Stapes surgery in osteogenesis imperfecta: retrospective analysis of 18 operated ears.

PURPOSE: To evaluate short and long term results of stapes surgery in patients with osteogenesis imperfecta (OI), METHODS: Retrospective case series of 18 primary stapes surgeries performed on 11 hearing-impaired OI patients with evidence of stapes fixation, in a Tertiary referral center. We analysed pre-operative and post-operative hearing results at 1 month and at least 1 year RESULTS: The main operative findings were stapes fixation, thickened footplate and fragile or fractured stapes crura. No revision surgery was necessary. Hearing improvement was achieved in 94% of the cases. We obtained an air-bone gap closure to within 10 dB in 46% of the cases and to within 15 dB in 92% of the cases at 1-year follow-up. The mean hearing gain in air conduction (at 0.5, 1, 2 and 4 kHz) was 18.4 dB at 1 month and 22.4 dB at 1 year. CONCLUSION: Stapes surgery in OI gives good results with few complications in our series. A hearing gain is often obtained in spite of the sensorineural hearing loss caused by the natural progression of the disease.

Sensorineural hearing loss in patients with vestibular schwannoma correlates with the presence of utricular hydrops as diagnosed on heavily T2-weighted MRI.

PURPOSE: The purpose of this study was to assess whether the volume of the vestibular endolymphatic space correlates with the degree of hearing loss using heavily T2-weighted fast imaging employing steady-state acquisition with cycle phase (FIESTA-C) MRI. MATERIALS AND METHODS: A total of 23 patients with vestibular schwannoma, as diagnosed on typical image findings, who underwent FIESTA-C MRI were included. There were 13 women and 10 men with a mean age of 63.5±9.3 (SD) years (range: 49-88years). Two radiologists independently evaluated the volume of the utricle and saccule. Correlation between tumor volume, vestibular endolymphatic space volume and degree of hearing loss - as evaluated with the levels of pure-tone average and speech recognition threshold - were searched for. RESULTS: The mean saccular, utricular and tumor volumes were 3.17±1.1 (SD) mm3 (range: 1.45-5.7mm3), 14.55±5 (SD) mm3; (range: 6.6-23.9mm3) and 17.4±5.5 (SD) mm3; (range: 8.3-25.4mm3), respectively. There was a moderate correlation between the volume of the utricle and the degree of hearing loss as evaluated with the levels of pure-tone average (rho=0.5; P=0.015) and speech recognition threshold (rho=0.58; P=0.004). There were no significant correlations between saccular and tumor volumes and the degree of hearing loss. CONCLUSION: The volume of the utricle in patients with obstructive vestibular schwannoma moderately correlates with the degree of hearing loss.

Comparison of enhancement of the vestibular perilymph between gadoterate meglumine and gadobutrol at 3-Tesla in Meniere's disease.

PURPOSE: To compare the degree of enhancement of the perilymph between two macrocyclic gadolinium-based contrast agents (gadobutrol and gadoterate meglumine) in patients with Meniere's disease at 3-T magnetic resonance imaging (MRI). MATERIALS AND METHODS: The MRI examinations of 20 patients with Meniere's disease obtained 4hours after a single intravenous dose of macrocyclic gadolinium-based contrast agents were retrospectively compared. Ten patients (median age: 58.5 years; median body mass index [BMI]: 25) have received a single intravenous dose of gadoterate meglumine and 10 patients (median age: 45.5 years; median BMI: 25.4) have received a single-dose of gadobutrol. Two radiologists independently measured the signal intensity ratio (SIR) by using region of interest analysis and performed a visual assessment in order to evaluate the perilymph of each semicircular canal and of the vestibule. RESULTS: No differences in SIR of the symptomatic ear were found between gadobutrol (median SIR: 1.58) and gadoterate meglumine (median SIR: 1.3) (P=0.18). The SIR of the contralateral asymptomatic ear was significantly greater with gadobutrol (median: 1.62) than with gadoterate meglumine (median: 1.21) (P=0.009). No differences in endolymphatic structures visualization were found between gadobutrol and gadoterate meglumine in the symptomatic ears (P=0.27) but gadobutrol allowed a better assessment of endolymphatic structures and semicircular canals in the asymptomatic ear (P<0.001). CONCLUSION: Gadobutrol and gadoterate meglumine provide similar degrees of enhancement of the symptomatic ear in patients with Meniere's disease but gadobutrol provides better anatomical details regarding endolymphatic space and semicircular canals of asymptomatic, contralateral ear.

[Hippocampus, brainstem and brain dose-volume constraints for fractionated 3-D radiotherapy and for stereotactic radiation therapy: Limits and perspectives]. / Contraintes de dose en radiothérapie conformationnelle fractionnée et en radiothérapie stéréotaxique dans les hippocampes, le tronc cérébral et l'encéphale : limites et perspectives.

Cerebral radiation-induced toxicities after radiotherapy (RT) of brain tumors are frequent. The protection of organs at risk (OAR) is crucial, especially for brain tumors, to preserve cognition in cancer survivors. Dose constraints of cerebral OAR used in conventional RT, radiosurgery (SRS) and stereotactic radiotherapy (SRT) are debated. In fact, they are based on historical cohorts or calculated with old mathematical models. Values of α/ß ratio of cerebral OAR are also controversial leading to misestimate the equivalent dose in 2Gy fractions or the biological equivalent dose, especially during hypofractionated RT. Although recent progresses in medical imaging, the diagnosis of radionecrosis remains difficult. In this article, we propose a large review of dose constraints used for three major cerebral OAR: the brain stem, the hippocampus and the brain.

Elastic modulus of halloysite nanotubes.

This work reports measurements of the elastic modulus of halloysite nanotubes. Nanoscale three-point bending tests were performed on individual nanotubes using an atomic force microscope. Nanotubes exhibit elastic behaviour at small deformations. The stiffness of the tubes, and hence their elastic modulus, was deduced from force curve measurements using an appropriate mechanical model. The boundary conditions were also identified by recording the stiffness profile of a tube along its suspended length. An average elastic modulus of 140 GPa is obtained for a set of tubes with outer diameters ranging between 50 and 160 nm. Moreover, the elastic modulus increases with decreasing outer diameter, with a steep jump below 50 nm. The size dependence of the elastic modulus may be attributed to: (i) surface tension effects for thinner tubes and (ii) a non-negligible contribution of shear deformations to the total deflection for larger tubes.