Neurodegenerative diseases, infectious pathologies and liquid crystals: Hypothesis of a common information vector involving a multidisciplinary approach.

The existence of an information vector common to very different pathologies is the hypothesis of one of us, the argumentation and discussion of which we present here. It is a mesomorphic state of material called liquid crystal. The liquid-ordered (Lo) phase, made up of membrane rafts mediated by cholesterol, lies at the center of our concept. This mesophase is either preexistent and then modified by the pathogenic process, or initiated by the latter. The most notable disorders involved are Alzheimer's, Parkinson's, Charcot and Creutzfeldt-Jakob diseases, flu-like illnesses and acquired immunodeficiency syndrome (AIDS), although this list may well be extended to include other anisotropic, birefringent amyloid proteinopathies, which have properties compatible with those of liquid crystals. Incidentally, numerous conventional infectious pathologies can also induce a mesomorphic state in cell membranes. It has already been established that mesophases contain the chemical information transmitted from the intramolecular microscopic level, where covalent bonds are applied. Information is then transmitted at the intermolecular macroscopic level, where it is made up of informed, self-organized collections. Electrostatic interactions, coordination of metallic ions, van der Waals forces and donor-acceptor interactions of hydrogen bonding all come into play. These reactions are produced notably in the nanodomains enriched by cholesterol and sphingolipids. Lipids in the cell membrane are where the phase separations favoring elastic hydrodynamic instabilities conducive to the Lo phase take place. In addition, perturbations of the mesomorphic states of membrane rafts due, for example, to lipid dysfunction-even mild ones-with an intracerebral or generalized location could bring about a displacement of thermodynamic equilibrium favoring the initiation and progression of the pathologies under consideration here. Indeed, the most recent work has rendered our hypothesis highly probable. Moreover, our hypothesis is supported by medical and biological observations arising essentially from biophysics and widely documented in the literature. Thus, these facts expand the number of diagnostic and therapeutic perspectives that could be evoked and perhaps even demand exploration.

The early days of the multi channel cochlear implant: efforts and achievement in France.

On September 10th 2013, the clinical medical research Lasker award winners were rewarded for their work on multichannel cochlear implant. It has been my pleasure to see that such a major topic had caught the attention of the Members of the Jury for this prestigious award. That is why I accepted an invitation to participate in a special issue of Hearing Research devoted to the three winners. Here I highlight four scientific contributions made by the French team in late 1970s and early 1980s to modern multichannel cochlear implant development. 1) Chouard and MacLeod plotted an approximate frequency map of the whole length of the human cochlea, including its "hidden face" corresponding to speech frequencies. Moreover MacLeod suggested a sequential display of electrical stimulation as a function of each electrode, a precursor to today's electrodogram and interleaved stimulation. 2) Chouard performed total cochlear implantation in a deaf adult male with 8 electrically independent electrodes that were evenly distributed along the cochlea. 3) Chouard and MacLeod described in a patent detailed sound signal processing for a functional multichannel cochlear implant and reported speech discrimination without help of lip reading in some totally deafened patients. 4) Chouard experimentally demonstrated in the guinea pig the advantage of early cochlear implantation in treating profound neonatal deafness. This article is part of a Special Issue entitled .

[Fractal dimension of speech]. / Etude de la dimension fractale de la parole.

