Preoperative and postoperative auditory and facial nerve function in cerebellopontine angle meningiomas.

Preoperative and postoperative facial nerve and auditory function were reviewed retrospectively in 13 cases of cerebellopontine angle meningiomas. According to their location within the posterior fossa and with special reference to the internal auditory canal, they were classified into a premeatal and a retromeatal group. All the tumors were removed by an otoneurosurgical team by use of a retrosigmoid approach. Postoperative results (1 year after operation) were compared within the two groups with respect to preservation of hearing (normal hearing in 31% and preservation of preoperative hearing in 69% of the cases) and facial nerve function (no or mild postoperative impairment in 69% of the cases). Both preoperative and postoperative impairment of facial nerve and auditory function prevailed in the premeatal group. For preservation of vital vascular and central nervous structures, subtotal resection with consecutive fractionated radiation therapy had to be performed in 30% of the cases. Our results provide substantial evidence that in cerebellopontine angle meningiomas a precise preoperative study of tumor location will assist in improving individual operative strategy and thus postoperative functional results.

Human leukocyte antigens in patients with inner ear diseases of unknown etiology.

The immune response genes that control the immune response and recognition of 'self' from 'nonself' are closely linked with the human leukocyte antigen (HLA) complex. Sixty-six HLA antigens were typed in 42 Caucasian patients with inner ear diseases of unknown etiology. All of these patients had positive serum antibodies against the inner ear structures as detected by an indirect immunofluorescence assay. Results revealed that none of the 66 HLA antigens was associated with the inner ear diseases. Reviewing results from other studies on HLA association in inner ear diseases shows that the findings are inconsistent with each other. The conclusion that HLA associations occur with inner ear diseases cannot be reached.

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.

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.

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.

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.

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 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.

[Functional morphology of the outer hair cells of the human: new aspects]. / Funktionelle Morphologie der äusseren Haarzellen des Menschen: Neue Aspekte.

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.

Shifts in auditory brainstem response latencies following plasma-level-controlled aminoglycoside therapy.

The ototoxic effect of plasma-level-controlled netilmicin and tobramycin was monitored in 20 intensive care patients, using auditory brainstem responses (ABRs). ABRs were recorded at the onset and after 6 days of treatment. Significant shifts in the ABR wave V latency were observed independent of the type of medication received or whether the patients were intubated or not. Shifts were also observed in wave I latencies. These latter changes were only significant for the complete population, probably because this potential is more difficult to elicit and measure than is wave V. The I-V interlatency time was greater for netilmicin than for tobramycin. These results indicate that the cumulative effects of aminoglycoside ototoxicity may be different for the central and peripheral nervous systems, and therefore ABR measurements may be the most accurate way of controlling ototoxicity in intensive care patients.

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.

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.

[Otosclerosis. A paramyxovirus-induced inflammatory reaction]. / Die Otosklerose. Eine durch Paramyxo-Viren unterhaltene Entzündungsreaktion.

Despite intensive investigation the cause of otosclerosis remains unknown. Recent immunohistochemical and electron microscopic studies of otosclerotic stapes have revealed a possible viral aetiology. Therefore we investigated the histology, ultrastructure and immunohistochemistry of fragments of otosclerotic footplates. Immunoglobulins G (IgG) and A (IgA) were found in plasma cells, oseocytes, chondrocytes and connective tissue of the active lesions. Polyclonal and monoclonal antibodies against paramyxovirus and rubella virus antigens produced reproducible reactions with these antigens at different sites of otosclerotic stapes, especially in the epithelial cells of the overlying middle ear mucosa. Using specific T-lymphocyte and B-lymphocyte markers about 80% of the lymphocytes present in the otosclerotic footplate proved to be T-lymphocytes. There was neither deposition of immunoglobulins nor any expression of viral antigens in non-otosclerotic footplates which were investigated as controls. Our results indicate that otosclerosis is an inflammatory reaction of the otic capsule initiated or caused by paramyxovirus and/or rubella virus. The silent progress of the disease and its onset under certain conditions, e.g. endocrine upsets, show similarity to slow viral infections.

The role of stretch and vestibulo-spinal reflexes in the generation of human equilibrating reactions.

