An experimental study of inner ear injury in an animal model of eosinophilic otitis media

Conclusion:

As the periods of intratympanic injection of ovalbumin (OVA) to the middle ear became longer, marked eosinophil infiltration in the perilymphatic space was observed. Moreover severe morphological damage of the organ of Corti was observed in the 28-day antigen-stimulation side. These results indicate that eosinophilic inflammation occurred in the inner ear and caused profound hearing loss.

Objective:

The purpose of the present study was to elucidate the inner ear damage in a new animal model of eosinophilic otitis media (EOM) which we recently constructed.

Methods:

We constructed the animal model of EOM by intraperitoneal and intratympanic injection of OVA. Infiltrating cells and the inner ear damage were examined by histological study.

Results:

In the inner ear, a few eosinophils were seen in the scala tympani of the organ of Corti and the dilation of capillaries of the stria vascularis was observed in the 7-day stimulation side. In the 14-day antigen stimulation side, some eosinophils and macrophages were seen in not only the scala tympani but also the scala vestibule. In the 28-day antigen-stimulation side, severe morphological damage of the organ of Corti and many eosinophils, red blood cells, and plasma cells infiltrating the perilymph were observed.

Perilimphatic fistula test: a video clip demonstration

Perilymphatic fistula (PLF) is an abnormal condition in which a communication is present between the perilymphatic space of the inner ear and the middle ear or mastoid, secondary to a dehiscence in the otic capsule, oval or round window. LF may induce hearing loss, tinnitus, aural fullness, vertigo, disequilibrium, or a combination of these symptoms; the vagueness of symptoms caused by PLF and the lack of specificity of clinical signs and symptoms make the diagnosis elusive. We report a video of a positive PLF test induced by the application of pressure on the tragus, just anterior to the left external auditory canal in a patient with cholesteatoma and PLF of lateral semicircular canal confirmed by CT scan imaging. https://www.youtube.com/watch?v=x5MhSILF9O4.

Recurrent Diving-Related Inner Ear Barotrauma

OBJECTIVE

To present two cases of recurrent diving-related inner ear barotrauma (IEB) and to discuss the possible cause and pathogenesis of the increased inner ear vulnerability.

STUDY DESIGN

Case series.

SETTING

Tertiary referral center.

PATIENTS

Two scuba divers suffering from repeated cochleovestibular barotrauma.

INTERVENTIONS

Neurotological evaluation, perilymphatic fistulae repair, and conservative treatment.

MAIN OUTCOME MEASURE

The increasing popularity of scuba diving expose the individuals involved in this sport to unique pathologies that are not common under terrestrial conditions. The otolaryngologist who is involved in the care of these patients is required to diagnose and treat diving-related ear injuries and to consider the risk for recurrent inner ear injury when diving is resumed.

CONCLUSION

IEB carries a risk for permanent hearing loss and chronic vestibulopathy. We recommend complete neurotological evaluation including high-resolution CT of the temporal bones as a routine workup for IEB. The presence of a significant residual sensorineural hearing loss, evidence for noncompensated vestibular damage, and CT findings of possible enhanced cerebrospinal fluid-perilymph connection should be considered when a return to diving activity is considered.

Noise-induced perilymph fistula

Perilymph fistulae are difficult to diagnose because they present with a wide variety of signs and symptoms, they are associated with many etiologies, and they often mimic other conditions. In this article, we describe a case of perilymph fistula that featured one of its more rare causes: acoustic trauma--specifically, damage from a loud blast from the siren of a fire engine. We also review the literature and discuss the difficulties of diagnosis and treatment and the possible mechanisms by which acoustic trauma and other etiologies cause perilymph fistulae.

Persistence of perilymph fistula mechanism in a completely paretic posterior semicircular canal

The three dimensional eye movements (search coil technique) of a patient with a completely paretic left posterior semicircular canal as a result of a perilymph fistula (PLF) were studied. The patient still exhibited pressure induced nystagmus that obeyed Ewald's first law. This finding cannot be explained by otolith stimulation, but might indicate that PLF mechanisms either persist in canal plugging or act on the ampulla by directly deflecting the cupula.

Ventriculoperitoneal shunt as treatment for perilymphatic fistula: a report of six cases

We report six cases of perilymphatic fistula in patients who received ventriculoperitoneal shunts as part of their final mode of therapy. The last of our 6 patients actually received a ventriculoperitoneal shunt as her initial mode of therapy. All but one had benign intracranial hypertension. All six felt better (less disequilibrium, tinnitus, and pressure and occasional hearing improvement) after LP with removal of 15-20 ml of cerebrospinal fluid.

