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[Diagnosis of vestibular disorders in the hypothalamic syndrome].

Employing clinical and electrophysiological research methods, 40 patients with the hypothalamic syndrome (HS) were examined with special emphasis on the function of the vestibular system. Polygraphic recording (EEG, ENG, EMG and ECG) was made in the alert state, during drug-induced sleep, and immediately after awakening. An analysis of the clinical and electrophysiological correlations prompted the conclusion that the HS is associated with variable disturbances of vestibular function which objectively confirm the presence of the HS and may contribute to the differential diagnosis of the disease.

Adolescent↗

Unilateral testing of utricular function.

A modified rotatory chair test is reported in which radial acceleration, generated by eccentric displacement of the subject during constant angular velocity, is exploited as a unilateral stimulation to the otolith organs. During constant angular rate rotation, the test subject is displaced laterally on the rotating turntable by 3.5 cm, so that one labyrinth becomes aligned with the rotatory axis while the second - eccentric - labyrinth is solely exposed to the altered gravito-inertial acceleration (GIA). Previously reported results showed that the direction of the response is independent of the direction of turntable rotation, ruling out any canal influence, and indicated that in a normal population the response, measured in one eye, was symmetrical for displacement of the left and right labyrinths. This mode of stimulus thus appears to elicit a unilateral otolith-ocular response (OOR). Examination of this unilateral OOR was extended in the present study; comparative testing with head-tilt to gravity, i.e. involving bilateral stimulation to the otolith organs, was carried out. Movements of both eyes were recorded (by three-dimensional video-oculography), in order to examine response conjugacy. To verify the specificity of the unilateral stimulus, tests were performed with patients who had previously undergone unilateral section of the vestibular nerve as treatment for acoustic neuroma. The eccentric displacement profile (EDP) and head-tilt stimulus each included ten cycles of left-right oscillation in order to permit signal averaging. In the normal subjects (n=12) the torsional component of the OOR proved to be both labyrinth-symmetrical and conjugate, during both bilateral and unilateral otolith stimulation. OOR gain (ocular torsion/GIA tilt) was higher for bilateral than unilateral stimulation. Bilateral OORs, obtained from three of the five unilaterally deafferented patients, proved less symmetrical and conjugate than in the normals. Unilateral OORs in all five patients were characteristically asymmetrical, with little or no response during stimulation of the diseased labyrinth.

Acceleration↗

Pathophysiology of endolymphatic hydrops.

Endolymphatic hydrops of the nonprogressive type occurs in response to a single traumatic or toxic insult of limited duration and although it may result in permanent deficits in sensorineural function, there is total subsidence of vestibular symptoms. Endolymphatic hydrops of the progressive type, on the other hand, appears to be the result of permanent impairment of endolymph resorption and is caused principally by disorders of the endolymphatic sac. It occurs in Menière's disease, syphilitic labyrinthitis and the delayed hydrops syndrome. In addition to deafness of varying extent, it is characterized by episodic vertigo and sometimes by Hennebert's sign. Histological studies suggest that the acute vertiginous episodes are caused by potassium intoxication following ruptures of the membranous labyrinth and that Hennerbert's sign is caused by vestibular fibrosis.

Aged↗

Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerised tomography in aetiological diagnosis and management.

OBJECTIVES: The objective of this study was to identify factors correlated with the CT outcome and to examine the contribution of the CT scan in the aetiological diagnosis and management of unilateral sensorineural hearing loss in childhood. METHODS: The records of 35 consecutively investigated patients by the Audiology Department of Great Ormond Street Hospital between January 1996 and June 1998 were reviewed. The CT results, population sample characteristics, initiation of further investigations after the CT results and management decisions based on the CT results were tabulated and analysed. RESULTS: In a series of 35 consecutively investigated children with unilateral sensorineural hearing loss, 11 CT scans were identified as abnormal. The CT findings were: labyrinthitis ossificans (3), unilaterally dilated vestibular aqueduct (2), bilaterally dilated vestibular aqueduct (2), unilateral deformity of the cochlea ('Mondini') (1), unilateral severe labyrinthine dysplasia (1), unilateral markedly narrow internal acoustic meatus (1), bilaterally dilated lateral semicircular canals (1). The presence of progressive hearing loss was a significant predictor of abnormal CT outcome, while the severity of hearing loss was not. The CT scans offered valuable information regarding the aetiological diagnosis in all cases and, in addition, prompted the appropriate vestibular rehabilitation in three cases, further investigations in four (with dilated vestibular aqueduct) and hearing preservation counselling in two (bilateral DVA) (seven out of 35 = 20%). CONCLUSION: All children with unilateral sensorineural hearing loss should have a CT scan of the petrous pyramids/IAMs performed at some stage, as not only aetiology but also prognosis and management of these cases may be significantly influenced by the CT outcome.

