Before the intrathecal baclofen or placebo bolus is administered, patients will be evaluated for neuropathic pain, using the Neuropathic Pain Inventory Scale, Brief Pain Inventory and Numerical Rating Scale. Spasticity and spasms will also be measured by the Modified Ashworth Scale, the Visual Analogue Scale and the Penn Spasm. After that, patients will also undergo, early in the morning when the intrathecal baclofen or placebo bolus will be administered, a neurophysiology assessment (warm perception threshold, heat pain perception threshold, evoked pain perception and contact heat evoked potentials).