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PubMedDate not supplied

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.

Adult↗
PubMedDate not supplied

[The effects of methodical factors on the microphonic potential in the guinea pig cochlea with perfusion of perilymph].

The decreas in microphonic potentials detected from the round window (RMP) is negligible only if the bores are located very close to the round window, whereas it will increase with increasing distance from it. Only at pressures of more than +/- 30 cm water column, in rare cases even below that, will a sharp decrease in the RMP occur, possibly because of a lesion of either the oval or the round windown membrane. At a perfusion pressure above +5.6 cm water column, the perfusion liquid will enter the cerebrospinal fluid space. At a lower pressure the perfusion liquid is diluted by cerebrospinal fluid via the cochlear aqueduct. The perfusion speed of 1 to 50 mul/min has no effect on the function of the organ of Corti.

Action Potentials↗
PubMedDate not supplied

[Experimental perilymphatic fistula: the electrocochleographic findings].

The aim of the present study was to evaluate the effect of experimental perilymphatic fistula on cochlear electrophysiological responses. Six albino guinea pigs, in which recording electrodes were implanted in order to record the electrocochleogram, were used. Experimental protocol investigated cochlear responses before the induction of the fistula in the round window membrane perforation and then two month later. Compound action potential thresholds increased immediately after perforation of the round window membrane. The thresholds rapidly recovered. This phenomenon was accompanied by clear-Out reduction in amplitude upon suprathreshold stimulation. This latter observation associated with a decrease in the amplitude of the threshold seems to be a specific audiologic sign of the fistula. The clinical implication are discussed.

Acoustic Stimulation↗
PubMed2003

Perilymphatic gusher in stapedectomy: demonstration of a fistula of internal auditory canal.

Gusher is a very rare phenomenon, generally associated with congenital stapes fixation or otosclerosis in adult age, that may present during stapedectomy. A sudden perilymph flow occurs following platinotomy, due to congenital malformation (abnormally wide cochlear aqueduct or internal auditory canal fistula), that causes an abnormal connection between subarachnoid and perilymphatic spaces. This report deals with a case of bilateral gusher, occurring during stapedectomy, caused by an osseous fistula between bottom of internal auditory canal and the osseous labyrinth later observed at computed tomography scan. The usefulness of a radiologic examination is stressed for a correct therapeutic approach in the even contralateral ear stapedectomy.

Cochlea↗
PubMed1992

Etiology and treatment of fluid retention (hydrops) in Ménière's syndrome.

For years low sodium diets have been recommended in the treatment of Ménière's syndrome. Elevated levels of insulin play an important role in sodium retention in renal tubules. Insulin production is stimulated by high carbohydrate diets. Adrenaline, cortisone, and glucagon levels may be increased by stress or food or inhalant allergies, further elevating insulin levels. The end result of prolonged hyperinsulinemia includes vasoconstriction and eventually arterial smooth muscle hypertrophy. Individual susceptibility to Ménière's syndrome may occur as a result of inflammatory changes in the endolymphatic sac or cochlear aqueduct secondary to primary or latent viral infections, thus predisposing to fluid retention. Long term medical treatment of Ménière's should be directed towards preventing sodium retention through sodium restriction and carbohydrate management. Other factors including stress and allergy should also be considered.

Dietary Carbohydrates↗
PubMed2004

[Round window area temporal bone section versus CT].

OBJECTIVE: To locate round window area and its related structure on auris transection and CT for anatomical evidence of image diagnosis and clinical operation. METHODS: Fifteen normal head specimen fixed with 10% dehyde were scanned by high-resolution computed tomography on canthomeatal line. CT image (depth 1.00 mm, thick 1.00 mm) was obtained. Temporal bone-centered tissues were taken, decalcified, desiccated and socked with collodion, then embedded and made into sequential transactions (thick 1.00 mm). Lower surface of section was observed by both naked eyes and microscope, then scanned and photographed. Versus CT image, auditory ossicle, osseous semicircular canals, vestibule, round window, niche, cochlea, pyramidal eminence, internal acoustic meatus and cochlear aqueduct were identified respectively. RESULTS: There were 18-22 layers of temporal transection on CT image. Round window and round window niche always appeared on the 10th layer (R) and the 11th layer (L). The mean of the depth of anterior wall was 0.92 mm (R) and 0.90 mm (L), and depth 1.89 mm (R) and 2.04 mm (L). The average distance from niche to jugular fossa wall was 2.10 mm (R) and 2.39 mm (L). No significant difference among of thickness, depth and distance from niche to jugular fossa wall. CONCLUSIONS: Temporal bone transection specimen had a clear picture of anatomical position between round window area and its related structure. Versus CT, the result contributed to image diagnosis and operation on auris diseases.

