Annals of Otology,Rhinology & Laryngology

Dizziness is a common symptom in disorders of the brain and the ear. In a retrospective study of 1,000 cases, dizziness is attributed to a peripheral disorder in 25%, to a CNS disorder in 46%, and to undetermined causes in 29% of the cases. Peripheral disorders can be defined in terms of histopathological changes; the most frequent is cupulolithiasis, followed by endolymphatic hydrops and vestibular neuritis. These vestibular disorders are reviewed and discussed in connection with accepted facts and current hypotheses.

Mammalian otoconia are made up of inorganic calcium carbonate crystallites and organic substance, which is thought to be sulfated glycosaminoglycans and glycoprotein. Mouse otoconia are formed in situ, and the primitive otoconia assume spindle, trigonal, dumbbell, or quadrilobed forms. As the otoconia mature, they assume the typical barrel-shaped body with pointed tips formed by three surfaces. A variety of otoconial disorders have been reported. Otoconial degeneration can result from ototoxic drugs, infection, trauma, and aging. Abnormal otoconia are also known to occur as a result of genetic mutation, as well as ototoxicity. Otoconial deficiency may be genetic or caused by certain drugs, such as carbonic anhydrase inhibitors or tetracycline, or manganese deficiency during the critical period of gestation when the otoconia are formed in utero. Otoconial deficiency has been found to produce head tilting, swimming difficulty, and reduction or failure of the air-righting reflexes in animals.

Schuknecht's description of a degenerated otoconial mass embedded in the cupula of the posterior canal crista of the downmost ear in the Hallpike test has been termed cupulolithiasis to reflect the pathophysiology in the syndrome described by Barany. The hypothesis that the otoconial mass renders the cupula of the posterior canal gravity-sensitive has received considerable experimental and clinical support. Clinical support is provided here by the observation that complete relief of the paroxysmal positional vertigo followed transection of the posterior ampullary nerve (singular nerve) in 31 ears of 29 patients complaining of chronic cupulolithiasis. Two patients in the series exhibited bilateral cupulolithiasis and were relieved by sequential bilateral singular neurectomies. Twenty-seven patients were relieved by unilateral singular neurectomy. Although there were three instances of sensorineural hearing loss following surgery in the first 15 patients, no hearing loss has been observed following surgery in the last 16 operations. This low incidence of sensorineural hearing loss has resulted from modifications in surgical technique.

From review of recent findings, the pathology of Meniere's disease is described and correlated with clinical signs. Since Meniere's disease can be seen only in humans, assessing its natural history is important. A recent survey of 500 patients demonstrated the three major symptoms to be vestibular, auditory, and aural pressure. Meniere's disease (idiopathic) is distinguished from Meniere's syndrome (symptoms with likely cause), which accounted for approximately one fourth of the patients. Atypical forms include vestibular and cochlear Meniere's disease. A recent review of our temporal bone collection and detailed study of the pathological conditions of 134 temporal bones described in the literature revealed characteristic pathological findings. Patients with clear-cut histories of Meniere's disease may demonstrate little or no endolymphatic hydrops at death. Nevertheless, hydrops of the pars inferior remains the most significant pathological correlate of Meniere's disease. On the basis of these findings, the pathogenesis of the disease (malabsorption of endolymph) and the pathophysiology of the symptoms (physical and chemical) are discussed.

Fistulization at various parts of the membranous labyrinth has been currently in use as one of the treatments for the symptoms of Meniere's disease. The present report concerns our experience with membranous fistulae in experimental animal ears with and without manifestation of endolymphatic hydrops. The materials presented are mostly new; however, our previous data are also incorporated in order to bring this issue into better perspective. The first part describes the nonproduction aspect of endolymphatic hydrops in the rat, chinchilla, and squirrel monkey after obliteration of the endolymphatic duct in relation to the occurrence of spontaneous fistulae. The second part describes surgical fistulization of the vestibular membranous labyrinth and cochlear duct in order to prevent or control development of endolymphatic hydrops in the guinea pig, the species in which hydrops can be produced consistently. These results are tabulated and analyzed in terms of the pathological consequences that can be expected in performing fistulization of the membranous labyrinths in animals as well as in humans.

