Optical spectroscopy and microscopy techniques for assessment of neurological diseases

Neurological diseases are a category of disease that deals with any damageable changes in the nervous system. Neurodegenerative diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and a few others also come under this category. Detection of the cause of such diseases can be mainly studied by digging deep into the anatomical and physiological features of the nervous system. Hence, various imaging techniques have been profusely developing recently that aim to discover the anatomical as well as physiological changes in the brain and spinal cord that lead to specific neurological diseases. This review discusses some of the spectroscopic and microscopy techniques that are beneficial in diagnostic procedures of neurological diseases. Listed down techniques are mainly categorized based on fluorescence, scattering, and infrared absorption principle and include the information on resolution, magnification, and penetration depth of each technique, respectively. In this review, the applications of confocal fluorescence microscopy, two-photon fluorescence microscopy, harmonic generation microscopy including second harmonic generation (SHG), third harmonic generation (THG), coherent Raman scattering including coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), fluorescence and near-infrared spectroscopy are discussed with an advantage in diagnosis but a few being more advantageous than others.