Biomedical subjects
Publications and source records attributed to M Ouaknine.
A 51 year-old man developed an extensive osteolytic response to wear debris in an uncemented porous-coated total hip arthroplasty, with metal/polyethylene interface, which had been implanted eighteen years previously. This reaction, which involved the upper femur and the ilium, produced a mass which compressed the pelvic viscera.
Coupling between the vocal folds is one of the nonlinear mechanisms allowing regulation and synchronization of mucosal vibration. The purpose of this study was to establish that modulations such as diplophonia and abnormalities observed in vocal signals that may be observed in some cases of laryngeal pathology can be considered as nonlinear behavior due to the persistence of some physical interaction (coupling). An experimental model using excised porcine larynx was designed to create tension asymmetry between the vocal folds and to obtain vocal signals with modulations. Signals were analyzed by spectral analysis and the phase portrait method. Results were compared with computer-generated synthetic signals corresponding to nonlinear combinations of sinusoid signals. Under these conditions, evidence of nonlinear behavior was detected in 85% of experimental signals. These findings were interpreted as a demonstration of vocal fold interaction. Based on these findings, the authors conclude that (1) coupling must be taken into account in physical models of laryngeal physiology, and that (2) methods of nonlinear dynamics may be used for objective voice analysis.
It has been shown that voice signal abnormalities, particularly in unilateral laryngeal paralysis (ULP), are not always randomly distributed and that "statistical" indexes of regularity, such as jitter and shimmer, may be unreliable in these cases. The techniques of nonlinear dynamics, particularly phase portraits, have been used to demonstrate that some of the abnormalities observed were the consequence of nonlinearity of glottic function. From a theoretical point of view, determination of Lyapunov exponents allows quantification of the complexity of the phase portraits. The authors studied vocal signals recorded in 12 normal subjects and 26 patients with ULP and calculated the largest Lyapunov exponent (LLE). In normal subjects, LLE mean value was 0.380 (SD = 0.182). In patients with ULP, LLE mean value was 0.570 (SD = 0.337). The difference is significant at P = 0.031. Determination of LLE was compared to more "classical" indexes such as jitter and oral airflow during phonation. A principal component analysis showed that information contained in LLE was not redundant but complementary to the other parameters.
A case of epithelioid sarcoma localized in the palm of the left hand in a 32-year-old woman is reported. The tumor evolved for many years, clinically and microscopically simulating palmar fibromatosis. Epithelioid sarcoma is an uncommon malignant tumor, often misdiagnosed by surgeons and pathologists. It occurs in young patients and is often localized at the upper distal extremity. Microscopically, epithelioid sarcoma shows nodules manifesting fibrous hyaline cores with central necrosis. It contains epithelioid and spindle cells immunoreactive to keratin, epithelial membrane antigen and vimentin. Recurrences, lymph node metastases and lung metastases are frequent. Surgical literature tends to recommend wide "en bloc" excision or amputation, combined or not with adjuvant radiation therapy.
We investigated the possibility of obtaining an anteroposterior body response to galvanic vestibular stimulation (GVS) by applying an equivalent stimulus to both sides of the vestibular apparatus. An original 'double fronto-mastoidal' stimulation was used on eight subjects standing with their head facing forwards. Both the onset and the cut-off of the current did induce an anteroposterior body tilt, without any lateral component. The amplitude of the tilt increased as a function of stimulus intensity. GVS evokes anteroposterior or lateral sway of similar spatio-temporal features according to the stimulation configuration. We suggest that the central nervous system makes use of the discrepancy between the left and right vestibular activity to orientate the response: equivalent afferent flows would result in an anteroposterior body response whereas lateral sway is obtained with discrepant ones.
Amputation for tumours is rarely carried out nowadays and has few specific technical features, apart from the rare cases where ingenuity is required to gain a few centimetres in length of a stump. As far as possible, the decision for amputation should not be imposed; it is better that the patient himself should take the initiative. The prosthesis and its constraints should be described honestly to avoid subsequent disappointment. Prevention of a painful phantom limb must always be undertaken, and based on certain operative and perioperative precautions. The most important factors are treatment by psychotropic agents and the quality of the human relationships between patient and surgeon.
One of the main factors involved in the laryngeal dynamic's non-linearity is the coupling between the two vocal folds. Evaluation of the different coupling elements requires various investigations. The present work evaluate the non-linearity effects in clinical situations such as unilateral laryngeal paralysis using Lyapunov's coefficients. It also demonstrate the coupling effects on excised larynx made experimentally asymmetrical, using a specially designed device to measure vibrations from each vocal fold (opto-reflectometer).
