Search PubMed⌕ Search

Biomedical subjects

C R Pfaltz

Publications and source records attributed to C R Pfaltz.

At least 19 recordsLinked to original sources
PubMed1992

The influence of age on the results of stapedectomy.

In a retrospective study, we investigated the results of 384 stapedectomies performed between 1962 and 1989. The purpose was to determine the possible influence of age on the postoperative functional result. The operative technique uniformly consisted of a total stapedectomy, seal of the oval window with perichondrium and replacement of the stapes by a free tragal cartilage graft. The audiometric data at 0.5, 1, 2, and 4 kHz were compared. The patients were divided into five groups based upon chronological age: under 30, 30-40, 41-50, 51-60, over 60 years. Although the preoperative airbone gap (ABG) increased with age at all frequencies, and thus the chance for surgery to improve the ABG, the youngest group showed the best improvement in ABG (P less than 0.05). Using a technique with total removal of the footplate, bone conduction thresholds improved in the frequencies up to 2 kHz. At 4 kHz, they deteriorated in the four oldest groups. The greatest improvement in bone conduction thresholds occurred in the youngest group of patients (P less than 0.05), with a parallel decline in age and postoperative results occurring. The causes of these differences are not yet clear, although spontaneous recovery and greater resistance to operative trauma in the younger age groups might be of influence.

Adult↗
PubMed1992

Human auditory-evoked potentials before and after magnetic resonance imaging.

The effect of magnetic fields on auditory brainstem responses (ABRs) was examined under two conditions. The first involved recording ABRs before and immediately after magnetic resonance imaging (MRI). ABRs were then recorded as the static magnetic field was increased stepwise to 2T. No significant changes in ABR latencies were noted under either condition. These results indicate that MRI has no measurable effect on the transmission latencies of auditory brainstem neural pathways.

Adult↗
PubMed1992

A randomized, double-blind, placebo-controlled study of dextran/pentoxifylline medication in acute acoustic trauma and sudden hearing loss.

The effectiveness of any therapy in acute acoustic trauma or sudden hearing loss of unknown origin has not been demonstrated convincingly. The assessment is difficult because of a relatively high rate of spontaneous recovery. Nevertheless, many different forms of treatment are recommended. We tested one form, treatment with rheoactive substances, in a prospective, randomized, double-blind trial and compared treatment with (a) infusions of dextran-40 with pentoxifylline, (b) saline infusions with pentoxifylline, and (c) saline infusions with placebo medication. Pure-tone hearing thresholds served as control parameters and were taken before treatment and at 1 and 4 weeks after the onset of therapy. Three hundred eighty-two patients were included in the trial, 331 (87%) could be analyzed, 184 patients were treated because of sudden hearing loss, 147 because of acute acoustic trauma. The three treatment groups were comparable in their basic characteristics including the amount of initial hearing loss. In patients with sudden hearing loss, no significant differences of hearing recovery were detected between the three treatment groups. Hearing recovery was also similar in patients with acute acoustic trauma. A power analysis of the study revealed that possible true treatment differences of a hearing recovery of 10 dB would have lead to significance with a probability of over 90%. It is concluded that there were, in fact, no clinically relevant differences in hearing gains of sudden hearing loss or acute acoustic trauma between treatments with saline infusions together with placebo medication and treatment with dextran-40 and/or pentoxifylline.

Acoustic Stimulation↗
PubMed1991

Diagnosis and surgery of cerebellopontine-angle tumors.

The present report is based on the analysis of clinical data collected from 80 patients with cerebellopontine-angle tumors. Special reference is made to the history of the patient, the neurootologic test battery, particularly to the sensitivity and specificity of audiological and vestibular diagnostic procedures. The postoperative findings are evaluated especially with respect to postoperative morbidity and the preservation of facial nerve and auditory functions.

Audiometry↗
PubMed1991

The effect of age on the visuo- and vestibulo-ocular reflexes of elderly patients with vertigo.

To evaluate the effect of age and vestibular deficit on the vestibulo-ocular and associated visual reflexes, rotating chair (VOR), eye tracking test (ETT) and optokinetic (OKN) responses were investigated using comparisons between three populations: young normals, vertiginous elderly patients, and age-matched normal elderly subjects. The gain of ETT and OKN responses were reduced for both elderly populations as compared to young normals, but less so for the vertiginous elderly. VOR gain was more significantly reduced in the vertiginous elderly, though VOR time constant was as reduced as for the normal elderly. These results indicate that visual inputs, even in the elderly, are probably employed to compensate for a vestibular deficit.

Aged↗
PubMed1991

Classification of peripheral and central (pontine infarction) vestibular deficits. Selection of a neuro-otological test battery using discriminant analysis.

