A posture control model and balance test for the prediction of relative postural stability.
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Accidental Falls↗
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Results for “LABYRINTH DISEASES”
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Vestibular dysfunction in occupational chronic solvent intoxication.
Neurotoxic volatile organic solvents used by house and car painters may lead to professional toxic encephalopathy after several years of exposure. The symptoms are memory impairment, fatigue, personality changes, headache and dizziness. Vestibular dysfunction was found in 55% of 113 painters examined, mainly in the form of reduced caloric vestibular reactions. No correlation between vestibular dysfunction and the duration of exposure, cerebral atrophy or intellectual impairment could be demonstrated. Vestibular examination may be helpful in detecting early changes in exposed persons and in determining more accurate safety limits for harmful chemicals.
Adult↗
Post-caloric secondary phase nystagmus.
Spontaneous direction reversal of a peripherally induced nystagmus, known as secondary phase nystagmus, can be found following a thermal stimulus. In 120 patients with various vestibular symptoms, post-caloric secondary phase nystagmus has been examined and its diagnostic value is discussed. Although the mechanism responsible for the post-caloric secondary phase nystagmus is not clear, there seem to be three factors that play a role in its occurrence: a the intensity of the stimulus; b the sensitivity of the vestibular and optokinetic systems; c the anatomical features of the external and middle ear. Because of these multiple factors, it is difficult to define the diagnostic value of the secondary phase nystagmus. However, we assume that secondary phase nystagmus is due to the adaptation of the organism to the peripheral vestibular stimulus, and factors mentioned above may induce or suppress its occurrence.
Adolescent↗
Central compensation of vestibular deficits. IV. Responses of lateral vestibular neurons to neck rotation after labyrinth deafferentation.
The response characteristics of neurons located in the lateral vestibular nucleus (LVN) to neck rotation at 0.026 Hz, 10 degrees peak displacement, have been investigated in precollicular decerebrate cats submitted to ipsilateral acute (aVN) or chronic vestibular neurectomy (cVN). On the whole, 105 units were tested after aVN (i.e., during the first postoperative hours) and 132 units after cVN (i.e., after full compensation of the postural and locomotor deficits). The neurons were histologically located either in the rostroventral (rvLVN) or the dorsocaudal part (dcLVN) of Deiters' nucleus, which are known to project mainly to the cervical and the lumbosacral cord, respectively. Moreover, 55 units in the former group and 66 units in the latter group were identified as vestibulospinal neurons projecting to lumbosacral segments of the spinal cord. The responses of these 237 LVN neurons to the neck input were then compared with those of 120 LVN neurons recorded previously in decerebrate cats with intact labyrinths. Whereas 58.3% of the LVN units recorded in control experiments were responsive to neck rotation, 69.5% of the units were affected by this stimulation at the acute stage of the neurectomy and 74.2% at the chronic stage. This increase in responsive units after aVN and cVN with respect to the controls was found exclusively in the dcLVN. The mean discharge rate of the responsive LVN neurons decreased from 40.7 +/- 48.9 (SD) imp/s in control experiments to 22.1 +/- 15.8 (SD) imp/s after a VN. Similar value was also obtained after cVN [25.0 +/- 17.2 (SD) imp/s], suggesting that compensation of the postural deficits elicited by the vestibular neurectomy results from a redistribution of the excitatory drive within different populations of LVN neurons. Indeed, the relation found in control experiments, i.e., that the faster the conduction velocity of vestibulospinal axons the lower was the unit discharge at rest, was lost after aVN, due to a decrease in resting discharge of the slow units. The mean discharge rate of the slow units, however, recovered after cVN, so that the negative correlation between resting discharge rate and axonal conduction velocity was reestablished. The average gain and sensitivity of the first harmonic response of the LVN neurons to neck rotation recorded after aVN and cVN were comparable to those obtained in preparations with the vestibular nerves intact.(ABSTRACT TRUNCATED AT 400 WORDS)
Adaptation, Physiological↗
Diagnostic significance of summating potential in sensorineural deafness.
The polarity of the summating potential wave induced by electrocochleographical examination has an important bearing upon the pathophysiology or the prognostic evaluation of sensorineural deafness. Electrocochleographical examination was performed on cases of sudden deafness, Ménière's disease, progressive sensorineural deafness, sensorineural deafness due to barotrauma, etc. When the polarity of the summating potential showed an increased negative wave, physiological blockage in sensorineural structures was revealed. In other words, under such conditions sensorineural structures have a potential for activity although hearing acuity was damaged. On the other hand, when the summating potential has an increased positive polarity wave, gradual decrease of the hearing acuity was revealed.
