[Deafness. Diagnostic orientation].
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Deafness↗
Biomedical subjects
O Sterkers
Publications and source records attributed to O Sterkers.
Changes in the electrochemical composition of cochlear fluids after intracisternal application of doxorubicin in the rat.
Since doxorubicin (Adriamycin) is known to bind on membranous negative surface charges, its effect on the electrochemical composition of the cochlear fluids was studied in rats. Doxorubicin was infused into the cerebrospinal fluid via the lateral cerebral ventricle. The endocochlear resting potential was recorded, and endolymph and perilymph of the scala vestibuli were collected from the basal cochlear turn before and 1, 2, and 4 h after the drug application. Na+, K+, and Cl- concentrations and osmolality of the endolymph and perilymph were measured in 1 nl aliquots. In perilymph, Cl- concentration increased 4 h after doxorubicin treatment to reach a concentration 8 mM higher than recorded initially. In endolymph, the endocochlear potential decreased by 5 mV/h while its K+ concentration and osmolality increased by about 3 mM/h and 4 mosmol/kg H2O per hour, respectively. These results suggest that the negative surface charges demonstrated on Reissner's membrane may play a role in the homeostasis of endolymph.
Animals↗
Facial nerve neuromas: MR imaging. Report of four cases.
Four cases of facial nerve neuroma were evaluated by computed tomographic (CT) scan and magnetic resonance imaging (MRI). The extension of the tumor in the petrous bone or the parotid gland was well defined by MRI in all cases. CT scan was useful to demonstrate bone erosions and the relation of the tumor to inner ear structures. In cases of progressive facial palsy, CT and MRI should be combined to detect a facial neuroma and to plan the surgical approach for tumor removal and nerve grafting.
Adult↗
Haemangioma of the petrous bone: MRI.
Gd-DTPA-enhanced MRI provided accurate demonstration of the site and extension of a haemangioma of the petrous bone. Enhanced-MRI could allow early detection and differentiation from the other more common tumours of the geniculate ganglion area, thereby permitting the surgeon to remove the tumour, while preserving the facial nerve. CT is, however, required to display the characteristic ossification in these tumours.
Contrast Media↗
Secretion of endolymph by the isolated frog semicircular canal.
Secretion of endolymph is localized in some structures of the inner ear, namely the stria vascularis in the cochlea and the dark cells in the vestibule and in the lower vertebrate inner ear. In isolated semicircular canal it is possible to study separately the endolymphatic composition in the ampulla, which contains the dark cells, and in its non-ampullar part, which is devoid of these cells. Further, in vitro preparation of the semicircular canal provides access to both faces of the epithelium so that different agents can be applied separately to the apical or to the basolateral membranes of the epithelium. In this structure, the following results were obtained: i) in vitro, the semicircular canal secreted a K-rich, positively polarized fluid; ii) this fluid was secreted only in the ampulla of the semicircular canal; iii) the secretion of endolymph was dependent on basolateral Na+, K(+)-ATPase, inhibited by ouabain, and basolateral Na-K-Cl co-transporter, inhibited by bumetanide; iv) approximately 60% of luminal Na absorption occurred across a luminal Na channel inhibited by amiloride; v) the permeability of the paracellular pathway of the semicircular canal epithelium was 7.10(-7) cm/s. These results indicate that endolymph secretion involves basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter. An Na channel has been shown at the apical membrane.
Animals↗
Time-related alteration of endolymph composition in an experimental model of endolymphatic hydrops.
The electrochemical changes of the inner ear fluids were studied in the guinea pig during the development of endolymphatic hydrops in an experimental model of Meniere's disease obtained by the blockage of the vestibular aqueduct. The endocochlear potential (first and third turns) was recorded, and the sodium, potassium, and chloride concentrations, and osmolality of the endolymph (first and third turns) and perilymph were determined at different intervals from 2 to 24 weeks after the induction of the hydrops. The development of hydrops was monitored by the compound action potential once a week during the observation period. In normal, nonoperated guinea pigs, longitudinal endolymphatic gradients of endocochlear potential, potassium and chloride concentrations, and osmolality, increasing from the apex to the base of the cochlea, were observed. After 2 weeks of hydrops, no alteration of this pattern was detected. After 6 and 9 weeks of hydrops, a progressive decrease of endocochlear potential, potassium and chloride concentrations, and osmolality was noticed at the first turn (6 and 9 weeks) and then at the third turn (9 weeks) which resulted in the disappearance of longitudinal gradients. At 24 weeks, the endocochlear potential was still diminished by 60%, whereas potassium and chloride concentrations and osmolality increased as compared to 9-week values but remained lower than in controls. The changes in composition of endolymph induced by the development of the hydrops could be related to the progressive alteration of the ionic permeability of the cochlear epithelium, which should be localized at the distended Reissner's membrane.
