What Are Hemiplegia and Hemiparesis?

Hemiplegia is total or nearly complete paralysis on one side of the body. This significantly or entirely limits someone’s ability to voluntarily move the affected parts (e.g., an arm, leg, or one side of the face).

In contrast, hemiparesis is one-sided weakness. In other words, there is some motor strength remaining in the weakened area, though one’s day-to-day functioning may still be impacted.

Hemiplegia is permanent, but it does not get worse over time, whereas partial or even full recovery may be possible with hemiparesis. Often, people with hemiplegia and hemiparesis get stronger and improve their mobility with physical therapy.

This article explains how hemiplegia and hemiparesis overlap and, more importantly, how they differ. It reviews symptoms and causes, as well as how these conditions are diagnosed and treated.

Symptoms

The most prominent symptom of these conditions is the inability to move (hemiplegia) or weakness (hemiparesis) on one side of the body.

In addition, you may experience the following with these conditions:

• Loss of balance
• Trouble walking
• Difficulty grasping items
• Muscle weakness
• Lack of coordination
• Stiff muscles
• Difficulty swallowing
  

With hemiplegia, symptoms may be more severe. For example, rather than having trouble walking or muscle weakness, you may not be able to move one side of your body at all.

In addition, hemiplegia and hemiparesis can result in emotional and behavioral symptoms. These may vary depending on which part of the brain is affected. For example, a left brain injury may result in someone being anxious and cautious, while a right-sided brain injury may result in impulsivity and over-confidence.

Causes

Muscle movement is controlled by signals sent to the body by the brain and spinal cord. Hemiplegia and hemiparesis both result from damage to one of these parts of the body.

When brain or spine damage occurs, the signals cannot direct the muscles to move (or move well). The milder the damage, the more likely hemiparesis will occur. On the other hand, more significant damage results in hemiplegia.

There are several variations of paralysis. They are classified as:

• Partial: Retaining some control of the muscles
• Complete: Inability to move any muscle
• Permanent: Muscle control does not come back
• Temporary: Some muscle control returns
• Flaccid: Muscles become flabby and may shrink
• Spastic: Muscles become stiff and may spasm

Hemiparesis is partial and may be permanent or temporary, while hemiplegia is complete and permanent. Either may result in flaccid muscles due to underuse. In addition, spasticity can result in both conditions, especially in the case of degenerative diseases or stroke.

Most cases of hemiplegia and hemiparesis occur as a result of a stroke (disrupted blood flow to the brain). Other causes of paralysis include:

• Spinal cord injury, such as a broken back or neck
• Cerebral palsy, brain damage (typically occurring before birth) that affects motor function
  
• Multiple sclerosis (MS), autoimmune disease that destroys nerve cells in the brain, spinal cord, and eyes
• Autoimmune diseases, condition in which the immune system attacks your body
• Bell’s palsy, condition that causes one-sided facial weakness
• Spina bifida, congenital (at birth) disorder where vertebrae do not close correctly around the spine
• Brain tumor
• Brachial plexus (nerves that travel from the neck to the armpit) injury

Paralysis is generally not progressive. However, in the case of a tumor or a degenerative disease, it is possible for hemiparesis to become more severe or develop into hemiplegia as a tumor grows or disease progresses.

Why Is Only One Side of the Body Affected?

The human brain and spinal cord each have two identical “halves” on the right and the left sides of the body:

• The outermost layer of the brain (cerebral cortex) contains what’s called the primary motor cortex (sometimes called the “motor homunculus”). The left-hand side of the primary motor cortex controls movement on the right-hand side of the body, and vice-versa.
• The spinal cord contains regions called the corticonuclear (or corticobulbar) tract—which controls the muscles of the face, head, and neck—and the corticospinal tract—which controls the muscles of the rest of the body. The left side of the spinal cord controls that same side of the body and vice versa.

Injuring one of these areas impacts only the side of the body it controls. For example, an injury to the left side of the cerebral cortex can result in right-sided hemiplegia, an injury to the right side of the spinal cord can result in right-sided hemiparesis, and so on.

Diagnosis

Evaluation of hemiplegia and hemiparesis involves a physical exam. Your healthcare provider will test your reflexes and muscle strength using a rubber reflex hammer. They may also press on your limbs while you do your best to resist their efforts.