[Validation of a clinical scale for the diagnosis of perilymphatic fistula]

INTRODUCTION

The diagnosis of perilymphatic fistula (PLF) is difficult because no single clinical situation gives the diagnosis for sure. The goal of this article is to study the clinical situations where you must suspect a PLF and to support a clinical scale described in a previous work (Bussières et al 2003).

METHODS

Retrospective study of 15 patients that had an exploratory tympanotomy with a PLF not confirmed preoperatively. An analysis of the symptoms, signs and complementary exams were done. The surgical technique and findings and the postoperative evolution were noted.

RESULTS

There is 66.7% of hypoacusis the most frequently symptom (postoperative improvement of 26.7%); after came vertigo present in 60% (postoperative improvement of 44.4%) and tinnitus present in 53.3% (postoperative improvement of 25%). The trauma history is always positive, most of then is typical (80%) and the other one are atypical (20%).The diagnosis of PLF has been determined in 5 patients in the follow-up according to the improvement of the symptoms. These patients had a score > 7 at the clinical scale.

CONCLUSION

The sensibility and specificity scores of the clinical scale are respectively 100% and 70% in this study.

Sudden hearing loss due to large vestibular aqueduct syndrome in a child: should exploratory tympanotomy be performed?

A 16-year-old girl applied to our ENT clinic with a 3-day history of right hearing loss, tinnitus, and pressure in the right ear. She had had surgery for right perilymph fistula two times, one at the age of 7 and the second at the age of 9. She had recovered after both of these surgeries. This time she had exploratory tympanotomy and perylymh fistula was detected. Computerized tomography investigation obtained after 5 days postoperatively showed bilateral large vestibular aqueducts and otherwise normal inner ear structures. Thyroid function tests and neck palpation were normal. It was an unusual case with both large vestibular aqueduct syndrome (LVAS) and simultaneous spontaneous perilymph fistula.

Evaluating patients with vertigo: bedside examination

Dizziness and vertigo are common complaints in patients referred for neurological evaluation. With a basic understanding of vestibular physiology and proper examination techniques, a correct diagnosis can generally be made at the bedside. This article reviews the most common peripheral and central vestibular syndromes as well as the key elements of the bedside vestibular system examination.

Can low frequency sound stimulation during posturography help diagnosing possible perilymphatic fistula in patients with sensorineural hearing loss and/or vertigo?

Perilymphatic fistula (PLF) is often difficult to diagnose because of the similar symptomatology, such as vertigo, tinnitus and hearing loss, which is found in several inner ear diseases. We attempted to correlate a positive result of low frequency sound (LFS) stimulation tests in posturography with the presence or absence of a PLF confirmed by transtympanic endoscopy in 209 patients with various inner ear diseases (Meniere's disease ( n=128), vestibulopathy ( n=41), cochleopathy ( n=28) and sudden deafness ( n=12). LFS provoked unsteadiness in posturography without PLF in 24 patients with Meniere's disease, in 5 patients with vestibulopathy, in 3 patients with cochleopathy and in 2 patients with sudden deafness. In one patient, tympanoscopy revealed fistula in the round window membrane that was covered with a fibrinous layer. In four cases there was abnormal light reflex in the round window but without PLF. In eight cases, Hennebert's sign was present with nystagmus, without PLF. We conclude that pathological responses to the LFS test in posturography can also be encountered in other inner ear diseases without PLF.

Contrast enhancement of the cochlear aqueduct in MR imaging: its frequency and clinical significance

There have been no previous reports on contrast enhancement of the cochlear aqueduct in magnetic resonance imaging. The purpose of the present study was to evaluate the frequency and significance of this finding. Thirty-one patients (15 men and 16 women; age range 18-81 years) with otologic symptoms (sudden sensorineural hearing loss, vertigo, or tinnitus) were examined using contrast-enhanced imaging on a 1.5-T MR scanner. The normal ear served as the control. Two radiologists evaluated contrast enhancement in the area of the cochlear aqueduct. Forty-eight of 62 ears (77.4%) showed contrast enhancement of the cochlear aqueduct, but no significant differences in the frequency of contrast enhancement were observed between patients with and patients without vertigo, tinnitus, sensorineural hearing loss, cerebellopontine angle tumors, or a high-riding jugular bulb. In addition, no gender- or age-related differences were noted. Contrast enhancement of the cochlear aqueduct was frequently observed, but the frequency of enhancement in symptomatic ears was not significantly higher than in control ears. The results of this study may prove helpful in avoiding unnecessary examinations and potential diagnostic confusion.

