Future perspectives
During the past 5 years an abundant amount of data has been published concerning the degree and pattern of striated muscle involvement in inherited muscle disease. These data have led to a new era in the non-invasive diagnosis of neuromuscular diseases. The diagnostic flowcharts presented in this review are based on these data collected during the past few years. However, this is just a beginning, and we have still a long way to go. Continuously new genetic disease entities leading to muscle dystrophy can be identified and described by using new diagnostic tools. Therefore, the role of neuromuscular imaging has to be considered as a dynamic field of research that will gain even more importance in the near future. While the first imaging approaches focussed mainly on certain muscle groups primarily of the lower limbs, current and future imaging protocols should consider a “whole-body approach” such as whole-body muscle MRI including the muscle of the trunk, shoulder girdles and upper extremities. This can extend the possibilities for pattern description and recognition.
In addition to the available cross-sectional data, it would be interesting to gain more longitudinal data in order to understand the disease evolution and the prognostic role of subclinical changes detected by MRI or ultrasound. In particular, the possible role of imaging for treatment monitoring is of great interest, and first approaches in metabolic diseases are promising [69, 70].
The potential role of advanced MRI techniques such as perfusion-weighted imaging, diffusion-weighted imaging and MR spectroscopy is currently unknown. It can be suggested that some of these techniques can further increase the sensitivity in the detection of subtle changes in the striated muscle and contribute to a better understanding of the underlying pathophysiological mechanism [32–35]. It is of great interest whether these imaging techniques will show additional diagnostic and prognostic value. High-field MRI is increasingly being used in the clinical setting [71, 72]. Due to a substantial increase in the signal-to-noise ratio, in vivo imaging at higher magnetic field allows faster image acquisition and higher spatial resolutions. The first whole-body high-field muscle MRI protocols have been recently described [27, 51, 67]. Future studies have to investigate whether structural and quantitative (perfusion MRI, MR spectroscopy) high-field MRI protocols do have added value in the diagnosis of hereditary, metabolic or inflammatory muscle disease.
The role of contrast-enhanced imaging US and MRI techniques is still unclear. The first imaging studies using gadolinium(Gd)-based contrast-enhanced MRI have been published in denervated muscles and inherited dystrophic muscle disease [31, 73]. However, whether Gd-based contrast MRI leads to be an improvement in the diagnosis of hereditary muscle dystrophies is not clear. Perhaps more specific contrast media agents such as small iron oxide particles (SPIO) can contribute to a better visualisation and understanding of inflammatory and degenerative changes in striated muscles.