Treatment of vocal tremor with bilateral magnetic resonance imaging-guided focused ultrasound of the ventral intermediate thalamic nucleus: illustrative case

BACKGROUND

Essential vocal tremor is a difficult disease entity to treat with a poor response to existing medical management and limited options for surgical management of the disease. Magnetic resonance imaging-guided focused ultrasound (MRgFUS) is an emerging treatment modality with encouraging results for limb tremor in patients with essential tremor, but data are limited for the treatment of vocal tremor.

OBSERVATIONS

This is the case of a 69-year-old male with a history of essential vocal tremor severely limiting his ability to perform his occupation as an opera singer. He underwent staged bilateral ventral intermediate nucleus of the thalamus thalamotomy with MRgFUS for the treatment of his bilateral upper extremity tremor with near complete resolution of his vocal tremor after a second procedure.

LESSONS

Bilateral MRgFUS may be a safe and efficacious option for the treatment of essential vocal tremor. Further research into optimal patient selection, precise target location, and treatment parameters is needed.

Ipsilesional Mu Rhythm Desynchronization and Changes in Motor Behavior Following Post Stroke BCI Intervention for Motor Rehabilitation

Loss of motor function is a common deficit following stroke insult and often manifests as persistent upper extremity (UE) disability which can affect a survivor's ability to participate in activities of daily living. Recent research suggests the use of brain-computer interface (BCI) devices might improve UE function in stroke survivors at various times since stroke. This randomized crossover-controlled trial examines whether intervention with this BCI device design attenuates the effects of hemiparesis, encourages reorganization of motor related brain signals (EEG measured sensorimotor rhythm desynchronization), and improves movement, as measured by the Action Research Arm Test (ARAT). A sample of 21 stroke survivors, presenting with varied times since stroke and levels of UE impairment, received a maximum of 18-30 h of intervention with a novel electroencephalogram-based BCI-driven functional electrical stimulator (EEG-BCI-FES) device. Driven by spectral power recordings from contralateral EEG electrodes during cued attempted grasping of the hand, the user's input to the EEG-BCI-FES device modulates horizontal movement of a virtual cursor and also facilitates concurrent stimulation of the impaired UE. Outcome measures of function and capacity were assessed at baseline, mid-therapy, and at completion of therapy while EEG was recorded only during intervention sessions. A significant increase in r-squared values [reflecting Mu rhythm (8-12 Hz) desynchronization as the result of attempted movements of the impaired hand] presented post-therapy compared to baseline. These findings suggest that intervention corresponds with greater desynchronization of Mu rhythm in the ipsilesional hemisphere during attempted movements of the impaired hand and this change is related to changes in behavior as a result of the intervention. BCI intervention may be an effective way of addressing the recovery of a stroke impaired UE and studying neuromechanical coupling with motor outputs. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT02098265.

Behavioral Outcomes Following Brain-Computer Interface Intervention for Upper Extremity Rehabilitation in Stroke: A Randomized Controlled Trial

Stroke is a leading cause of persistent upper extremity (UE) motor disability in adults. Brain-computer interface (BCI) intervention has demonstrated potential as a motor rehabilitation strategy for stroke survivors. This sub-analysis of ongoing clinical trial (NCT02098265) examines rehabilitative efficacy of this BCI design and seeks to identify stroke participant characteristics associated with behavioral improvement. Stroke participants (n = 21) with UE impairment were assessed using Action Research Arm Test (ARAT) and measures of function. Nine participants completed three assessments during the experimental BCI intervention period and at 1-month follow-up. Twelve other participants first completed three assessments over a parallel time-matched control period and then crossed over into the BCI intervention condition 1-month later. Participants who realized positive change (≥1 point) in total ARAT performance of the stroke affected UE between the first and third assessments of the intervention period were dichotomized as "responders" (<1 = "non-responders") and similarly analyzed. Of the 14 participants with room for ARAT improvement, 64% (9/14) showed some positive change at completion and approximately 43% (6/14) of the participants had changes of minimal detectable change (MDC = 3 pts) or minimally clinical important difference (MCID = 5.7 points). Participants with room for improvement in the primary outcome measure made significant mean gains in ARATtotal score at completion (ΔARATtotal = 2, p = 0.028) and 1-month follow-up (ΔARATtotal = 3.4, p = 0.0010), controlling for severity, gender, chronicity, and concordance. Secondary outcome measures, SISmobility, SISadl, SISstrength, and 9HPTaffected, also showed significant improvement over time during intervention. Participants in intervention through follow-up showed a significantly increased improvement rate in SISstrength compared to controls (p = 0.0117), controlling for severity, chronicity, gender, as well as the individual effects of time and intervention type. Participants who best responded to BCI intervention, as evaluated by ARAT score improvement, showed significantly increased outcome values through completion and follow-up for SISmobility (p = 0.0002, p = 0.002) and SISstrength (p = 0.04995, p = 0.0483). These findings may suggest possible secondary outcome measure patterns indicative of increased improvement resulting from this BCI intervention regimen as well as demonstrating primary efficacy of this BCI design for treatment of UE impairment in stroke survivors. Clinical Trial Registration: ClinicalTrials.gov, NCT02098265.

