Aim of this randomized, double-blind, placebo-controlled, cross-over study is to investigate cannabinoid-induced changes in neurophysiological parameters in a group of 40 patients with secondary or primary progressive Multiple Sclerosis (MS).

Inclusion Criteria:

• Aged 18 years or above
• Willing and able to comply with the protocol for the duration of the study
• Diagnosis of Secondary-Progressive or Primary-Progressive MS from at least 12 months
• Relapse free from at least 3 months before screening visit
• Lower limb spasticity
• EDSS from > 3.0 and < 6.5
• Moderate to severe spasticity due to MS from at least 6 months and with stable drug treatment not able to relieve symptoms as a whole, deserving a specific add-on treatment
• Immunomodulatory or immunosuppressant therapies not modified during the study and 6 months before starting the study
• Stable doses of anti-spasticity agents from at least 2 months prior to screening visit
• Have given written informed consent

Exclusion Criteria:

• Any concomitant disease that may cause spasticity or that could interfere with subject's spasticity
• Botulinum Toxin injection for spasticity in the 4 months prior to screening visit
• Any known or suspected history of psychotic illness, alcohol or substance abuse, epilepsy, hypersensitivity to cannabinoids
• Significant cardiac, renal or hepatic disease
• Female subjects of child bearing potentials and male subjects whose partner is child bearing potential, unless willing to ensure that they or their partner use contraception during the study
• Female subjects who is pregnant lactating or planning pregnancy during the course of the study and for three months thereafter
• Sativex® SmPC contraindications