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Biomedical subjects

J B Snow

Publications and source records attributed to J B Snow.

At least 73 records · Page 4Linked to original sources
PubMed1977

Central auditory imperception.

The development of clinically applicable techniques for the evaluation of hearing impairment caused by lesions of the central auditory pathways has increased clinical interest in the anatomy and physiology of these pathways. A conceptualization of present understanding of the anatomy and physiology of the central auditory pathways is presented. Clinical tests based on reduction of redundancy of the speech message, degradation of speech and binaural interations are presented. Specifically performance-intensity functions, filtered speech tests, competing message tests and time-compressed speech tests are presented with the emphasis on our experience with time-compressed speech tests. With proper use of these tests not only can central auditory impairments by detected, but brain stem lesions can be distinguished from cortical lesions.

Animals↗
PubMed1977

Neoplasms of the nasopharynx in children.

Neoplasms of the nasopharynx are rare in children, but they threaten the child's life when they do occur. The nasopharynx tends to harbor dysontogenetic neoplasms. After classification into benign and malignant groups, nasopharyngeal neoplasms in children can be further characterized according to the age of the patients in which the clinical manifestations usually appear. Dermoids and teratomas are the most frequently encountered neoplasms of the nasopharynx in infants and may produce airway obstruction and dysphagia. Among the benign tumors of the nasopharynx in children, the juvenile angiofibroma deserves the most attention. With the onset in puberty, these neoplasms may cause recurrent massive bleeding and orbital and intracranial complications. Evaluation of the extent of the neoplasm and the source of the blood supply has been improved with bilateral selective internal and external carotid angiography. Intracranial and orbital invasion is regarded as an indication for radiotherapy. Surgery has been made somewhat safer by preoperative estrogen therapy and angiographic embolization of the major arterial supply. Patients with squamous cell carcinoma of the nasopharynx have immunologic similarities to patients with Burkitt's lymphomia and infectious mononucleosis; The etiologic role of the Epstein-Barr virus is considered. The parts played by radiation therapy, surgery, chemotherapy, and cryosurgery in the treatment of children with carcinoma of the nasopharynx are discussed. The value of radical neck dissection after radiation therapy is critically reviewed. The prognosis in patients with carcinoma of the nasopharynx is better in females than in males and better in children than in adults.

Adolescent↗
PubMed1976

Effects of head blow on the development of hearing loss.

The effects of the direction and intensity of the head blow and the effects of the lapse of time after a head blow on the development of hearing loss were studied in guinea pigs. The electrical responses from the right inferior colliculus (ER) and from the left round window (CP) to acoustic stimuli were measured. The elevation in threshold of the ER in the presence of normal CP in guinea pigs after a head blow suggests that the site of the lesion is central to the cochlea.

Animals↗
PubMed1976

Histopathologic correlates of otoneurologic manifestations following head trauma.

The clinical course of patients dying of head trauma and the physiologic evaluation of audition in guinea pigs subjected to several forms of head trauma are correlated with the histopathologic findings in the brains and temporal bones. In the patients there was wide spread hemorrhage, edema, disorganization and disruption of neural tissue. Loss of Purkinje cells and other neural elements was prominent. The temporal bone findings in the patients included laceration of and hemorrhage into the VIIIth nerve as well as bleeding into the scala tympani. The membranous labyrinths demonstrated no specific changes secondary to the trauma. The guinea pigs developed a central form of hearing loss with elevated thresholds for evoked responses from the inferior colliculus and normal AC cochlear potentials. In the animals hemorrhage in the substance of the brain, necrosis of neural tissue, edema, disorganization and disruption were prominent. Although there was extravasation of blood in the tympanic and vestibular scalae, the membranous structures of the inner ears were well preserved.

Adolescent↗
PubMed1975

Parapharyngeal rhabdomyoma.

