[Clinical, radiographic, prognostic and therapeutic aspects of demelinating disease with tumefactive demyelinating lesions]. / Aspects cliniques, radiologiques, pronostiques et thérapeutiques des lésions démyélinisantes extensives.

BACKGROUND: Demyelinating diseases presenting with a tumefactive demyelinating lesion (TDL) raise questions about classification, diagnosis, prognosis, and treatment. Their long-term course is not well described in literature. PATIENTS/METHODS: In a retrospective study, we describe the main characteristics of 29 patients with TDLs. In a case control study, we compared two cohorts of multiple sclerosis (MS) patients: 24 MS patients with TDL versus a reference cohort of patients with relapsing remitting MS. We compared the extended disability status score (EDSS) concerning the first demyelinating event (DE) with TDL, EDSS score at the end of follow-up and treatment intake. The objective was to discuss the prognosis and the management of TDL. RESULTS: In our study, the prognosis was better for patients with non-prevalent TDL (first DE without TDL) compared with patients with prevalent TDL (first DE with TDL) and was not different compared with the MS reference cohort. At the end of follow-up, there was no significant difference between patients treated with immunosuppressors after a first DE with TDL and patients with classical MS. The EDSS at the end of follow-up was statistically more severe for untreated patients after a first DE with TDL than for classical MS patients (P=0.0047). DISCUSSION: The prognosis of patients with TDL is difficult to assess because of its multifactorial nature (underlying disease and treatment impact). In our cohort, outcome of MS patients whose first severe DE involved a TDL was better when they received an early immunosuppressive treatment.

Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm.

We present a detailed investigation of the different processes responsible for the optical nonlinearities of silicon nanocrystals at 1550 nm. Through z-scan measurements, the bound-electronic and excited carrier contributions to the nonlinear refraction were measured in presence of two-photon absorption. A study of the nonlinear response at different excitation powers has permitted to determine the change in the refractive index per unit of photo-excited carrier density sigma(r) and the value of the real bound-electronic nonlinear refraction n(2be) as a function of the nanocrystals size. Moreover at high excitation power, a saturation of the nonlinear absorption was observed due to band-filling effects.