Acoustic Evoked Potentials Research Articles

Long-Term Outcomes of Management of Inferior Alveolar Neuropathy Following Orthognatic Surgeries in Patients with Mandibular Anomalies and Deformities

Introduction. Orthognatic surgery is a routine method to manage mandibular anomalies and deformities.
 Objective: To assess long-term outcomes of rhythmic peripheral magnetic stimulation (rPMS) in patients with neuropathy of the inferior alveolar nerve (IAN) resulting from the surgical treatment of mandibular anomalies and deformities.
 Materials and methods. The study included 8 males and 16 females aged 32 ± 12 years with IAN neuropathy following the surgical treatment of mandibular anomalies and deformities. Therapeutic rPMS was performed with the Neuro-MS magnetic stimulator (Neurosoft, Ivanovo, Ivanovo Region, Russian Federation). Trigeminal and brainstem acoustic evoked potentials (EPs) were registered with Neuro-MVP (Neurosoft) to assess rPMS both at baseline (in 10 days) and in long term (in 18 ± 2 months).
 Results. Sensory disorders and pain prevailed in postoperative IAN neuropathy. Sensory disorders improved in 20 patients following 10-day rPMS. The clinical effect persisted in re-assessment. In long term, acoustic brainstem EPs normalized and trigeminal EPs did not change negatively.
 Conclusion. The use of rPMS in IAN neuropathy following orthognatic surgeries contributes to the functional improvement and stabilization of the peripheral and central brainstem and the trigeminal system.

Acoustic evoked potentials characteristics in patients with vertebral artery hypoplasia and posterior circulation stroke

Background/Aim. Acoustic evoked potentials (AEPs) represent an electrophysiological method used in diagnosing pathological changes of the brain stem (BSt), the acoustic nerve (its peripheral and central part), in patients in coma, in the confirmation of cerebral death, etc. The response includes seven negative waves which are generated in the structures of the BSt vascularized by the arteries of the posterior circulation. However, in everyday practice, due to their constancy, the first five waves are followed. The vertebral artery hypoplasia (VAH) is assumed to affect the AEPs finding. The current definition of VAH includes the criterion that the diameter of the blood vessel is ? 2 mm and that the ratio of the diameter of the left and right vertebral artery is ? 1 : 1.7. VAH is found in 5.3% of cases of the total population and its presence increases the risk of posterior circulation stroke (PCS). The aim of this study was to show a higher frequency of pathological findings of AEPs in patients with VAH and PCS and demonstrate the characteristics of AEP in that group of patients. Methods. This prospective study included 163 patients diagnosed with PCS over a period of two years. Computed tomography (CT) and magnetic resonance (MR) imaging (MRI) established the diagnosis of PCS. Suspicion of VAH was found by Color Doppler ultrasonography and confirmed by CT and MR angiography. All patients underwent AEPs testing. Wave amplitudes and interwave latencies (IWL) were monitored. Results. There was no statistically significant difference between gender (?2 = 1.823; p = 0.176) and age in relation to VAH (p = 0.815). A statistically significant greater number of patients with multiple PCS had a positive VAH finding (VAH group, 42.3%) compared to those without VAH (noVAH group, 26.6%) (?2=4.278; p=0.038). A statistically significant greater number of pathological AEPs was found in the group of patients with PCS and VAH (?2 = 4.899; p = 0.026). A statistically significant IWL change accompanied by low amplitude waves in the VAH group has been determined (?2 = 4.465; p = 0.034). Conclusion. The distribution of VAH is not gender- or age-related. The frequency of pathological AEPs findings (presence of associated changes in wave amplitudes and prolonged IWL) is statistically significantly higher in patients with VAH and PCS.

Facial Nerve Function After Microsurgical Resection in Vestibular Schwannoma Under Neurophysiological Monitoring.

