Hemiparesis

Hemiparesis is weakness affecting one side of the body, usually resulting from injury or disease of the brain or spinal cord. It is a form of paresis and commonly arises from damage to the corticospinal pathways or motor areas. Because most motor pathways cross to the opposite side in the brainstem, hemiparesis is typically contralateral to the lesion.

The most common cause is a stroke, including ischemic and hemorrhagic types. Other causes include traumatic brain injury, brain tumors, infections such as encephalitis, demyelinating diseases like multiple sclerosis, and spinal cord lesions above the level where the pathways cross. In children, unilateral weakness can be due to cerebral palsy or perinatal injuries.

Symptoms usually involve weakness or reduced strength of the face, arm, and leg on one side. There may be accompanying spasticity, hyperreflexia, a positive Babinski sign, sensory loss, and problems with coordination or gait. Language and facial movement may be affected if the dominant hemisphere is involved.

Diagnosis is based on neurological examination and imaging. CT or MRI helps identify stroke or other structural causes and guides treatment. Additional evaluation may include vascular studies, laboratory tests, and functional assessments to determine the underlying cause and to plan rehabilitation.

Treatment targets the underlying cause and the motor impairment. In acute stroke, therapies may include thrombolysis or thrombectomy, antiplatelet agents, and blood pressure management. Rehabilitation, including physical and occupational therapy, is central to recovery and may address gait, dexterity, spasticity management, and the use of assistive devices. Prognosis varies with the cause, extent of impairment, and timeliness of treatment.