Hemiparesis

Muscle Weakness on One Side of the Body and What Causes It

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Hemiparesis is partial weakness on one side of the body. It may involve the arms, hands, legs, face, or a combination.

Stroke is the most common cause of hemiparesis; about 80% of stroke survivors experience it.A stroke occurs when brain cells are damaged due to either a blockage of blood flow or a break in a blood vessel supplying the brain. People who have hemiparesis are still able to move the affected side of the body, but with limited strength.

This article will explore additional causes of hemiparesis, its common symptoms, and the treatment and recovery process.

Hemiparesis Symptoms

Laura Porter / Verywell

Causes

Hemiparesis is a common result of injuries or disease of the nervous system, which includes the brain, spinal cord, and nerves. In addition to stroke, hemiparesis can be caused by a number of other medical conditions:

  • Traumatic brain injury, such as from a fall, sports injury, or car accident
  • Traumatic injury that affects the nerves or spinal cord—the part of the nervous system that connects the brain to the rest of the body
  • A tumor, or abnormal growth of tissue, of the brain or spinal cord
  • Multiple sclerosis (MS), an autoimmune disorder in which the immune system mistakenly attacks the protective covering of nerves
  • Medical conditions that are present from birth, such as cerebral palsy that can affect the ability to walk and move
  • Infection of the brain, spine, or meninges (protective tissue that covers the brain and spinal cord)
  • Postictal paralysis, which is temporary weakness after a seizure
  • Psychological and psychiatric conditions that can cause temporary weakness

Recap

Medical conditions that affect the brain, spinal cord, or nerves often cause hemiparesis. This includes stroke, traumatic injuries, and tumors.

Symptoms

The most obvious symptom of hemiparesis is weakness of one side of the body. Symptoms correspond to the side of the brain or spine that has been damaged.

An injury to the left side of the brain typically results in weakness on the right side of the body. An injury to the right side of the brain typically results in weakness on the left side of the body.

Depending on the type of spine injury and the level of injury within the spine, hemiparesis may involve the same side of the body as the spine injury or may involve the opposite side.

Symptoms of hemiparesis also can include:

  • Inability to maintain balance
  • Difficulty walking
  • Inability to grasp objects
  • Decreased precision in movement
  • Muscle fatigue
  • Lack of coordination
  • Leaning to one side while standing, walking, or sitting
  • Loss of bowel or bladder control

Most often affecting the arms, legs, or both, hemiparesis makes it difficult to maintain a normal level of independent daily activities, and it is one of the leading causes of disability.

Recap

An injury to one side of the brain typically causes weakness on the opposite side of the body. Hemiparesis can make balance, coordination, walking, and grasping things difficult.

Diagnosis

If you complain of any symptoms of hemiparesis, your healthcare provider will do a physical examination. It can be difficult to determine whether your symptoms are the result of weakness, pain, or another cause.

The physical examination includes a test of your reflexes, sensation, and strength. Your healthcare provider will rate your strength on a scale of 1-5.

This rating can also help when the same healthcare provider or other healthcare providers assess your strength at a later time, as it can be used as a comparison.

Muscle Strength Rating Scale

The rating scale for muscle strength is as follows:

  • 0/5: No movement
  • 1/5: Mild muscle twitching
  • 2/5: Movements from side to side, but cannot lift the arm or leg up against gravity
  • 3/5: Can move up against gravity, but not against any force, such as mild pushing by the examiner
  • 4/5: Can move against force, such as pushing by the examiner, but not with normal expected strength
  • 5/5: Can move against force with expected strength

One side of the body may become completely weak; this condition is called hemiplegia.

Diagnosis of the cause of hemiparesis or hemiplegia can also be confirmed with imaging of the brain or spine and may include:

  • Computerized tomography (CT) scan, which uses multiple X-rays and a computer to get three-dimensional view
  • Magnetic resonance imaging (MRI), which uses a magnetic field and computer to get two- or three-dimensional images

Recap

Diagnosis often includes test of your reflexes, sensation, and strength and imaging of the brain and/or spine.

Treatment and Recovery

Treatment of hemiparesis is first directed towards targeted treatment of the cause, whether it's a stroke, brain tumor, infection, or another condition.

The goal of long-term treatment of hemiparesis is to strengthen motor skills and coordination and to improve your ability to manage everyday activities. Recovery and partial recovery from hemiparesis are possible with rehabilitation and therapy.

Therapy and Rehabilitation

Physical and occupational therapy are often important in the short-term and long-term recovery process. It can help stroke survivors regain movement even years after the stroke.

Therapy and rehabilitation may include:

  • Modified constraint-induced therapy (mCIT), a practice of using the weakened part of the body and limiting use of the unaffected side of the body
  • Electrical stimulation, which involves placing small electric pads on weakened muscles to give an electric charge that forces the muscle to contact
  • Cortical stimulation, which sends electrical currents to the brain during exercises
  • Mental imaginary, which involved dedicated visualization practices where you imagine you're moving the weakened side of the body
  • Assistive devices, such as braces, canes, walkers, and wheelchairs and practicing activities using these devices

Home Modifications

Modifications to the home may need to be made to accommodate and help increase mobility. Some of the modifications may include:

  • Grab bars
  • Ramps
  • Raised toilet seats
  • A bench in the tub
  • Non-slip adhesive strips in the bathtub
  • Electric toothbrushes
  • Electric razors

Fortunately, hemiparesis is not a progressive, or worsening, condition unless there is evidence of an aggressive growing brain tumor.

Summary

Hemiparesis is a weakness of one side of the body that can make mobility and everyday activities difficult. It commonly occurs due to injuries or conditions that affect the nervous system and the most common cause is stroke.

Therapy and rehabilitation are an important part of the recovery process and can help with strength and mobility improvements over time.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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