Anatomic landmarks of the glossopharyngeal nerve: a microsurgical anatomic study

OBJECTIVE

Compared with other lower cranial nerves, the glossopharyngeal nerve (GPhN) is well hidden within the jugular foramen, at the infratemporal fossa, and in the deep layers of the neck. This study aims to disclose the course of the GPhN and point out landmarks to aid in its exposure.

METHODS

The GPhN was studied in 10 cadaveric heads (20 sides) injected with colored latex for microsurgical dissection. The specimens were dissected under the surgical microscope.

RESULTS

The GPhN can be divided into three portions: cisternal, jugular foramen, and extracranial. The rootlets of the GPhN emerge from the postolivary sulcus and course ventral to the flocculus and choroid plexus of the lateral recess of the fourth ventricle. The nerve then enters the jugular foramen through the uppermost porus (pars nervosa) and is separated from the vagus and accessory nerves by a fibrous crest. The cochlear aqueduct opens to the roof of this porus. On four sides in the cadaver specimens (20%), the GPhN traversed a separate bony canal within the jugular foramen; no separate canal was found in the other cadavers. In all specimens, the Jacobson's (tympanic) nerve emerged from the inferior ganglion of the GPhN, and the Arnold's (auricular branch of the vagus) nerve also consisted of branches from the GPhN. The GPhN exits from the jugular foramen posteromedial to the styloid process and the styloid muscles. The last four cranial nerves and the internal jugular vein pass through a narrow space between the transverse process of the atlas (C1) and the styloid process. The styloid muscles are a pyramid shape, the tip of which is formed by the attachment of the styloid muscles to the styloid process. The GPhN crosses to the anterior side of the stylopharyngeus muscle at the junction of the stylopharyngeus, middle constrictor, and hyoglossal muscles, which are at the base of the pyramid. The middle constrictor muscle forms a wall between the GPhN and the hypoglossal nerve in this region. Then, the GPhN gives off a lingual branch and deepens to innervate the pharyngeal mucosa.

CONCLUSION

Two landmarks help to identify the GPhN in the subarachnoid space: the choroid plexus of the lateral recess of the fourth ventricle and the dural entrance porus of the jugular foramen. The opening of the cochlear aqueduct, the mastoid canaliculus, and the inferior tympanic canaliculus are three landmarks of the GPhN within the jugular foramen. Finally, the base of the styloid process, the base of the styloid pyramid, and the transverse process of the atlas serve as three landmarks of the GPhN at the extracranial region in the infratemporal fossa.

[When to suspect a perilymphatic fistula?]

INTRODUCTION

The diagnosis of perilymphatic fistula (PLF) is difficult since no single clinical situation gives the diagnosis for sure. The goal of this study is to clarify the clinical situations where you must suspect a PLF.

METHODS

Retrospective study of 20 patients that had an exploratory tympanotomy with a PLF confirmed peroperatively. An analysis of the symptoms, signs and complementary exams was done. The surgical findings and the postoperative evolution were noted.

RESULTS

100% of patients reported a hearing loss, 80% vertigo, 70% a tinnitus and 35% equilibrium problems. Every patient had an etiological event to explain the PLF (trauma 85%), stapedotomy (10%), other ear surgeries. Five patients had a positive fistula or Vasalva test. All patients except one had an hearing loss on the audiogram (sensorineural, mixte or conductive). 50% had a CT scan, 70% of which were abnormal. A VNG was done on 3 patients. The sites of the PLF were as follows: 90% oval window, 5% round window and 5% both windows. The hearing got better or was stabilised in 95% of patients after the operation. 64% saw an improvement of their tinnitus and 87% of their vertigo.

CONCLUSION

The diagnosis of PLF is difficult and a high index of suspicion is mandatory. One must look for an etiologic situation to explain the PLF. The audiogram is almost always modified, a mixte hearing loss being common due to the high incidence of ossicular trauma associated with PLF. The clinical clinical situations where you must suspect a PLF were identified as follows: An old trauma, a recent trauma, a history of otologic surgery particularly on the stapes and a preexisting hearing loss that aggravates. A diagnosis scale to evaluate the risk of PLF, based on clinical situations, physical exam and complementary exams was done to help the clinician in the evaluation of PLF.

