The Role of SAtivex® in Robotic-Rehabilitation

Overview

Spasticity is frequently experienced by people with Multiple Sclerosis (MS), negatively impacting on patient's motor functional outcome, including walking. Currently, none of the available MS disease-modifying medications has been shown to stop or reverse gait disability. Recently the nabiximols has been tested for the treatment of spasticity and walking impairment in MS. Nabiximols (trade name Sativex®) is an oromucosal spray formulation containing 1:1 fixed ratio of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) derived from cloned Cannabis sativa L. plant. The main active substance, THC, acts as a partial agonist at human cannabinoid receptors (CB1 and CB2), and may modulate the effects of excitatory (glutamate-GLU-) and inhibitory (gamma-aminobutyric acid -GABA-) neurotransmitters, leading to muscle relaxation, which in turn is responsible for spasticity improvement. Cannabinoid receptors may modulate both excitatory and inhibitory transmission at central synapses, and have been heavily implicated, in animal models, in multiple forms of synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). Indeed, in a previous study implying transcranial magnetic stimulation (TMS) technique, it has been hypothesized that the activation of cannabinoid receptors by Sativex® could modulate the balance between LTP and LTD like plasticity by changing the state of cortical excitability. In a recently study it has been proposed that Sativex may modulate the cortical excitability changing the activity of inhibitory GABAergic cortico-cortical synapses. Aim of our study is to clarify the role of Sativex coupled to a robotic neurehabilitation training in MS patients in improving the motor outcome, by means of clinical, kinematic, beside some neurophysiological and measures.

Forthy MS patients affected by gait disturbances and moderate-severe spasticity will be enrolled: 20 out of them in treatment with Sativex (Group A) considered as responders and 20 treated only with the most common antispastic used in MS (Group B). All the 40 subjects, divided into two groups (A: Sativex+Lokomat Training and B: other antispastic+Lokomat Training), will perform a neurorobotic-assisted gait training (RAGT, each session will last at least 45', 3 times per week, for a total amount of 20 treatment's sessions). All patients will undergo a complete blind physical and neurological examination, including evaluation of disability by means of the Expanded Disability Scale (EDDS) and assessment of spasticity using the Modified Ashworth Scale (MAS) and the numerical rating scale (NRS). To clarify the role of Sativex® in improving spasticity gait-related symptoms the following scales will be also administered: ten meters walking test (10wt), Ambulation Index (AI). Quality of life will be evaluated by means of MSQOL 54. The skilled clinician will be blind to the drug treatment.Moreover, some electrophysiological parameters to test cortical excitability will be also evaluated: motor evoked potentials (MEP) amplitude, short intracortical inhibition (SICI) and facilitation (ICF) from the abductor pollicis brevis muscle (APB) of the most affected side. The same assessment will be applied in baseline, at the end of the robotic training (T1) and 30 days after the end of the nerehabilitation training (T2).