This paper describes the author's 10-year experience using streptomycin sulfate in the treatment of Meniere's disease in the following: the classical Schuknecht ablation of the vestibular system in bilateral Meniere's disease (eight patients); the classical Schuknecht ablation of the vestibular system in unilateral Meniere's disease in the only hearing ear (five patients); the intratympanic treatment of unilateral Meniere's disease (four patients); and low dose intramuscular outpatient treatment in unilateral Meniere's disease (five patients). The results of bilateral vestibular ablation were similar to those obtained previously by Schuknecht and others: patients developed profound ataxia with a wide-based gait and oscillopsia, which improved rapidly over a period of months; approximately 30% of patients experienced significant improvement in hearing, which usually deteriorated again after several months; and all patients were relieved of vertigo. Patients with unilateral Meniere's disease in the only hearing ear responded similarly, and hearing was preserved in all cases. Intramuscular streptomycin ablation of the vestibular system is strongly recommended in place of surgery in the only hearing ear in Meniere's disease. Controlled intratympanic injection of streptomycin is not successful as yet because of difficulty in controlling the dose. Low dose subototoxic streptomycin treatment on an outpatient basis offers promise for relief of Meniere's attacks, and may improve hearing in some cases without producing the temporary disabling effects of ataxia and oscillopsia. Streptomycin and similar drugs which may reduce endolymph production may eventually be the treatment of choice for Meniere's disease.

The endolymphatic volume of the utricle and the saccule and the surface area of the saccular macula were measured in eight mammalian species, including humans. The results confirmed that all measurements increased slowly but consistently correlating with increases in body weight. However, differences in these endolymphatic volumes or macular surface areas might also be influenced by functional characteristics among different species rather than simply reflecting geometrical comparability.

A surgical procedure was performed on 24 cats in which the oval window was entered and the vestibular sense organs were ablated. The operation incited a severe reparative response in the vestibule, characterized by proliferation of fibrous tissue and bone and blockage of the longitudinal flow of endolymph. One inner ear became infected resulting in degeneration of the labyrinth. Of the remaining 23 ears, 20 showed cochlear endolymphatic hydrops (EH) and three did not. All three ears without cochlear EH (as well as two ears with cochlear EH) had fistulae of their endolymphatic systems. The findings are consistent with the concept that fistulization of the membranous labyrinth prior to the blockage of longitudinal flow will prevent the formation of EH. Similarly, fistulization occurring after the onset of EH should arrest its progression. These observations are relevant for surgical procedures designed to control intractable vertigo caused by EH.

Surgery for resection of acoustic neurinomas (vestibular schwannomas) has been performed by way of the middle fossa craniotomy, suboccipital route, and translabyrinthine operation. The author has preferred the translabyrinthine operation for small tumors (less than 2 cm) for patients with poor hearing and the suboccipital approach for large tumors and for small tumors when attempting to preserve hearing. This paper proposes an operation designed for better tumor removal results, an improved technique for preservation of hearing, and fewer complications. During the first part of the operation, the posterior fossa dura posterior to the labyrinth, and also bound by the superior petrosal and sigmoid venous sinuses, is exposed by the mastoidectomy route. The mastoid is obliterated with adipose tissue. The suboccipital route is then used to resect large tumors and small tumors when attempting to preserve hearing. This operation would 1) facilitate dissection of the internal auditory meatus, 2) reduce chance for injury to the labyrinth with a resulting total hearing loss, and 3) eliminate the rather frequent (less than 10%) incidence of postoperative CSF otorhinorrhea and its complications.

