The mismatch negativity cortical evoked potential elicited by speech in cochlear-implant users.

The mismatch negativity (MMN) event-related potential is a non-task related neurophysiologic index of auditory discrimination. The MMN was elicited in eight cochlear implant recipients by the synthesized speech stimulus pair /da/ and /ta/. The response was remarkably similar to the MMN measured in normal-hearing individuals to the same stimuli. The results suggest that the central auditory system can process certain aspects of speech consistently, independent of whether the stimuli are processed through a normal cochlea or mediated by a cochlear prosthesis. The MMN shows promise as a measure for the objective evaluation of cochlear-implant function, and for the study of central neurophysiological processes underlying speech perception.

Hearing results in retrolabyrinthine vestibular neurectomy.

Patients having retrolabyrinthine vestibular neurectomy (RLVN) may have complications that compromise hearing. While most reviews have emphasized sensorineural loss, less attention has been given to conductive hearing loss, which may complicate RLVN. Hearing results of 25 consecutive cases of RLVN performed for Meniere's disease with incapacitating vertigo were tabulated according to 1985 American Academy of Otolaryngology (AAO) guidelines. Nine patients (36%) had improved hearing postoperatively, 5 (20%) had no change in hearing, and 11 (44%) had worse hearing postoperatively. The most commonly observed audiometric change was low-frequency conductive hearing loss, presumably secondary to partial ossicular fixation by bone dust or fat fibrosis in the attic and antrum. Five patients (20%) had low-frequency conductive hearing losses that increased by 10 dB or greater over preoperative levels. An additional 7 patients had lesser losses at low frequencies. One patient had a flat conductive hearing loss. Six (24%) of the patients had a decrease in bone levels of greater than 10 dB. Overall hearing results in this study are comparable to those of other series in the literature. Causes and prevention of conductive hearing loss in RLVN are discussed, and a format for presentation of hearing data that will highlight conductive hearing loss after surgery for Meniere's disease is presented.

An holistic approach to Ménière's disease. Medical and surgical management.

A review of the medical and surgical management of 195 patients with Meniere's disease is presented. In order to avoid a piecemeal approach to the problem of Meniere's disease, the "whole" patient must be treated. Psychological counseling, medical management, and when indicated selective surgical management is advocated. The diagnosis of Meniere's must be confirmed through careful history, physical, neurological evaluation and selective testing. The majority of patients can be controlled medically; however, in this study 52 (26%) patients underwent surgical therapy. Twenty-eight patients underwent some type of saccus surgery for Meniere's disease with overall relief of 71%; however, better relief of vertigo was seen with labyrinthectomy and nerve section. The most common indication for surgery was disabling vertigo. However, fluctuating progressive sensorineural loss, may be an important reason to advise surgery. Surgical techniques for Meniere's disease continue to evolve. A graduated approach is preferred, starting with endolymphatic-mastoid shunt, proceeding to middle fossa vestibular nerve section when medical status and hearing and adequate. When hearing is socially inadequate, labyrinthectomy with or without vestibular nerve section is preferred. A good working relationship with a neurosurgeon is advised for otolaryngologists performing middle fossa surgery.

Skull base mapping.

Early experience with medium to large tumors of the temporal region has re-emphasized the value of radiologic preoperative plotting of these space occupying lesions in the sagittal, coronal, and horizontal planes. Attention to probable pathology, neurovascular structures and patient's medical status has been important in determining resectability. A standard format of the interior and exterior of the skull base and cervical spine has been employed to map these lesions. Such devices have been used by otolaryngologists in the past to depict laryngeal lesions; and provide for the skull base surgeon a common base of comparison of tumor size, chart documentation, and a means to facilitate communication among other specialists. Experience with 36 cases of skull base tumors seen since July 1979 has emphasized the occult manner in which these lesions may present.

The retrolabyrinthine approach and vascular loop.

