Partial labyrinthectomy petrous apicectomy approach to neoplastic and vascular lesions of the petroclival area.

OBJECTIVE: To study the value of an improvement of the presigmoid petrosal approach to the petroclival area by the addition of partial labyrinthectomy and petrous apicectomy and to document hearing and other results. METHODS: Thirty-six consecutive patients treated by this technique during a 2-year period were studied prospectively. The lesions treated included 33 petroclival neoplasms (25 meningiomas, 5 chordomas, 1 chondrosarcoma, 1 trigeminal schwannoma, and 1 epidermoid cyst) and 3 vertebrobasilar aneurysms. The patients underwent clinical, radiological, and neuro-otological examinations. RESULTS: There was no perioperative mortality. Cranial nerve deficits involving Cranial Nerves III, IV, V, and VI occurred in 17 patients (47%) postoperatively. Cerebrospinal fluid leak occurred in 12 patients (33%). Four of these patients were treated by lumbar drainage, two patients were treated by lumboperitoneal shunt, and six patients required reoperation and repacking of the middle ear. Hydrocephalus occurred in five patients (13.9%). There was one case of meningitis and another of systemic sepsis. All 36 patients underwent postoperative audiometric evaluation. When serviceable hearing was present preoperatively (Gardner-Robertson Grades I or II), it was determined to be preserved at postoperative follow-up in 81% of the patients (26 of 32 patients). CONCLUSION: The partial labyrinthectomy petrous apicectomy approach provided improved access to neoplasms of the clivus and petrous apex and the posterior cavernous sinus area and to vertebrobasilar aneurysms in the midclival area. This improvement in access permits more controlled and thorough treatment of these lesions, with reduced brain retraction and acceptable morbidity with respect to auditory function.

Endodermal cysts of the posterior fossa. Report of three cases and review of the literature.

The pathogenesis of endodermal cysts of the posterior fossa is still incompletely understood. The authors reviewed three new cases and those reported in the literature to clarify the clinical, pathological, radiological, and surgical characteristics of these lesions. A total of 49 cases were reviewed. Details on demographic profiles, clinical characteristics, histopathological and radiological features, and surgical methods were collected. These cysts have a predominance in male patients (61%) and can occur at any age (birth-77 years). In patients with posterior fossa endodermal cysts there is a bimodal age distribution and headache is the most frequent complaint. On immunohistopathological examination, endodermal cysts were reactive for epithelial membrane antigen and for keratin immunostains whenever the latter were tested. The cysts were reactive for carcinoembryonic antigen in nine of 11 cases. Endodermal cysts were located anterior to the brainstem in 51% of cases and in the fourth ventricle in 21% of cases. They frequently appeared hypodense on computerized tomography scans, and in five cases, the lesion was missed. The cyst's appearance on magnetic resonance imaging is variable. Resection was complete in 19 cases and partial in 11; marsupialization was achieved in two cases. Three recurrences have been reported. Total excision with preservation of neurological function should be the goal. Cranial base approaches are helpful for surgical access in selected examples of these lesions.

Acoustic neuromas: results of current surgical management.

OBJECTIVE: In this article, we review the surgical outcomes of 179 patients with acoustic neuromas. METHODS: Most of the tumors (84%) were operated on using a retrosigmoid, transmeatal approach. A transpetrosal, retrosigmoid approach was used in 10% of the patients, most of whom had large tumors. The translabyrinthine (4%) and transmastoid, transpetrosal, partial labyrinthectomy approaches (2%) were used selectively. The operative approaches are discussed. Tumors were categorized according to their cerebellopontine angle dimensions as small (< 2 cm), medium (2.0-3.9 cm), and large (> or = 4 cm). RESULTS: House-Brackmann evaluation of postoperative facial nerve function revealed excellent results (Grade I or II) in 96% of small tumors, 74% of medium tumors, and 38% of large tumors. A fair postoperative function (Grade III or IV) was achieved in 4% of small tumors, 26% of medium tumors, and 58% of large tumors. Functional hearing preservation, defined as Gardner-Robertson Class I or II, was achieved in 48% of small tumors and 25% of medium tumors. Hearing was not preserved in any of the three patients with large tumors in whom hearing preservation was attempted. Treatment complications consisted mainly of cerebrospinal fluid leakage (15% of the patients). The majority of the patients who experienced cerebrospinal fluid leakage were treated successfully with lumbar spinal drainage; only four patients (2% of the total group) required subsequent surgery for correction of cerebrospinal fluid leakage. There were two deaths (1%) in this series. One death occurred as the result of myocardial infarction and the other as the result of severe obstructive lung disease. One patient sustained disability because of cerebellar and brain stem injury. Complete tumor resection was accomplished in 99% of the patients, and there was no evidence of recurrence in this group. Only 1 of the 179 patients underwent incomplete tumor resection; he required subsequent surgery for symptomatic tumor regrowth. Our patient follow-up had a mean duration of 70 months and a median of 65 months (range, 3-171 mo). CONCLUSION: Our results are similar to those of other large microsurgical series of acoustic neuromas. Unless a patient has major medical problems, microsurgery by an experienced team of surgeons is preferred over radiosurgery.