BackgroundThe use of intraoperative neurophysiological monitoring, including direct nerve stimulation (especially the facial nerve), acoustic evoked potentials (AEP) and somatosensory evoked potentials (SSEP), is a helpful tool in the microsurgery of vestibular schwannoma to prevent nerve injury. Patient characteristics and intraoperative and postoperative variables might also influence the postoperative facial nerve function. The study was performed to investigate these variables and the intraoperative neurophysiological monitoring values.MethodsSeventy-nine patients with vestibular schwannoma were included consecutively into this study. Intraoperative neurophysiological monitoring, including SSEP, AEP, and direct nerve stimulation for facial and trigeminal nerve electromyography, was performed utilizing digital data storage in all cases. The intensity (in volts) of the direct stimulation and the latency (in ms) for the orbicularis oculi and the orbicularis oris muscle and the amplitude (in mV) was measured. Univariate and multivariate statistical analyses concerning the different parameters was performed directly after the operation and in the subsequent follow-ups 3 and 6 months after the operation.ResultsThe mean intensity was 0.79 V (SD.29). The latency and amplitude for the oris muscle was 5.2 ms (SD 2.07) and 0.68 mV (SD.57), respectively. The mean latency for the occuli muscle was 5.58 ms (SD 2.2) and the amplitude was 0.58 mV (SD 1.04). The univariate and multivariate statistical analyses showed significance concerning the postoperative facial nerve function and the amplitude of the direct stimulation of the facial nerve in the orbicularis oris muscle (p = 0.03), so repeated direct nerve stimulation might show FN function deterioration. The mean diameter of the tumors was 24 mm (range 10–57 mm). Cross total resection and near total was achieved in 76 patients (96%) and subtotal in three patients (4%). The preoperative House–Brakeman score (HBS) 1 was constant in 65 (82%) cases. The mortality in our series was 0%; the overall morbidity was 10%. The HBS was not influenced concerning the extent of resection. The mean follow-up was 28 months (range 6 to 60 months). The limitations of the study might be a low number of patients and the retrospective character of the study.ConclusionIntraoperative neurophysiological monitoring is crucial in vestibular schwannoma surgery. Repeated direct nerve stimulation and a detected decreased amplitude might show facial nerve function deterioration.

P 242. Changes of mental activity and acoustic evoked potentials (AEP) under the influence of repetitive transcranial magnetic stimulation of premotor cortex on normal subjects and patients after severe head injury

Introduction Repetitive transcranial magnetic stimulation (rTMS) is among perspective medical influences of activating character at patients with long posttraumatic unconscious state. Our previous researches of such patients revealed distinct positive changes of their state and increase of consciousness level after rTMS. Objective This study is aimed at analysing the changes of mental and bioelectric activity on low-frequency repetitive rTMS on normal subjects and on patients with post-traumatic unconsciousness after severe head injury for specification of separate functional characteristics “sensitivity” to this influence. Method Functional effects sub-threshold (60–80% of a motor threshold) low frequency rTMS 1–2 Hz of premotor cortex in three series of researches were estimated. (1) At 5 healthy volunteers analyzed influence of placebo and single rTMS on memory and attention indicators in psychologic tests, and also on the N100, N200, P300 AEP components to and in 1 h after influence. (2) At 7 patients with post-traumatic unconsciousness (the vegetative condition or an akinetic mutizm) estimated dynamics of state and separate clinical symptoms, and also AEP. (3) At 4 if 7 of these patients in the same way estimated effects of 7-day rTMS course. Dynamics of patients state estimated on stages of consciousness [Dobrokhotova et al. (1996)] and also on our ball scale of the functional activity, based on Glasgow, NIHSS, and UPDRS scales-with emphasis on the attention and movement sphere. AEP were recorded on 18 cannels by two-stimulus oddball paradigm, in the in tasks of listening sounds and accounts of the target. The latency and amplitude of N100, N200, P300 AEP were analyzed, and also spatial syncronization of each component according integrated coefficient of wavlet-synchronism. Results At healthy people after single rTMS strengthening of any attention according to neuropsychological tests was observed. It was accompanied by increase of power of P300 AEP in frontal and central departments of the left hemisphere along with strengthening intra-and interhemispheric functional weyvlet-communications of the left frontal area. At injury distinct positive changes of state are revealed at 5 of 7 patients both after single, and course rTMS. They concerned increase of consciousness level-along with increase of any movements, decrease in raised initially muscular tone. Increase of any attention was expressed more distinctly after course rTMS. Clinical dynamics was accompanied by normalization of amplitude and latency of all AEP components, as well as indicators of their spatial synchronism, especially for P300, connected in literature with any attention. Conclusion The most distinct changes under the influence of the rTMS this mode concern function of any attention: its activization in norm, and also emergence or improvements in pathology. Dynamics of clinical symptoms at patients with brain injury reflects, in our opinion, positive shifts both dofaminergic, and holinergic brain systems. Supported by RHGR 1 11-06-01-060.