Action Potentials↗
Vestibular training after sudden loss of vestibular functions.
12 cases of unilateral labyrinthectomy, 3 cases of VIIIth nerve section, 22 cases of streptomycin sulfate infusion into the middle ear cavity and 8 cases of bilateral vestibular a-functions underwent vestibular training. Our training is very useful for regaining equilibrium and for evaluating the effects of training on equilibrium by recording the gravity center movements.
Adult↗
Statistical identification of the extent of a peripheral vestibular deficit using vestibulo-spinal reflex responses.
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Adult↗
Masking level differences for cochlear and brain stem lesions.
Masking level differences (MLD) for 500 Hz pure tones and for spondees were obtained from 48 subjects. Twelve were without otologic or neurologic complaints (normal), 12 had high frequency, noise-induced hearing losses, 12 were diagnosed otologically as having Ménière's disorder, and 12 had neurologically diagnosed central nervous system (CNS) disorders. Results indicated that high frequency, noise-induced hearing losses do not affect MLD for 500 Hz stimuli, but do diminish the size of MLD for speech. Masking level differences for both 500 Hz and spondees were decreased for the Ménière's disorder group. The group of patients having CNS disorders attributed to multiple sclerosis, to inflammatory lesion of the pons, to degenerative processes of the cerebellum and adjacent nervous tissue, or to brain stem cerebrovascular accident had normal hearing according to conventional pure tone and speech testing, but attained smaller than normal MLD for 500 Hz and spondees. These findings agree closely with results obtained in an earlier study and continue to suggest that, given normal peripheral auditory function, MLD tests may have unique value in detection of subtle lesions of the central auditory nervous system.
Auditory Perception↗
Visual suppression test.
Visual suppression of caloric nystagmus was studied in normal adults and in 98 clinical cases in order to justify the application of the procedure as a clinical test. The maximum slow phase velocity during ten seconds in darkness and the slow phase velocity during ten seconds in light were taken from the recordings and measured. The mean values of these slow phase velocities were calculated and the mean slow phase velocity in darkness was assigned a value of 100%. The value which the slow phase velocity in light subtracts from the slow phase velocity in darkness, represents the visual suppression. It was determined that visual suppression of the slow phase velocity of caloric nystagmus was 48 +/- 10% in 22 normal adults. This was caused by the visual fixation mechanisms. Cases in which lesions were diagnosed in the cerebellum, such as spinocerebellar degeneration and cerebelitis, showed reduced or abolished visual suppression. The lesion side can be determined by this test. Compensation following unilateral sudden loss of inner ear function can be measured by the visual suppression test.
Adult↗
Perilymph fistulas. Diagnostic criteria and therapy.
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Adult↗
Acute cochlear disorders: the combination of hearing loss, recruitment, poor speech discrimination, and tinnitus.
The combination of hearing loss, recruitment, poor speech discrimination and tinnitus, which is characteristic of acute cochlear disorders, can be accounted for on the basis of a decoupling of hair cells from their drive system, the tectorial membrane. Decoupling may either be caused by a temporary reduction of ciliary stiffness (shown to occur during periods of noise-induced temporary threshold shifts) or by temporary and/or chronic ciliary pathology (demonstrated to exist in cases of antibiotic ototoxicity and in endolymphatic hydrops). Since ciliary coupling is elastic in nature, the decoupling is only partial. The hearing loss and the tinnitus are manifestations of the reduced coupling per se, the magnitude of the loss depending on the degree of decoupling and the number of hair cells involved. Recruitment and poor speech discrimination result from center-clipping of the signal waveform applied to an involved hair cell, the direct corollary of partial, ciliary decoupling.
Acute Disease↗
Sensorineural hearing loss following chronic ear surgery.
The incidence and characteristics of postoperative sensorineural hearing loss were analyzed in 2,303 cases of chronic otitis and its sequelae, representing our total series from 1965 to 1980. Sensorineural hearing loss occurred in a total of 1.2% of cases: 0.5% became totally deaf, and 0.7% acquired a high tone loss, most often at 4 kHz only. The incidence was highest in congenital malformations, granulating otitis and cholesteatoma, mastoidectomy (especially canal-down), and during the period from 1965 to 1974. The most common causes of anacusis were removal of cholesteatoma from the semicircular canal and removal of the fistula membrane. Different types of severe high tone loss are described and, in addition, 19 patients with mild high tone loss are discussed.