Saphenous vein graft bypass of the sigmoid sinus and jugular bulb during the removal of glomus jugulare tumors. Report of two cases.

Glomus jugulare tumors always invade the jugular bulb and sigmoid sinus, making it difficult to resect these tumors totally without sacrificing the involved sinus. Although the sinus can be sacrificed safely in most patients, a few patients will have serious consequences. Reconstruction of the jugular bulb using a saphenous vein graft may enable tumor resection in these patients without complications. The authors describe two cases of saphenous vein grafting used to bypass the sigmoid sinus. The first case is that of a 61-year-old man with a glomus jugulare tumor that invaded the dominant sigmoid sinus, which was poorly collateralized. Temporary occlusion of the sinus during surgery caused a 15-mm Hg increase in intrasinus pressure, without brain swelling or changes in evoked potentials. A saphenous vein graft was used to bypass the sigmoid sinus and jugular bulb and to allow for total tumor removal. The patient had a good outcome. The second case is that of a 41-year-old man with a left glomus jugulare tumor and another smaller tumor on the opposite, dominant sinus. The left glomus jugulare tumor was resected via a two-stage procedure. A saphenous vein graft was used to reconstruct the left sigmoid sinus because of the presence of contralateral disease, with the potential for bilateral sigmoid sinus occlusion. An evaluation of the venous collateral circulation during jugular foramen surgery and the prevention of complications are also discussed.

Malignant otitis externa in AIDS patients: case report and review of the literature.

Malignant otitis externa is a necrotizing infection of the external ear canal and surrounding soft tissue and bone, usually caused by Pseudomonas aeruginosa. The infection classically occurs in diabetic patients, however recently, several patients with the acquired immunodeficiency syndrome (AIDS) have been reported to have malignant otitis externa. A patient with AIDS who had malignant otitis externa with skull base osteomyelitis is presented and reported cases in patients with AIDS are reviewed. Predisposing factors include immunologic abnormalities (notably neutropenia), dermatitis, medications, neoplasm, and iatrogenic procedures, e.g., ear lavage. Treatment of malignant otitis externa has traditionally included anti-pseudomonal cephalosporins/penicillins and aminoglycosides for prolonged durations. Recently, ciprofloxacin has been shown to be effective as an oral regimen. With the increasing number of patients with AIDS being seen in the outpatient clinics, the diagnosis of malignant otitis externa should be considered in any patient with persistent ear pain or otorrhea who does not respond to conventional treatment for external otitis.

Postoperative pain following excision of acoustic neuroma by the suboccipital approach: observations on possible cause and potential amelioration.

Incisional pain and headache have been reported following cerebellopontine angle surgery via the suboccipital approach. The high incidence and severity of pain determined in a retrospective study of acoustic tumor patients prompted the present prospective study. Various modifications of the suboccipital approach have been employed in an attempt to isolate a possible cause and potential method of minimizing this problem. The results of this study suggest that pain may be caused, in part, by adherence of healing nuchal soft tissue to underlying dura following suboccipital craniectomy. The substitution of a craniotomy with bone flap replacement, which prevents such adhesion, appears to have significantly reduced the postoperative pain associated with the suboccipital approach.

Intratympanic gentamicin instillation as treatment of unilateral Menière's disease: update of an ongoing study.

A prospective study using intratympanic gentamicin instillation as treatment for disabling unilateral Meniere's disease has been ongoing at our institution for 4 years. Treatment effectiveness is evaluated based on the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) 1985 guidelines. This report is based on 30 patients who have become eligible for assessment. We conclude that gentamicin intratympanic instillation as currently used in our protocol is an effective, safe, and easily administered method of achieving a predictable measure of vertigo control.

Pain after surgery for acoustic neuroma.

Postoperative pain after surgery in the cerebellopontine angle (CPA) is acknowledged to occur, but is rarely taken into account as a factor in the analysis of morbidity of such surgery. It is widely acknowledged that some patients, having undergone such surgery, particularly by means of the suboccipital approach, report significant post-operative pain and headache. This study was undertaken to determine the incidence and severity of pain after excision of acoustic neuromas and to establish whether this differed between the suboccipital and translabyrinthine routes. Ninety-one percent of all patients (n = 58), who had the suboccipital approach used for removal of their tumor, were surveyed. A smaller group (n = 40), matched for tumor size, age, and sex, but in whom the translabyrinthine approach was used, was similarly studied. A standard questionnaire, designed to detect and quantify postoperative pain, was administered to each patient. Of patients who underwent tumor excision by means of the suboccipital approach, 63.7% experienced significant local discomfort and headache, whereas this was notably absent in all those who had undergone translabyrinthine excision. In view of the significant morbidity noted to follow the suboccipital approach, several modifications of the surgical technique used were devised.