Adult↗
PubMed1992

Electrocochleography in the diagnosis of perilymphatic fistula: intraoperative observations and assessment of a new diagnostic office procedure.

The intraoperative electrocochleogram (ECochG) was investigated during stapedectomy surgery and during cochleostomy surgery. This provided the justification for obtaining recordings with the oval window (OW) or round window (RW) intact and then when there was a definite fistula. It was noteworthy that no ECochG changes occurred on merely opening the OW or RW, but that marked changes occurred on removing perilymph, even by gentle suction. On raising the intrathoracic pressure and replacing the perilymph, the ECochG potentials usually recovered. Based on these intraoperative observations, an office procedure was designed. The subject was asked to raise the intrathoracic pressure on several occasions and changes in the amplitude of the ECochG potential were noted. An increase of over 15 percent in the action potential (AP), with or without a decrease in the negative summating potential (SP) during the period of raised intrathoracic pressure, was used as the diagnostic criteria for a perilymphatic fistula. A decrease in the AP with or without an increase in the negative SP immediately on relaxing after a period of raised intrathoracic pressure was also treated as a positive diagnostic criterion. Seventy-one normal ears were investigated and a positive result was recorded in two ears (false positive rate: 2.8%). Two hundred and six ears, strongly suspected as having a perilymph leak on the basis of the clinical history and vestibular signs have been investigated over the past 4 years. Ninety positive diagnoses have been reached and 46 of these ears have been surgically explored.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed2005

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.

Adult↗
PubMed2006

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.

Adult↗
PubMed1976

Experimental viral infections of the inner ear. I. Acute infections of the newborn hamster labyrinth.

Acute viral infections of the inner ear were produced in neonatal hamsters. Viruses were inoculated percutaneously through the temporal cartilage into the endolymphatic and perilymphatic spaces of the labyrinth or were inoculated intracerebrally to reach the perilymphatic spaces via the cochlear aqueduct. Selective vulnerability of inner ear structures was demonstrated using a variety of viruses. Influenza virus infected only the mesenchymal cells of the perilymphatic channels of the cochlea; mumps virus infected principally endolymphatic structures; herpes simplex virus infected primarily the sensory cells of the labyrinth; and rubeola and vaccinia viruses infected both perilymphatic and endolymphatic cells.

Acute Disease↗
PubMed1991

[Congenital cerebrospinal fluid pressure labyrinth].

The audiograms and CT scans of three children with a bilateral congenital mixed deafness are presented. Two children underwent an exploratory tympanotomy revealing a fixed stapes footplate: a perilymph gusher arose during platinotomy in both cases. The gusher was controlled successfully with a large fat graft in both children, and hearing remained unchanged. Two of the children were brothers: they had no other deformities except an enlarged fundus of the auditory canal on CT scans, and no clearly defined bony barrier to the vestibule, suggesting a cerebrospinal fluid fistula. Neither a patent nor an abnormal cochlear aqueduct could be detected in all three cases. It is likely that the three patients present an X-linked mixed deafness syndrome with fixation of the stapedial foot plate and perilymph gusher. A classification of congenital perilymph-CSF shunts is proposed.

Cerebrospinal Fluid Otorrhea↗
PubMed1990

[Effects of perilymphatic perfusion with cisplatin on the cochlear potential in guinea pigs].

The effects of three concentrations of cisplatin, administered by acute perilymphatic perfusion on the endocochlear potential (EP) and the cochlear microphonic potential (CM) of the guinea pig cochleae, at 1 kHz are reported. No change in EP magnitude was discovered and a concentration-dependent reduction in CM amplitude occurred during 60 minutes' perfusion period. The results suggest that cisplatin-induced hearing loss is not necessarily progressive degradation of EP.