Audiometry↗
Early hair cell loss in experimental hydrops.
One, 2, and 4 months after surgical obliteration of the endolymphatic sac, the sequence of degenerative changes in the organ of Corti of the guinea pig was studied. The block surface technique with interference differential (Nomarski) microscopy was used for this investigation to study the morphological changes in the organ of Corti. The hair cell loss was calculated and mapped in cytocochleograms. One month postoperatively a minimal loss of only outer hair cells was observed in the apical cochlear turn. At 2 months a progression of outer hair cell loss was seen, which proceeded in the 4-month group. At 4 months the inner hair cells showed a slight tendency to degenerate, again beginning in the most apical part of the cochlea.
Animals↗
Neurogenic tumors of the skull base.
This review article summarizes the subject of neurolemmomas in and around the temporal bone and was written as a component paper for a symposium on surgery of the skull base. The paper primarily discusses solitary schwannomas of the facial nerve, vestibular schwannomas, and jugular foramen schwannomas relative to incidence, signs and symptoms, and preferential diagnostic and therapeutic options. General considerations such as multiple neurofibromatosis, current nomenclature, and malignancy are defined.
Adult↗
Chronic perilymphatic fistula: experimental model in the guinea pig.
Chronic perilymphatic fistulas were created in guinea pig cochleas using silicone rubber tubing placed into the scala tympani through the round window. Fistula patency was determined by fluorescein perfusion into cerebral spinal fluid. Fistula were found to be patent in 6 of 6 animals at 7 days and 8 of 13 animals at 28 days. Analysis of ABRs revealed threshold increases of 10 to 15 dB across all frequencies at 1 hour and 7 days. However, thresholds returned to pre-fistula levels by 28 days. Animals with acute fistulas (simple laceration of the round window) had similar threshold increases at 1 hour; however, recovery to baseline levels occurred by day 7. Control animals with intact round windows did not have threshold shifts. Scanning electron microscopy revealed hair cell loss localized to the apical and basal turns of the cochlea. The morphologic changes observed occurred acutely (within 7 days) and were not progressive, despite the presence of a fistula. Hair cell loss or degeneration did not correlate with hearing loss.
Animals↗
Intracranial complications of otitic origin.
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Adolescent↗
Theoretical and practical implications for plasmapheresis in autoimmune inner ear disease.
Immune-mediated inner ear disease, by convention called autoimmune inner ear disease (AIED), has established clinical profile guidelines for diagnosis. Treatment consists of steroid and/or cytotoxic drug immunosuppression. The role of plasmapheresis (PMP) in the treatment of AIED has not been defined. Lack of a precise serological marker prevents accurate immunological understanding. Definition is, of course, difficult in a disease whose natural history is not well delineated. Successful use of PMP in one steroid and cytotoxic drug intolerant patient with AIED led to its use in a total of eight patients. The rationale for PMP was based on its known effectiveness in other autoimmune diseases and thus, its potential use in AIED. Improved auditory function occurred in 6 of the 8 patients, 3 of whom have been followed for over 3 years. Three of the six no longer require immunosuppressant medication. PMP can be used as an alternative or adjunctive therapy in AIED. These preliminary results suggest PMP can stabilize or improve auditory and vestibular symptoms in selected patients. Its use as a first line therapy followed by cytotoxic immunosuppressants bears consideration.
Adult↗
Computer analysis of optokinetic nystagmus in patients with spontaneous nystagmus of peripheral vestibular origin.
The bias of slow phase velocity (SPV) of optokinetic nystagmus (OKN) caused by an acute labyrinthine lesion was examined in 8 patients using differnet optokinetic stimulus velocities. In all patients a directional preponderance of OKN-SPV was found corresponding to spontaneous nystagmus. This was due to enhancement of nystagmus SPV to the side of the lesion and depression of SPV in the opposite horizontal direction. The preponderance of OKN on the average increased with the intensity of spontaneous nystagmus and decreased along with recovery. These vestibularly induced differences in OKN-SPV range up to 70%. A differentiation is discussed between OKN preponderances caused by labyrinthine lesions and brain stem lesions.
Acute Disease↗