||It has been suggested that this article be merged into Hemiplegia. (Discuss) Proposed since September 2014.|
|Classification and external resources|
|ICD-9||342.9, 094.89, 438.2|
Hemiparesis is weakness on one side of the body. It is less severe than hemiplegia — the total paralysis of the arm, leg, and trunk on one side of the body. Thus, the patient can move the impaired side of their body, but with reduced muscular strength.
Hemiparesis can be caused by a number of medical conditions, most related to the brain or spinal cord. Some of the conditions that have hemiparesis as either an indicative symptom or as a result of the condition itself include migraine, head trauma, muscular dystrophy, stroke, brain tumors, or cerebral palsy.
- 1 Anatomic localization
- 2 Other effects of hemiparesis
- 3 Treatment
- 4 See also
- 5 References
Movement of the body is primarily controlled by the pyramidal (or corticospinal) tract, a pathway of neurons that begins in the motor areas of the brain, projects down through the internal capsule, continues through the brainstem, decussates (or cross midline) at the upper medulla, then travels down the spinal cord into the motor neurons that control each muscle. In addition to this main pathway, there are smaller contributing pathways (including the anterior corticospinal tract), some portions of which do not cross the midline.
Because of this anatomy, injuries to the pyramidal tract above the medulla generally cause contralateral hemiparesis (weakness on the opposite side as the injury). Injuries at the lower medulla, spinal cord, and peripheral nerves result in ipsilateral hemiparesis.
In a few cases, lesions above the medulla have resulted in ipsilateral hemiparesis:
- In several reported cases, patients with hemiparesis from an old contralateral brain injury subsequently experienced worsening of their hemiparesis when hit with a second stroke in the ipsilateral brain. The authors hypothesize that brain reorganization after the initial injury led to more reliance on uncrossed motor pathways, and when these compensatory pathways were damaged by a second stroke, motor function worsened further.
- A case report describes a patient with a congenitally uncrossed pyramidal tract, who developed right sided hemiparesis after a hemorrhage in the right brain.
Other effects of hemiparesis
Depending on the type of hemiparesis diagnosed, different bodily functions can be affected. Some effects are expected (i.e., partial paralysis of a limb on the affected side). Other impairments, though, can at first seem completely non-related to the limb weakness but are, in fact, a direct result of the damage to the affected side of the brain.
Loss of motor skills
People with hemiparesis often have difficulties maintaining their balance due to limb weaknesses leading to an inability to properly shift body weight. This makes performing everyday activities such as dressing, eating, grabbing objects, or using the bathroom more difficult. Hemiparesis with origin in the lower section of the brain creates a condition known as ataxia, a loss of both gross and fine motor skills, often manifesting as staggering and stumbling. Pure Motor Hemiparesis, a form of hemiparesis characterized by sided weakness in the leg, arm, and face, is the most commonly diagnosed form of hemiparesis.
Loss of using or understanding speech
Right-sided hemiparesis involves injury to the left side of the person's brain, which is usually the side of the brain which controls speech and language. People who have this type of hemiparesis often experience difficulty with talking and understanding what others say.
Loss of ability to distinguish left from right
In addition to problems understanding or using speech, persons with right-sided hemiparesis often have difficulty distinguishing left from right. When asked to turn left or right, or to raise a left or right limb, many affected with right-sided hemiparesis will either turn/raise limb/etc. in the wrong direction or simply not follow the command at all due to an inability to process the request.
Loss of short-term memory and/or attention span
Left-sided hemiparesis involves injury to the right side of the person's brain, which controls learning processes, certain types of behavior, and non-verbal communication. Injury to this area of a person's brain may also cause people to talk excessively, have short attention spans, and have problems with short-term memory.
“Pusher syndrome” is a clinical disorder following left or right brain damage in which patients actively push their weight away from the nonhemiparetic side to the hemiparetic side. In contrast to most stroke patients, who typically prefer more weight-bearing on their nonhemiparetic side, this abnormal condition can vary in severity and leads to a loss of postural balance. The lesion involved in this syndrome is thought to be in the posterior thalamus on either side, or multiple areas of the right cerebral hemisphere.
With a diagnosis of pusher behaviour, 3 important variables should be seen. The most obvious of which is spontaneous body posture of a longitudinal tilt of the torso toward the paretic side of the body occurring on a regular basis and not only on occasion. The use of the nonparetic extremities to create the pathological lateral tilt of the body axis is another sign to be noted when diagnosing for pusher behaviour. This includes abduction and extension of the extremities of the non –affected side, to help in the push toward the affected (paretic) side. The third variable that is seen is that attempts of the therapist to correct the pusher posture by aiming to realign them to upright posture are resisted by the patient. 