Early Findings on Functional Connectivity Correlates of Behavioral Outcomes of Brain-Computer Interface Stroke Rehabilitation Using Machine Learning

The primary goal of this work was to apply data-driven machine learning regression to assess if resting state functional connectivity (rs-FC) could estimate measures of behavioral domains in stroke subjects who completed brain-computer interface (BCI) intervention for motor rehabilitation. The study cohort consisted of 20 chronic-stage stroke subjects exhibiting persistent upper-extremity motor deficits who received the intervention using a closed-loop neurofeedback BCI device. Over the course of this intervention, resting state functional MRI scans were collected at four distinct time points: namely, pre-intervention, mid-intervention, post-intervention and 1-month after completion of intervention. Behavioral assessments were administered outside the scanner at each time-point to collect objective measures such as the Action Research Arm Test, Nine-Hole Peg Test, and Barthel Index as well as subjective measures including the Stroke Impact Scale. The present analysis focused on neuroplasticity and behavioral outcomes measured across pre-intervention, post-intervention and 1-month post-intervention to study immediate and carry-over effects. Rs-FC, changes in rs-FC within the motor network and the behavioral measures at preceding stages were used as input features and behavioral measures and associated changes at succeeding stages were used as outcomes for machine-learning-based support vector regression (SVR) models. Potential clinical confounding factors such as age, gender, lesion hemisphere, and stroke severity were included as additional features in each of the regression models. Sequential forward feature selection procedure narrowed the search for important correlates. Behavioral outcomes at preceding time-points outperformed rs-FC-based correlates. Rs-FC and changes associated with bilateral primary motor areas were found to be important correlates of across several behavioral outcomes and were stable upon inclusion of clinical variables as well. NIH Stroke Scale and motor impairment severity were the most influential clinical variables. Comparatively, linear SVR models aided in evaluation of contribution of individual correlates and seed regions while non-linear SVR models achieved higher performance in prediction of behavioral outcomes.

Machine Learning Classification to Identify the Stage of Brain-Computer Interface Therapy for Stroke Rehabilitation Using Functional Connectivity

Interventional therapy using brain-computer interface (BCI) technology has shown promise in facilitating motor recovery in stroke survivors; however, the impact of this form of intervention on functional networks outside of the motor network specifically is not well-understood. Here, we investigated resting-state functional connectivity (rs-FC) in stroke participants undergoing BCI therapy across stages, namely pre- and post-intervention, to identify discriminative functional changes using a machine learning classifier with the goal of categorizing participants into one of the two therapy stages. Twenty chronic stroke participants with persistent upper-extremity motor impairment received neuromodulatory training using a closed-loop neurofeedback BCI device, and rs-functional MRI (rs-fMRI) scans were collected at four time points: pre-, mid-, post-, and 1 month post-therapy. To evaluate the peak effects of this intervention, rs-FC was analyzed from two specific stages, namely pre- and post-therapy. In total, 236 seeds spanning both motor and non-motor regions of the brain were computed at each stage. A univariate feature selection was applied to reduce the number of features followed by a principal component-based data transformation used by a linear binary support vector machine (SVM) classifier to classify each participant into a therapy stage. The SVM classifier achieved a cross-validation accuracy of 92.5% using a leave-one-out method. Outside of the motor network, seeds from the fronto-parietal task control, default mode, subcortical, and visual networks emerged as important contributors to the classification. Furthermore, a higher number of functional changes were observed to be strengthening from the pre- to post-therapy stage than the ones weakening, both of which involved motor and non-motor regions of the brain. These findings may provide new evidence to support the potential clinical utility of BCI therapy as a form of stroke rehabilitation that not only benefits motor recovery but also facilitates recovery in other brain networks. Moreover, delineation of stronger and weaker changes may inform more optimal designs of BCI interventional therapy so as to facilitate strengthened and suppress weakened changes in the recovery process.