Action Potentials↗
[Imaging of the facial nerve and the petrous apex].
From its origin in the pons to its extracranial exit with a long intrapetrous course, the facial nerve raises various diagnostic problems related to the site and extent of the lesions, which involves the whole field of petrous pathology. The study of the pathology of the neighbouring petrous apex completes this regional analysis. Today, in accordance with the anatomical loco-regional complexity, MRI is the predominant modality of diagnostic imaging (but must be associated with CT to allow the more accurate detection of subtle bone changes); it will be at best directed by the clinical and functional data which reflect the underlying pathophysiologic mechanisms.
Cranial Nerve Diseases↗
[Laser microsurgery of meningioma. An analysis of a consecutive series of 164 cases treated surgically by using different lasers].
Over a six years period, 224 laser procedures were performed in our clinic, of these 164 (72%) involved meningiomas of various intracranial and spinal locations; 82 (50%) tumors were located in the posterior fossa, 36 (32%) were suprasellar or parasellar meningiomas: a carbon dioxide laser was used in 56 cases, a double wave length YAG laser in 101 cases, and recently a simultaneous Nd YAG and CO2 combolaser in 7 cases. Complete tumor removal was accomplished in 83% of cases and overall mortality was 3%. We think that microscope guided laser techniques represents a significant advancement in the ability to remove deep situated meningiomas that might prove difficult to extirpate by conventional microsurgery. The advantages of these methods include: 1. reduced brain retraction; 2. the ability to operate with smaller and different exposures; 3. a reduced amount of mechanical manipulation by vaporizing in first the dural attachment; 4. improved operative precision and 5. decreased intra operative blood loss.
Adult↗
[Hemangioma of the petrous bone. Diagnosis and treatment].
Hemangiomas of the temporal bone are benign, vascular and are tumors. The diagnosis is in most cases made during the operation because the symptoms are non conclusive. Two cases were recently observed: one simulating a Meniere disease while the tumor was developed close to the jugular bulb and the endolymphatic sac; the second invaded the geniculate area and the petrous apex and was revealed by a progressive facial palsy.
Facial Paralysis↗
[Isolated vertigo disclosing infarction in the area of the posterior and inferior cerebellar arteries].
We report three cases of small cerebellar infarcts mimicking labyrinthine dysfunction. A sudden rotatory vertigo might be the only presenting symptom of a cerebellar infarct. In these cases, the clinical features may closely mimick an acute peripheral labyrinthine disorder. However, the absence of nystagmus or a direction changing nystagmus with different eye position and the normality of caloric responses may be suggestive of a cerebellar infarct. This syndrome may be explained by the involvement of the nodulus, part of the flocculo-nodular complex, that has primary vestibular connections. Cerebellar infarcts mimicking labyrinthine dysfunctions involved usually the cerebellar territory of the posterior inferior cerebellar artery (PICA). Infarcts may be limited to the territory of the medial branch of the PICA which supplies the nodulus.
Arteries↗
Antidiuretic hormone stimulation of adenylate cyclase in semicircular canal epithelium.
Basal adenosine 3',5'-cyclic monophosphate (cAMP) content and the modulation of its production were studied in the frog's semicircular canal epithelium. This epithelium secretes endolymph, a K(+)-rich, positively polarized fluid. The basal cAMP content measured by microradioimmunoassay was 244 +/- 14.2 fmol/structure per 5 min (n = 30). This content was increased about 8 times by 10(-5) M forskolin. Vasotocin, the frog antidiuretic hormone, increased the cAMP production by factors of 1.3 and 3.3 at concentrations of 10(-8) M and 10(-7) M, respectively. This stimulatory effect of vasotocin was blunted by the addition of alpha 2-adrenergic agonists, such as 10(-8) M-10(-5) M norepinephrine, in the presence of 10(-5) M propranolol, or 10(-5) M clonidine. Prostaglandin E2 at a concentration of 10(-8) M, which did not affect the cAMP production, did not modify the response to vasotocin. Glucagon (10(-6) M), calcitonin (10(-6) M), and parathyroid hormone (10 units/ml) did not affect the cAMP content. Prostaglandin E2 (10(-7) M) and the beta-adrenergic agonist isoproterenol (10(-6) M) stimulated the cAMP production by a factor of 1.6. These results indicate that the frog semicircular canal is a target of both vasotocin and catecholamines and that catecholamines through alpha 2-receptors modulate vasotocin-induced cAMP generation. Further, this interaction might be of physiological relevance in the modulation of ion transport in this structure.
