Biomedical subjects

Dietmar Basta

Publications and source records attributed to Dietmar Basta.

14 recordsLinked to original sources

PubMed2006

The application of vestibular-evoked myogenic potentials in otoneurosurgery.

OBJECTIVE: To evaluate the applicability of vestibular-evoked myogenic potentials (VEMPs) in the diagnostics, intraoperative monitoring, and postoperative follow-up of patients in otoneurosurgery. STUDY DESIGN: A prospective study of patients who underwent either cochlear implantation (CI, n = 18) or were diagnosed with an acoustic neuroma (AN, n = 9) or with neuro(micro)vascular compression of the VIIIth nerve (NVC, n = 27) in the period 2002 to 2004. The follow-up was 1 year for all patients. SETTING: A tertiary-referral unit. RESULTS: VEMPs could be recorded in 64% of all patients before CI and in 22% after surgery. The patients with AN had normal VEMPs in 22% of all cases when first diagnosed. Normal VEMPs were found in 37% of those patients with NVC. From the 5 AN patients who had to be operated, only 1 had intact VEMPs after surgery. In contrast, after microvascular decompression all patients (4) had normal VEMPs. CONCLUSIONS: VEMPs are helpful in diagnosing patients with vertigo to better identify saccular defects. They are highly sensitive in the early diagnosis of retrocochlear lesions. SIGNIFICANCE: VEMPs can help to reliably identify patients with a retrocochlerar lesion at an early stage and can be used in intraoperative, neurophysiological monitoring. EBM RATING: C-4.

Adolescent↗

PubMed2006

Perioperative recordings of vestibular-evoked myogenic potentials in otosclerosis.

OBJECTIVES: The aim of the present study was to investigate saccular function in patients with otosclerosis. Furthermore, the influence of stapedotomy on the vestibular-evoked myogenic potentials (VEMPs) should be demonstrated. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. METHODS: Bone-conducted tone-burst-evoked VEMPs were measured in 23 patients (25 ears) with unilateral or bilateral otosclerosis preoperatively and postoperatively. RESULTS: Preoperatively, VEMPs could be recorded in 11 ears (44%). There was no statistically significant correlation among the extent of preoperative sensorineural hearing loss, age, and VEMP measurements. Postoperatively, VEMPs were found in 14 ears (56%). In three cases (12%), VEMPs reappeared after surgery. The rare cases of preoperative vertigo could not be correlated to the nonappearance of VEMPs. CONCLUSION: Stapedotomy surgery does not influence VEMPs, implying that the saccular receptors are not injured by surgery. Moreover, in some cases, the elicitability of VEMPs was improved by stapedotomy surgery. Seemingly, otosclerosis can influence the generation of VEMPs most probably due to an involvement of the otolith organ's saccular receptors. No correlation was found between the clinical occurrence of vertigo and the elicitability of VEMPs.

Adult↗

PubMed2005

Vestibular dysfunction of patients with mutations of Connexin 26.

The gap junctional network of the inner ear plays an important role in cochlear ionic homoeostasis. Mutations of connexin 26 can induce different types of hearing loss and even deafness. Therefore, it is hypothesized that gap junctions of the human vestibular organ are functionally impaired by mutations of connexin 26. In a prospective, nonrandomized study, the functional status of the semicircular canals and the otolith organs was assessed in one homozygous and six heterozygous carriers of connexin 26 mutations. Five out of seven patients (71.4%) had pathological vestibular evoked myogenic potentials, indicating a loss of saccular function. The utricular function (as tested by subjective haptic vertical) and the function of the semicircular canals (as tested by recording the vestibuloocular reflex) were largely normal. Thus, connexin 26 mutations can be associated with saccular defects of the vestibular receptors.

Adult↗

PubMed2005

Quality of pronase dissociation of mature inferior colliculus neurons.

