigmoid approach at Addenbrooke's Hospital, Cambridge, during a 10-year period are presented. The hearing-preservation rate, using audiometric criteria set by others as "serviceable hearing" (Wade PJ, House W. Otolaryngol Head Neck Surg 1984;92:1184-93; Silverstein H, et al. Otolaryngol Head Neck Surg 1986;95:285-91; Cohen NL, et al. Am J Otol 1993;14:423-33) was 8% (4 of 50 cases). When the more stringent selection criteria of near-normal hearing and reporting criteria of socially useful hearing preservation (pure-tone average < 30 dB/speech discrimination score > 70%) is used, the hearing-preservation rate is 4.8% (1 of 21 cases). The only preoperative factor that may predict a favorable hearing-preservation outcome is normal auditory brain stem response morphology (Fisher's exact 2-tailed test, P < 0.001). The number of suitable candidates for hearing-preservation surgery are few. Reasonable indications for attempted vestibular schwannoma surgery with hearing preservation are discussed.

Auditory brainstem implant: I. Issues in surgical implantation

Most patients with neurofibromatosis type 2 (NF2) are totally deaf after removal of their bilateral acoustic neuromas. Twenty-five patients with neurofibromatosis type 2 have been implanted with a brainstem electrode during surgery to remove an acoustic neuroma. The electrode is positioned in the lateral recess of the fourth ventricle, adjacent to the cochlear nuclei. The present electrode consists of three platinum plates mounted on a Dacron mesh backing, a design that has been demonstrated to be biocompatible and positionally stable in an animal model. Correct electrode placement depends on accurate identification of anatomic landmarks from the translabyrinthine surgical approach and also on intrasurgical electrophysiologic monitoring. Some tumors and their removal can result in significant distortion of the brainstem and surrounding structures. Even in the absence of identifiable anatomic landmarks, electrode location can be adjusted during surgical placement to find the location that maximizes the auditory evoked response and minimizes activation of other monitored cranial nerves. Stimulation of the electrodes produces auditory sensations in most patients, with results similar to those of single-channel cochlear implants. A coordinated multidisciplinary team is essential for successful application of an auditory brainstem implant.

Preservation of hearing in bilateral acoustic neurinomas by deliberate partial resection

With the aim of preserving hearing, 20 acoustic neurinomas in 17 patients with neurofibromatosis 2 were intentionally submitted to an incomplete (80%) tumour removal. In 12 cases this was an operation on the last hearing ear with total deafness of the contralateral ear. If an auditus existed in both ears the better hearing ear was selected for the primary intervention. Early audiological controls evidenced residual hearing in 19 of the 20 cases operated on by the enlarged middle fossa approach, which was utilized inspite of the tumour diameters being between 1 and 6 cm in the cerebello-pontine angle. The oncologic and functional follow-up over 1 to 7 years showed different patterns of slow progression of hearing loss and of persistent auditory function over 2 to 7 years. Facial nerve function was excellent in 16 of the 18 controlled cases. Continued CT or MRT imaging revealed no signaling in 2 cases, constant tumour sizes in 10 cases and slow progression in 3 cases. With regard to the importance of an auditory communication in the younger adult, the described treatment modality appears to be the first choice method.

The enlarged middle cranial fossa approach for surgery of the temporal bone and of the cerebellopontine angle

Due to the fact that the temporal bone has broad segments of bone anterior to and behind the internal auditory canal which are empty of functionally important structures, a broad exposure of the cerebellopontine angle may be obtained from above. This technique is adequate for the management of acoustic neurinomas up to 3 cm in diameter. A low postoperative morbidity and a high percentage of hearing preservation with total tumor removal were obtained in a series of 190 cases. This report underlines the advantages of the procedure and points to various other indications.