Equilibrating reactions in standing humans were examined for evidence that either vestibulo-spinal or proprioceptive long loop stretch reflexes from ankle muscles, or both, are responsible for the control and organization of rapid postural responses. Specifically, the hypothesis was tested that the same postural response could be evoked by rotation of the support surface that mimics the ankle rotation occurring during support surface translations. Rotation perturbations evoked postural responses in leg and trunk muscles that were different in strategy, synergy and coactivation from translation responses, even though the short-latency response in the stretched triceps surae muscles was equal in latency and size. Movement patterns consisted of a stiffening strategy and hardly any compensating ankle rotation for rotation stimuli, and a multi-link strategy with motion focused about the neck, hip and ankle joints for translation stimuli. Dorsiflexion rotations caused earlier and stronger responses in tibialis anterior and quadriceps muscles just post to the onset of paraspinal muscles, whereas rearward translation activated soleus and abdominals strongest, both just prior to hamstring muscles. Correlated activation strengths of agonist and antagonist activity was a common feature for both types of perturbation, albeit, only in the ankle muscles for rotations and only in the trunk muscles for translations. These data suggest that sensory inputs, other than those generated in the lower leg predominate, in the triggering and modulation of equilibrating reactions. Possible candidates are those of the vestibular system or proprioceptive inputs from the trunk.

Automatic electronystagmus analysis and documentation: recent advances in the study of vestibular, optokinetic and pursuit tracking function.

A normal or pathologically altered peripheral vestibular system and associated brainstem structures can be diagnosed from the pattern of eye movement responses elicited by appropriate stimuli. Recent advances in two stages crucial to an accurate assessment of pathological or normal responses are described in this article. The first stage involves the automatic analysis of electronystagmus signals to yield the main parameters of clinical and scientific interest, slow phase eye velocity and fast phase frequency. Since four algorithms based on the first derivative of eye position perform this task remarkably well on-line, it is not necessary to employ features of the stimulus to separate the slow and fast phases of nystagmus. Examples are used liberally to illustrate the accuracy, advantages and limitations of the algorithms. The second stage involves a numerical and graphical comparison of measurements from a patient's analyzed responses with normal responses. This documentation phase permits immediate recognition of normal, borderline, or pathological optokinetic, eye tracking, caloric and rotating chair test results. Selected examples of pathological responses illustrate the documentation technique.

Indicators of the influence a peripheral vestibular deficit has on vestibulo-spinal reflex responses controlling postural stability.

For a controlled sway stabilization task, the areas underlying EMG responses in ankle and neck muscles, as well as amplitudes of ankle torque responses, were shown to be significantly correlated with the clinically defined extent of a patient's peripheral vestibular deficit. The responses, elicited by ankle dorsiflexion of the support surface on which the subject stood, were statistically examined in order to select those measurements which would best indicate differences between a normal, a patient with a unilateral deficit, or one with a bilateral deficit. For this purpose, a stepwise discriminant analysis was performed on measurements of head and trunk angular accelerations in addition to muscle EMG and ankle torque signals. The primary measurements selected to optimally assign a subject to a population were the periods of ankle torque and neck extensor activity associated with correcting for the imposed body displacement backwards and maintaining upright head position respectively. The resulting division into populations was 100% correct. However, within the population of unilateral deficit patients, the technique failed to correctly identify those with acute from those with compensated deficit. This technique of investigating vestibulo-spinal reflex responses is more specific and sensitive than Romberg tests, because it will quantify and specify the underlying cause of the patient's balance and ambulatory disorder.

Long-term modifications of vertical and horizontal vestibulo-ocular reflex dynamics in man. I. After acute unilateral peripheral vestibular paralysis.

Horizontal (HOR) and vertical (VERT) vestibulo-ocular reflex (VOR) responses to whole-body triangular velocity profiles with constant accelerations of 10, 15 and 20 deg/s2 were studied in two populations: normals, and patients with acute unilateral peripheral vestibular paralysis. The effect of this type of unilateral deficit on VOR gain and long time constant were determined as well as the time course of the compensation processes for HOR and VERT VOR dynamics. In the patient population, HOR VOR gain was asymmetric post deficit, being, on average, 50% and 75% of normal for rotations toward and away from the deficit, respectively. For the VERT VOR, on average, a symmetric 66% reduction occurred. The VERT VOR time constant was marginally affected by the deficit. HOR time constants were reduced for both directions of rotation. HOR and VERT VOR gain was within normal limits 1-3 months following an acute paralysis; time constants required a longer recovery period. Our results indicate that a unilateral deficit causes a markedly different alteration for HOR VOR dynamics compared to the effect on VERT VOR.