One major advantage of acutely dissociated inferior colliculus (IC) neurons in electrophysiological investigations is their complete isolation from the surrounding cellular network. In this way, patch-clamp recordings can be performed under controlled conditions to study membrane properties of IC neurons in more detail. The aim of the present study was to adapt a dissociation method for immature IC neurons to the highly sensitive, fragile and vulnerable mature IC neurons of mammals (mice). The modification of a pronase-based dissociation protocol with respect to concentration, incubation time and handling (trituration) of the cells yielded intact, live IC neurons with a clean cell surface so that they were well suited for further electrophysiological investigations in our study. The largely modified dissociation protocol is described in detail and critically discussed.

Humans↗

PubMed2005

Noise-induced cell death in the mouse medial geniculate body and primary auditory cortex.

Noise-induced effects within the inner ear have been well investigated for several years. However, this peripheral damage cannot fully explain the audiological symptoms in noise-induced hearing loss (NIHL), e.g. tinnitus, recruitment, reduced speech intelligibility, hyperacusis. There are few reports on central noise effects. Noise can induce an apoptosis of neuronal tissue within the lower auditory pathway. Higher auditory structures (e.g. medial geniculate body, auditory cortex) are characterized by metabolic changes after noise exposure. However, little is known about the microstructural changes of the higher auditory pathway after noise exposure. The present paper was therefore aimed at investigating the cell density in the medial geniculate body (MGB) and the primary auditory cortex (AI) after noise exposure. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun, 10:1). After 1 week, auditory brainstem response recordings (ABR) were performed in noise exposed and normal hearing animals. After fixation, the brain was microdissected and stained (Kluever-Barrera). The cell density in the MGB subdivisions and the AI were determined by counting the cells within a grid. Noise-exposed animals showed a significant ABR threshold shift over the whole frequency range. Cell density was significantly reduced in all subdivisions of the MGB and in layers IV-VI of AI. The present findings demonstrate a significant noise-induced change of the neuronal cytoarchitecture in central key areas of auditory processing. These changes could contribute to the complex psychoacoustic symptoms after NIHL.

Acoustic Stimulation↗

PubMed2005

Erratum to "Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices".

The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. It was, therefore, the aim of the present study to investigate the effects of noise exposure on the spontaneous electrical activity of single neurons in a slice preparation of the isolated mouse IC. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun 10:1). After one week, auditory brainstem response (ABR) recordings and extracellular single-unit recordings from spontaneously active neurons within the IC slice were performed in noise-exposed and in normal hearing control mice. Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.

Acoustic Stimulation↗

PubMed2005

Normative data for P1/N1-latencies of vestibular evoked myogenic potentials induced by air- or bone-conducted tone bursts.

OBJECTIVE: The response characteristics of acoustically elicited vestibular evoked myogenic potentials (VEMPs) largely depend on the stimuli applied. A tone-burst stimulation of 500 Hz seems to be clinically most appropriate because those VEMPs can be elicited at the lowest stimulus intensity possible. The aim of the present paper was to describe normative data for tone-burst evoked VEMPs. METHODS: VEMPs of 64 healthy subjects were recorded ipsilaterally during air- or bone-conducted tone burst stimulation. The EMG of the tonically activated sternocleidomastoid muscle was recorded ipsilaterally by surface electrodes. Averages were taken for P1/N1-latencies and -amplitudes of male and female volunteers within 3 different age groups. RESULTS: The latencies did not show any significant differences between female and male volunteers or between air- and bone-conducted stimulation. The latencies did also not show any significant difference among the 3 age groups. The limits for normal latencies (mean + 2 SD) are, therefore, 20.3 ms for P1 and 28.0 ms for N1. Although the P1/N1-amplitudes were decreased with increasing age, the tonic muscle activity was not significantly different between the age groups. CONCLUSIONS: The present findings strongly suggest the evaluation of VEMP latencies by using normative values obtained exactly with the same stimulus parameters. SIGNIFICANCE: Normative data as described in the present study are required to detect isolated saccular defects which are indicative of a vestibular disorder.

Acoustic Stimulation↗

PubMed2005

Postural control in otolith disorders.