[Perilymphatic fistula: report of a case which resolved spontaneously in five days and literature review]

AIMS

We report a patient with a perilymphatic fistula and review the literature on this topic.

CASE REPORT

The patient was a 50 years old male with a five days history of intense and continuous vertigo associated with nausea, vomiting and sweating, which was initiated after a sudden noise in the left ear. The symptoms resolved spontaneously over five days, without surgical treatment. The clinical picture resembles those previously reported for perilymphatic fistula. The current literature on this topic has been reviewed in this article.

CONCLUSION

The patient presented an early recovery, what corroborates the current tendency of waiting a few weeks before indicating surgery.

Perilymphatic fistula

A perilymph fistula is an abnormal connection between the inner and middle ear that allows escape of perilymph fluid into the middle ear compartment. The clinical symptomatology that follows leakage of fluid is by and large indistinguishable from a number of other pathologies that affect inner ear function. Definite diagnostic proof of a perilymph fistula remains elusive, and methods of diagnosis remain controversial. Traumatic tears in the oval or round windows remain a major cause of perilymph fistula, yet an index of suspicion in traumatic brain injury frequently remains low. The diagnosis of perilymph fistula must always be considered in the appropriate clinical setting of head trauma, barotrauma, and in patients with unresolved and undiagnosed episodes of recurrent vertigo or hearing loss. Surgical treatment with patching of oval and round windows remains the mainstay of therapy for this condition.

[Inner ear and subarachnoid spaces: relations and diseases]

The purpose of this article is to describe, with 5 clinical cases, the physiological communications between the inner ear and the subarachnoid spaces (SAS) and present the imaging features with regard to. Therefore we briefly illustrate abnormal communications between SAS and perilymphatic fluids in certain cochlear and internal acoustic meatus (IAM) malformations and their consequences. Imaging features may depict diffusion pathway of bacterial meningitis to membranous labyrinth via the cochlear aqueduct or via the IAM. Rarely, in some patients referred for cochleovestibular symptoms, imaging features may display skull base tumors involving the area of cochlear or vestibular aqueduct aperture. Therefore, in patients referred for cochleovestibular symptoms, MR and CT study should carefully scrutinise not only the IAM but also the aperture of the cochlear and the vestibular aqueducts and the cerebellopontine meninges.

MR cisternography of the cerebellopontine angle: comparison of three-dimensional fast asymmetrical spin-echo and three-dimensional constructive interference in the steady-state sequences

BACKGROUND AND PURPOSE

MR cisternography has been used as the noninvasive screening tool of the cerebellopontine angle. The purpose of this study was to directly compare two currently dominant types of sequences for heavily T2-weighted MR cisternography.

METHODS

Three-dimensional fast asymmetric spin-echo (3D-FASE) sequences, which are 3D half-Fourier rapid acquisition with relaxation enhancement and 3D constructive interference in the steady-state (3D-CISS) sequences, were compared on a clinical 1.5-T MR unit using the same scan times. In five healthy volunteers, the contrast-to-noise ratio (C/N) between CSF and the cerebellum was measured at three locations. Then, for qualitative analysis, the quality of the labyrinth was scored on the original source multiplanar reformatted images, the virtual endoscopic images, and the maximum intensity projection (MIP) images. In 20 consecutive patients with suspected cerebellopontine angle tumors, visualization of the tumors was evaluated using 3D contrast-enhanced spoiled gradient-echo imaging as the standard of reference.

RESULTS

Both sequences showed comparable mean C/N values; however, in qualitative analysis, the scores for 3D-CISS on the source, virtual endoscopic, and MIP images were significantly lower than those on the images obtained with 3D-FASE, owing to more prominent flow and magnetic susceptibility artifacts on the 3D-CISS sequences. In all subjects, discontinuity of the semicircular canals was seen on the virtual endoscopic and MIP images obtained with 3D-CISS, owing to susceptibility artifacts, but not on those obtained with 3D-FASE. All 12 tumors were detected by both sequences, but 3D-CISS gave one false-positive result.

CONCLUSION

3D-FASE is considered the method of choice because artifacts are reduced and specificity is increased.

