Azimuthal sound source localization of various sound stimuli under different conditions.

AIM: To evaluate azimuthal sound-source localization performance under different conditions, with a view to optimizing a routine sound localization protocol. MATERIAL AND METHOD: Two groups of healthy, normal-hearing subjects were tested identically, except that one had to keep their head still while the other was allowed to turn it. Sound localization was tested without and then with a right ear plug (acute auditory asymmetry) for each of the following sound stimuli: pulsed narrow-band centered on 250Hz, continuous narrowband centered on 2000Hz, 4000Hz and 8000Hz, continuous 4000Hz warble, pulsed white noise, and word ("lac" (lake)). Root mean square error was used to calculate sound-source localization accuracy. RESULTS: With fixed head, localization was significantly disturbed by the earplug for all stimuli (P<0.05). The most discriminating stimulus was continuous 4000Hz narrow-band: area under the ROC curve (AUC), 0.99 [95% CI, 0.95-1.01] for screening and 0.85 [0.82-0.89] for diagnosis. With mobile head, localization was significantly better than with fixed head for 4000 and 8000Hz stimuli (P<0.05). The most discriminating stimulus was continuous 2000Hz narrow-band: AUC, 0.90 [0.83-0.97] for screening and 0.75 [0.71-0.79] for diagnosis. In both conditions, pulsed noise (250Hz narrow-band, white noise or word) was less difficult to localize than continuous noise. CONCLUSION: The test was more sensitive with the head immobile. Continuous narrow-band stimulation centered on 4000Hz most effectively explored interaural level difference. Pulsed narrow-band stimulation centered on 250Hz most effectively explored interaural time difference. Testing with mobile head, closer to real-life conditions, was most effective with continuous narrow-band stimulation centered on 2000Hz.

Sound source localization.

Sound source localization is paramount for comfort of life, determining the position of a sound source in 3 dimensions: azimuth, height and distance. It is based on 3 types of cue: 2 binaural (interaural time difference and interaural level difference) and 1 monaural spectral cue (head-related transfer function). These are complementary and vary according to the acoustic characteristics of the incident sound. The objective of this report is to update the current state of knowledge on the physical basis of spatial sound localization.

Glycine preserves function and decreases necrosis in skeletal muscle undergoing ischemia and reperfusion injury.

BACKGROUND: Glycine (GLY) is a neutral amino acid that has been shown to be cytoprotective in the kidneys of dogs and rabbits undergoing ischemia-reperfusion injury. To investigate whether GLY exhibits a protective effect on skeletal muscle subjected to ischemia and reperfusion injury, we used a well-described gracilis muscle model in canines. METHODS: Twelve adult mongrel dogs were subjected to 6 hours of ischemia in 1 randomly selected side. The dogs were randomized into 2 groups: group 1 (6 animals) underwent 15 minutes of perfusion with 2.2% GLY, and group 2 (6 animals) underwent 15 minutes of perfusion with normal saline solution (NS) only. Both groups had normothermic reperfusion for 1 hour along with the corresponding perfusate. Muscle biopsy specimens were taken, frozen in liquid nitrogen, and stored at -70 degrees C. Muscle injury was evaluated at 48 hours by measuring weight gain (edema), maximal contractile force, and percent of muscle necrosis. Adenosine triphosphate (ATP) and phosphocreatine (Pcr) (an energy store for ATP synthesis) levels were determined by using high performance liquid chromatography. RESULTS: In group 1, the average weight gain was 57% +/- 11.27% while in group 2 it was 100% +/- 12.48%. Maximal muscle contractile force was 712.5 +/- 68 g for group 1 and 511 +/- 27.91 g for group 2. The amount of muscle necrosis was 30 +/- 3.7% in group 1, as opposed to 63 +/- 10% in group 2. The ATP content was 0.07 +/- 0.03 nmol/mg wet tissue weight (post-ischemia with NS) and 0.21 +/- 0.08 nmol/mg wet tissue weight (post-ischemia with GLY). Pcr content was 0.19 +/- 0.04 mmol/mg wet tissue weight (post-ischemia with NS) and 0.27 +/- 0.04 micromol/mg wet tissue (post-ischemia and infused with GLY) (P <.05). CONCLUSIONS: These data show that GLY preserves muscle function, decreases edema and the amount of muscle necrosis and preserves energy stores in this canine model. Because GLY can be safely given systemically in human beings in higher concentrations than that given in our model, as it is given in parenteral nutrition, its mechanism of action should be further investigated for its potential use in the clinical setting of ischemia and reperfusion injury.

