Role of High Frequency Ultrasound in Demyelinating Polyneuropathies

The use of neuroimaging in the evaluation of neuromuscular pathologies is a promising and rapidly expandinf field. Among the different imaging techniques employed, nerve ultrasound is of particular interest given it's non invasivity, lack of side effects, accesibility and low cost. This exam provides complementary data to electroneuromyography (ENMG), enabeling the physician to visualise the morphological correspondents of electrophysiological abnormalities with a spatial resolution at least as good as MRI.

Chronic Inflammatory Demyelinating Polyradiculoneuritis (CIDP), Multifocal Motor Neuropathy with Conduction Blocks (MMNBC), Lewis and Sumner syndrome (L-S syndrome) and anti-MAG antibody-associated neuropathies (anti-MAG) are among the main chronic inflammatory neuropathies of autoimmune etiology. The diagnosis of these diseases is based on clinical, paraclinical and ENMG examinations. Several recent studies have highlighted the valuable role of ultrasound not only in the diagnosis but also for follow up of patients afflicted by this group of diseases.

However, the current ultrasound imaging techniques does not allow for a detailed study of the internal structure of the nerves. The developement of technologies with improved resolution contribute to further the knowledge in this innovative field and to better understand the pathophysiological mechanisms responsible for initiation and progression of inflammatory nerve disorders.In the Department of Ultrasound at the Nice University Hospital in France the team have at its disposal a high frequency untrasound that the team use to explore the peripheral nervous system.

The scientific hypothesis of this pilot study rests on the premise that demyelinationg neuropathies are a heterogenous group where different types present with different morphological characteristics not only at the level of the nerve as a whole, but also at the level of the nerve fascicles and of the peri- and intra-neural vascular structures. In this respect, high frequency ultrasound allows us to visualise different segments of affected nerves and to obtain morphological details which the team then compare with existing ultrasound data in the literature (high frequency ultrasound: 10-20 MHz). Thanks to this non-invasive and painless technique, the nerve can be rapidly visualised along its entire length in static and dynamic mode. In addition, high frequency ultrasound will give us access to complementary data on the morphology of the soft tissues and the peri- and intra-neural vascular structures which may be useful in shedding light on the underlying pathophysiologycal processes. Another important aspect is the opportunity to make electromyographic and clinical correlations The main parameter The team will study in ultrasound will be hypertrophy, corresponding to an increase in the cross-sectional area of the nerve. the team will also conduct analysis on other less codified parameters, such as epineural and endoneural vascularisation (using the Doppler mode), as well as nerve fascicles anatomy (size, organisation). Identification of different characteristics may be of diagnostic interest in cases where the clinical, paraclinical and ENMG examinations do not allow us to make a diagnostic and therapeutic decision, but it can also prove useful in the follow-up of patients and response to treatment.

This is a descriptive, pilot, mono-centric, multiparametric and retrospective analysis study on patients followed in our centre with a diagnosis of CIDP, NMMBC, L-S syndrom and anti-MAG