Rhabdomyoma is a benign tumor of striated muscle origin that is very rare in young children. Review of the world literature revealed 20 cases of extracardiac adult-type rhabdomyoma in the head and neck area. All reported cases have been encapsulated and easily excised. A 22 1/2-month-old girl with a parapharyngeal rhabdomyoma is unique in that her tumor had atypical histology and lacked a capsule; it could not be "shelled-out".

Age Factors↗
PubMed1975

Pathogenesis of hearing loss in head injury. Studies in man and experimental animals.

This study reports on the histopathologic findings in the temporal bones and brain of a patient who died of head injury. A common type of head injury in man was simulated in guinea pigs by shaking them. A hearing loss was demonstrated with Preyer reflex audiometry although the cochlear potential thresholds remained normal. Only minor pathologic changes were found in the membranous labyrinths. Laceration and hemorrhage in and around the cerebrum, rhombencephalon, and eighth nerves were noted in most of the experimental animals. Auditory manifestations following head injury may very frequently be due to damage to the central auditory pathways rather than to the end organ.

Animals↗
PubMed1975

Pathologic features of the inner ear in congenital deafness.

We present the morphologic findings of the temporal bones and brain of a patient with congenital deafness. We discuss these findings in relation to pathologic observations in other reported cases of congenital deafness. Morphologic abnormalities in the patient were mainly in the pars inferior of the membranous labyrinths. The osseous labyrinths were well developed. There was severe dilation of the cochlear duct with herniation of the Reissner membrane, extensive atrophy of the stria vascularis that was associated with calcified thrombi to the strial vessels, encasement of the tectorial membrane in a syncytium, and dyspiastic or regressive degeneration of the organ of Corti. Absence of spiral ganglion cells and their fibers was a prominent feature. The extensive and varied pathologic changes that were present in our patient simultaneously suggest a congenital abnormality in endolymph production and raise the possibility of anomalous development of the labyrinthine vasculature.

Aged↗
PubMed1975

Electrophysiological responses from the cochlea and inferior colliculus in guinea pigs after head injury.

Electrical responses from the inferior colliculus (ER) and round window (CP) to acoustical stimuli were compared in control and experimental guinea pigs which had received a single blow to the freely movable head. After the blow to the head, all of the animals showed signs of commotio cerebri, and some of them died. The experimental animals were divided into two groups so that the physiologic responses to sound could be evaluated one day (early group) and seven days (intermediate group) following the head blow. The animals of the early group had elevated ER thresholds over the entire frequency range tested with an average threshold of 37.8 db. The animals of the intermediate group also had elevated ER thresholds which averaged 23.9 db. Input-output intensity function of ER for the experimental animals showed a recruitment-like phenomenon. The CP thresholds in the injured animals did not differ significantly from those in the control group. Damage to the VIIIth nerve and higher central pathways is very likely a more frequent cause of the otoneurologic manifestations following head injury than end organ damage.

Action Potentials↗
PubMed1975

Control of the microcirculation of the inner ear.

In general, many similarities are seen between cerebral blood flow and cochlear blood flow in response to vasodilating drugs. Cochlear vessels appear to be weakly controlled by the adrenergic nervous system. Cholinergic agents dilate cochlear vessels, although the vasodilation in the cochlea does not necessarily cause an increase in cochlear blood flow because of the associated hypotension. The effect on the systemic circulation is too profound to make these agents clinically useful. Papaverine, dipyridamole, amyl nitrite, and the plasma kinins produce transient increases in cochlear blood flow. Ten per cent carbon dioxide and 90 per cent oxygen product progressive vasodilation as long as the mixture is inhaled. Hydralazine produces too profound an effect on systemic blood pressure. Histamine and betahistine increase cochlear blood flow but only in doses that produce bronchiospasm in the guinea pig. Nicotinic acid and nicotinyl tartrate have no effect on cochlear blood flow. If one considers safety and efficacy as well as patient tolerance, papaverine appears to be the drug of choice for increasing cochlear blood flow clinically. Histamine and betahistine appear to be acceptable alternatives. Betahistine is no longer available for clinical use because of the failure to demonstrate clinical efficacy of therapy.

Cochlea↗