The results obtained from a complete neuro-otological test battery were examined statistically in order to select measurement variables which would optimally indicate significant differences between four groups: normal patients, patients with partially compensated unilateral peripheral vestibular deficit, patients with an acoustic neurinoma and patients with central (brainstem) vestibular deficit. A stepwise-discriminant analysis was performed on measurements of slow-phase velocity obtained from each test. The primary measurements selected to assign a subject optimally to one population were the canal paresis (CP) of the caloric test, the eye-tracking gain contralateral to the deficit for a 15 deg/s stimulus, the gain asymmetry for optokinetic nystagmus with a 30 deg/s stimulus, and the level of spontaneous nystagmus. The resulting classifications were 100% correct for normal and central deficit patients. However, the division between peripheral deficit and acoustic neurinoma patients overlapped causing about 30% false classifications of neurinoma patients: some 20% of the peripheral deficit patients were classified as normal. If the CP was not available the discriminant analysis substituted the rotating chair response for 5 deg/s2, in place of CP. This substitution caused a 10 to 20% decrease in classification accuracy.

Diagnosis, Differential↗
PubMed1990

Regional variations in the expression of cytokeratin proteins in the adult human cochlea.

In the adult human cochlea, a cytokeratin (Ck) network exists along the entire surface of the organ of Corti, enclosing it like a shell. Only the surfaces of the outer and inner hair cells are not integrated in this network. In temporal bone specimens, Ck filaments in Hensen's cells were found to be arranged parallel with and closely apposed to the plasma membrane. In the stria vascularis, Cks were identified only in the marginal cells. Cells in Reissner's membrane and spiral prominence showed varying degrees of immunoreactivity to different monoclonal antibodies directed against Cks. A distinct positivity for Cks was found in most spiral ganglion cells, indicating their presence in all cells. The principal pattern of immunoreactivity was the same in the organ of Corti of the entire cochlea. However, a quantitative gradient in the expression of Cks was observed, with more Cks at the apex than at the base. This was correlated to a difference in the number of Hensen's cells between the two regions. The distinct shell configuration of the Ck network in Corti's organ gives it a tonotopically related difference in rigidity which must be of considerable importance for the perception of sound in the cochlea. The absence of Cks in inner and outer sulcus cells gives them cytoskeletal characteristics of mesenchymal cells with a possible regenerative potential.

Adult↗
PubMed1990

[Functional morphology of the outer hair cells of the human: new aspects].

Serial sections through the outer hair cells of the human organ of Corti were investigated using high-resolution electron microscopy. Delicate monostratified tubular structures of differing lengths are located on the cytoplasmic side of the hair-cell membrane. They are connected to the cell membrane via short fibers (pillars) arranged in pairs. The tubular structures, which are also termed subsurface cisterns (SSC), constitute an extensive network. This network lines the entire inner surface of the outer hair-cell membrane, and in contrast to the mammals investigated so far, also lines the base of the cell. The postsynaptic cisterns of the efferent synapses are integrated into this system. At the surface of the inner lamina of the cisterns, pores 8.5 nm in diameter are to be found. These are surrounded by protein complexes with a stellate arrangement. Similar protein complexes are located on the inner lamina of the postsynaptic cisterns. Pores 8.5 nm in diameter are also present in the outer lamina of the SSC. These constitute the base for the pillar filaments. At high magnification, the pillars are seen to have a lumen about 6 nm in diameter. Pores about 8 nm in diameter are again to be found where the pillars are anchored in the outer cell membrane. The pillars, consisting of actin, are probably ionic channels, and the pores of the inner lamina of the SSC surrounded by protein complexes are thought to be acetylcholine receptors. Since the postsynaptic cisterns of the efferent innervation of the outer hair cells are part of the overall system of the SSC, and acetylcholine is regarded as the neurotransmitter of efferent innervation, it would seem possible to regulate the subsurface cisterns, as a wall-stabilizing, contractile system, via the efferent innervation. On the basis of serial sections, a three-dimensional, true-to-scale model of the contractile wall system of the human outer hair cell was reconstructed.

Adult↗
PubMed1990

Characteristics of electrically evoked 'auditory' brainstem responses elicited with the nucleus 22-electrode intracochlear implant.

Electrically evoked auditory brainstem responses (EABRs) were measured in cochlear implant patients fitted with the Nucleus 22 electrode system. The typical response waveform consisted of a series of two to three peaks. The largest peak was similar in form to the wave V of acoustically evoked ABRs and was most prominent for stimulus intensities nearly equal to the patients' maximum comfortable (MC) behavioural stimulus level for the test electrode. The first identifiable wave V amplitude was observed at stimulus levels greater than the patients' psychophysical threshold. With increasing stimulus intensity, wave V amplitude increased rapidly to plateau at a level highly correlated with the patients' MC level at the EABR stimulus rate of 17/s. Wave V peak latency was generally shorter than normal ABRs (4.0 cf. 5.5 ms) and varied with electrode position: apical electrodes had shorter latencies than basal electrodes by approximately 0.4 ms. These results suggest that EABRs can be used as an objective estimate of a patient's electrode-specific MC level, once the correlation of EABR growth functions at 17/s to those at clinically employed rates of 250/s has been determined. EABRs may indicate differences in nerve action potential generation for apical and basal electrodes.

