Audiology & neuro-otology
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Audiology & neuro-otology · Jan 2012
ReviewAnalysis of hearing preservation and facial nerve function for patients undergoing vestibular schwannoma surgery: the middle cranial fossa approach versus the retrosigmoid approach--personal experience and literature review.
To compare hearing preservation and facial nerve function outcomes in patients undergoing vestibular schwannoma surgery performed using either the middle cranial fossa approach (MCFA) or the retrosigmoid approach (RSA). ⋯ No statistically significant difference in hearing preservation was identified when comparing tumors operated upon via the MCFA versus the RSA. However, our results indicate that a higher risk of facial nerve function impairment exists if the surgery is performed via the MCFA under circumstances where the tumor extends to the cerebellopontine angle.
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Audiology & neuro-otology · Nov 1999
ReviewFunctional recovery in the avian ear after hair cell regeneration.
Trauma to the inner ear in birds, due to acoustic overstimulation or ototoxic aminoglycosides, can lead to hair cell loss which is followed by regeneration of new hair cells. These processes are paralleled by hearing loss followed by significant functional recovery. After acoustic trauma, functional recovery is rapid and nearly complete. ⋯ The permanent functional deficits after the regeneration process in these areas are most likely associated with functional deficits in the regenerated hair cells or shortcomings in the synaptic reconnections of nerve fibers with the regenerated hair cells. In conclusion, the avian inner ear appears to be much more resistant to trauma than the mammalian ear and possesses a considerable capacity for functional recovery based on repair processes along with its capacity to regenerate hair cells. The functional recovery in areas with regenerated hair cells is considerable but incomplete.
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Audiology & neuro-otology · Nov 1999
ReviewStructural recovery from sound and aminoglycoside damage in the avian cochlea.
Hair cell regeneration in the mature avian cochlea occurs in response to trauma that causes the death of some or all of the existing hair cell population. In general, this trauma has been introduced experimentally by either sound overexposure or treatment of the bird with high doses of aminoglycoside antibiotics. When injured hair cells are ejected from the sensory epithelium, the nonsensory supporting cells respond by re-entering the cell cycle and proliferating or by transdifferentiating directly into hair cells without a mitotic event. ⋯ It will define how hair cells and nerve endings are lost and the tectorial membrane is damaged by the traumatizing stimuli and how the supporting cells and nerve fibers respond by producing new hair cells, a new tectorial membrane and new synaptic connections during recovery. Finally, it will focus on mechanisms that control the proliferation and transdifferentiation of supporting cells and the differentiation of new hair cells. This structural review is accompanied by a companion review that covers the fundamental issues concerning functional recovery in the avian cochlea associated with hair cell regeneration.
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Audiology & neuro-otology · Mar 1998
ReviewLearning-induced physiological memory in adult primary auditory cortex: receptive fields plasticity, model, and mechanisms.
It is well established that the functional organization of adult sensory cortices, including the auditory cortex, can be modified by deafferentation, sensory deprivation, or selective sensory stimulation. This paper reviews evidence establishing that the adult primary auditory cortex develops physiological plasticity during learning. Determination of frequency receptive fields before and at various times following aversive classical conditioning and instrumental avoidance learning in the guinea pig reveals increased neuronal responses to the pure tone frequency used as a conditioned stimulus (CS). ⋯ This prediction has been confirmed. Additional tests of the model are described. RF plasticity is thought to translate the acquired significance of sound into an increased frequency representation of behaviorally important stimuli.
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Neck afferents not only assist the coordination of eye, head, and body, but they also affect spatial orientation and control of posture. This implies that stimulation of, or lesions in, these structures can produce cervical vertigo. ⋯ Neurological, vestibular, and psychosomatic disorders must first be excluded before the dizziness and unsteadiness in cervical pain syndromes can be attributed to a cervical origin. To date, however, the syndrome remains only a theoretical possibility awaiting a reliable clinical test to demonstrate its independent existence.