Several researchers have made progress toward determining the cause of hemifacial spasm, tinnitus, and episodic vertigo. During the past 5 years, we have encountered a vascular loop in six of 36 patients who were undergoing retrolabyrinthine vestibular neurectomy for recurrent disequilibrium and vertigo. In five of these six patients, disequilibrium improved after neurectomy. This report describes the clinical symptomatology and the results of preoperative cochleovestibular testing for those patients found intraoperatively to have a vascular loop and suspected neurovascular compression syndrome. Audiograms, although varied, characteristically did not demonstrate the low-frequency sensorineural hearing loss characteristic of Meniere's disease. No preoperative marker, with the single exception of computed tomography pneumocisternography, dependably predicted the presence of a vascular loop.

Pitfalls in the diagnosis of hemifacial spasm.

Hemifacial spasm (HFS), a condition characterized by involuntary unilateral facial spasms, is a disabling disorder resulting in functional compromise, patient frustration, cosmetic deformity, and social embarrassment. Compression of the seventh nerve at the root entry zone via vascular loop is presently the most widely accepted causative theory. Although less common, there are other entities that can result in HFS. Basic evaluation, including a thorough history, physical examination, and magnetic resonance imaging (MRI) scan, is important to confirm the diagnosis and rule out other causes. The relation of vascular loop syndrome to HFS is well enough established that radiologic documentation of a vascular loop is probably not necessary in every case. Here we present 12 cases of HFS, 6 without VLS. The etiology and evaluation of HFS are reviewed.

Canal wall reconstruction: a newer implantation technique.

An innovative hydroxylapatite canal wall implant underlies a new technique for reconstructing canal wall defects in well-pneumatized "disease-free" mastoid cavities. Previous primary reconstruction involving soft-tissue techniques were not always optimal, depending on the size of the defect. The new hard implant provides lasting canal wall contour, and the implantation technique can be duplicated by other otolaryngologists. Our experience with the implant is described in 11 patients (implant duration 2 to 37 months) using a modification of the technique described by Grote (1986). The implant is biocompatible, being incorporated into surrounding tissues. Indications, contraindications (relative and absolute), and the intraoperative sculpturing method are presented. Long-term and short-term complications are reviewed with suggestions to minimize complications.

Congenital aural atresia.

Congenital aural atresia is an unusual anomaly that is difficult to surgically correct. Altered anatomical landmarks, especially of the facial nerve, and variability of the middle ear configuration, contribute to the difficulty of the procedure. In addition, the unpredictable healing process can make for variable outcomes. Choosing appropriate candidates for surgical repair minimizes risks and enhances patient care. This report reviews the outcome with evaluation and management of 17 patients with congenital aural atresia. Surgical techniques for repair, including use of a hydroxylapatite canal wall prosthesis to help reconstruct the posterior canal wall are described. As expected, patients with less severe anomalies had better postoperative hearing results. Lateralized tympanic membrane, canal stenosis, and meatal narrowing were complications encountered. The anatomy and embryology of the ear and facial nerve are reviewed to assist surgeons in safe, successful surgery.

Surgical treatment of vertigo with retrolabyrinthine vestibular neurectomy.

Results for control of vertigo and preservation of hearing in patients who have had a retrolabyrinthine vestibular neurectomy (RVN) by our group were analyzed retrospectively. This procedure consists of selective section of the vestibular nerve in the posterior cranial fossa. Vertigo was completely controlled in all but two of 31 patients, one of whom required revision surgery to control attacks. Analysis of these two cases suggests that the cause of persistent vertigo is incomplete neurectomy. With our current surgical technique in patients with Meniere's disease, hearing results were not statistically different from our results with surgery of the endolymphatic sac. Control of vertigo was much more successful with the RVN than endolymphatic sac surgery.

Tumor involvement of the facial nerve.

Tumors involving the facial nerve are rare and challenging in both diagnosis and treatment. In this paper we report 18 cases of benign and malignant neoplasms involving the temporal portion of the facial nerve. The selection of those patients with facial paralysis who require detailed evaluation is discussed. Often, despite thorough evaluation of these patients, a preoperative diagnosis is unavailable or erroneous. An occasional patient may require surgical exposure of the nerve from the middle cranial fossa to the parotid gland.

Panel discussion: glomus jugulare tumors of the temporal bone. The surgical management of glomus tumors.