Fractal dimension (D) quantifies the roughness of a temporal signal and estimates its degree of freedom, allowing a good approach of its fluctuations and roughness. Using a 16 kHz time sampling and the box-counting method, we studied Ds of some of the main French phonemes, i.e. [a], [e], [i], [o], [y], and consonants in a consonant-vowel context pronounced 4 times by 10 males and 10 females. For D measurement of long phonemes we used the dyadic Box Counting method and its 10 points D measurement (10pD). For plosion part of plosives consonants, we designed a Semi Continuous Box Counting method devoted to D measurement of short single dimension temporal signal. In the aim to approach infinitely small time scales, and to appreciate at least the tendency of these 10 points set, we calculated also the slope of the 3 last points (3pD). Our study consistently demonstrates that vowels are not fractal; plosive consonants are not fractal; long fricative consonants are fractal; males Ds are significantly higher females Ds, as far as only vowels and long voiced consonants are concerned; there is a significant difference (p < 0.01) between 3pD values of vowels (couple [a] [y] excepted), and fricative consonants (couple [[symbol: see text]]] [f] excepted). In case of nasal consonants, this categorisation is efficient using both 3pD and 10pD measurements (p < 0.05). These results will be commented and discussed, in the aim of clinical use, i.e. dysphonia follow up and auditory prosthesis speech signal processing.

[Urban noise pollution]. / Les nuisances sonores dans la ville.

Noise is responsible for cochlear and general damages. Hearing loss and tinnitus greatly depend on sound intensity and duration. Short-duration sound of sufficient intensity (gunshot or explosion) will not be described because they are not currently encountered in our normal urban environment. Sound levels of less than 75 d (A) are unlikely to cause permanent hearing loss, while sound levels of about 85 d (A) with exposures of 8 h per day will produce permanent hearing loss after many years. Popular and largely amplified music is today one of the most dangerous causes of noise induced hearing loss. The intensity of noises (airport, highway) responsible for stress and general consequences (cardiovascular) is generally lower. Individual noise sensibility depends on several factors. Strategies to prevent damage from sound exposure should include the use of individual hearing protection devices, education programs beginning with school-age children, consumer guidance, increased product noise labelling, and hearing conservation programs for occupational settings.

A fractal approach to the features of speech consonants.

Fractal dimension (D) quantifies the roughness of a temporal signal and estimates its degree of freedom, allowing a good approach for its fluctuations. This present study of consonants follows the D-assessment of vowels which was presented at the Copenhagen Collegium Meeting. Using a 16 kHz time sampling the D-values of consonants were studied in the consonant-vowel context of the French language. Each consonant was pronounced four times by six males and six females. For D-measurement of long consonants the same method was used, i.e. the dyadic box-counting method and its 10 points of D-measurement (10pD) as that used for vowels. In the aim to approach infinitely small time scales, and to appreciate at least the tendency of the 10-point set, i.e. the D value to which tends this set, the slope of the three last points (3pD) was also calculated. For the plosion part of plosive consonants, a semi-continuous box-counting method devoted to the D-measurement of a short, single-dimension temporal signal was designed. This study consistently demonstrates that (i) there is a significant difference between males and females, as far as voiced and non-plosive consonants are concerned; (ii) plosive consonants are not fractal; (iii) among long consonants, D-value of fricatives are significantly different (p < 0.01), as far as 3pD measurement is considered; and (iv) in the case of nasal consonants [m] and [n], this categorization is efficient for both 3pD and 10pD measurements (p < 0.05). There results will be commented on and discussed with the aim of clinical use.

[Q.A.L.Y. index and assessment of cost efficiency of the cochlear implant in acquired profound deafness]. / Index Q.A.L.Y. et appréciation du rapport efficacité-coût de l'implant cochléaire chez l'adulte sourd profond post-lingual.

Cost utility analysis is a method of cost-effectiveness analysis which provides results in terms of cost per quality-adjusted life-year (Q.A.L.Y.). This method is progressively largely used for medical technology assessment. It permits cost-effectiveness comparisons between medical interventions. The cost per Q.A.L.Y. of cochlear implant was determined in 30 adult patients suffering from acquired profound deafness. This study indicates that this technology provides significant improvements and is quite cost-effective. However, as far as profound deafness is concerned, the reliability of Q.A.L.Y. needs to be improved.

A fractal approach to normal and pathological voices.