Hereditary spherocytosis and other hemolytic anomalies distort diabetic control by glycated hemoglobin

Glycated hemoglobin (%HbA1c) has become a well established and reliable long term parameter indicative of the mean glucose load of the preceding 8 -10 weeks. A normal life span of approximately120 days of the red blood cells (RBC) is an essential condition. Hemolytic affections are characterized by a shorter life span, reducing the overall glucose uptake and %HbA1c. Measured %HbA1c is no longer correlated with mean blood glucose of the preceding period, simulating false low values. Underestimation of this kind is demonstrated for several hemolytic conditions, among them hereditary spherocytosis (HS). This latter, often harmless anomaly may lead to serious underestimation of glucose load. Recent investigations show not only a much higher incidence of HS than hitherto admitted (approximately 1 in 250 persons) but also an abnormally high incidence of diabetes in this hemolytic affection. In the presence of hemolysis %HbA1c is to be interpreted with caution. This justifies systematic detection of HS in routine hematology using--if available--the increase of the percentage of hyperchromic RBC.

HbSC hemoglobinopathy suspected by chest x-ray and red blood cell morphology

Thorax scan was performed for elucidation of a pulmonary problem in a Nigerian immigrant. The aspect of the vertebrae suggested sickle cell disease, of course without specification of the genotype. Routine hematological tests seemed compatible with an HbSC disease, showing typical laboratory features, namely a significant proportion of hyperchromic RBC, corresponding to secondary, non hereditary spherocytosis, presence of numerous target cells and occasional HbC crystals on Pappenheim stained blood films. The diagnosis of HbSC disease was confirmed by HPLC, iso-electric focusing and citrate agar electrophoresis of hemoglobin and by reverse phase HPLC of globin-chains. This case illustrates the importance of screening for hemoglobin anomalies as it is performed in a multiethnic country such as the Grand Duchy of Luxembourg

[Domestic abuse of dementia patients: data collection in a difficult research area]

In the context of a longitudinal dementia caregiver stress study, a short questionnaire was developed in order to assess domestic abuse of dementia patients. By embedding the sensitive topic of domestic violence in a different research context, good compliance in the sample could be achieved which results in high prevalence rates.

Influence of urea on HbA1c-determinations by Menarini HA-8140 and on the difference between immunoturbidimetric and HPLC-HbA1c-results

A secondary peak (#C) included in the HbA1c-calculation by the HA-8140 HPLC (Menarini) shows a fairly good correlation with serum urea. The correlation with HbA1c and with serum glucose is at first glance significant but reveals at a closer look being biased by some incorrect assumptions. The difference between immunoturbidimetric determination (Tinaquant HbA1c II Roche) and HPLC shows a similar behaviour to urea as does the #C-peak of the chromatographic separation. This peak as well as the difference between both determinations of HbA1c could be attributed to carbamylated haemoglobin. The definitive identity has to be proven. This peak could be a monitoring tool for long-time urea. The integration of this peak into total HbA1c by the HA-8140 (Menarini) can lead to a false diagnosis of diabetes in non-diabetic patients with elevated urea.

Multicenter evaluation of the Micral-Test II test strip, an immunologic rapid test for the detection of microalbuminuria

OBJECTIVE

To assess the performance of the Micral-Test II immunologic test strip for the detection of microalbuminuria, a multicenter evaluation in eight European study sites was performed.

RESEARCH DESIGN AND METHODS

Using both the Micral-Test II test strip and the routine method for the determination of albumin concentration, we investigated 2,228 urine samples from diabetic patients. Additionally, interperson variability, color stability, and possible interfering factors (temperature, pH, leucocyturia, erythrocyturia, and drugs) were tested.

RESULTS

For a cutoff concentration of 20 mg/l with respect to the routine methods, a sensitivity of 96.7% and a specificity of 71% were calculated for the Micral-Test II test strip. The negative predictive value was 0.95, and the positive predictive value was 0.78, with a prevalence of positive samples (laboratory method) of 52%. The interperson variability of color interpretation showed 93% concordant readings. The interference study showed an influence of oxytetracycline, leading to higher readings. There was no interference from pH. A sample temperature of < 10 degrees C led to lower readings. In the case of samples with massive leucocyturia and erythrocyturia that may delete the chromatographic process, waiting an additional 1-2 min is needed before reading.