The forced voice corresponds with increased peri-laryngeal tension during phonation caused by inappropriate muscle action. It is usually accompanied by a characteristic posture (the face thrust forwards, tension in the neck muscles etc...). This posture may cause dysfunction of the cords themselves, leading to dysphonia, and perhaps requiring laryngeal microsurgery. Our project aimed to put forward and validate a system of objective, non-invasive measurements of the postural features of the forced voice, in order to improve the management of these patients. The study was prospective, comparing a control group with no previous vocal problems with a group of patients with problems of laryngeal dysfunction. We carried out a number of simultaneous measurements of postural and segmental activity during phonation, using in parallel an accelerometer, a method of cine-analysis, and a postural platform. Recordings were made during phonation, but only analysed during the resting phase. It turned out that the speed of displacement of the centre of gravity was the most useful discriminating factor. The mean value was 0.07 (displacement type 0.126) for the control group, and 0.32 (displacement type 0.211) for the patient group. The discrimination between these two groups was significant (p < 0.001, Mann-Whitney test). The reliability of this measurement allows us to envisage the inclusion into the clinical investigation package of measurements of the postural and segmental changes in the forced voice.
Vestibular inputs tonically activate the anti-gravitative leg muscles during normal standing in humans, and visual information and proprioceptive inputs from the legs are very sensitive sensory loops for body sway control. This study investigated the postural control in a homogeneous population of 50 unilateral vestibular-deficient patients (Ménière's disease patients). It analyzed the postural deficits of the patients before and after surgical treatment (unilateral vestibular neurotomy) of their diseases and it focused on the visual contribution to the fine regulation of body sway. Static posturographic recordings on a stable force-plate were done with patients with eyes open (EO) and eyes closed (EC). Body sway and visual stabilization of posture were evaluated by computing sway area with and without vision and by calculating the percentage difference of sway between EC and EO conditions. Ménière's patients were examined when asymptomatic, 1 day before unilateral vestibular neurotomy, and during the time-course of recovery (1 week, 2 weeks, 1 month, 3 months, and 1 year). Data from the patients were compared with those recorded in 26 healthy, age- and sex-matched participants. Patients before neurotomy exhibited significantly greater sway area than controls with both EO (+52%) and EC (+93%). Healthy participants and Ménière's patients, however, displayed two different behaviors with EC. In both populations, 54% of the subjects significantly increased their body sway upon eye closure, whereas 46% exhibited no change or significantly swayed less without vision. This was statistically confirmed by the cluster analysis, which clearly split the controls and the patients into two well-identified subgroups, relying heavily on vision (visual strategy, V) or not (non-visual strategy, NV). The percentage difference of sway averaged +36.7%+/-10.9% and -6.2%+/-16.5% for the V and NV controls, respectively; +45.9%+/-16.8% and -4.2%+/-14.9% for the V and NV patients, respectively. These two distinct V and NV strategies seemed consistent over time in individual subjects. Body sway area was strongly increased in all patients with EO early after neurotomy (1 and 2 weeks) and regained preoperative values later on. In contrast, sway area as well as the percentage difference of sway were differently modified in the two subgroups of patients with EC during the early stage of recovery. The NV patients swayed more, whereas the V patients swayed less without vision. This surprising finding, indicating that patients switched strategies with respect to their preoperative behavior, was consistently observed in 45 out of the 50 Ménière's patients during the whole postoperative period, up to 1 year. We concluded that there is a differential weighting of visual inputs for the fine regulation of posture in both healthy participants and Ménière's patients before surgical treatment. This differential weighting was correlated neither with age or sex factors, nor with the clinical variables at our disposal in the patients. It can be accounted for by a different selection of sensory orientation references depending on the personal experience of the subjects, leading to a more or less heavy dependence on vision. The change of sensory strategy in the patients who had undergone neurotomy might reflect a reweighting of the visual and somatosensory cues controlling balance. Switching strategy by means of a new sensory selection of orientation references may be a fast adaptive response to the lesion-induced postural instability.