DYNAMIC STUDY OF EVOKED POTENSIALS IN CLINICAL PRACTICE IN PATIENTS WITH MULTIPLE SCLEROSIS

DYNAMIC STUDY OF EVOKED POTENSIALS IN CLINICAL PRACTICE IN PATIENTS WITH MULTIPLE SCLEROSIS

Acoustic evoked potentials (AEP) caused by different complexity stimuli in prognosis of mental recovery in posttraumatic unconscious state

Acoustic evoked potentials (AEP) caused by different complexity stimuli in prognosis of mental recovery in posttraumatic unconscious state

Ascorbic Acid Reduces Noise‐Induced Nitric Oxide Production in the Guinea Pig Ear

Noise-induced hearing loss can be caused, among other causes, by increased nitric oxide (NO) production in the inner ear leading to nitroactive stress and cell destruction. Some studies in the literature suggest that the degree of hearing loss (HL) could be reduced in an animal model through ascorbic acid supplementation. To identify the effect of ascorbic acid on tissue-dependent NO content in the inner ear of the guinea pig, we determined the local NO production in the organ of Corti and the lateral wall separately 6 hours after noise exposure. Prospective animal study in guinea pigs. Over a period of 7 days, male guinea pigs were supplied with minimum (25 mg/kg body weight/day) and maximum (525 mg/kg body weight/day) ascorbic acid doses, and afterwards exposed to noise (90 dB sound pressure level for 1 hour). The acoustic-evoked potentials were recorded before and after noise exposure. The organ of Corti and the lateral wall were incubated differently for 6 hours in culture medium, and the degree of NO production was determined by chemiluminescence. Ascorbic acid treatment reduced the hearing threshold shift after noise exposure depending on concentration. When the maximum ascorbic acid dose was substituted, NO production was significantly reduced in the lateral wall after noise exposure and slightly reduced in the organ of Corti. Oral supplementation of the natural radical scavenger ascorbic acid reduces the NO-production rate in the inner ear in noisy conditions. This finding supports the concept of inner ear protection by ascorbic acid supplementation.

Mutations in the Gene Encoding Peroxisomal Sterol Carrier Protein X (SCPx) Cause Leukencephalopathy with Dystonia and Motor Neuropathy

In this report, we describe the first known patient with a deficiency of sterol carrier protein X (SCPx), a peroxisomal enzyme with thiolase activity, which is required for the breakdown of branched-chain fatty acids. The patient presented with torticollis and dystonic head tremor as well as slight cerebellar signs with intention tremor, nystagmus, hyposmia, and azoospermia. Magnetic resonance imaging showed leukencephalopathy and involvement of the thalamus and pons. Metabolite analyses of plasma revealed an accumulation of the branched-chain fatty acid pristanic acid, and abnormal bile alcohol glucuronides were excreted in urine. In cultured skin fibroblasts, the thiolytic activity of SCPx was deficient, and no SCPx protein could be detected by western blotting. Mutation analysis revealed a homozygous 1-nucleotide insertion, 545_546insA, leading to a frameshift and premature stop codon (I184fsX7).

Endothelial nitric oxide synthase upregulation in the cochlea of the guinea pig after intratympanic gentamicin injection

Single-shot transtympanic gentamicin therapy has become a popular treatment modality for Meniere's disease despite the known possible ototoxic properties of this drug. It was shown recently that NO production and iNOS were upregulated after gentamicin application, which was interpreted as a possible effect of ototoxicity. In this study we analyzed the expression of eNOS after gentamicin application to determine a possible correlation of this enzyme with gentamicin-induced ototoxicity. We compared eNOS expression in gentamicin-treated and non-treated guinea pigs in the second turn of the cochlea, an area corresponding to speech perception in humans. Gentamicin (4 mg) was injected intratympanically into the middle ear of guinea pigs ( n =3) and the reduction of the hearing threshold level was determined by recording acoustic-evoked potentials (AEP) before and 5 days after gentamicin application. Morphological alterations in the organ of Corti were analyzed by light and electron microscopy. Gold-labeled anti-eNOS antibodies were counted in eight different cell areas for quantification of eNOS expression. Seven animals were analyzed as controls. After gentamicin application, a deterioration of hearing level was observed varying from 10 to 30 dB. A high degree of vacuolization was identified in the third row of outer hair cells. At the subcellular level, the subsurface cisterns in outer hair cells were dissociated from the basolateral cell membrane, and the mitochondrial membranes were frequently damaged. Statistically significant upregulation of eNOS was observed in all cell types analyzed. Depending on the various cell types the amount of gold-labeled eNOS antibodies was 2.5 to 5.7 times higher after gentamicin application. We observed significant eNOS upregulation after gentamicin application in the cochlea, in conjunction with cellular damages and decreased hearing.

L'impiego dei Potenziali Evocati nella Sclerosi Tuberosa

Evoked potentials (EP) allow the assessment of the functional integrity and degree of maturation of the main pathways of sensory afference (visual, acoustic and somaesthetic). For this reason, EP can be used in the study of patients with tuberous sclerosis. In clinical practice, EP serve to give information for early diagnosis and a better prognostic assessment of the individual patient. A recent analysis of visual evoked potentials (VEP) and brain stem acoustic evoked potentiials (BAEP) in children with tuberous sclerosis disclosed an increased average latency of some components of both VEP (component IV or P2) and BAEP (V wave and I-V interpeak). Impaired responses were present in 80% of VEP and 85% of BAEP. In addition, impaired BAEP were also present in patients without subtentorial structural abnormalities. EP serve as a useful instrument for early diagnosis of tuberous sclerosis. Given the anatomofunctional differences of the systems stimulated and the preferential location of lesions in certain areas, the various different EP have varying degrees of sensitivity in disclosing abnormalities: visual and brain stem acoustic EP are more sensitive than somatosensory EP.