CONCLUSIONS

The results of the multicenter evaluation show that the Micral-Test II test strip permits an immediate and reliable semiquantitative determination of low albumin concentrations in urine samples with an almost user-independent color interpretation.

Screening for oligoalbuminuria by means of Micral-Test II. A new immunological test strip

A new dip-and-read test strip for systematic detection of oligoalbuminuria was assessed. The test is based on a competition for gold-labelled anti-albumin antibodies between specimen albumin and albumin molecules immobilised in the test strip. The final detection area is coloured by excess free antibodies. The colour reaction is compared to a colour scale reflecting 0, 20, 50 and 100 mg/l albumin. Method comparison with an immuno-turbidimetric quantitative technique was performed on 747 unselected specimens. The correlation coefficient was 0.938, the Spearman rank coefficient 0.863. In spite of considerable overlap of the results attributed to the 4 colour blocks, the test was found to be perfectly useful as a 2-class-test, as there were practically no false negative tests and as all the specimens yielding reactions stronger than the 20 mg/l colour block were found to contain 20 mg/l albumin or more by the reference method. The colour block 20 mg/l represents the inevitable grey zone, results in this range being found to be normal and increased above this pathological cut-off by the reference method. Follow-up by quantitative albumin dosage in timed morning urine for all specimens found positive by the dipstick confirms the existence of oligoalbuminuria, eliminating the cases of orthostatic albuminuria, of oligoalbuminuria simulated by low diuresis and the false positives due to oversensitivity of the test strip. The test strip is easy to handle. The reaction time is short and the colour reaction is stable and easy to read. Systematic use of this test in routine urine chemistry is suggested.

Evaluation of the humoral immune response to different antigens in Arkansas Regressor and Progressor chickens

Arkansas Regressor and Progressor chickens were re-evaluated for their immune response to different antigens. Chickens received i.v. injection of either SRBC (10 birds per line) or Salmonella pullorum (SP; 10 birds per line) at 7 wk of age, and sera were collected at 6, 13, and 20 d postimmunization. A third group of birds (10 birds per line) received and i.m. injection of GAT emulsion at 7 and 12 wk of age, and sera were collected at 10 and 14 wk of age. There were significant differences between the two lines in their humoral immunity to SRBC, SP, and GAT. Such results suggest genetic control of humoral immunity to these antigens in these lines. It is unknown whether humoral immunity to these antigens is correlated to regression of tumors induced by Rous sarcoma virus.

Coexistence of two distinct populations of neutrophilic granulocytes, one normal and one partial MPO-deficient

A case of double neutrophilic population in a more or less symptomless patient is described. The diagnosis is made on one hand by the presence of 2 distinct neutrophil clusters on the PEROX display of the H* 1 hematological automate, on the other hand by cytochemical peroxidase staining which clearly confirms the existence of two populations. One of the populations shows normal MPO activity, whereas the second one is characterized by partial MPO deficiency.

Auditory brain stem response monitoring during middle ear surgery

Conductive hearing loss can be determined in the course of middle ear surgery by sound probe stimulation and simultaneous recording of auditory brain stem responses. Mechanical properties of the ossicular chain, usually judged subjectively by the surgeon's visual and tactile senses, can be quantified objectively. Thus, disarticulation of ossicles can be localized precisely, and fixation of the head of the malleus can be differentiated from stapes fixation. Moreover, the function of the reconstructed ossicular chain or prosthesis may be ascertained.

[Is measuring impedance following ear operations an aid in the analysis of postoperative sequelae?]

While the diagnostic value of pre-operative tympanometry is undisputed, there are very few publications on its application in postoperative control of sound conduction development. We measured otoadmittance several times after middle ear surgery in 42 cases. A significant increase of maximal admittance is found over a period of up to 24 months in case of tympanoplasty type I (16 cases, Fig. 1), and after stapedectomy (8 cases, Fig. 3). After a tympanoplasty of type III (Wullsteins classification) many tympanograms were flat, even in the follow-up examination, but a tendency to improvement can also be observed (Fig. 2). In none of the groups was hearing loss correlated with otoadmittance. Thus, tympanometry is not suitable for postoperative evaluation of conductive hearing loss. Nevertheless, our results indicate that the healing process after tympanoplasty modifies middle ear sound transmission for quite a long time.