The authors describe the diagnosis and surgical management of 70 glomus tumors seen at the Otology Group in an 8 yr. period. The need for bilateral arteriograms to detect associated tumors (carotid body and intervagale) is stressed. A new surgical technique, the modified intratemporal fossa approach, is described for the removal of large glomus jugulare tumors involving the carotid artery. Complications and results are discussed in detail.

Rehabilitation of the face following traumatic injury to the facial nerve.

Etiology, diagnosis, and surgical management of facial paralysis due to traumatic injury of the VIIth cranial nerve are discussed. Sixty patients are reviewed who underwent some type of surgical procedure for the repair of the facial nerve. These cases are categorized according to etiology, which includes temporal bone fractures, iatrogenic injuries, and penetrating wounds of the head and neck. The results of a poll of eight leading otologists on their approaches to several aspects of the surgical management of these injuries are presented in the Discussion section. The diagnostic and prognostic studies associated with facial paralysis, as well as the more common surgical procedures available for repair of the facial nerve, are briefly reviewed.

Surgical management of brain tissue herniation into the middle ear and mastoid.

In the well pneumatized temporal bone, the temporal lobe of the brain is separated from the middle ear and mastoid process by a thin layer of bone known as the tegmen. Congenital defects, infection, and trauma can alter this structure in such a way that cerebral tissue herniates into the ear. This unusual condition may precipitate numerous otologic problems such as hearing loss, trapped squamous epithelium, and the potential for meningitis or encephalitis. The purpose of this paper is to define the problem as well as discuss the diagnosis and surgical management. The authors feel this should be a team effort, in many cases employing the assistance of a neurosurgeon, as the repair must often be intradural. Case histories and an extensive review of the literature are to be included.

Vascular anomalies of the middle ear.

The patient presenting with a red mass behind the eardrum and a pulsating tinnitus may well have a vascular tumor. One must be ever mindful, however, that the mass may represent a congential vascular anomaly. The most common one seen is the uncovered jugular bulb in which the vessel extends superiorly into the middle ear to or above the incudostapedial joint. More rare is the uncovered and posteriorly displaced carotid artery. The purpose of this paper is to review the literature on the subject of vascular anomalies of the middle ear and temporal bone and to discuss the diagnosis and management of these lesions. Illustrative case reports with color photographs are presented as well.

Brain stem evoked response audiometry in a clinical practice.

Brain stem evoked response audiometry (BERA) is an effective method of evaluating the auditory pathway from the peripheral endorgan through the brain stem. The authors have found this test to be a valuable adjunct to the neurotologic evaluation and have applied the study to over 500 patients (639 ears) in a 22 month time span. BERA has an excellent success rate (98%) in determining the presence of cerebellopontine angle lesions and is helpful in establishing whether a hearing loss is of cochlear or retrocochlear type. The authors have found BERA of use in the diagnosis of multiple sclerosis as well as other neurologic diseases affecting the brain stem. It is a valid method of dealing with suspected malingerers and those who cannot respond to standard audiometric techniques. BERA has been helpful in determining the threshold of hearing in these patients. The authors conclude that BERA is a clinical study of practical significance and that more otolaryngologists should consider adding it to their diagnostic protocol.

Brain herniation and space-occupying lesions eroding the tegmen tympani.

Technological advances in neuroradiology and the development of skull base surgery in neurotology have improved diagnosis and management of lesions eroding the tegmen tympani. The diagnosis of brain hernia is to be suspected in patients with a history of complicated chronic ear surgery and a slowly developing pulsatile mass with CSF leak. Patients are best evaluated in the upright position, with an otomicroscope and by magnetic resonance imaging (MRI). Over 6 years, our group has treated seven patients with eight space-occupying lesions eroding the tegmen. Five of the lesions were repaired with a temporalis muscle flap, 2 with fascia and bone, and 1 with Marlex. A review of new technology in the diagnosis of brain hernia and a modification of previous techniques is given.

Computed tomography: how accurate a predictor for cochlear implantation?