Presentation of large vestibular aqueduct syndrome to a dizziness unit.

An abnormally enlarged vestibular aqueduct has been associated with sensorineural hearing loss in children. Vestibular complaints, in this patient population, have not been characterized. Several patients have presented to the dizziness unit at Sunnybrook with vestibular related complaints. These patients all had sensorineural hearing loss noted in childhood. All provided recollections of periods of imbalance and vertigo. High resolution CT scan documented the presence of bilateral enlarged vestibular aqueducts. The Large Vestibular Aqueduct Syndrome (LVAS) will be discussed with reference to the pathophysiology of the vestibular complaints.

Conservative management of acoustic neuromas.

The results of this study and others document the biologic behavior of acoustic neuromas. In view of the evidence presented, which describes both variable rates of individual tumor growth and spontaneous regression in size, it would seem prudent that before selecting a nonsurgical treatment modality, the growth rate for the particular tumor in question should be established. To date, none of the literature that addresses the use of focused irradiation has attempted to do so. Our study as well as those of others suggests that the growth rate of acoustic neuromas becomes predictable over time. Based on this observation, a conservative (nontumor excision) management strategy is proposed for selected individuals. Patients to whom this management philosophy has been recommended or who themselves have chosen this option are seen twice yearly. Each visit consists of a thorough neurotologic examination as well as high-definition CT or MRI. Careful comparison of the clinical course as well as calculation of the tumor size is carried out in each instance. If the clinical course and rate of tumor growth remain unchanged over a 3-year follow-up, annual assessments are recommended. In the event of tumor enlargement, surgery may or may not be recommended, depending on the rate of growth and the age of the patient. Our experience suggests that a rate of growth equal to or exceeding 0.2 cm per year constitutes an indication for tumor removal.

Recurrence rates of acoustic neuroma in hearing preservation surgery.

Several authors have detailed the microscopic appearance of the acoustic neuroma/cochlear nerve interface. Others have highlighted the anatomic relationships existent between the lateral end of the internal auditory canal (fundus) and the otic capsule, as viewed from the posterior fossa. Based on these findings, several have suggested that hearing preservation attempts are likely associated with tumor persistence. They therefore question the feasibility of hearing preservation surgery. In this study, computerized tomography or magnetic resonance imaging was carried out on 28 patients having previously undergone excision of an acoustic neuroma with intraoperative sparing of the cochlear and facial nerves. Scans were done at least 5 years following surgery. Results of this study and a discussion of the literature follow.

Chemical labyrinthectomy: local application of gentamicin for the treatment of unilateral Menière's disease.

The use of aminoglycosides for selective vestibular function ablation without hearing alteration is described in the literature. Parenteral administration of streptomycin for the alleviation of vertigo in cases of bilateral Meniere's disease is well accepted. The instillation of aminoglycosides into the middle ear to produce a similar result, has been successfully used in the treatment of unilateral Meniere's disease. However, the use of chemical vestibulectomy has not gained acceptance as a practical means of treatment when compared to vestibular neurectomy. The reason for this is not clear, but may stem from the lack of definitive protocol for the application and lack of treatment results that have been assessed according to an acknowledged standard (i.e., the American Academy of Otolaryngology Criteria). A prospective study was undertaken to examine the efficacy of chemical vestibulectomy as the treatment for vertigo in unilateral, incapacitating Meniere's disease. A standardized drug administration protocol was utilized, and academy criteria for the assessment of treatment were applied. This report details the first group of patients to complete 2 years of post-treatment follow-up. Based on our experience, we conclude that chemical vestibulectomy is an efficient alternative to surgery. A standardized regimen of drug administration that can be carried out on an outpatient basis is put forward.

Morphophysiology of synaptic transmission between type I hair cells and vestibular primary afferents. An intracellular study employing horseradish peroxidase in the lizard, Calotes versicolor.

Intracellular records with glass microelectrodes filled with horseradish peroxidase (HRP) were taken from primary afferents of the horizontal semicircular canal in the lizard, Calotes versicolor. A coefficient of variation (CV) of the interspike intervals of spontaneous action potentials (APs) was calculated and correlated with the terminal morphologies of afferents within the canal crista. Irregular fibers with CV greater than 0.4 always correlated with a nerve chalice or calyx afferent terminal expansion surrounding one or more type I hair cells; more regular fibers with CV less than 0.4 always correlated with a dimorphic or bouton only terminal expansion of afferents. Afferents with a CV greater than 0.4 demonstrated miniature excitatory postsynaptic potentials (mEPSPs) that summated to initiate APs. APs were blocked by tetrodotoxin and mEPSP frequency was modulated by caloric stimulation. Cobalt application reversibly blocked mEPSPs. Electron microscopic examination of physiologically studied afferents with CV greater than 0.4 revealed synaptic profiles consisting of typical synaptic bodies and synaptic vesicles in the type I hair cell presynaptic to the nerve chalice. Examples of the interspike baseline in regular and irregular afferents suggest differential modes of impulse initiation in these two fiber types.