Adolescent↗

Mycotic infection of the temporal bone.

Herein is a histopathologic study of the temporal bone changes in three patients with fatal systemic fungal infections. All three patients were compromised hosts who failed to respond to adequate chemotherapy. Interestingly, one patient with cryptococcosis had a unilateral hearing loss as the sole manifestation of cerebral cryptococcosis. The most common histopathologic change consisted of a fungal infiltration of the nerves in the internal auditory canal, with moderate infiltration of the sense organs of the membranous labyrinth.

Adult↗

The vestibular aqueduct and endolymphatic sac and duct in endolymphatic hydrops.

The histologic features of the endolymphatic sac and duct in 23 serially sectioned temporal bones with idiopathic or secondary endolymphatic hydrops were blindly compared with 22 randomly selected, normal temporal bones. In idiopathic hydrops, the pars rugosa of the endolymphatic sac extended out of the vestibular aqueduct into the dura in 29% of bones, compared with none of normal bones (P less than .01). In the other 71%, the pars rugosa in the vestibular aqueduct was surrounded by dura more commonly than normal. Functional studies are required to assess the relationship of these findings to hydrops. In secondary hydrops (eg, due to labyrinthitis), the endolymphatic duct was obliterated in the isthmus of the vestibular aqueduct by bone or fibrosis in seven of nine bones. Because of similar ossification and fibrosis elsewhere in the vestibular labyrinth, a direct relationship with hydrops cannot be assumed.

Adult↗

Labyrinthine ossificans and cochlear implants.

We report two clinical and five histopathological examples of labyrinthitis ossificans and discuss the possible cause of this condition. Diagnosis can be established by polytomography. The advent of the cochlear implant makes ossification of the cochlea (labyrinthitis ossificans) of more than academic interest, since it requires alteration of the insertion of an electrode into the scala tympani and minimizes the chances of successful stimulation. Hearing losses due to meningitis, advanced cochlear otosclerosis, and trauma are likely to be due to cochlear ossification. Therefore, it is important to rule out this condition by means of polytomography in individuals being considered for cochlear implant surgery.

Adult↗

Therapeutic initiatives for the avoidance of aminoglycoside toxicity.

Aminoglycosides continue to be indispensable in the management of serious and life-threatening aerobic gram-negative infections. On an annual basis in the United States, they are used in the management of four million patients. Despite their clinical utility, they continue to manifest a high profile of toxic side effects such as nephrotoxicity and ototoxicity with the rare occurrence of neuromuscular toxicity. Animal experimental models have been invaluable in elucidating the pathophysiologic mechanisms by which aminoglycosides damage the kidney and the inner ear. However, it is from clinical therapeutic experience and prospective clinical trials that we have been able to solidly define the risk factors that accentuate the development of aminoglycoside-related toxicity. The clinical toxicity of these agents can be kept to a minimum by ensuring the use of an appropriate dose, for periods of time not exceeding nine to ten days, in a well-hydrated, normokalemic patient. Special subpopulation groups such as the elderly, the obese, those with preexisting renal disease, or patients who need the concurrent use of other nephrotoxins, require special care in the monitoring of their aminoglycoside therapy to ensure a safe and effective clinical outcome.

Aminoglycosides↗

Pseudomonas labyrinthitis.

Pseudomonas aeruginosa is the gram-negative bacterial rod which is often isolated from chronic aural discharge. This microorganism may also cause necrotizing infection of the external auditory canal in certain patients with impaired host-defense mechanisms. Involvement of the inner ear by this microbe is extremely rare. In this communication, we report a case of pseudomonas labyrinthitis which resulted from traumatic middle ear injury. Infection produced massive granulations and extensive bone destruction of the otic capsule. This case shows that while P.aeruginosa is usually an avirulent opportunistic pathogen, it may also cause a highly destructive labyrinthitis if the inner ear is entered.

Aged↗

Inner ear damage induced by Mycobacterium fortuitum.

We used electron microscopy to investigate Mycobacterium fortuitum-induced changes in the inner ears of mice. We found that the inner and outer hair cells had degenerated and disappeared in the organ of Corti. Changes in the lower turn of the cochlea were more severe than those of the upper turn while the changes of the outer hair cells were more severe than those of the inner hair cells. Disappearance, fusion and ballooning of the sensory hairs were observed in the vestibular organs. The bacterial extract also induced inner ear damage which was similar to that caused by live M. fortuitum.

Animals↗