Adenylyl Cyclases↗
Adenylate cyclase in the semicircular canal. Hormonal stimulation and ultrastructural localization.
The modulation of the cyclic AMP (cAMP) production and the cytochemical localization of adenylate cyclase were studied in isolated semicircular canal epithelium of the frog. The basal cAMP content, as measured by radioimmunoassay, was 344 +/- 37.8 fmoles/structure/5 min (mean +/- SEM, n = 41). This content was increased 6- to 8-fold by forskolin (10(-7) M to 10(-5) M). Among the tested drugs, only prostaglandin E2, isoproterenol, and vasotocin increased the cAMP production: 1.7-fold by prostaglandin E2 (1.5 X 10(-7) M) and isoproterenol (10(-6) M), and 1.3- and 3.3-fold by vasotocin at 10(-8) M and 10(-7) M, respectively. The addition of alpha 2-adrenergic agonists blunted the stimulatory effect of vasotocin. The adenylate cyclase was evidenced in both the basolateral and apical membranes of the dark cells. Vasotocin stimulated only the apical adenylate cyclase of dark cells. These results indicated that the adenylate cyclase located in the apical dark cells of the semicircular canal was stimulated by the antidiuretic hormone which may be involved in the regulation of the endolymph secretion.
Adenylyl Cyclases↗
[Experimental endolymphatic hydrops. Biochemical data in the guinea pig].
The electrochemical and osmotic composition of the inner ear fluids has been studied during experimental endolymphatic hydrops in guinea pig. The data showed that the modifications of the electrochemical composition of endolymph has been detected only after more than 2 weeks after the hydrops induction. The endocochlear potential, the K and Cl concentrations, and the osmolality progressively decreased between 6 and 9 weeks of hydrops. The longitudinal gradients disappeared. After 24 weeks of hydrops, the endocochlear potential was 50% of the initial value whereas the K and Cl concentrations and the osmolality were higher than that measured at 9 weeks but remained lower than contralateral, normal values. These results suggest that the alterations of the electrochemical and osmotic composition of endolymph that were observed during the evolution of experimental endolymphatic hydrops in guinea pig are related to an alteration of the permeabilities of the Reissner's membrane induced by an increase of hydrostatic pressure.
Animals↗
[Conference at the Salpêtrière. March 1989. Chronic unilateral conjunctivitis and progressive hearing loss in a 40-year-old woman].
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Adult↗
[Infratemporal extension of tumors of the skull base].
The tumors of the middle and posterior portion of the skull base may extend extracranially. The spread of the tumors towards the infratemporal fossa is rare. Among 23 skull base tumors with extracranial extension which were diagnosed during the last 5 years, only two middle ear epidermoid carcinomas extended into the infratemporal fossa. Subtotal surgical removal of tumors was obtained in both cases through a subtotal petrectomy with an ultrasonic aspiration of the extracranial extension followed by transcutaneous irradiation. One case is followed free of disease 2 years and a half after the beginning of the treatment. The spread of the tumor into the infratemporal fossa might not be of poor prognosis.
Aged↗
[Contribution of magnetic resonance imaging in the evaluation of chronic otitis].
Thirty four patients with a chronic otitis were evaluated prospectively by magnetic resonance imaging (MRI) to delineate its contribution in the diagnosis of middle ear masses. The results were correlated to the CT and the surgical and pathological findings. MRI permitted to differentiate the inflammatory tissues from either cholesteatoma, cholesterol granuloma and cerebromeningeal hernia.
Chronic Disease↗
[Meningocerebral hernia and defects of the tegmen. Diagnosis and surgical treatment].
Eight defects of the tegmen tympani or antri have been operated on during the last two years. Among these cases, 4 brain herniae were associated with the defect of the tegmen. Magnetic resonance imaging permitted to evaluate accurately the space occupying lesions into the mastoid cavity and disclosed the brain and/or meningeal herniations. The defect of the tegmen was oblitered through a middle fossa approach whereas the hernia was resected through a mastoid approach when necessary.
Adult↗