Conduction of thermal stimuli in the human temporal bone

Temperature changes at different locations in the labyrinth were measured in human temporal bone preparations after syringing with water. In order to simulate physiological conditions, the preparations were placed in a water bath at 37 degrees C. The maximum temperature changes in the horizontal semicircular canal after syringing with temperatures symmetrical to body temperature (44 degrees or 30 degrees C) were found to be clearly asymmetrical (with mean values of 0.6 and -0.3K). From measurements in the external auditory meatus, findings showed that the reference temperature was 34 degrees C in front of the tympanic membrane, which explains the asymmetry recorded. Measurements at different locations showed that the temperature first changes in the regions of the ampullae of the horizontal and the superior semicircular canals. In the vestibule the onset and decay of the temperature change is delayed. The time courses of the temperature difference between locations demonstrate that the temperature difference across the horizontal semicircular canal, which would be responsible for any convective effect in the endolymph, is of shorter duration than the absolute temperature change, which would be responsible for any temperature-mediated volume changes.

[Effect of the stimulus medium--water or air--in thermal evaluation of the vestibular apparatus]

The influence of the stimulus medium in thermal vestibular tests has been investigated by many authors, comparing nystagmus reactions after air and water irrigations. We first measured temperature changes in the ear canal and in the horizontal semicircular canal after both kinds of stimuli, using human temporal bone preparations, which were placed in a water bath of 37 degrees C. Irrigations were done with air of 45 and 27 degrees C with a flow of 5 l/min during 45 s and with 100 ml water of 44 and 30 degrees C during 30 s. The maximum temperature changes in the ear canal are almost equal after both kinds of irrigation (see Figs. 2 and 3). The change of temperature, however, lasts longer after water irrigation. The time constants are 20 and 57 s for the decay after warm and cold water irrigation and 9 and 20 s after air irrigation, respectively. The maximum temperature change in the lateral part of the horizontal semicircular canal is 0.4 and -0.3 degree after warm and cold irrigation with water. The corresponding values after irrigation with air are 0.1 and -0.15 degree. In addition, we investigated the effect of irrigating temporal bone preparations with perforated tympanic membranes (Fig. 4). After irrigation with air of 45 degrees C, the temperature in the horizontal semicircular canal decreased due to evaporation of humidity in the tympanic cavity. The equipment of choice for the irrigation of such ears is a stimulator reported by Scherer, where water flows through a silicon bubble which coats the ear canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced platelet phenylalanine hydroxylating activity in a subgroup of untreated schizophrenics

Considering that platelet phenylalanine hydroxylase represents a rather high percentage of the total body hydroxylating activity, the encountered deficiency may very well be considered as one of the exacerbing factors of psychosis of this type. Further biochemical and clinical characterization of the described subgroup is in progress.

Solvent flow in osmosis and hydraulics: network thermodynamics and representation by bond graphs

A tutorial introduction to network thermodynamics and bond graphs as a modeling technique for any physiochemical system is presented with a particular emphasis on reaction diffusion systems. It combines the generality of nonequilibrium thermodynamics with the advantages of a graph theory. It is applied to the representation of osmotic and hydraulic flows across a semipermeable membrane on the basis of the solvent diffusion theory of osmosis. This theory allows for an easy derivation of the van't Hoff law of osmotic pressure from the Fick law of diffusion. Molar flows and volume flows are transformed into one another by transducers, the modulus of which is the partial molar volume of water, in such a way that power is conserved by a reciprocal transformation between the chemical potential and the pressure. Osmotic and hydraulic resistances are calculated, and their dependence on pore size is estimated.

[Problems with electronic data processing in the practice of an established otorhinolaryngologist]

Theoretically the computer would be a useful tool to help the practitioner with his multiple medical and administrative duties. At present however the modalities of the data input and their poor acceptability for the patient are an obstacle on the way to a wider use of electronic data processing in the physician's office.

