Non-invasive Spinal, Cortical, and Sensorimotor Biomarkers in Motor Neurone Disease

Background: Substantial variability exists in the onset, and rate of degeneration across individuals with Motor Neurone Disease (MND) or Amyotrophic Lateral Sclerosis (ALS). This variability requires biomarkers that accurately classify and reliably track clinical subtypes as the disease progresses. Degeneration occurs in the brain and spinal cord, however, non-invasive diagnosis of spinal cord function remains highly challenging due its unique alignment in the spine. Disruption of complex spinal and cortical circuits that transmit and process neural signals for position sense and movement has not been adequately captured in the neurophysiological profiling of ALS patients. Aim: To develop, test, and employ non-invasive techniques to explore (dys)function between motor, sensory brain, and spinal networks in ALS. The project will address if the electrical activity of the cortical-spinal network by the of use peripheral stimulation (vibration, electrical nerve stimulation) to probe and reveal the normal or abnormal communication between brain and spinal networks. It is expected to reveal novel neurophysiological signatures in ALS patients compared to healthy controls. Study Design \& Data Analysis: Surface electrodes will be mounted over the targeted regions in conjunction with High-Density EEG and High-density Electromyography (EMG). A physical and mathematical model of the underlying sources of electric activity (source localization) will be carried out at rest, during task, and with non-invasive peripheral nerve stimulation (PNS) and TMS. A separate paradigm will augment sensorimotor communication between the primary motor cortex (M1) and the somatosensory cortex (S1). Mild vibration (5N/\< 500 grams) will be applied to the wrist and/or bicep tendon transcutaneously. Vibration in conjunction with non-invasive peripheral nerve stimulation will induce transient changes (30 seconds maximum) in the intrinsic excitability of motor neurons in the spinal cord. Surface EMG will capture altered MN activity at the spinal level and the anticipated augmented communication in cortical networks (S1-M1) will be captured with EEG through connectivity analysis. Non-invasive transcranial magnetic stimulation in conjunction with vibration/nerve stimulation will be recorded to explore upper motor neurone influences on the altered intrinsic excitability of spinal motor neurons. Data collection: EXG-EEG-EMG and TMS/Peripheral Stimulation recordings will be conducted using a BioSemi® ActiveTwo system with 128 active sintered Ag-AgCl electrodes and headcaps (BioSemi B.V., Amsterdam, The Netherlands). The TMS system is a Brainbox DuoMAG (Brainbox Ltd., Cardif, Wales, UK) which can be used with a Digitimer peripheral stimulator.