Many anatomic studies have shown that a loop of the anterior inferior cerebellar artery is frequently found in the cerebellopontine angle and internal auditory canal. The concept of vascular cross-compression has been extended to the eighth cranial nerve, and patients with symptoms of hearing loss, tinnitus, and vertigo have been treated surgically by separating the vascular loop from the nerve. Previous reports have emphasized vascular anatomy, surgical approaches, and treatment results. Our study provides details of audiometric and vestibular system test results in a series of ten patients with prominent vascular loops in the internal auditory canal diagnosed by computerized tomography after subarachnoid space air injection (pneumo-CT). All patients had a unilateral (or asymmetric) hearing loss on the side of the lesion, and no vascular loops were detected on the contralateral sides. Hearing losses ranged from mild to profound. Audiometric findings were generally of a cochlear type, and most patients had excellent speech discrimination. Spontaneous nystagmus was detected in all patients during neurotologic testing, and half of the patients had normal caloric test results. The variability of audiometric and vestibular system test results is probably a reflection of anatomic variations of the vascular loop and its branches. Auditory and vestibular symptoms may be due to a complex interaction between the eighth cranial nerve and the vascular loop, in which the loop compresses the nerve and the nerve compromises circulation to the inner ear. Although symptoms from vascular loops and eighth nerve tumors are similar, the findings of a cochlear type of hearing loss, excellent speech discrimination, and normal caloric test results should raise the suspicion of a vascular loop. Pneumo-CT is effective in diagnosing and differentiating a vascular loop from a tumor.

The temporal bone is the primary site for approximately 10% of rhabdomyosarcomas of the head and neck in children. Until recently it has been a uniformly fatal tumor despite treatment with radical surgery and radiation therapy. Although experience with the Intergroup Rhabdomyosarcoma Study protocol-II is of relatively short duration, treatment of these children with radiation therapy and multiple-drug intravenous and intrathecal chemotherapy holds promise of significantly improved control rates.

A major new insight into cochlear mechanisms is the recognition of an active process, the cochlear amplifier, that contributes energy to the mechanical movement of the basilar membrane at low sound intensities. The extra energy makes possible the great sensitivity of hearing and also the very sharp tuning of individual neural units, ie, the tips of their tuning curves. The inner hair cells are the final receptor cells, but the outer hair cells are essential for the amplifier action. The amplifier is much more sensitive to anoxia, ototoxic drugs, noise, etc, than the inner hair cell system alone. Severe impairment of the amplifier causes a sensorineural hearing loss with recruitment. Only the tails of tuning curves remain. Thus the cochlea is a dual sensory system, a robust but insensitive broadly tuned passive component sided by a vulnerable, sensitive sharply tuned active component.

The process of retrograde secondary degeneration is described and its mechanism discussed. The extent of degeneration following transection of the central or peripheral axon and following various types of damage to the organ of Corti, including the time course of degeneration, is presented in animal experimentation and human temporal bones. Of greatest practical importance is secondary neuronal degeneration induced by alteration in the organ of Corti. The effect of damage to the outer hair cells, inner hair cells, supporting structures in the Corti, and nerve endings or peripheral dendrites is analyzed and related to different types of inner ear disease.

Click-evoked gross potentials were recorded from the round windows of 29 cats previously exposed to high-level sounds. The latency and amplitude of the gross neural components of these responses were determined and compared with the patterns of threshold shift measured in single auditory nerve fibers from the same 29 animals. Both of these electrophysiological measures were compared with the patterns of hair cell loss as seen in celloidin sections through the temporal bone. The correlations between single-unit abnormalities and cochlear pathology in these cases have been documented elsewhere. In this report, the correlations between gross-potential abnormalities and cochlear pathology are examined. The diagnostic potential of these correlations is discussed.

Nerve survival estimates in totally deaf ears of cats and humans can be easily obtained by auditory brainstem responses to electrical stimulation at the round window. In humans, electrically induced auditory brainstem responses require considerably more current than concurrently observed perceptual thresholds and “maximum loudnesses,” and there is much variability from patient to patient. In cats, in which we also compared efficacy of stimulation sites, preliminary data analysis suggests that the scala tympani is clearly much more efficient than the round window, and the round window better than the promontory in ears with large populations of ganglion cells. In ears with no or nearly no ganglion cells, scala tympani and round window stimulations are about equal.

Fifty-eight fetal and neonatal temporal bones were studied to evaluate the mechanisms of development of the hiatus of the facial canal, hypotympanic fissures, periotic duct, tympanomeningeal fissures, and fetal inner ear vascularity. These were correlated with the clinical pathologic entities of temporal bone trauma, glomus jugulare tumor extension within the temporal bone, CNS-temporal septic conduits, and inner ear vascularity. Temporal bone developmental anatomy and histopathology provide rich sources of information on which to base the scientific and clinical study of otology.