Temporal bone findings in multiple endocrine neoplasia type 2B

To our knowledge, present case is the first published report of temporal bone findings in multiple endocrine neoplasia type 2B (MEN-2B). We describe a 43-year-old Japanese man with medullary thyroid carcinoma (MTC), pheochromocytoma, mucosal neuroma and a Marfanoid body habitus. The collateral adrenal tumors and MTC were removed surgically. However, 14 years after surgery, the MTC and pheochromocytoma recurred and the patient died of intracranial hemorrhage due to hypertension. During the autopsy, metastatic MTC was detected in the liver, lungs, kidneys, pancreas and cervical lymph nodes. Recurrent pheochromocytoma was present in the right kidney. Mucosal neuromas were found in the tongue, gastrointestinal tract and vesical nerve plexus. The following histopathological findings were seen in both temporal bones: metastatic MTC was found as well as neuromas and the cochlear aqueduct was widely patent.

[Rupture of the round window--detection with fluorescence endoscopy]

Rupture of the round window membrane as a special cause of inner ear deafness is widely accepted after changing pressure levels, e.g. in diving. However, even without a barotrauma before, the spontaneous rupture of the round window membrane is suspected occasionally in patients with sudden hearing loss and/or vertigo and tinnitus. To carry through the tympanotomy is decided by ENT surgeons often in cases of progressive hearing loss despite infusion therapy. Perilymph fistulas have been detected relatively seldom, compared to the number of reported operations by several authors. However, covering the round niche with connective tissue leads to the improvement of symptoms sometimes even in cases without microscopical evidence of fistula. Within the last 3 years 14 patients suffering sudden hearing loss of one ear underwent tympanotomy in our department. Of these patients 8 reached restitution of the hearing ability. Especially 2 patients with sudden deafness caused by spontaneous rupture of the round window membrane are reported in the following article. Perilymph fistulas were detected in these cases by IV-application of fluorescein and fluorescence endoscopy of the middle ear. Both patients obtained a normal hearing curve within 1 week after surgical intervention and obliteration of the round niche.

Petrous high jugular bulb: a histological study

PURPOSE

A high jugular bulb (JB) is thought to affect structures of the inner ear and possibly cause symptoms there, but clear histological findings of an anatomical relationship between a high JB and the inner ear have not yet been described.

MATERIALS AND METHODS

We surveyed horizontal sections of 1,591 temporal bones from the collection of the Otopathology Laboratory at the University of Minnesota in Minneapolis, Minnesota, defining a high JB as a JB extending above the inferior margin of the basal cochlear turn.

RESULTS

In 65 specimens (16%), we found a high JB with its vascular wall obviously thinner than that of a low JB. Bony resorption was occasionally observed around high JBs. Sixteen specimens showed a bony deshiscence between the JB and the endolymphatic sac. Clinical charts showed no obvious symptoms associated with a high JB.

CONCLUSIONS

Our findings suggest that the JB may have potential to expand upward postnatally. Although our study confirmed occasional bony dehiscence between the JB and the endolymphatic sac, JBs with this involvement may have only a minor effect on function in the inner ear.

Beta-2 transferrin assay in the identification of perilymph

HYPOTHESIS

Western blot assay for beta-2 transferrin protein is a clinically useful method for the detection of human perilymph and should be used for the diagnosis of perilymph fistulas (PLFs).

BACKGROUND

Considerable controversy exists regarding the diagnosis of PLF. Recent studies suggest that the detection of beta-2 transferrin protein may be useful in the identification of perilymph.

METHODS

To evaluate the usefulness of the beta-2 transferrin assay for identifying human perilymph, paired perilymph samples and negative controls were collected on Gelfoam pledgets from 20 patients who had surgery that opened the inner ear. Blinded immunoelectrophoretic assay (Western blot) for beta-2 transferrin was performed on each specimen.

RESULTS

Only one (5%) of the known perilymph samples and none of the control specimens were definitely positive for beta-2 transferrin. Combined with historical data, this assay has 29% sensitivity, 100% specificity, 100% positive predictive value, and 31% negative predictive value.

CONCLUSIONS

These findings suggest that the beta-2 transferrin protein assay may not be a reliable method for detecting human perilymph when performed using this technique.

Sudden hearing loss: frequency of abnormal findings on contrast-enhanced MR studies

BACKGROUND AND PURPOSE

Our purpose was to determine the frequency of abnormal findings on contrast-enhanced high-resolution MR imaging studies in patients with sudden hearing loss.

METHODS

Seventy-eight consecutive patients with sudden hearing loss underwent contrast-enhanced MR imaging of the temporal bone, cerebellopontine angle, and brain. Additional tests included audiologic examination, electrocochleography, fistula tests, and serologic tests for viral agents and autoimmune disorders.