It was the aim of the present paper to investigate the influence of otolith disorders on human postural control by different methods. The 33 patients of our study had undergone a minor head injury and suffered subsequently from an utricular or sacculo-utricular disorder as evidenced by vestibular evoked myogenic potential recordings and eccentric rotation recordings of the otolith-ocular responses. Postural control was assessed by performing stance/gait tests (standard balance deficit test, SBDT) and by evaluating trunk sway (using angular velocity sensors). Moreover, classical tests of the posterior column of the spinal tract (Romberg/Unterberger) and the dynamic posturography (sensory organization test, SOT) were included. It could be shown that SBDT tasks with reduced proprioceptive and visual cues (e.g. standing on foam, eyes closed) are most sensitive for an otolith disorder. The patients showed an increased trunk sway in the pitch plane (i.e. linear motion as adequate utricular stimulus) and an increase in sway velocities (i.e. tilting movements as adequate saccular stimulus) compared to controls. The SOT was most sensitive for combined (sacculo-utricular) otolith disorders (78%) while vestibulospinal tests are not enough sensitive. In essence, otolith disorders evidently impair human postural control and have been possibly underestimated as a source of posttraumatic postural imbalance as yet.

Adult↗

PubMed2005

Management of posttraumatic vertigo.

OBJECTIVE: To evaluate patients after blunt trauma of the head, neck, and craniocervical junction (without fractures) with vertigo and to report the results of treatment after extensive diagnostics. STUDY DESIGN: Prospective study of consecutive new cases with vertigo after trauma at different periods of onset. During 2000-2002, 63 patients were examined and treated. SETTING: Regional trauma medical center for the greater Berlin Area, tertiary referral unit. RESULTS: The primary disorders included labyrinthine concussion (18), rupture of the round window membrane (6), and cervicogenic vertigo (12). The secondary disorders included otolith disorders (5), delayed endolymphatic hydrops (12), and canalolithiasis (9). The patients were free of vertigo symptoms (except cervicogenic and otolith disorder) after treatment, which consisted of habituation training, medical and surgical therapy options. The follow-up was 1 year. CONCLUSION: Posttraumatic vertigo can be treated with a high success rate once the underlying disorder has been identified. The extent of the neurotological test battery determines the precision and quality of diagnostics. Surgical measures should be an integral part of treatment modalities if conservative treatment is not effective. SIGNIFICANCE: Minor trauma of the head, neck, and craniocervical junction can have major impact on the vestibular system at different sites. Patients need to be carefully diagnosed, even if the onset of vertigo occurs a few weeks or months after the initial trauma.

Adolescent↗

PubMed2005

The "pull-back" technique for Nucleus 24 perimodiolar electrode insertion.

OBJECTIVE: To observe the influence of electrode pull-back after cochlear implant insertion of Nucleus 24 perimodiolar electrodes. STUDY DESIGN: In a prospective intraoperative study, we analyzed the impedances, neural response telemetry responses, and the spread of excitation after cochlear implant electrode insertion and compared these data to those obtained after a subsequent, controlled pull-back of the electrode. Postoperative depth of electrode insertion was controlled by x-ray. SETTING: Tertiary referral center. SUBJECTS: Six patients (4 male, 2 female; 18 to 69 years) were implanted with a Nucleus 24 (RCA) cochlear implant with a perimodiolar electrode. RESULTS: After a controlled pull-back, a significant decrease of the spread of excitation at the stimuli electrodes 5, 10, 15, and a nonsignificant decrease at stimuli electrode 20 compared to the recordings after the primary normal insertion procedure was found. The mean electric compound action potential amplitude was increased with an apical-to-basal tendency. Impedances remained unchanged by the pull-back. Mean insertion depth at the postoperative x-ray control was 372 degrees (+/- 10.2). CONCLUSION: Controlled cochlear implant electrode pull-back is a novel technique that optimizes objective intraoperative electrophysiological recordings in patients implanted with a Nucleus 24 perimodiolar cochlear implant by a greater approximation of the electrode to the modiolus.

Adolescent↗

PubMed2004

Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices.