This study investigated congenital anomalies occurring in the inner ear, with particular attention to their features, localizations, and frequencies. Seventy-seven human temporal bones obtained from 53 individuals, aged one day to 39 years, each of whom had anomalies of the external ear, middle ear, and/or inner ear, were used for this study. The temporal bones had been removed at autopsy, fixed, dehydrated, embedded in celloidin, and sectioned horizontally or vertically at 20 μm. Every tenth horizontal section or every 20th vertical section was stained with hematoxylin and eosin, mounted, and studied under a light microscope. There were 206 inner ear anomalies (117 in the vestibular system, 79 in the cochlea, 10 in the internal auditory meatus) in the 51 bones studied. Fifty-four different features of anomalies were present at 33 different locations in the inner ear. The most frequent anomalies observed were shortened cochlea (23 bones), enlarged vestibule (17 bones), wide cochlear aqueduct (16 bones), absence of lateral semicircular canal (14 bones), and large osseous lateral semicircular canal (10 bones). The most common site of inner ear anomalies was thus the lateral semicircular canal, which was involved in 46 of the 206 anomalies observed; the anomalies in this organ were variable in type. The implications of inner ear anomalies are discussed as they relate to fetal development, inner ear dysfunction, and clinical interpretation of polytomographic studies.

Certain conditions (Alport's syndrome, kidney transplantation, dialysis) are followed by a progressive inner ear hearing loss. On the other hand, pharmacological substances that act on the transport mechanisms of the tubular epithelium may also produce inner ear disturbance. Experimental data on the possible pathomechanisms are discussed in reference to results reported in the literature.

Factors present in cholesteatoma connective tissue induce bone resorption in chronic otitis media. The presence of skin and its products appears to exacerbate the destructive influence of connective tissue. One exacerbating factor is pressure, shown in an animal model to increase bone resorption by influencing the subepithelial connective tissue. Consideration of pathogenic factors provides a rationale for modifications in the treatment of middle ear cholesteatoma.

Based on biochemical and morphological studies, the significance of cholesterol in cholesteatoma and cholesterol granuloma is discussed. In cholesteatoma, cholesterol is synthesized through desmosterol and Δ⁷-cholestenol (lathosterol), possibly in the matrix. Cholesterol crystal might have educed from keratin layers or a cell-disintegrated layer adjacent to the matrix by a physicochemical rather than by a biochemical process. Production of cholesterol in the matrix may differ depending on the cell cycle. In cholesterol granuloma, cholesterol may be derived from blood with some other compositions such as albumin and cholestanol. although other sources cannot be denied. Crystallized cholesterol is treated by the surrounding tissue as a foreign body; this results in formation of granuloma. The Δ⁷-cholestenol is not involved in the biosynthesis of cholesterol in cholesterol granuloma.

Although acute mastoiditis and intracranial otogenic complications occur less frequently in our time than in the preantibiotic period, the disease is nevertheless still a rather severe medical problem. Its mortality rate remains relatively high and the severity of its symptoms is ofter underrated or misinterpreted by the inexperienced physician. On the basis of some personal clinical observations made during the last decade, attention has been drawn to the most common intracranial and extracranial otogenic complications in adults and children. It may therefore be concluded that otitis media must still be considered a dangerous disease, necessitating fundamental knowledge of its underlying pathology, which provides a basis of early correct diagnosis and adequate intensive therapy.

A series of 79 otic capsule fistulae occurring in 792 consecutive cases of chronic mastoiditis undergoing mastoidectomy was analyzed. The incidence (10%) is the same as in other large series, the primary difference being the location of the fistula. In all series cited, 90% of fistulae were in the lateral semicircular canal whereas in this series the comparable incidence was 75%. The 20 (25%) fistulae located in areas other than the lateral semicircular canal enabled us to document a method of “reading” the fistula test preoperatively to establish its precise location. Eye responses to the test and the fistula site were entirely consonant with the physiology of the vestibular system. The location of the fistula, in other words, can be reliably predicted by the eye movement. Clinicopathologic correlates are cited.