What can cause spastic paralysis on the right side of the body?

Anatomy: Causes include focal lesions of brain and spinal cord, and some underlying problems could include trauma, stroke, multiple sclerosis, infections, even primary lateral sclerosis.

Central lesion: Brain injury from trauma, bleed, tumor, aneurism, ischemia, infection, or spinal cord injury from similar mechanisms all can cause an upper motor lesion resulting in both paralysis and spasticity simultaneously.