Proprioceptive manipulations in orthograde posture modulate postural control in low back pain patients: a pilot study.

As we stand upright, perceptual afferences are crucial to successfully help generating postural motor commands. Non-Specific Low Back Pain patients frequently demonstrate a lack of proprioceptive acuity, often translating into postural control deficiencies. For the first time, to our knowledge, we studied the postural effects of proprioceptive manipulations in orthograde posture on Non-Specific Low Back Pain patients. Using static posturography recordings, we computed sway speed, speed variance, and the main direction of sway. We also addressed the patient's subjective feedbacks after being manipulated. Five minutes after the proprioceptive manipulations, our results revealed decreased speed and speed variance outcomes, but the main direction of sway was not modulated. Furthermore, after the proprioceptive manipulations, the patients also self-reported improved clinical outcomes. These findings provide new knowledge opening new fields of research as well as potential treatment strategies in Low Back Pain patients.

The very first cry: a multidisciplinary approach toward a model.

OBJECTIVES: In previous work, we showed that a rigid larynx-like geometry can generate a sound by itself. However, very little is known about the exact mechanisms and control of the larynx during the first cry of life. The goal of this work was to understand how the very first cry is generated. METHODS: Simultaneous high-speed imaging and sound recording on 2 excised 38-week term human fetus larynges were performed. The behaviors of the vocal folds and the false vocal folds were studied separately. The behavior of the vocal folds after resection of the supraglottic structures was also analyzed. A comparative acoustic analysis of the first cry and of the sound generated by the excised organs was performed. RESULTS: Our data showed that the vocal folds in a larynx with the pressure conditions of the first cry do not generate sound themselves, but induce aerodynamic conditions leading to vibrations of other parts of the larynx. CONCLUSIONS: The similarities between the sound generated by an excised larynx and the first cry suggest a lack of neurologic control of the larynx during production of the first cry. A model-algorithm is proposed.

Postural dynamics and vocal effort: preliminary experimental analysis.

OBJECTIVES: One postural characteristic of increased vocal effort is stiffening of the whole body, which in turn induces some postural instability. The study of postural instability can shed some insight into behavior or causes associated with vocal hyperfunction. PATIENTS AND METHODS: A posturography platform was used to measure the root mean square of the velocity of variation of the center of pressure (VCOP rms) of control subjects standing upright on the platform. Four conditions were analyzed: (1) standing with eyes open versus eyes closed (n: 9); (2) standing at rest versus holding a 3-kg weight (n: 15); (3) standing while reading a dialogue at normal voice level versus loud voice (n: 17), and (4) standing while reading a dialogue in a calm versus noisy (Lombard effect) ambiance (n: 19). RESULTS: Conditions leading to a stiffening of the body (eyes closed and weight holding) were associated with an increased instability assessed by the VCOP rms. In phonatory conditions leading to vocal effort, the mean VCOP rms was significantly increased: in 19 subjects reading a dialogue in a calm ambiance the mean VCOP rms was at 11.19 mm/s, and the VCOP rms raised 16.69 mm/s with surrounding noise at 82 db (Lombard effect). CONCLUSION: Increased vocal effort is associated with increased VCOP rms in most subjects studied. The effects of VCOP rms as a postural index allowing noninvasive assessment of the voice in pathology warrants further study.

Using the relaxation oscillations principle for simple phonation modeling.

Well-known multimass models of vocal folds are useful to describe main behavior observed in human voicing but their principle of functioning, based on harmonic oscillation, may appear complex. This work is designed to show that a simple one-mass model ruled by laws of relaxation oscillation can also depict main behavior of glottis dynamic. Theory of relaxation oscillation is detailed. A relaxation oscillation model is assessed through a numerical simulation using conventional values for tissue characteristics and subglottal pressure. As expected, raising the mass decreases the fundamental frequency and increases the amplitude of vocal fold vibration: for a mass ranging from 0.01 to 0.4 g, F0 decreased from 297.5 to 42.5 Hz and vibrational amplitude increased from 1.26 to 3.25 mm (for stiffness k=10Nm(-1), damping r=0.015 N s m(-1), and subglottal pressure=1 kPa). Stiffness value has the opposite effect. The subglottal pressure controls the fundamental frequency with a rate ranging from 20 to 50 Hz/kPa. The vibrational amplitude is also controlled linearly by subglottal pressure from 0.22 to 0.26 mm/kPa. The range of phonation threshold pressure (PTP) is close to the values currently proposed, that is, 0.1 to 1 kPa and varies with the fundamental frequency. The relaxation oscillator is a simple and useful tool for modeling vocal fold vibration.

