What other conditions cause spasticity and weakness of muscles?

Muscle spasticity and weakness can also be caused by other conditions including (but not limited to) Primary Lateral Sclerosis, spinal cord injury or tumors, cerebral palsy, multiple sclerosis, amyotrophic lateral sclerosis, vitamin absorption, and thoracic spine herniated disks.

There is a virus-caused disease called Tropical Spastic Paraparesis and conditions called Lathyrism and Konzo caused by toxins in the plants lathyrus sativus and cassava that also cause muscle spasticity and weakness.