Recovery of head postural control after unilateral vestibular neurectomy was investigated in the alert cat by chronically recording the spontaneous neck muscle EMG activity from splenius capitis on both sides and the vestibulocollic reflexes evoked during roll and pitch tilts. Neuronal correlates occurring within the lateral (Deiters) vestibular nuclei (LVN) were also recorded during the time-course of recovery. During the acute phase (1-2 weeks), the cats exhibited strong imbalance in spontaneous neck muscle activity, characterized by increased muscular tone in the ipsilateral splenius capitis muscle and hypoactivity in the contralateral one. At the same time, the mean resting activity of Deiters' neurons strongly decreased on the deafferented side, while a slight but significant decrease was observed on the intact side. Vestibulocollic reflexes were totally lacking during the acute phase, whatever the direction and the amplitude of tilt. Recovery developed in the following weeks, leading to complete rebalance of spontaneous EMG activity as well as near to normal static vestibulocollic reflexes 5 weeks after the lesion. However, compensation remained sub-normal during roll tilts while overcompensation was found during pitch tilts, suggesting that the intact labyrinth would play a leader role in the recovery process but that bilateral cooperation of the two labyrinths is required for proper head postural control. Five weeks are also needed for a partial rebalancing of resting activity between both LVN. These results indicate that changes in neck muscle activity observed in the acute cats and that recovery found in the compensated animals could result from modifications in neural networks controlling neck musculature, such as the LVN.
A two-axis rotation monitor is described which determines the relative displacement between a pair of ultrasonic detectors using the phase difference of a continuous ultrasound wave generated by a single, distant source. The monitor has been used to measure head rotations around the vertical and horizontal axes, but can easily be adopted to other body segment rotations or translations. The device produces high sensitivity recordings of wide spatial and dynamic range. Although the device is quite linear with good isolation between channels, a computer-based linearization/calibration routine is described which further increases linearity and reduces crosstalk. The device is unobtrusive, inexpensive, and has proven reliable and easy to use.
Functional treatment of humeral shaft recent fractures by A. Sarmiento's method was described in 1977. It is based on fixation with a plaster or plastic sleeve individually molded. This sleeve keeps free the adjacent joints, allowing an early functional rehabilitation and a fast consolidation. A 50 cases serial study from 1983 to 1987, confirms the advantages of a method which allies reasonable means, safety and complete reliability to obtain a good and rapid consolidation (one case of non-union due to a technical failure), and rapidly recovered function. We had frequently resulting axial defects: 16 patients have mal-union with more than 10 degrees of angular deformity but without any functional consequences. The advantage of this method compared to usual orthopaedic, or surgical treatments leads us to propose it to most of our patients.
Optical corrections may produce, during the first days of wearing, behavioral and psychophysiological changes such as a sensation of illusory motion of the visual world upon head rotation and errors in the manipulation of objects under visual guidance. After a few days, adaptation takes place, leading to the recovery of adequate sensory-motor performance. We describe an experimental system designed to study the adaptation of the visuo-manual system after exposure to optical corrections. The systems consists of a data tablet/digitizer and a micro computer. The quantification of the adaptation is based on the comparison of the average performance of a subject in a visuo-manual pointing task before and after a practice period consisting of pointing at visual targets through the optical corrections. Preliminary results from tests executed with normal subjects show that the system is perfectly suitable to determine the ability of an individual to adapt to optical corrections. This system can be used to systematically study the adaptation phenomena resulting from the alteration of the normal visuo-manual relationship by optical systems.
This study describes a novel system allowing the noncontact measurement of vibration of each vocal fold. The system is based on reflectometry, i.e. measurement of light bouncing off a vibrating object. The system works in natural light and is sensitive, compact, and inexpensive. We have used this system for separate and simultaneous detection of the vibration of each vocal fold in excised porcine larynges. Normal conditions of vibration and asymmetry of tension leading to biphonations were studied. Analysis of each vibrating cycle reveals interaction between the vocal folds allowing synchronous vibration despite their physical asymmetry or episodes of period doubling.
Neurological deficiency can occur during or after spinal surgery. The most severe complications are seen after instrumental correction for scoliosis or kyphosis. Regression of paraplegia, paraparesia and Brown-Sequard syndrome is never a certainty and usually incomplete. Preoperative manoeuvres and evoked potentials do not provide absolute security and metal instrumentation should always be used prudently. The main risk factors are vertebral malformation, major kyphosis, preoperative signs of neurological deficit, excessive correction and double anterior and posterior access. Finally, the canal is poorly vascularized from T4 to T8 or T9 which can raise further problems. Cordal deficiency during or following almost always requires removal of the metal implant, and exploration of the canal possibly with MRI. Injury include direct contusion of the spinal cord, devascularization and compressive haematomas. The frequency of neurological complications is currently about 1% and only extreme prudence and knowledge of causes can reduce this rate.