Normal voice in children between 6 and 12 years of age: database and nonlinear analysis.

This study was carried out using a transversal design. It aimed to investigate possible changes of the normal voice in children before mutation, to create a database for the parameters used in the study, and to examine the use of fractal dimension and the largest Lyapunov exponent (LLE) in the assessment of nonpathological phenomena. Two hundred twelve children were enrolled: 111 females and 101 males; and 9 six-year-olds, 24 seven-year-olds, 18 eight-year-olds, 25 nine-year-olds, 27 ten-year-olds, 55 eleven-year-olds, and 54 twelve-year-olds. Fundamental frequency (Fo) decreased with age and was lower in boys than in girls. Jitter and shimmer did not significantly differ with age or gender. Fractal dimension and LLE were significantly lower in boys; LLE decreased with age. The present series confirmed the established findings that Fo is lower in boys than in girls, even before mutation, and decreases with age; two other classical voice analysis parameters, jitter and shimmer, also showed the same behavior as described in the literature. The study of nonlinear parameters (fractal dimension and LLE) showed that laryngeal dynamics is more stable in boys than in girls, and that stability is correlated with age.

Voice improvement in unilateral laryngeal paralysis during loud voicing: theoretical impact.

Voice of patient with unilateral laryngeal paralysis (ULP) shows a nonlinear behaviour with sudden octave jumps, bifurcations and chaos. Such a behaviour may be due to an increased number of freedom degrees in the glottal system. We hypothesized that voice intensity (with increasing sub glottal pressure) could improve vocal signal stability with less freedom degrees in vibrating system, and then a decrease of nonlinearities. A prospective study of 32 consecutive voices of patients with ULP and severe dysphonia was conducted. Jitter and Lyapunov exponent from vocal signals were compared at comfortable and loud voicing with Wilcoxon's test. In 23 out of 32 patients, jitter significantly decreased from 5 (median) in normal voice to 1.2 in loud voice (P < 10(-3)), Lyapunov exponent decreased from 1,495 bit/s (median) to 708 bit/s (P < 10(-4)). Two patients had paradoxical results regarding jitter (higher in loud voice) and 2 regarding Lyapunov exponent. From the 23 cases of voice improvement, 15 cases showing a marked improvement of the acoustic analysis supported our hypothesis (65%). Nonlinear phenomena detected in vocal signals of ULP with severe dysphonia may be reduced in loud voice.

Modern management of vestibular schwannomas.

Within the last 3 decades, microsurgery and stereotactic radiosurgery (SRS) have become well-established management options for vestibular schwannomas (VSs). Advancement in the management of VSs can be separated into three periods: the microsurgical pioneer period, the demonstration of SRS as a first-line therapy for small and medium-sized VSs, and currently, a period of SRS maturity based on a large worldwide patient accrual. The Marseille SRS experience includes 1,500 patients, with 1,000 patients having follow-up longer than 3 years. A long-term tumor control rate of 97%, transient facial palsy lower than 1%, and a probability of functional hearing preservation between 50 and 95% was achieved in this large series of patients treated with state-of-the-art SRS.

Optoreflectometry determination of the resonance properties of a vocal fold.

A new method of measuring the resonance properties of a vocal fold using electromagnetic excitation and laser optoreflectometry for response monitoring is described. Two resonance peaks were experimentally identified with one magnet stuck on the vocal fold at frequencies F0(1m)=54.7 Hz and F0'(1m)=35.8 Hz. The addition of a second magnet allowed calculation of the actual viscoelastic properties of the vocal fold: F0=71.8 Hz; quality factor Q=8.03; mass m=0.057 g; stiffness k=11.6 Nm; and damping zeta=0.0032 Nm(-1). A numerical simulation of a two-layered model verified the experimental data.