RESULTS

Probable causes of the sudden hearing loss in these patients included viral or immune-mediated disease, Meniere disease, vascular disorder, syphilis, neoplasm, multiple sclerosis, and perilymphatic fistula. Twenty-four (31%) of the 78 patients were found to have abnormal imaging results early in the course of their work up and treatment.

CONCLUSION

The prevalence of abnormal findings on contrast-enhanced MR studies is higher than previously reported in patients with sudden hearing loss.

The cochlear aqueduct: an important landmark in lateral skull base surgery

The cochlear aqueduct (CA) is used as a landmark in lateral skull base surgery. In this study anatomic relationships between the CA and adjacent neurovascular structures were examined by dissecting 32 temporal bones. Observations of the relationship of the external opening (EO) of the CA with the ninth, tenth, and eleventh cranial nerves, inferior petrosal sinus (IPS), and intrapetrous carotid artery (ICA) were noted. In addition to the distance of the EO of the CA to the vertical portion of the ICA, the entire length of the CA and the width of the EO were also measured. The ninth nerve was the only structure lodged at the EO of the CA in 34.4% of bones. However, in 40.6% of bones only the IPS crossed the EO of the CA, although the ninth nerve was situated just anteroinferiorly in the vicinity of the EO. In 15.6% of bones it was possible to observe both the ninth nerve and the IPS crossing the EO. In 9.4% of bones the EO of the CA was found to be occupied by the tenth and eleventh nerves. It was also observed that the ICA was located anteriorly on the same sagittal plane with the EO in 15.6% of bones. It was concluded that although in 90% of cases the EO of the CA was in close relation with the ninth nerve, other structures such as the IPS, the tenth and eleventh cranial nerves, and the ICA were also at risk during drilling in this area because of their intimate relationships with the EO of the CA.

The cochlear aqueduct in pediatric temporal bones

The cochlear aqueduct is a bony channel which contains the fibrous periotic duct and connects the perilymphatic space of the basal turn of the cochlea with the subarachnoid space of the posterior cranial cavity. Previous histological studies suggested that patency depended on age, whereas a more recent study showed no statistical correlation between age and patency. To clarify patency in pediatric cochlear aqueducts, we selected 21 temporal bones from 12 infants and children, varying in age from birth to 9 years, in which the cochlear aqueduct was fully visible on one histological section. Photographs were taken for documentation and the length and width of the orifice of the external aperture of the aqueduct at the scala tympani were measured and followed to the internal aperture at the subarachnoid space. The lumen of the duct was examined for mononucleated cells, blood cells and fibrous tissue. Measurements revealed that the mean length of the cochlear aqueduct was 4.6 mm (range, 2.4-10.7 mm), mean width of the external aperture was 484 microm (range, 225-869 microm), and mean width of the internal aperture was 1293 microm (range, 699-2344 microm). The mean diameter of the narrowest part (isthmus) was 151 microm (range, 75-244 microm). In all temporal bones the cochlear aqueduct was patent, with one exception. This latter temporal bone was from a 2-month-old girl with multiple intralabyrinthine anomalies, with the missing cochlear aqueduct believed to be due to an aplasia. Our results support prior measurements of the cochlear aqueduct and demonstrate a short and patent cochlear aqueduct in newborns. With growth, a significant increasing length of the duct was found.

High-resolution T2-weighted MR imaging of the inner ear using a long echo-train-length 3D fast spin-echo sequence

The purpose of this study was to assess the value of a long echo-train-length 3D fast spin-echo (3D-FSE) sequence in visualizing the inner ear structures. Ten normal ears and 50 patient ears were imaged on a 1.5T MR unit using a head coil. Axial high-resolution T2-weighted images of the inner ear and the internal auditory canal (IAC) were obtained in 15 min. In normal ears the reliability of the visualization for the inner ear structures was evaluated on original images and the targeted maximum intensity projection (MIP) images of the labyrinth. In ten normal ears, 3D surface display (3D) images were also created and compared with MIP images. On the original images the cochlear aqueduct, the vessels in the vicinity of the IAC, and more than three branches of the cranial nerves were visualized in the IAC in all the ears. The visibility of the endolympathic duct was 80%. On the MIP images the visibility of the three semicircular canals, anterior and posterior ampulla, and of more than two turns of the cochlea was 100%. The MIP images and 3D images were almost comparable. The visibility of the endolymphatic duct was 80% in normal ears and 0% in the affected ears of the patients with Meniere's disease (p < 0.01). In one patient ear a small intracanalicular tumor was depicted clearly. In conclusion, the long echo train length T2-weighted 3D-FSE sequence enables the detailed visualization of the tiny structures of the inner ear and the IAC within a clinically acceptable scan time. Furthermore, obtaining a high contrast between the soft/bony tissue and the cerebrospinal/endolymph/ perilymph fluid would be of significant value in the diagnosis of the pathologic conditions around the labyrinth and the IAC.

