Cerebral palsy
Direct physical trauma to the affected limb
Central nervous mass lesion, including tumor, hematoma, or abscess
Complicated migraine
Epilepsy
Head or spinal trauma
Hereditary brachial neuritis
Hereditary neuropathy with liability to pressure palsy
Neonatal brachial plexus paralysis
Neuropathy
Plexopathy
Traumatic peroneal neuropathy
Vaccine-associated paralytic poliomyelitis
Hemiparetic seizures
Monomeric spinal muscular atrophy
StrokeSpecifically, monoplegia in the lower extremities is typically caused by Brown Sequard syndrome and hematomas in the frontoparietal cortex near the middle that could produce a deficit such as this, but this is a very uncommon occurrence. Mechanism
In monoplegia, the spine and the proximal portion of nerves are usually the abnormal sites of limb weakness. Monoplegia resulting from upper extremity impairments following a stroke occurs due to direct damage to the primary motor cortex, primary somatosensory cortex, secondary sensorimotor cortex, sensorimotor cortical areas, subcortical structures, and/or the corticospinal tract. It is often found that impairments following stroke are either caused by damage to the same or adjacent neurological structures. A combination of these impairments is more likely than just one in isolation. Damage to the corticospinal system results in an inability to activate muscles with enough force or in a coordinated manner, which can lead to paresis, loss of fractional movement, and abnormal muscle tone. Damage to the somatosensory cortical areas causes loss of somatosensation which results in an impaired ability to monitor movement.Considering monoplegia as it relates to cerebral palsy, in premature infants, the most common cause of cerebral palsy is periventricular hemorrhagic infarction. In term infants, the underlying causes are often cerebral malformations, cerebral infarction, and intracerebral hemorrhage.
Self-abuse may refer to:

Self-harm, the intentional, direct injuring of ones own body without suicidal intentions
Self-destructive behaviour, patterns of behaviour to inflict metaphorical or literal harm on oneself
Self-inflicted wound, harming oneself without psychological problems to take advantage of being injured

See also
Algolagnia, deriving sexual pleasure and stimulation from physical pain
Abuse § Self-abuse
Violence § Self-directed violence