A long-term study of hearing in children following neonatal hyperbilirubinemia

We conducted a long-term study of 85 children with known transient neonatal hyperbilirubinemia to determine if their hearing had been affected. None of the children had neural symptoms such as kernicterus. The children ranged in age from birth to 9 months and were studied by means of brainstem evoked response audiometry (BERA). Thirty-four of the children were studied sequentially between 15 and 80 months after the initial examination. Our results showed that there was no significant correlation between serum bilirubin concentrations and BERA thresholds or latencies. These findings indicate that, unlike manifest cases of kernicterus, neonatal hyperbilirubinemia does not affect neonatal hearing when treated promptly.

Experimental investigations on the suitability of the carbon dioxide laser for stapedotomy

Surgery of the footplate may cause a number of possible complications such as cochlear hearing defects or even complete loss of hearing. This has made it necessary to look for improved techniques. When a laser is used for stapedotomy, the energy transmitted to the cochlea must be reduced to the lowest possible level. We thus investigated the carbon dioxide laser to determine whether it would prove to be more advantageous than the argon laser. Animal experiments showed that CO2 laser irradiation is well tolerated. Tests performed on isolated petrous bone resulted in the development of a new surgical instrument suitable for stapedotomy using the CO2 laser. Temperature and pressure measurements were carried out on a simplified model of the human cochlea. Our findings indicated that, with both types of laser, the irradiation required to perforate the otosclerotically thickened footplate adversely affects temperature and pressure development in the cochlea.

[Use of a body acoustic probe and the conduction of brain stem potentials for the determination of sound conduction during tympanoplasty]

A new procedure of evoking brain stem potentials is introduced. Contrary to evoking brain stem potentials by acoustic stimulation via earphone or loudspeaker, we touch the middle ear apparatus at various locations using a piezoelectric transducer with a screwed-on probe, thus causing physiological movements within the sound conducting structures (Fig. 3). As a reaction to this kind of stimulation--1000 clicks with a duration of 0.1 ms were given--far field brain stem potentials can be recorded. The calibration of this special sound probe--not bigger than a pencil (Fig. 1)--was made by equalizing the mechanically and acoustically evoked guinea-pig brain stem potentials (Fig. 2). The intraoperative control of sound transmission to the inner ear is ascertained by the mechanically evoked potential's latency and amplitude. In order to apply the procedure in tympanoplasty we made a number of recordings after having simulated various kinds of middle ear pathology in the guinea pig. Four cases of various kinds of ear disease (interruption of the ossicular chain - Fig. 4 -, soft tissue bridge between incus and stapes - Fig. 5 -, otosclerosis - Fig. 6 -, Torp prosthesis - Fig. 7 -) are presented. As a result of our intraoperative recordings we can demonstrate that the presented method may be a valuable contribution to the examination of acoustic transmission through the middle ear during tympanoplasty under general anesthesia.

[Functional effect of the argon laser on the hearing organ of the guinea pig]

While numerous histological findings point towards a possible destruction of inner-ear structures by the Argon-Laser we still miss a satisfactory statement concerning functional impact of stapedectomy or stapedotomy using laser beams. To investigate this we irradiated the promontorium of each of 10 guinea-pigs with laser powers between 0.6 W and 2.2 W ten times for 0.5 s. Then, and on the first, fifth and tenth postoperative day we recorded the brainstem potential evoked by bone-conducted clicks. We found that after the application of laser power up to 1.2 W a reversible threshold shift of up to 20 dB took place. Above powers of 1.2 W a permanent threshold shift was found (Fig. 1). Before sacrificing the animals we recorded the course of temperature in the perilymph during laser irradiation (Fig. 2 and 3). In order to set application limits of power within we consider laser impact functionally critical we compared the temperature increment during single shots and permanent elevation of the temperature above body temperature with values we have found earlier at the human petrous bone (Fig. 2 and 3). This led us to the conclusion that the temperature increment during the shot might be the limiting factor as far as the deterioration of inner-ear function is concerned. This may very well coincide with our hypothesis (Thoma and coworkers, 1981) that the vaporization of endocochlear fluid during the shot is a possible cause of cochlear malfunction after stapedectomy by laser.