Cochlea↗
PubMed1979

On the interaction of vestibular and optokinetic nystagmus in man.

The interaction of vestibular and optokinetic nystagmus (OKN) was investigated by applying periods of ipsi- and contradirectional optokinetic stimulation during perand postrotatory vestibular nystagmus in healthy humans. Slow phase velocity and cumulative eye displacement of OKN was enhanced by vestibular nystagmus beating in the same direction of decreased by contradirectional vestibular nystagmus. A distinct correlation between the intensity of vestibular stimulation and the modification of OKN could be demonstrated by averaging the responses obtained in different subjects. On the other hand there was also a modification (enhancement or decrease) of vestibular nystagmus slow phase velocity by preceding OKN. Considering the intensity of these modifications, large interindividual differences were observed.

Electronystagmography↗
PubMed1978

Occult cholesteatoma of the middle ear.

A clinico-pathological study of 10 cases (including histopathology) indicates that occult cholesteatoma is neither a congenital cholesteatoma nor an epidermoid cyst, originating in the attic through a melaplastic process of middle ear mucosa behind an intact tympanic membrane. Occult cholesteatoma is due to retraction and active immigration of the epidermal layer of the tympanic membrane into the narrow compartments of the epitympanic area and its causative factor is a chronic inflammatory stimulus. Symptomatology is insiduous because extension of destruction depends entirely on the direction of its growth which for its part is guided by the mucosal folds of the epitympanic space.

Adolescent↗
PubMed1978

[Symptomatology and diagnosis of vestibular disorders following head injury (author's transl)].

One hundred cases of head injuries were submitted to thorough repeat neuro-otological examinations. The results were evaluated with respect to the diagnostic importance of vestibular symptoms. Positional nystagmus was found to be the most common symptom (51%). In 25% of the cases, spontaneous nystagmus could be demonstrated up to two years following head injury. Pathologic caloric responses were found in only one-third of the patients. Positional and positioning nystagmus were found to be the most important symptoms of a vestibular disorder following head injury, and seem to be the most reliable criteria for the assessment of disability and working capacity.

Adult↗
PubMed1977

Studies on habituation of vestibulospinal reflexes. Effects of repetitive optokinetic and vestibular stimuli upon the stepping test.

The influence of repetitive applications of optokinetic and vestibular stimuli upon the vestibulospinal responses, measured by the stepping test, was investigated both in an optokinetic training and vestibular habituation test series. Repeated applications of optokinetic and vestibular stimuli modified the rotation angles of the stepping test, i.e. vestibulospinal responses, resulting in a response decline of rotation angles which was still present after 1 month.

Habituation, Psychophysiologic↗
PubMed1977

The influence of optokinetic training upon vestibular responses induced by repetitive sinusoidal stimuli.

Optokinetic and vestibular training alternatively applied during two cycles, using sinusoidal pendular rotation and a stationary projection optokinetic stimulator, resulted in a progressive vestibular response decline. This response decrement was only revealed by the parameter of the slow-phase velocity. Combined optokinetic and vestibular training shows a facilitating effect upon vestibular habituation which cannot be induced by repetitive pendular rotation alone. Both a response decline, expressed by the parameter of the slow-phase velocity and a response increment, expressed by the number of nystagmus beats, were observed during one cycle of the pendular rotation. Both phenomena could be induced by alternative optokinetic and vestibular training and were interpreted as typical visual-vestibular interaction mechanisms.

Eye Movements↗
PubMed1977

Optokinetic training and vestribular habituation.

The present study deals with the interaction of the visual and vestibular system with special reference to habituation. The results indicate that vestibular responses are modified by repeated uni- and bidirectional optokinetic stimulation. This transfer mechanism is more evident in test subjects after wide angle (foveo-peripheral) than after narrow angle (foveal) optokinetic stimulation. The modification of vestibular responses by means of repetitive optokinetic stimuli is characterized by an enhancement on the one side and a decline of the responses on the other, depending entirely on the nature of the optokinetic stimulus (uni- or bidirectional, foveal or foveo-peripheral). There is some evidence to suggest that these phenonomena are habituation transfer mechanisms. They seem to subserve the improvement of the gain of the vestibulo-ocular reflex. They help the vestibular system to improve the assessment of self-rotation within the environment and to impede the development of visual-vestibular conflicts.

Adolescent↗