[The monaural pseudo-stereophonic hearing aid (BAHA) in unilateral total deafness: a study of 29 patients]. / Appareillage mono pseudo stéréophonique par BAHA dans les cophoses unilatérales: à propos de 29 patients.

For many years, unilateral total deafness has been considered a minor handicap which does not require the fitting of a hearing aid. If the condition did give a major problem, the usual recommendation for this type of hearing loss was a CROS system which, in addition to problems of function and aesthetics, gave poor results. Faced with increasing demands from these patients, and given the good performance of bone conduction implants (BAHA), we decided to try to implant these devices on the deaf side, which allowed, by way of transcranial conduction, stimulation of the functioning ear and the re-establishment of a certain degree of stereophonic hearing. This study of 29 patients who were tested by stereophonic audiometry pre- and post-implantation shows that this type of aiding is beneficial, with improvement of the threshold of intelligibility against background noise of between 5 and 15 dB during Hirsch's test, correction of the "dead angle" on the deaf side, and improvement in localisation of sound in space. From the functional point of view, 88% of patients were satisfied with their aid, which they wore for 8 or 9 hours per day, and had a marked improvement in their hearing performance under various conditions which had proved very difficult for them before they were fitted with the aid. These results all demonstrate the effectiveness of the implant used in this way. The fact that sounds are received on the totally deaf side goes a long way towards establishing satisfactory hearing. True stereophonic hearing could not be established in any of the cases, because this requires input from two ears. It is for this reason that we have termed this type of aid as monaural pseudo-stereophonic.

[Prosthetic rehabilitation of unilateral anakusis. Study with stereoaudiometry]. / Réhabilitation prothétique B.A.H.A des cophoses unilatérales. Etude par la stéréaudiométrie.

We studied the clinical and stereoaudiometric results in two patients with unilateral anakusis who were rehabilitated with a bone-transmission prosthesis (B.A.H.A.) on the deaf side. Clinically, both patients improved considerably, recovering their capacity to communicate, particularly in a noisy environment. Sound localization tests demonstrated that the sound source was not precisely localized in space. Inversely, the spatial discrimination tests and the multidirectional tests showed an important improvement in comprehension of speech, particularly in the dead space of the defective hemifield. This recovery was certainly related to improved perception of high frequencies via intracranial transmission enabled by the prosthesis.

Saphenous vein thrombophlebitis (SVT): a deceptively benign disease.

PURPOSE: The association between deep vein thrombosis (DVT) and the hypercoagulable state is a well-established entity. However, the association between saphenous vein thrombophlebitis and coagulation abnormalities has not been investigated. Although thrombosis of varicose veins typically runs a benign course, phlebitis of the saphenous system may propagate to the deep system or saphenofemoral junction that requires more aggressive therapy. Given the potential similarity in clinical outcome between saphenous vein thrombophlebitis (SVT) and DVT, we have investigated the coagulation profile of patients presenting with isolated SVT. METHODS: Seventeen consecutive patients who presented to our vascular laboratory with isolated SVT had a coagulation profile performed that included antithrombin III (AT III), protein C (PC), protein S (PS) antigen and activity levels, activated protein C (APC) resistance, factor V DNA mutation, and coagulation factors II and X. All patients had duplex scans performed on both the superficial and deep venous systems. Patients with SVT only were treated with nonsteroidal antiinflammatory drugs (NSAIDs) and warm soaks as outpatients, whereas those patients found to have DVT or a clot at the saphenofemoral junction were fully anticoagulated with heparin and coumadin therapy. All 17 patients had at least one repeat coagulation profile performed up to 5 months after their SVT occurrence to ensure that the results of hypercoagulability were not transient. RESULTS: Ten (59%) of the 17 patients with SVT had abnormal coagulation profiles on initial presentation. All 10 patients who were hypercoagulable had repeat tests and 6 (35%) remained abnormal. Four patients who had abnormal results converted to normal values. Seven patients with normal coagulation profiles on initial presentation had repeat tests and all remained normal. CONCLUSION: The incidence of the hypercoagulable state in patients with SVT is high. Thirty-five percent of patients with isolated SVT had consistently abnormal coagulation profiles. Patients with SVT may be prone to the development of DVT or saphenofemoral junction thrombophlebitis and should be closely followed after the initial diagnosis of hypercoagulability.