Objective voice analysis in dysphonic patients: new data including nonlinear measurements.

OBJECTIVES/HYPOTHESIS: This report describes a comparative study of objective voice evaluation using a multiparametric protocol including aerodynamic parameters and linear and nonlinear acoustic parameters recorded on an EVA(R) workstation and perceptual voice analysis by a jury. STUDY DESIGN: A total of 449 samples were retrospectively selected including 391 patients with pathological voices (308 women and 141 men) and 58 controls with normal voices (38 women and 20 men). A prospective complementary study concerning 43 female patients and 3 controls is presented. METHODS: Objective measures included fundamental frequency (Fo), intensity, jitter, signal-to-noise ratio (SNR), Lyapunov coefficient (Lya), oral airflow (OAF), estimated subglottic pressure (ESGP), maximum phonatory time (MPT) and vocal range. A jury of 4 experienced listeners was instructed to classify voice samples (continuous speech) according to the G (overall dysphonia) component of the GRBAS score on a Visual Analogue Scale (VAS) secondarily transformed in a scale ranging from 0 for normal to 3 for severe dysphonia. RESULTS: It was shown that a nonlinear combination of only 7 parameters in women (vocal range, Lya, ESGP, MPT, OAF, SNR, and Fo) and 6 parameters in men (vocal range, Lya, OAF, ESGP, Fo, SNR) allowed classification of 81% voice samples in the same grade as the jury in women and 84% in men. In the prospective study, 80.5% were correctly classified with the same set of objective measurements. DISCUSSION: The relative importance of the different objective parameters in this type of discriminant analysis is dealt with. Special emphasis is placed on Lya.

Vibratory pattern of vocal folds under tension asymmetry.

OBJECTIVE: The aim of this study was to describe and analyze the vibratory pattern of vocal folds in an asymmetric situation. STUDY DESIGN AND SETTING: Cricothyroid muscle unilateral action was simulated on excised larynges on an experimental bench. Increasing airflow rates were applied to achieve vocal fold vibration. Electroglottography and an optoreflectometer device allowed analysis of separate and simultaneous vocal fold vibration. Spectra of the signals were obtained for each level of airflow variation. RESULTS: All experiments showed periodic vibration. A phase shift was noted between the two vocal folds. Subharmonics and biphonation were identified in all the experiments. CONCLUSION: Lax vocal folds were more susceptible to spectral changes with increasing airflow. SIGNIFICANCE: Knowledge of the consequences of mass, tension, and position asymmetries of the vocal folds is crucial for diagnosis making and defining therapeutic strategies in dysphonic patients. This study may contribute to the understanding of physiology of vocal fold interaction and its compensatory mechanisms.

Experimental study of the effects of surface mucus viscosity on the glottic cycle.

Numerous clinical findings indicate that viscosity of laryngeal mucosa is a crucial factor in glottal perfomance. Experience using experimental test benches has shown the importance of humidifying air stream used to induce vibration in excised larynges. Nevertheless, there is a lack of knowledge particularly regarding the physicochemical properties of laryngeal mucus. The purpose of this study was to research vocal fold vibration in excised larynges using artificial mucus of precisely known viscosity. Eight freshly harvested porcine larynges were examined. Parameters measured were Fo and vocal fold contact time. Measurements were performed under three conditions: basal (no fluid application on vocal cord surface), after application of a fluid of 60cP viscosity (Visc60), and after application of a fluid of 100cP viscosity (Visc100). Electroglottographic measurements were performed at two different times for each condition: 1 s after airflow onset (T1) and 6 seconds after airflow onset (T2). Statistical analysis consisted of comparing data obtained under each condition at T1 and T2. The results showed a significant decrease in Fo after application of Visc60 and Visc100 fluids and a decrease in Fo at T2. Closure time was significantly higher under Visc60 conditions and under Visc100 conditions than under basal conditions. Application of artificial mucus to the mucosa of the vocal folds lowered vibratory frequency and prolonged the contact phase. Our interpretation of this data is that the presence of mucus on the surface of the vocal folds generated superficial tension and caused adhesion, which is a source of nonlinearity in vocal vibration.