There are many causes of weakness on one side of the body, including:

Stroke- A stroke occurs when the blood supply to part of the brain is interrupted, causing damage to brain cells. This can lead to weakness, numbness, paralysis, and other symptoms on the opposite side of the body from the stroke.

Traumatic brain injury- A traumatic brain injury (TBI) can damage the brain and lead to weakness on one side of the body. TBIs can be caused by car accidents, falls, sports injuries, and other types of trauma.

Multiple sclerosis- Multiple sclerosis (MS) is a chronic disease that affects the central nervous system. MS can cause weakness, numbness, and other symptoms on one or more sides of the body.

Guillain-Barré syndrome- Guillain-Barré syndrome (GBS) is a rare autoimmune disorder that affects the nervous system. GBS can cause weakness, numbness, and paralysis, which can affect one or both sides of the body.

Cerebral palsy- Cerebral palsy is a group of permanent movement disorders that are caused by damage to the brain before, during, or shortly after birth. Cerebral palsy can cause weakness, spasticity, and other motor problems on one or both sides of the body.

Spinal cord injury- A spinal cord injury can damage the spinal cord and lead to weakness, numbness, and paralysis on one or both sides of the body. Spinal cord injuries can be caused by car accidents, falls, sports injuries, and other types of trauma.

Brain tumor- A brain tumor is a mass of abnormal cells that grows in the brain. Brain tumors can cause a variety of symptoms, including weakness on one side of the body.

Infection- An infection, such as meningitis or encephalitis, can damage the brain and lead to weakness on one side of the body.

Medication side effect- Some medications, such as chemotherapy drugs and steroids, can cause weakness as a side effect.

Degenerative diseases- Some degenerative diseases, such as Parkinson's disease and Alzheimer's disease, can cause weakness on one side of the body.

Diagnosis of hemiparesis:

Medical history: The healthcare provider will interview the patient to gather information about the onset, duration, and progression of symptoms, as well as any associated factors or previous medical conditions.

Physical examination: A thorough physical examination will be performed to assess muscle strength, reflexes, coordination, sensation, and other neurological functions. The healthcare provider will focus on the affected side of the body to identify specific patterns of weakness or sensory loss.