Perilymph detection by beta 2-transferrin immunoblotting assay. Application to the diagnosis of perilymphatic fistulae

beta 2-Transferrin, the asialotransferrin, is found in cerebrospinal fluid (CSF) and inner ear perilymph, but is absent from serum and other body fluids or secretions except the aqueous humor. The detection of this asialo-fraction of the transferrin in ear fluid microsamples with an immunoblotting technique is of great interest when a perilymphatic fistula (PLF) is suspected. beta 2-Transferrin was detected on microsamples collected by syringe or on micro-collagen sponges from 30 patients undergoing ear surgery. The problem is reviewed, the technique and sample preparation are explained and the results discussed. beta 2-Transferrin detection in the ear fluid allows the identification of perilymph, except in the CSF oto- or rhinorrheal context, and is proposed as a promising test to confirm perilymphatic fistula.

On the pathomechanism of cochlear dysfunction in experimental perilymph fistulas

The mechanism leading to hearing impairment in perilymph fistulas was investigated in guinea pigs with perforated round window membranes (RWM) by analyzing alterations of inner ear fluid pressure, changes of auditory function following manipulations to get presumed air bubbles out of the cochlea ("positional audiometry"), and temporal bone sections. The instantaneous loss of normal positive inner ear fluid pressure after RWM perforation had no immediate effect on auditory function. Inner ear pressure was restored 4 days following RWM perforation. "Positional audiometry" was negative in guinea pigs with perforated RWM. All ears in which auditory thresholds had increased had additional iatrogenic lesions at the spiral lamina. Fistulas in the RWM per se do not affect auditory thresholds. The question of the surgical repair of fistulas was not directly addressed; it only can be concluded that there are no direct sequelae of an isolated fistula which induce auditory impairment and which could be prevented by surgical repair of the fistula.

Hearing loss and pneumococcal meningitis: an animal model

Clinical studies of predisposing factors in the development of hearing loss secondary to bacterial meningitis have produced conflicting results. An animal model of meningogenic labyrinthitis was developed for more precise study of these parameters. Rabbits were inoculated intrathecally with 10(5) pneumococci to induce meningitis. Hearing thresholds were measured using auditory-evoked responses to 1 kHz, 10 kHz, and click stimuli before infection and every 12 hours thereafter. Profound deafness occurred in all subjects at an average of 48 hours following infection. The incidence and severity of hearing loss was strongly correlated with the duration of meningitis. Temporal bone histology revealed acute inflammation of all perilymphatic spaces including the cochlear aqueduct. This model demonstrated that the risk and severity of hearing loss increase with the duration of meningitis and suggested that the cochlear aqueduct is an anatomic pathway for the extension of infection from the cerebrospinal fluid to the cochlea. The implications for therapy in humans is discussed.

Venous communications of the cochlea after acute occlusion of the vein of the cochlear aqueduct

The vein of the cochlear aqueduct (VCAQ) is the principal drainage vein of the cochlea in the guinea pig. Morphological observations of the VCAQ and its adjacent structures were made by studying serial sections of the cochlea. We detected the presence of two collateral vessels from the mucoperiosteal veins of the middle ear which communicated with the VCAQ. Following acute occlusion of the VCAQ, marked dilatations of these vessels were observed in corrosion cast preparations. Our findings suggest that these vessels act as collateral veins following acute venous congestion of the inner ear.

Morphological changes in the cochlear aqueduct following herpes simplex virus inoculation into the subarachnoid space

Type 1 herpes simplex virus (HSV-1) was inoculated into the subarachnoid space through the cisterna magna of guinea pigs to study morphological changes of the inner ear and the ability of the cochlear aqueduct to protect the inner ear. Although most of the animals developed clinical manifestations of meningoencephalitis within a few days after inoculation, Preyer's reflex remained intact. Scanning electron microscopy revealed some significant changes in the cochlear aqueduct. Lymphocytes and macrophages were predominant, with narrowing of reticular tissue spaces caused by the swelling of the periotic duct tissue. The cribriform structure of the internal orifice of the cochlear aqueduct appeared to be completely obstructed, whereas it was normal in the presence of bacterial infection as previously reported (1). The morphological changes were confined to the cochlear aqueduct.

