This study aims to refine the capability of MSOT to characterise muscle tissue and to determine non-invasive, quantitative biomarkers for the disease assessment in patients with spinal muscular atrophy (SMA) using Multispectral Optoacoustic Tomography (MSOT).

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 children. However, most clinical trials lack primary outcomes other than clinical testing. At the moment there are no prospective, quantitative biomarkers available to detect muscle atrophy at an early age, and to follow up disease progression. As a new imaging modality, optoacoustic imaging (OAI) combines benefits of optical (high contrast) and acoustic (high resolution) imaging. Multispectral optoacoustic tomography (MSOT) is therefore 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, such as melanin, hemoglobin, deoxyhemoglobin and lipids. Previously, it was demonstrated that MSOT is capable to monitor disease severity in Crohn's disease by detecting different signal levels of hemoglobin as markers of intestinal inflammatory activity. In this study we want to refine the capability of MSOT to characterize muscle tissue and to determine a non-invasive, quantitative biomarker for the disease assessment in SMA patients from birth using MSOT.

Inclusion Criteria:

• genetically proven SMA

Exclusion Criteria:

• Pregnancy
• Tattoo on skin to be examined
• For healthy volunteers only: suspected muscular disease/myopathia

Individual participant data that underlie the results reported in the primary publication, after deidentification (text, tables, figures, and appendices)

Beginning 9 months and ending 36 months following article publication.

The data sets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request as follows:

• Individual participant data will not be available
• Study Protocol and Statistical Analysis Plan will be available
• The data will be available beginning 9 months and ending 36 months following article publication.
• The data will be available to researchers who provide a methodologically sound proposal.
• The data will be available for individual participant data meta-analysis, only.
• Proposals may be submitted up to 36 months following article publication. After 36 months the data will be available in our University's data warehouse but without investigator support other than deposited metadata. Information regarding submitting proposals and accessing data may be found at https://www.uk-erlangen.de.

Restrictions may apply due to patient privacy and the General Data Protection Regulation.