Animals↗
PubMed1990

[Transient medium- and deep-tone hearing disorders following spinal anesthesia].

In a prospective study, 100 patients who underwent general surgical or urological operations under spinal anesthesia were examined to determine whether there was a relation between the anesthesia and postoperative hearing loss. Audiograms were performed preoperatively and as the 1st, 2nd, 3rd, and 5th postoperative days. It was found that 16 patients had impairment of hearing. The average ages of these patients were similar to those of the total population. The hearing loss was typical: only the frequencies between 125 and 2000 Hz were affected. It began on the 2nd day after spinal anesthesia and disappeared within 3 days without special therapy. The cause of this typical hearing loss after spinal anesthesia is a drop in cerebrospinal fluid pressure transmitted to the perilymph via the cochlear aqueduct. The change in the endoperilymphatic pressure difference results in a change in the oscillation of the basilar membrane. Because 16% of patients may suffer hearing loss after spinal anesthesia, it seems reasonable from a medicolegal point of view to explain the possibility of defective hearing to the patient.

Adult↗
PubMed1990

[Inner ear hearing loss following cerebrospinal fluid puncture: a too little appreciated complication?].

Lumbar puncture for myelography, spinal anaesthesia and aspiration of cerebrospinal fluid is a very common procedure. Although it has been known for a long time that hearing impairment may be a late complication, only a few case reports have been published, and not all have included audiograms. We present nine cases of hearing loss following myelography, lumbar puncture and spinal anaesthesia. It appears likely that this rare complication arises only in subjects with a wholly or partially patent cochlear aqueduct, allowing loss of perilymphatic fluid into the cerebrospinal space. Hearing loss was seen in eight of nine patients in the lower frequencies and in six of nine patients on both sides. Hearing recovered in six of nine patients. Transient hearing loss may occur more often than is generally assumed, and the symptom can remain unnoticed. Since not all of these hearing losses proved to be fully reversible, we suggest to inform patients about this complication for medico-legal reasons.

Adult↗
PubMed1989

[Idiopathic perilymph fistula].

This article presents 6 cases with idiopathic perilymph fistulae. The etiology of idiopathic perilymph fistula may be congenital malformation of the otic capule. Diagnosis of idiopathic perilymph fistula primarily depends on history and exploratory tympanotomy, but ENG-fistula test and positional audiometry are worth of diagnosing. During microsurgical procedure, attention must be paid to the presence of membrane of the round window niche. If a good repair of fistula is not followed by a good result, other lesions such as double labyrinth membrane rupture should be considered.

Adult↗
PubMed1989

Tolerance of membranous inner ear structures to pressure.

Pressure tolerance of round and oval labyrinthine windows and a cochlear segment represented by a part of the cochlear duct were investigated in experiments on cadaveric human temporal bones. The cochlear segment is less resistant than both the windows. Inner ear spaces are protected from pressure changes in the surroundings of the temporal bone by a system of narrow and comparatively long connections and some of them include also other structures strengthening the protective function (the valve described near the place where the cochlear aqueduct leads to scala tympani). Experiments with guinea pigs showed significance of inner ear integrity in protection from pressure changes. Tolerance of both windows was significantly higher in live animals than in cadaveric guinea pig bullae. Pressure tolerance of the windows was in turn higher in bullae than in isolated inner ear labyrinth. Conclusions were arrived at on the basis of the above facts that the inner ear is considerably resistant to pressure changes around it under normal circumstances. Ruptures in its parts appear only under special conditions and a number of factors participate in them. Window ruptures accompany most frequently injuries in other inner ear structures to which different degrees of hearing loss correspond. An isolated injury of windows is, from this viewpoint, rare even though it can be found and treated surgically best.

Animals↗
PubMed1979

[The venous drainage of the vestibular labyrinth in man (author's transl)].

The venous drainage of the vestibular division of the inner ear presents two different and separated routes. One, draining the central part of the sensorial areas (maculae and cristae), ends up into the vein of the cochlear aqueduct. The other drains the perypheral part of the sensorial areas as well as the simple endolymphatic walls and ends into the vein of the vestibular aqueduct. The latter vein shows close relationships to the endolymphatic sac.

Cochlea↗