Using the box-counting method, we demonstrated recently that the stationary signal of vowels is not fractal, but provides the opportunity to design in the smallest scale a kind of signature for each vowel. This fractal approach to these components of speech allows us to quantify the roughness of the voice, between I (sinusoidal complex signal) and 2 (white noise). We used this method to compare these values in normal and pathological voices. We studied the speech of 10 normal speakers, 6 patients suffering from unilateral vocal fold palsy and 6 suffering from various other dysphonias. The meaning of this fractal measurement is discussed and compared with electroglottogram and spectrographic analysis.

A study of speech fractal dimensions.

The fractal dimension (D) of a signal gives an estimate of its degree of freedom, which allows estimation of its fluctuations. Using 16 kHz time sampling and the box counting method we studied the Ds of some of the main stationary parts of French speech, the phonemes [a], [e], [i], [o], [y], pronounced 4 times by 10 males and 10 females. Our study demonstrated that the stationary signal of vowels is not fractal, but may, at the smallest scale, provide a kind of signature for each vowel, though the present categorization is not totally significant. Since the box counting method objectifies and quantifies the roughness of the signal, this procedure may be useful for clinical applications. In case of dysphonia, moreover, these signatures could be perhaps be included in the speech signal processing of cochlear implants.

CT and MR findings of Michel anomaly: inner ear aplasia.

In 1863, Michel described a condition characterized by a total absence of differentiated inner ear structures associated with other skull base anomalies, including an abnormal course of the facial nerve and jugular veins. Michel aplasia clearly differs from Michel dysplasia, in which arrest of embryologic development occurs later. Recently, the role of otic capsule formation on mesenchymal differentiation was reported as well as the impact of the genetic deletion of the homeobox gene on the development of the ear, cranial nerves, and hindbrain. We report two patients with a total absence of inner ear structures bilaterally, illustrating the characteristic appearance of Michel aplasia and associated skull base anomalies.

[A report of two familial cases of Michel syndrome (bilateral agenesis of the inner ear)]. / A propos de deux cas familiaux de syndrome de Michel (agénésie bilatérale de l'oreille interne).

In two siblings, wearing conventional hearing aid, presenting profound but not total congenital deafness, with no particular antecedents, the imaging destined to confirm the indication of a cochlear implant revealed a total bilateral agenesis of the inner ear. In one of the children, this imaging was confirmed by an exploration of the middle ear performed during a tonsillectomy that was otherwise necessary. We will summarize the literature concerning Michel's Disease, exceptional in its princeps form, and we will discuss the manner of action of conventional devices in these cases which are a priori without any sensorial element.

[Digital multi-filter auditory prosthesis: study of its efficiency in function of number of filters and their programming]. / Prothèse auditive numérique multifiltres: étude de l'efficacité en fonction du nombre de filtres et de leur programmabilité.

We designed a prototype of a 7-filter digital auditory prosthesis table prototype. For each of these filters frequency band width, amplification and compression were programmable in order to adapt these parameters to the deaf patient's audiometric particularities. We compared the hearing improvement it was possible to obtain either with the 3-analogue-filter auditory prosthesis Triton 3004 from Siemens, or with our prototype as a function of the number of filters (3, 4 or 7) and their frequency band width programmability. We tested 21 patients suffering from middle or severe neurosensory hearing loss. This study allows to demonstrate that to overpass the present analogue T004 device a 7 programmable-width-filter strategy seems to be the most appropriate. Further studies benefiting with material improvement of our prototype and finer audiometric adjustment of filter strategies as well as long term clinical studies have to be carried out.

[Cochlear implant and cerebral dominance]. / Implant cochléaire et dominance cérébrale.

