What Is It, Causes, and More

Author: Nikol Natalia Armata

Editors: Alyssa Haag, Ian Mannarino, MBA, MD

Illustrator: Abbey Richard

Copyeditor: Sadia Zaman, MBBS, BSc

What is hemiplegia?

Hemiplegia refers to the severe or complete loss of motor function on one side of the body. Depending on the side of the body that is affected, hemiplegia is further classified as right or left hemiplegia. Hemiplegia is usually caused by brain damage localized to the cerebral hemisphere opposite the affected side. For example, injury to the left side of the brain will cause right hemiplegia and vice versa. Less frequently, brain stem lesions, peripheral nervous system disorders, cervical spinal cord injury and other conditions may present as hemiplegia

Hemiplegia may appear soon after birth (i.e., up to approximately two years of life), where it is known as congenital hemiplegia, or hemiplegic cerebral palsy. On the other hand, acquired hemiplegia presents later in life as a result of injury or other pathology.

Osmosis-style illustration of person with paralysis on one side of the body due to affected cerebral hemisphere on the opposite side of body.

What is the difference between hemiplegia and hemiparesis?

Hemiplegia refers to a severe or complete loss of strength leading to paralysis, whereas hemiparesis presents as a slight loss of strength. Mild to moderate nerve or brain damage will produce hemiparesis, while moderate to severe damage of nerves or parts of the brain that are involved in the connection between the brain and muscles (e.g., primary motor cortex [M1] along the precentral gyrus), will result in hemiplegia. Both terms imply loss of movement and possibly sensation on one side of the body, however, they differ in severity.

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What causes hemiplegia?

The most common cause of hemiplegia refers to vascular conditions, which include strokes, aneurysms, and cerebral hemorrhage. Traumatic causes, like cerebral lacerations (i.e., deep cuts within brain tissue), spinal cord lacerations (e.g., Brown-Séquard syndrome), and subdural hematomas, are also very common. Infections of the nervous system (e.g., encephalitis, meningitis, brain abscess), malignancies (e.g., gliomas, meningiomas), and demyelinating diseases of the central nervous system (e.g., multiple sclerosis) can also cause loss of motor function. Diabetes is a polysystematic condition that may also lead to hemiplegia as a result of damage to the nerves (i.e., diabetic neuropathy) and the vessels (e.g., atherosclerosis).  Cerebral palsy, a group of congenital disorders that affect an individual’s ability to move, maintain balance, and posture, can also cause hemiplegia. A rare cause of hemiplegia is when local anesthesia injections are given intravenously, instead of into the tissue surrounding a nerve branch. Lastly, a less concerning cause of hemiplegia is nocturnal hemiplegia, which involves brief unintended physical experiences of paralysis after waking from sleep. 

What are the signs and symptoms of hemiplegia?

Hemiplegia’s main clinical manifestation is severe or complete loss of motor function on only one side of the body. Sensation can also be lost completely or partially, on the affected side of the body. Further signs and symptoms range between individuals and largely depend on the severity of each case. Usually, both gross (i.e., walking, running, swimming) and fine (i.e., buttoning and unbuttoning clothes, writing, playing musical instruments) motor skills are affected. Less frequently, individuals may present with difficulty speaking (often characterized as slurred speech), difficulty swallowing and trouble breathing. Individuals with traumatic brain injuries may have a characteristic way of walking, in which they shift their body weight on the affected side, also known as Pusher syndrome.

How is hemiplegia diagnosed?

Hemiplegia is often diagnosed after reviewing the individual’s past medical history and performing a detailed neurological examination assessing sensory and motor functions. 

Additional tests can be conducted in order to determine the underlying cause of hemiplegia. Blood tests, including a complete blood count (CBC), erythrocyte sedimentation rate (ESR), coagulation tests (e.g., PT, aPTT) can help eliminate various underlying causes, such as infections or malignancies. Imaging, including magnetic resonance imaging (MRI) and computerized tomography (CT) scans of the head, are necessary in order to exclude most pathologies, including strokes, aneurysms, brain tumors, multiple sclerosis, and injuries. Lastly, electroencephalography (EEG), which measures the electrical activity of the brain, can be used for diagnostic purposes (e.g., reveal the part(s) of the brain from which seizures originate). 

How is hemiplegia treated?

Treatment of hemiplegia involves a multidisciplinary approach. Healthcare professionals including physicians, physical therapists, occupational therapists, and psychologists must all contribute in order to assist affected individuals in regaining their functionality. Treatment typically aims at improving sensation and motor abilities so that individuals can perform their daily activities with as much independence as possible; as well as treating any underlying pathology causing the hemiplegia

Medication can be used either for treating the individual’s symptoms or the underlying cause. For example, chlordiazepoxide (e.g., Librium) can be administered to relieve symptoms of anxiety. Other medications (e.g., phenytoin) are used to treat recurrent seizures, which frequently present as a complication of brain injury. Antibiotics may be used to treat any brain infections. Blood thinners, such as warfarin or heparin, can be administered to prevent blood clotting and consequently, strokes. In addition, neuromuscular electrical stimulation (NMES), a high-intensity electrical stimulator, used to maintain the size and functionality of the muscles, can help decrease spasticity and increase the individual’s awareness of their limbs.

More invasive protocols suggest surgical options, especially for treating conditions that arise secondarily to hemiplegia, such as muscle contractions, spinal damage, or damage to the ligaments or tendons. Surgery can additionally be used to treat aneurysms as well as to remove blood vessel narrowing in the brain.

What are the most important facts to know about hemiplegia?

Hemiplegia refers to severe or complete loss of strength leading to paralysis on one side of the body and is usually the result of brain damage in the cerebral hemisphere, opposite the side of paralysis. Hemiplegia may be caused by several vascular conditions, injuries, infections, and congenital disorders. Depending on the severity and the parts of the brain that are affected, signs and symptoms may vary from muscle weakness and loss of sensation, to impaired motor skills of the affected limbs and difficulty speaking. Diagnosis is mainly clinical, but further blood testing, imaging, and diagnostic testing like EEGs are needed to confirm the diagnosis. Treatment of hemiplegia involves a multidisciplinary approach, including physical therapy, medications, and when necessary, surgical intervention.

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Related links

Ischemic stroke
Brown-Sequard syndrome
Traumatic brain injury: Clinical practice

Resources for research and reference

Contact. (2022, January 11). What is hemiplegia? In Contact. Retrieved February 23, 2022, from  

National Center for Biotechnology Information. (2022). Hemiplegia. In U.S. National Library of Medicine. Retrieved February 22, 2022, from   

National Center for Biotechnology Information. (2022). Hemiplegia/hemiparesis. In U.S. National Library of Medicine. Retrieved February 23, 2022, from