History taking in dizziness. The most important diagnostic step

When faced with a complaint of dizziness, the primary care physician may be tempted to assume that the cause is inner ear dysfunction and that the patient needs to be referred to an otologist. According to Dr Hybels, however, most dizzy patients do not have an ear problem and a carefully executed history is likely to pinpoint the correct diagnosis. The following article delineates the fine points of history taking and discusses some of the most common causes of dizziness.

Defense mechanism of the cochlear aqueduct against infection. A morphological study in the guinea pig

Guinea pigs were used in this study. Physiological saline, india ink, and Staphylococcus aureus were injected into the cisterna magna, and S. aureus was also injected into the scala tympani. Changes in the microstructure of the cochlear aqueduct were observed by light microscopy and also by scanning electron microscopy, mainly by means of fracture preparations. From these experimental results, it could be confirmed that the periotic duct tissue of the cochlear aqueduct reacted especially to bacterial infection.

Cochlear aqueduct radiographic anatomy in temporal bone preparations and in sudden hearing loss

Sudden sensorineural hearing loss appears to have many possible etiologic factors. Shea has presented work indicating that a large cochlear aqueduct (CA) is frequently present on the side of an idiopathic sudden sensorineural hearing loss (ISHL). However, Valvassori, on performing temporal bone tomographic studies on several hundred patients complaining of ISHL, has not found enlargement of the CA in a statistically significant number of these cases. In an attempt to resolve this discrepancy, a single blind study was performed utilizing temporal bone polytomography to evaluate the presence or absence of the CA in 22 adult patients. One-half of these patients had a history of ISHL, while the remaining patients had other complaints as an indication for tomography. In all cases, the CA was identified. The CA was felt to be enlarged in 1 patient suffering from ISHL, in the nonaffected ear of 1 patient with unilateral ISHL, and in 2 control patients. There was, therefore, no positive correlation between CA enlargement and the occurrence of ISHL. In order to further elucidate the radiologic anatomy of the CA, 9 pairs of adult temporal bones removed at autopsy were studied by polytomography after cannulation and injection of radiopaque material. Measurements of the dimensions of the CA and its radiographic anatomy are discussed and compared to measurements obtained from histopathologic evaluation of the temporal bone.

Necrotizing ("malignant") external otitis histopathologic processes

The histologic findings in a serially sectioned temporal bone, from a patient who succumbed to brain abscess secondary to necrotizing ("malignant") external otitis, are described. The mechanism of invasion of the ear canal appears to be due to local bone necrosis. This in turn extends to the submucosal vasculature of the pneumatic spaces. The infective process extends submucosally, establishing one or several sites of bone destruction. The lumen of the pneumatic space is not involved. In this process, the periphery of the fibrous inflammatory tissue formation is the site of active bone destruction. In pneumococcal petrositis, the peripheral fibrous elements are protective. The process in malignant external otitis may extend directly to adjacent central nervous system structures inoculating the structure with Pseudomonas. Development of Pseudomonas brain abscesses can be slow, allowing for new bone closure of the site from which the infection spreads as demonstrated in this specimen. Therefore, apparent local control of the disease can be established while a central infective process progresses.

Congenital cerebrospinal otorrhea

Four locations for congenital cerebrospinal fluid fistula in the region of a normal labyrinth are reviewed. A congenital leak may occur through the petromastoid canal, a wide cochlear aqueduct, Hyrtl's fissure, or the facial canal. A fistula through the initial segment of the fallopian canal was successfully repaired in a two-year-old boy who had three episodes of meningitis following otitis media. Knowledge of these four sites of congenital defects provides a guideline for the surgeon in the identification and repair of cerebrospinal fluid leaks in the region of the labyrinth.

The cochlear aqueduct: structural considerations

Perusing 170 series of temporal bone sections, the course of the aqueduct was found to be a spindle shape, based on numerous dilatations in the middle section. Ample space was offered for development of bony excrescences such as exostotic depositions and osteoma-like protrusions of all sizes. These added considerably to the difficulties of a free passage through the aqueduct.