Muscle hypertonia may have an extrinsic component resulting from altered neural mechanisms acting on muscles, and an intrinsic component that refers to changes in the soft tissues composing muscles, tendons and joints. These components often coexist in the same patient, making it necessary to enable distinct interventions directed at the underlying impairments. While the quantification of extrinsic hypertonia is best performed by clinical neurophysiology, that of intrinsic hypertonia requires a wide range of skills ranging from biomechanics to US- or RM-based techniques. Having a reliable indicator of the overall state of the hypertonic muscle that complements both neural and not-neural components would certainly help in planning, performing and monitoring specific patient's treatment.
Recently, we set up a photonic-based, easy-to-apply, bed-side procedure able to provide a surrogate marker of the current biological state of the living muscle. A small-sized, portable, spectrophotometer is used to collect reflectance spectra from muscles in the near infrared region that are subjected to chemiometric analysis. In healthy subjects, this procedure distinguished upper limb flexors from extensors, and was sensitive to anthropometric variables (sex, age, and body mass index).
In this research project we will apply reflectance spectroscopy to patients with post-stroke spasticity and hypertonia who undergo periodical botulinum toxin treatment. We will acquire spectra in the visible short-wave infrared regions from the upper limb flexors and extensors before, one-, and three- months after the injection of incobotulinumA in the biceps muscle. Spectra off-line analysis will include PCA aimed to spectral grouping, PLS-DA for implementing discrimination/prediction models, correlation with clinical data. We aim to see whether photonic evaluation distinguish normal from affected muscles, affected from unaffected muscles in patients, muscle changes induced by chemo-denervation.
This is the first study investigating NIR spectra acquired in vivo from hypertonic muscles in post-stroke patients. We are interested to obtain an objective indicator of the current state of the spastic muscle which can be measured accurately, and reproducibly observed from outside the organ itself. We will investigate the reliability and accuracy of the visible and near infrared spectroscopy-application for authentication of muscle groups in the upper limb, identification of normal and hypertonic muscles, monitoring of the same muscle over time. Muscles spectral "fingerprints" will be modeled and classified, and will be subjected to rigorous and stringent analysis to test whether they change according to anthropometric or physiologic variables, and to the effect induced by the chemo-denervation.
At present, to our knowledge, no cheap, reliable, and widely applicable technique for non-invasive in vivo analysis of human muscles is available, and we wish to determine whether NIRS of muscles can be adopted in clinical investigation and possibly rehabilitation, without significant cost and time penalties.