Like all forms of cerebral palsy, spastic monoplegia results from brain damage. Distinguished from other manifestations of the disease, monoplegia (mono = one) is a movement defect of one of the limbs of the body, generally an arm, on either the right side or the left. It is very rare and many authorities consider it a form of the condition of Hemiplegia with very mild involvement of the other limb on the affected side of the body.

Monoplegia cerebral palsy results from a permanent lesion in the motor cortex area of the brain which may be complete or partial. Like all other types of cerebral palsy, the condition is irreversible meaning that there is no chance of recovery.At best, diagnosis of CP is effectively a process of elimination because there are many other illnesses that are nearly identical to this condition including Erbs palsy, brain tumours, metabolic disorders, brachial plexus palsy, etc.

There are risk factors which are associated with monoplegia cerebral palsy and in most instances the mother’s medical history provides important clues to establish the cause of the disease. In about 90% of cases, monoplegia is a naturally occurring phenomena (birth defect) during the developmental stages of pregnancy. The remaining cases are attributable to malpractice. The medical errors than can cause this monoplegia and all other types of cerebral palsy generally involve oxygen deprivation of the infant immediately before, during or shortly after birth. This could have been caused by a prolonged stay in the birth canal, a prolapsed umbilical cord (where the umbilical cord precedes the fetus’ exit from the uterus diminishing or eliminating blood and oxygen supply), inappropriate use of forceps or vacuum extraction and failure to perform a necessary c-section.