Intrinsic electrophysiology of neurons in thalamorecipient layers of developing rat auditory cortex

During early postnatal life, several critical events contribute to the functional development of rat sensory neocortex. Thalamocortical innervation of sensory cortex is completed during the first postnatal week and extrathalamic innervation develops over the first several weeks. In auditory cortex, acoustic-evoked potentials first occur in week 2 and develop most rapidly over weeks 2–3. Thus, rapid functional maturation of cortical circuits in sensory cortex occurs during the second and third postnatal weeks. The electrophysiological properties of cortical neurons that receive afferent inputs during this time may play an important role in development and function. In this study we examined the intrinsic electrophysiology, including spiking patterns, of neurons in layers II/III and IV of auditory cortex during postnatal weeks 2 and 3. Many neurons displayed characteristics consistent with previous descriptions of response classes (regular spiking, fast spiking, intrinsic bursting). In addition, we identified two groups, Rectifying and On-spiking neurons, that were characterized by (i) brief spike trains in response to maintained intracellular depolarizations, and (ii) striking outward rectification upon depolarization. Unusually brief spike trains (1–2 spikes) and short spike latencies (<10 ms) further distinguished On-spiking from Rectifying cells. Biocytin labeling demonstrated that On-spiking and Rectifying cells could be either pyramidal or nonpyramidal neurons. The intrinsic physiology of these cell groups may play an important role in auditory cortex function.

Changes in eeg power, acoustic evoked potentials and heart rate after mildly arousing non-acoustic priming stimuli in carp ( CYPRINUS CARPIO)

1. 1. Changes in EEG power spectrum of carp to a priming non-acoustic stimulus followed by acoustic clicks were compared to those due to acoustic clicks delivered alone. Recordings were made from the telencephalon, midbrain and medulla. Acoustic evoked potentials (AEPs) to the clicks were also recorded. 2. 2. EEG power changes to non-acoustic stimuli occurred over the whole 1–40 Hz frequency range and were regionally specific and consistent. 3. 3. The changes in the EEG midfrequency 12–24 Hz power spectrum to non-acoustic stimuli were significantly correlated with changes in the AEP to subsequent clicks. An elevated medullary AEP amplitude and reduced duration were correlated with increased medullary EEG power and increased midbrain AEP duration. 4. 4. Telencephalic EEG power changes were inversely related to changes in medullary and midbrain AEP amplitude.

Sustained potential shifts and changes in acoustic evoked potentials after presentation of a non-acoustic priming stimulus to carp ( CYPRINUS CARPIO)

1. 1. Recordings were made from the region of the midbrain tectum and torus semicircularis of sustained potential shifts (SPS) to a non-acoustic priming stimulus and the change in subsequent acoustic evoked potentials (AEPs) to-a train of six clicks after a long rest. 2. 2. In the absence of priming stimuli (a jet of saline or water to the flank) the AEP to the first click in a train had the highest amplitude; with these stimuli it became the most attenuated. 3. 3. The SPS to both non-acoustic stimuli was initially ( ca 4 sec) negative, then became positive for a similar time period. 4. 4. After saline jet the tectal and the torus AEP amplitude was significantly correlated with the torus SPS; after water jet, the tectal and the torus AEP durations were correlated with the SPS. 5. 5. Application of alumina gel to the posterior telencephalic border caused elevation of the torus AEP amplitude after some 5 hr.

Changes in early acoustic-evoked potentials by mildly arousing priming stimuli in carp ( Cyprinus carpio)

1. 1. Averaged acoustic-evoked potential (AEPs) in the medulla and midbrain were recorded, as were changes in heart rate, indicating arousal, to a previous non-acoustic priming stimulus. 2. 2. Useful AEP measures were amplitude of the early biphasic wave (< 10 msec) in medulla and amplitude and duration of this wave in midbrain. 3. 3. There was a negative regression of heart rate and medullary AEP amplitude especially evident for a 2 sec light stimulus. Decreased AEP amplitude in both regions was induced by water movement and an increase in midbrain AEP duration by the tactile stimulus. 4. 4. Arousal effects even on these early AEP measures are specific to the form of arousing stimulus.

Sleep and acoustic-evoked potentials of alcoholics in the withdrawal phase

Sleep and acoustic-evoked potentials of alcoholics in the withdrawal phase