Evaluation of Therapeutic Response in Spinal Muscular Atrophy Using Multispectral Optoacoustic Tomography (MSOT) and Magnetic Resonance Imaging (MRI)

SMA is an autosomal-recessive disorder, characterized by progressive muscle weakness and atrophy with an incidence of 1/10,000. The condition is caused by a homozygous deletion or mutation in the survival motor neuron 1 (SMN1), resulting in reduced expression of the survival motor neuron (SMN) protein. This leads to the degeneration of motor neurons in the spinal cord and brain stem. A nearby related gene, survival motor neuron 2 (SMN2), could partially compensate the loss of SMN1. Individuals with a higher copy number of SMN2 do in general have a milder phenotype. New therapeutic approaches, e.g. nusinersen (spinraza©), an antisense oligonucleotide medication that modulates pre-messenger RNA splicing of the survival motor neuron 2 (SMN2) gene, are promising to help the formerly incurable disease. However, most clinical trials lack primary outcomes other than clinical testing. Preliminary work shows that new methods such as multispectral optoacoustic tomography (MSOT) and magnetic resonance imaging (MRI) detect tissue changes very sensitively. Multispectral optoacoustic tomography (MSOT) is capable of visualizing the distribution of endogenous absorbers by initiating laser-induced thermoelastic expansion and detection of resulting pressure waves. This imaging technique enables the label-free detection and quantification of different endogenous chromophores. In addition to this technology, MRI imaging has advanced in the field of muscle diseases, with 23Na-MRI being the first example. With both methods, the molecular composition of muscle tissue can be determined non-invasively and quantitatively at the same time. In this first pilot study on patients with SMA, the investigators will now assess whether the differences in the muscle composition of SMA patients with or without therapy can be quantified and whether they can be used simultaneously as markers during therapy with nusinersen (spinraza©) . Ideally, both techniques can complement or validate each other. In the future, this could generate a completely new, non-invasive method for evaluating endogenous biomarkers for therapy response.