On right handed people the right ear is considered to transmit speech information, and the left ear musical and cognitive information. These dominating ear properties are not exactly symmetrical in the left handed population, and are more consistent in females than in males. CI efficacy assessment is strongly based on speech intelligibility performances, because these criteria allow to measure the social reinsertion and communication possibilities. Consequently, one may ask if the relationship of the implanted side and the patient's handness could not be an important factor of this CI efficacy. We studied this relationship on 71 post-lingually deaf adult implantees. We measured patients handness using the Schachter's version of the so called Edimburg questionnaire described by Geschwind; this measurement has been moderated to take count of ambidextrous and mixed-handed population. Post operative performances has been assessed using the Francophone Protocol devoted to adults. We found that there is no significant correlation between these post-operative performances and the studied relationship. We estimate: 1) This absence of correlation is probably due to the high number of data which lead to determine the ear for implanting. 2) As far as this choice is feasible, dominating ear must nevertheless be elected, not only for theoretical reasons, but because the dominating hand may be easily employed for antenna adjustment. 3) As handness is strongly evident only after 4 y.o., and as left-handness seems to be more frequent on a congenitally deaf population, this choice is more problematic on less than 2 y.o. deaf children.

[Cochlear implant in the aged patient]. / L'implant cochléaire chez le sujet âgé.

Despite the fact that elderly people live frequently alone and frequently have difficulties of vision, is it reasonable to refuse to supply a patient with a cochlear implant only because he is too old? We compare the results of 87 post-lingually implantees as a function of age, less than 60 years (young) and 60 years or more (old). We assessed the implant efficacy using the Protocole Francophone d'Evaluation (PFE), appreciated the speech-therapist's opinion and the patient's satisfaction, and counted the number of hours per day the implant was used (H/D). The PFE score was significantly higher in young than old. However the speech-therapist's opinion and the patient's satisfaction as well as H/D did not differ significantly in the 2 series. Elderly people are supplied with a great benefit from cochlear implants. Therefore age is not a contraindication for implantation.

[Indications for the cochlear implant in partial deafness of the adult]. / Les indications de l'implant cochléaire dans les surdités incomplètes de l'adulte.

The last (may 1995) NHI Consensus Development Conference on cochlear implant recommends to extend the use of cochlear implant for adult patient suffering from bilateral acquired severe hearing impairment. Its indications are a severe-to-profound sensorineural hearing loss bilaterally presenting an open-set sentence recognition scores less than or equal to 30 percent under best aided conditions. We report the results of our 4 first implantees responding to these criteria, and discuss the mechanisms of the speech intelligibility improvement which has been obtained.

[The cochlear implant. Study in the profoundly deaf adult from the standpoint of quality of life and therapeutic cost (QALY Index of Quality)]. / L'implant cochléaire. Etude chez l'adulte sourd profond, sous l'angle qualité de vie et coût thérapeutique (Index de qualité QALY).

Cost utility analysis is a method of cost-effectiveness analysis which provides results in terms of cost per quality-adjusted life-year (QALY). This method is progressively largely used for medical technology assessment. It permits cost-effectiveness comparisons between medical interventions. The cost per QALY of cochlear implant was determined in 30 adult patients suffering from acquired profound deafness. This study indicates that this technology provides significant improvements and is quite cost-effective. However, as far as profound deafness is concerned, the reliability of QALY needs to be improved.

Auditory performances of a 3-4-7 programmable numeric filter hearing aid.

We designed a non-portable prototype seven-filter digital auditory hearing aid. For each of the filters, frequency bandwidth, amplification and compression were programmable in order to adapt these parameters to the deaf patient's audiometric characteristics. We compared the hearing improvement it was possible to obtain either with the three-analogue filter auditory prosthesis Triton 3004 hearing aid from Siemens or with our prototype as a function of the number of filters (three, four or seven) and their frequency bandwidth programmability. We tested 21 patients suffering from moderate to severe sensorineural hearing loss. This study allowed us to demonstrate that a seven programmable-width filter strategy seems to be more effective than the present analogue T004 device. Further studies with improvement of our prototype and finer audiometric adjustment of filter strategies, together with long-term clinical studies, need to be carried out.