Movement of the body is primarily controlled by the pyramidal (or corticospinal) tract, a pathway of neurons that begins in the motor areas of the brain, projects down through the internal capsule, continues through the brainstem, decussates (or cross midline) at the lower medulla, then travels down the spinal cord into the motor neurons that control each muscle. In addition to this main pathway, there are smaller contributing pathways (including the anterior corticospinal tract), some portions of which do not cross the midline.
Because of this anatomy, injuries to the pyramidal tract above the medulla generally cause contralateral hemiparesis (weakness on the opposite side as the injury). Injuries at the lower medulla, spinal cord, and peripheral nerves result in ipsilateral hemiparesis.
In a few cases, lesions above the medulla have resulted in ipsilateral hemiparesis:
Prognosis[edit]
Hemiplegia is not a progressive disorder, except in progressive conditions like a growing brain tumour. Once the injury has occurred, the symptoms should not worsen. However, because of lack of mobility, other complications can occur. Complications may include muscle and joint stiffness, loss of aerobic fitness, muscle spasms, bed sores, pressure ulcers and blood clots.[46]
Sudden recovery from hemiplegia is very rare. Many of the individuals will have limited recovery, but the majority will improve from intensive, specialised rehabilitation. Potential to progress may differ in cerebral palsy, compared to adult acquired brain injury. It is vital to integrate the hemiplegic child into society and encourage them in their daily living activities. With time, some individuals may make remarkable progress.[46]