In addition, your doctor may order the following imaging tests and diagnostic procedures:

• X-ray
• Computed tomography (CT scan), X-ray images that are converted to a 3D image
• Magnetic resonance imaging (MRI), magnetic fields and radio waves that produce a 3D image
• Myelography, contrast dye and X-Ray or CT scan to view the spinal canal
• Electromyography (EMG), a small needle electrode that measures muscle activity
• Nerve conduction study (NCS), which measures the speed of electrical signals traveling through your nerves
• Complete blood count (CBC), a blood test that checks the levels of blood cells and platelets
  

Complications

Secondary conditions of hemiplegia and hemiparesis are problems that you might experience as a result of the weakness. Sometimes, these problems are not noticeable right away. Instead, they may develop months after you first notice weakness or paralysis.

Some of the complications of hemiplegia and hemiparesis include:

• Bladder problems, such as not fully emptying when you pee or urinating when you don’t intend to (incontinence)
• Bowel control problems
• Pain
• Deep vein thrombosis (DVT), when blood clot that blocks a large vein
• Autonomic dysreflexia, a sudden spike in blood pressure
• Depression
• Respiratory difficulties
• Heart disease
• Sepsis, infection in the bloodstream
• Pressure wounds (also called bedsores or pressure ulcers), which are skin sores that occur from lying in bed
• Tight, rigid, inflexible muscles
• Muscle atrophy (weakness)

Treatments

Sometimes, muscle strength may improve on its own. However, usually it requires supportive treatment. The goal of hemiplegia and hemiparesis treatment is to increase muscle strength and mobility.

While it used to be thought that maximal recovery would occur within the first year, more recent research has found that recovery can occur many years following the onset of hemiplegia and hemiparesis. That means treatment could be indicated and beneficial in the long-term.

Physical Therapy

Physical therapy is a first line treatment for hemiplegia and hemiparesis. Exercise is helpful to keep joints loose and flexible.

Carefully designed therapy techniques prevent muscle atrophy (the loss or decrease of muscle mass) and spasticity. Physical therapy also helps prevent the complications of hemiplegia and hemiparesis, such as heart disease, diabetes, pressure sores, obstructive pulmonary disease, and urinary tract infections.

Some physical therapists (PTs) use electrical stimulation, a mode of therapy that involves the application of electrical currents to strengthen muscles, reduce pain, and improve circulation.

In addition, PTs may instruct people on using mental imagery during therapy and at home. Mental imagery in hemiplegia and hemiparesis involves imagining the affected limbs moving. This activity works by stimulating nerves in the brain responsible for visualization and movement. Therefore, it’s a good brain training exercise.

Occupational Therapy

Occupational therapy is a type of therapy that focuses on learning how to take care of practical tasks and everyday activities, such as self-care.

Occupational therapists may utilize modified constraint-induced movement therapy (mCIMT). This treatment involves intensive muscle training with the upper limbs to build back function in the affected arm. Physical therapists may also use this technique.

Mobility Aids

Mobility aids can help you lead an independent, active life even if you have hemiparesis or hemiplegia. These aids include:

• Manual and electric wheelchairs
• Scooters
• Braces
• Canes
• Walkers

Assistive Technology and Equipment

Assistive technology includes the use of voice-activated devices, computers, telephones, and lighting systems. These are becoming more available and practical to use.

In addition, adaptive equipment, such as specially designed devices for driving, eating, and personal hygiene can help in practical day-to-day activities.

Summary

Hemiplegia and hemiparesis are related conditions that cause weakness on one side of the body. Hemiplegia is when the weakness causes paralysis, while hemiparesis is partial weakness.

The cause of these conditions is varied but usually results from an injury or illness to the spinal cord or brain. Physical and occupational therapy can sometimes help people regain some mobility. Mobility aids and assistive technology help people remain independent and active.

A Word From Verywell

Hemiplegia and hemiparesis are difficult conditions to adjust to. But there are steps you can take to make living with hemiplegia or hemiparesis easier.

Neurological illnesses that cause hemiplegia and hemiparesis are not uncommon. Talk to your doctor about resources that can help you through your recovery. They will be able to direct you to resources that can provide support with practical aspects of life.