Cochlear implantation is an accepted medical treatment for profound bilateral postlinguistically acquired hearing loss. Because cochlear implants are still in the process of development, a detailed evaluation of the results of implantation is essential. However, the capability of predetermining the auditory benefit of a cochlear implant is limited and depends upon a number of factors. This report focuses upon the ability of computed tomography (CT) to predict surgical success and audiological results of multichannel cochlear implantation. It also addresses how the disease state might affect the functional benefit of the implant. After undergoing routine clinical and audiological evaluations, 28 cochlear implant candidates underwent CT scans in order to evaluate cochlear patency prior to surgery. Subsequently, 24 patients were implanted with either a single-or 22-channel device. Surgical findings were noted and postoperative audiological assessments of sound detection and speech discrimination were made. The CT risk factors that diminish the likelihood of a successful cochlear implant result are discussed based upon a retrospective comparison of preoperative CT results, surgical findings, and postsurgical audiological evaluations of the 14 patients who received a 22-channel implant. Analysis of the predictive capability of CT will allow clinicians to use that procedure more effectively in the presurgical assessment of cochlear implant candidates.

Rethinking the use of auditory brainstem response in acoustic neuroma screening.

The ability of magnetic resonance imaging (MRI) to detect very small acoustic tumors has triggered many to rethink the use of auditory brainstem response (ABR) in the screening of acoustic tumors. To assess ABR accuracy, we conducted a retrospective study of 388 surgically treated patients. Of these patients, 111 had complete databases including both preoperative MRIs and ABRs. The ABR was abnormal by wave V interaural latency difference in 106 (95%) of the cases. Although our overall sensitivity was 95%, sensitivity varied according to tumor size. ABR was abnormal or absent for all tumors (100%) larger than 2 cm in diameter, for 98% of tumors 1.1 to 2 cm in diameter, and for only 89% of tumors less than or equal to 1 cm in diameter. Ramifications of this in the decision-making process are presented. Criteria for cut-off values are also discussed.

Hearing preservation after acoustic neuroma resection with tumor size used as a clinical prognosticator.

Three hundred sixty-four patients referred to the Chicago Otology Group for acoustic tumor removal between 1981 and 1995 were reviewed in a retrospective fashion. Of this group, 60 patients were candidates for hearing preservation surgery and thus underwent one of two surgical approaches to remove the tumor and preserve hearing. Eighteen patients had tumor removal via the middle cranial fossa approach, and 42 patients had tumor removed via the retrosigmoid approach. Of the 42 patients who underwent retrosigmoid removal, 33% had hearing preserved overall. Of the 18 patients in the middle fossa group, 44% had hearing preserved overall. The average tumor size of patients with preserved hearing in the retrosigmoid group was 1.4 cm, and in the middle fossa group was 0.74 cm. Of significance was the fact that in both groups of patients with a tumor of 1.5 cm or less there was a 50% chance of hearing preservation. In the group of patients with tumors larger than 1.5 cm there was only a 16% chance of preserving hearing. We propose that these data can be used for better counseling of patients preoperatively as to the chances of hearing preservation and the type of approach appropriate for each case.

Conservative management of patients with small acoustic tumors.

Of 432 patients referred for treatment of their cerebellopontine angle tumors, 53 with acoustic neuromas were managed initially without intervention but with adequate follow-up. Mean presenting tumor size in this subgroup of patients was 0.98 cm (range, 0.2 to 3.0 cm), and average growth rate was 0.16 cm per year. Twenty-one patients demonstrated tumor growth with a mean follow-up interval of 1.9 years. Of these 21 patients, 14 underwent microsurgical excision, 4 received radiation, 2 continued to be observed and 1 was lost to follow-up. The remaining 32 (60%) had no demonstrable growth with a mean follow-up of 2.13 years. Of these patients, 29 continue to be followed and 3 were lost to follow-up. Of the information evaluated, the only statistically significant relationship is with larger tumor size in elderly patients--most likely reflecting the propensity to opt for conservative treatment in elderly patients. Tumor growth rate was unrelated to presenting tumor size or patient age, which suggests that conservative treatment may be appropriate in selected patients.