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H Spoendlin

Publications and source records attributed to H Spoendlin.

70 records · Page 4Linked to original sources
PubMedDate not supplied

Factors inducing retrograde degeneration of the cochlear nerve.

The process of retrograde secondary degeneration is described and its mechanism, discussed. The extent of degeneration following transection of the central or peripheral axon and following various types of damage to the organ of Corti, including the time course of degeneration, is presented in animal experimentation and human temporal bones. Of greatest practical importance is secondary neuronal degeneration induced by alteration in the organ of Corti. The effect of damage to the outer hair cells, inner hair cells, supporting structures in the Corti, and nerve endings or peripheral dendrites is analyzed and related to different types of inner ear disease.

Acoustic Stimulation↗
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Retrograde degeneration of the cochlear nerve.

Retrograde degeneration of the cochlear neurons has been studied in different types and degrees of peripheral cochlear damage such as acoustic trauma, intoxication, heredodegenerative deafness and others. It starts only when the peripheral dendrites to the inner hair cells are irreversibly damaged. About 10% of the neurons are not affected by retrograde degeneration. They correspond to the type II and III neurons, which also survive after transection of the cochlear nerve and are mainly associated with the outer hair cells. Cochlear damage due to vascular impairment usually leads to a complete loss of cochlear neurons. In hereditary abiotrophic deafness, neuronal degeneration is slower and its extent varies considerably according to the various genetic syndromes.

Animals↗
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Regeneration in the VIII nerve.

After transection of the VIII nerve in the inner meatus, 95% of the cochlear neurons and practically all efferent fibres degenerate and disappear. In long-term survivals, different phenomena indicate the regeneration properties of many, probably efferent or vestibular nerve fibres. The few remaining afferent neurons react to the lesion of their central axon with enormous proliferations of their peripheral branches in the organ of Corti.

Animals↗
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The unmyelinated nerve fibres of the cochlea.

A quantitative analysis was made of the unmyelinated nerve supply to the cochlea in normal cats and after various nerve lesions with different survival times. The normal fibre distribution in the intraganglionic spiral bundle (IGSB) and the osseous spiral lamina (OSL) varies characteristically along the cochlear turns. The unmyelinated nerve fibres are mainly associated with the IGSB and originate partly in the superior cervical ganglion and partly in the brain stem. They seem to have an excellent capacity to regenerate.

Animals↗
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Electrocochleography and cochlear pathology.

In experimentally damaged inner ears the structural alterations were correlated to electrocochleographic responses of the ear. Sectioning of the cochlear nerve with degeneration of the type I neurons but intact sensory cells results in normal cochlear microphonics but very weak and atypical nerve responses. By contrast, damage of the organ of Corti with retrograde degeneration abolished primarily the cochlear microphonics, whereas the compound VIII nerve action potential is barely affected when only the outer hair cells are gone and even a small number of surviving inner hair cells is still compatible with a relatively strong compound action potential of the cochlear nerve.

Action Potentials↗
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Neural connections of the outer haircell system.

The afferent innervation of the outer hair cells consists of a special type of neuron, distinguished by its characteristic structure and particular degeneration behavior. The connections of these neurons to the sensory cell, the central nervous system and the other cochlear neurons have been studied from different aspects and under various experimental conditions. There is evidence that the neurons are not effectively connected to the central nervous system, have no functional interconnections to other neurons and their functional significance in the adult animal is only rudimentary.

Animals↗
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Scarpa's ganglion in the cat.

A quantitative analysis of characteristics of neurons in Scarpa's ganglion was performed with light and electron microscopy. Plotting the major axes of 340 neurons as a function of their nuclear diameters indicated that there are two types of cells: Large neurons with large nuclei and small ones with small nuclei. Small neurons have an excentric nucleus with indentations of the nuclear membrane. Large neurons have a spherical and central nucleus. Almost all cells are myelinated. Occasional unmyelinated cells or those surrounded by many myelin layers represent normal variations of large or small neurons. The inferior portion of the ganglion containing about one-third of the total number of neurons and innervating most of the saccular macula and the posterior crista has more than 10% small neurons. The superior portion of the ganglion with two-thirds of the total number of neurons and innervating the remaining sensory epithelia has about 5% small neurons. The significance of this observation concerning innervation patterns of vestibular sensory epithelia is discussed.

Animals↗
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Three-year results of combined modality therapy in locally advanced, resectable squamous cell carcinoma of the head and neck.

Results of a combined therapy, consisting of preoperative chemotherapy, radical resection and postoperative irradiation, of 51 locally advanced, previously untreated, resectable squamous cancers of the head and neck are reported. The overall response rate to chemotherapy was 58.5% (with 33% complete remissions) and higher in carcinomas of the oral cavity and hypopharynx than of the supraglottis and oropharynx. Three year survival was 53% for the entire group, 75% for hypopharyngeal, 58% for oral, 50% for supraglottic and 32% for oropharyngeal lesions, in responders to chemotherapy statistically significant higher than in non responders and only 18% in the fifteen patients who developed recurrences.

Adult↗
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The spiral ganglion and the innervation of the human organ of Corti.

Five human cochleas were evaluated using the block surface method. The numbers of hair cells, nerve fibres in the osseous spiral lamina, and spiral ganglion cells were determined and correlated. The ultrastructural organization corresponds essentially to that of the mammalian ear, with the exception of multiple synaptic contacts of afferent nerve fibres with inner hair cells and surprisingly large numbers of outer spiral fibres.

Cell Count↗
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Pigment anomaly-associated inner ear deafness.

In order to investigate the pathogenesis of pigment anomaly-associated hereditary deafness, we studied black-eyed white mutant mice, which become severely deaf in early life and lacked neural crest-derived melanocytes. In the inner ear, the primary alteration appears to be located in the stria, which remains much thinner than normal and lacks intermediate cells. Melanocytes are identified with the histochemical Dopa reaction. This reaction is positive in intermediate stria cells in many animals of different ages, proving that they are derived from melanocytes. No tyrosinase-positive reactions were found in the mutant mice. This clearly indicates that the lack of intermediate stria cells is the crucial factor in the pathogenesis of pigment anomaly-associated inner ear deafness.

Animals↗