Acoustic Stimulation↗

PubMed2004

Effects of salicylate on spontaneous activity in inferior colliculus brain slices.

Salicylate is a well-known substance to produce reversible tinnitus in humans and animals. It has been shown that systemic application of salicylate changes the neuronal spontaneous activity in several parts of the auditory pathway. Salicylate has also a direct influence on cochlear outer hair cell electromotility. The effects observed in the central auditory structures in vivo could therefore be based upon the change in afferent cochlear input to the auditory system and in addition by a direct action of salicylate on neurons within the auditory pathway. The present study investigated the direct effect of salicylate application on the spontaneous activity of mouse inferior colliculus neurons in brain slices. Out of 92 neurons, 87% responded statistically significantly to the superfusate by changing their firing rates. 70% increased and 17% decreased their firing rates, respectively. Salicylate superfusion induced a general increase of electrophysiological activity within the inferior colliculus brain slice preparation which was similar to those obtained during systemic application of salicylate. The results suggest that the salicylate sensitivity of inferior colliculus neurons can modulate to a great extent the salicylate-induced generation of tinnitus.

Action Potentials↗

PubMed2003

Membrane-based gating mechanism for auditory information in the mouse inferior colliculus.

In order to analyse the intrinsic membrane-based mechanisms of neurons in the mouse inferior colliculus that are likely to contribute to the processing of acoustic signals, this study use whole cell patch clamp recordings in brain slices to characterize the dependence of depolarization evoked inward and outward currents on different prestimulus membrane potentials. Eighty-seven of one-hundred and one inferior colliculus neurons reacted during depolarizing voltage steps from a holding potential of -60 or -80 mV with a fast inactivating inward current followed by a slow inactivating outward current (type I neurons). Fourteen neurons showed outward currents but no inward currents during depolarizing voltage steps from a holding potential of -60 mV (type II neurons). However, these neurons reacted with TTX-sensitive fast inward currents, if the holding potential was set to -80 mV before the voltage steps occurred. The resting potential was not significantly different between type I (-64.3+/-3.5 mV) and type II (62.7+/-2.9 mV) neurons. If the neuronal behavior is the same in vivo, type II neurons must receive an inhibition which hyperpolarizes the membrane potential prior to the arrival of excitatory inputs to be able to generate action potentials. This finding suggests a further function for feedforward inhibition in the IC, namely to open a gate for transmission of excitatory information within a distinct time window. With this membrane based gating mechanism it is possible to detect time related information within an acoustic stimulus (e. g. coincidence) which is an essential task e. g. in the neuronal processing of speech.

Action Potentials↗

PubMed2002

Early development of neuronal hypothalamic thermosensitivity in birds: influence of epigenetic temperature adaptation.

The aim of the study was to investigate the prenatal influence of different incubation temperatures on the early postnatal development of neuronal hypothalamic thermosensitivity in birds. The experiments were carried out in brain slices of 1-, 5- and 10-days-old Muscovy ducklings incubated at 35, 37.5 (control) or 38.5 degrees C during the last week of incubation. Firing rate of neuronal activity was recorded extracellularly during sinusoidal temperature changes. The results show that the temperature experienced prenatally has a clear influence on postnatal neuronal hypothalamic thermosensitivity. For instance, at the 10th day post-hatching, exposure to the cooler prenatal incubation temperature resulted in elevated neuronal hypothalamic warm sensitivity through an increased proportion of warm sensitive neurons and a reduced proportion of cold sensitive neurons in comparison with the control group. Exposure to the warmer prenatal incubation temperature induced the opposite effect. In these age group changes in neuronal hypothalamic thermosensitivity occur in relation to the prenatal temperature experienced (proximate adaptive). During the first days of life, prenatal temperature load induced a significant change in the thermosensitivity of hypothalamic neurons which was independent of the direction of change in incubation temperature in comparison with control conditions (proximate non-adaptive). Changes in the thermosensitivity of hypothalamic neurons after prenatal temperature experiences observed in all age groups may be the result of epigenetic temperature adaptation.

Adaptation, Physiological↗