In patients with acute stroke and hemiparesis, the disorder is present in 10.4% of patients. Rehabilitation may take longer in patients that display pusher behaviour. The Copenhagen Stroke Study found that patients that presented with ipsilateral pushing used 3.6 weeks more to reach the same functional outcome level on the Barthel Index, than did patients without ipsilateral pushing.
Pushing behavior has shown that perception of body posture in relation to gravity is altered. Patients experience their body as oriented “upright” when the body is actually tilted to the side of the brain lesion. In addition, patients seem to show no disturbed processing of visual and vestibular inputs when determining subjective visual vertical. In sitting, the push presents as a strong lateral lean toward the affected side and in standing, creates a highly unstable situation as the patient is unable to support their body weight on the weakened lower extremity. The increased risk of falls must be addressed with therapy to correct their altered perception of vertical.
Pusher syndrome is sometimes confused with and used interchangeably as the term hemispatial neglect, and some previous theories suggest that neglect leads to pusher syndrome. However another study, had observed that pusher syndrome is also present in patients with left hemisphere lesions, leading to aphasia, providing a stark contrast to what was previously believed regarding hemispatial neglect, which mostly occurs with a right hemisphere lesion. 
Karnath summarizes these two conflicting views, as they conclude that both neglect and aphasia are highly correlated with pusher syndrome possibly due to the close proximity of relevant brain structures associated with these two respective syndromes. However the article goes on to state that it is imperative to note that both neglect and aphasia are not the underlying causes of pusher syndrome.
Physical therapists focus on motor learning strategies when treating these patients. Verbal cues, consistent feedback, practicing correct orientation and weight shifting are all effective strategies used to reduce the effects of this disorder. Having a patient sit with their stronger side next to a wall and instructing them to lean towards the wall is an example of a possible treatment for pusher behaviour.
A new physical therapy approach for patients with pusher syndrome suggests that the visual control of vertical upright orientation, which is undisturbed in these patients, is the central element of intervention in treatment. In sequential order, treatment is designed for patients to realize their altered perception of vertical, use visual aids for feedback about body orientation, learn the movements necessary to reach proper vertical position, and maintain vertical body position while performing other activities.
Classification of Pusher Syndrome
Individuals who present with pusher syndrome or lateropulsion, as defined by Davies, vary in their degree and severity of this condition and therefore appropriate measures need to be implemented in order to evaluate the level of “pushing”. There has been a shift towards early diagnosis and evaluation of functional status for individuals who have suffered from a stroke and presenting with pusher syndrome in order to decrease the time spent as an in-patient at hospitals and promote the return to function as early as possible. Moreover, in order to assist therapists in the classification of pusher syndrome, specific scales have been developed with validity that coincides with the criteria set out by Davies’ definition of “pusher syndrome”. In a study by Babyar et al., an examination of such scales helped determine the relevance, practical aspects and clinimetric properties of three specific scales existing today for lateropulsion. The three scales examined were the Clinical Scale of Contraversive Pushing, Modified Scale of Contraversive Pushing, and the Burke Lateropulsion Scale. The results of the study show that reliability for each scale is good; moreover, the Scale of Contraversive Pushing was determined to have acceptable clinimetric properties, and the other two scales addressed more functional positions that will help therapists with clinical decisions and research.
Treatment for hemiparesis is the same treatment given to those recovering from strokes or brain injuries. Health care professionals such as physical therapists and occupational therapists play a large role in assisting these patients in their recovery. Treatment is focused on improving sensation and motor abilities, allowing the patient to better manage their activities of daily living. Some strategies used for treatment include promoting the use of the hemiparetic limb during functional tasks, maintaining range of motion, and using neuromuscular electrical stimulation to decrease spasticity and increase awareness of the limb. At the more advanced level, using constraint-induced movement therapy will encourage overall function and use of the affected limb. Mirror Therapy(MT) has also been used early in stroke rehabilitation and involves using the unaffected limb to stimulate motor function of the hemiparetic limb. Results from a study on patients with severe hemiparesis concluded that MT was successful in improving motor and sensory function of the distal hemiparetic upper limb. Active participation is critical to the motor learning and recovery process, therefore it’s important to keep these individuals motivated so they can make continual improvements.
Also speech pathologists work to increase function for people with hemiparesis.
- Detailed article about hemiparesis at Disabled-World.com
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- Song, Young-Mok; Jee-Young Lee, Jong-Moo Park, Byung-Woo Yoon, Jae-Kyu Roh (2005). "Ipsilateral Hemiparesis Caused by a Corona Radiata Infarct After a Previous Stroke on the Opposite Side". Archives of Neurology 62 (5): 809. doi:10.1001/archneur.62.5.809. ISSN 0003-9942.
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- Stroke in Physical Rehabilitation 2007, p. 746