Isolation of high and low molecular weight components from chicken sera that have Rous sarcoma virus neutralizing activity

Blood sera components from Arkansas regressor line (R-line) and progressor line (Pr-line) chickens are compared for the first time for Rous sarcoma virus neutralizing activity. Sera was fractionated by Sephadex G-100 filtration into a high molecular weight fraction I (HMW-I) and a low molecular weight fraction II (LMW-II) component (HMW-I greater than 14,000 daltons, LMW-II less than 5,000 daltons). Both fractions from each line of chickens exhibit activity against Rous sarcoma virus (RSV) judged by a wing web assay. Both HMW-I (principally antibodies) and LMW-II neutralized RSV when obtained from hyperimmune R-chickens and Pr-chickens with large progressing tumors. However, HMW-I and LMW-II obtained from R- or Pr-chickens before challenge contain so RSV neutralizing activity. The novel low molecular weight fraction II disappeared from the sera of R-line chickens 2 weeks after tumor regression, whereas the HMW-I persisted after tumor regression.

[Evoked response audiometry in circulatory disorders in the brainstem (author's transl)]

In the case of retrocochlear lesions evoked potentials from different stages of the auditory pathway were recorded. Four Patients with nearly normal hearing threshold and normal cortical potentials show reduced medium latency potentials show reduced medium latency potentials due to circulatory dysfunction in the brainstem. Desynchronisation effects on the brainstem level are completely compensated in the cortex. The damage of the auditory pathway could not be found by X-ray or other usual clinical methods. In the two cases described improvement under medical treatment can be demonstrated.

Diagnosis of abnormal hearing adaptation by brainstem potentials

Adaptation of the human brainstem potentials was investigated using three types of stimulation: paired clicks, varied click rates, and a gap in a continuous tone. Brainstem responses to the second of a pair of clicks is hardly influenced by pathological adaptation. In patients with a normal subjective threshold decay (Carhart test) peak V latencies of the brainstem potential for high click rates and for the tone gap were within the normal range. For a threshold decay of more than 20 dB, latencies were significantly prolonged. In cases of an unlimited Békésy decay the brainstem response was missing for the tone gap stimulus. Fast rate and tone gap stimulation are suitable for a sensitive illustration of the threshold tone decay.

[Measurement of temperature and sound pressure in the inner ear during application of the argon-laser (author's transl)]

Laser stapedectomy is looked upon as an operation method which may be less harmful to the inner ear. The purpose of this study was to investigate the course of temperature behind the footplate of isolated human petrous bones while using the Argon Laser. We found that a non-linear relationship exists between the power of the Laser beam, the duration of the impulse and the sudden temperature rise during the impulse. Another, though linear, relationship exists between the energy of the beam and the permanent elevation of temperature in the perilymph during repeated shots. The observation of tiny bubbles beneath the focus on the wall of a plastic tube (which we used as a model for flow studies) led us to assume that the same may be true for the perilymph, too. The bursting of these bubbles was thought to cause a sudden rise of pressure in the inner ear. We were able to measure this Laser-generated sound pressure which reached 59 dB (A) for a beam energy of 1.0 Ws. Very low frequencies, which were not determined by this method, might very well cause damage to the inner ear structures. Finally, we proved that the results found a the isolated petrous bone which we fixed in a 37 degree waterbath can be transferred to in vito conditions: The course of the temperature was investigated in the cochlea of live Guinea pigs and shortly after death without detecting any change of the results.

[Measurements of the acoustic reflex at variable static pressures (author's transl)]

Acoustic reflex measurements are made on thirty normal and three early stage otosclerotic ears at different static pressures in the ear canal and recorded as reflex-tympanogram at 200 Hz and 660 Hz probe-tone frequency. Acoustic reflexes were elicited contralaterally with a pure-tone stimulus at 2,000 Hz. This stimulus was chosen to avoid technical artifacts. An example of a normal acoustic reflex pattern as a function of variable static pressure is presented (Fig. 1). This record was made at 20 dB above the subjects reflex threshold, using 660 Hz probe-tone frequency. The reflex deflection of susceptance is positive up to pressures of plus or minus 50 mm H2O and then becomes negative. The reflex deflection of conductance is negative in the total range. A stiffened middle-ear system shows negative reflex deflection of both admittance components. The reflex-tympanograms (Fig. 2) show the admittance component curves as a function of variable static pressure with and without eliciting the acoustic reflex in case of a normal ear, using probe-tone frequencies of 220 Hz and 660 Hz at 10 dB and at 20 dB above the subjects reflex threshold. The reflex-tympanogram in case of an early stage otosclerotic ear shows negative reflex deflection of susceptance within the total pressure range indicating pathological stiffness (Fig. 3). The reflex related change of the dynamic properties was stimulated in a mathematical model of the middle-ear (Fig. 4). The measurements could be explained in a mathematical approach.