Hemiparesis, also called unilateral paresis, is the weakness of one entire side of the body (hemi- meaning 'half'). Hemiplegia, in its most severe form, is the complete paralysis of one entire side of the body. Either hemiparesis or hemiplegia can result from a variety of medical causes, including congenital conditions, blunt trauma, tumors, traumatic brain injury, and stroke.
Signs and symptoms Different types of hemiparesis can impair different bodily functions. Some effects, such as weakness or partial paralysis of a limb on the affected side, are generally expected. Other impairments can appear upon external examination to be unrelated to the limb weakness, but are nevertheless also caused by damage to the affected side of the brain.
Loss of motor skills People with hemiparesis often have difficulties maintaining their balance due to limb paralysis, leading to an inability to properly shift body weight. This makes performing everyday activities, such as dressing, eating, grasping 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, which often manifests as a staggering and stumbling gait. Pure motor hemiparesis, a form of hemiparesis characterized by one-sided weakness in the leg, arm and face, is the most commonly diagnosed form of hemiparesis.
Pusher syndrome
Pusher syndrome is a clinical disorder following left- or right-sided brain damage, in which patients actively push their weight away from the non-hemiparetic side to the hemiparetic side. This is in contrast to most stroke patients, who typically prefer to bear more weight on their nonhemiparetic side. Pusher syndrome 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 in multiple areas of the right cerebral hemisphere. A diagnosis of pusher syndrome includes observation of three behaviours. The most obvious one is the patient's regularly occurring (not just occasional) tendency to spontaneously hold a body posture in which the torso is longitudinally tilted toward the paretic side of the body. The second is the patient's use of the nonparetic extremities including abduction and extension of the extremities of the non-affected side, to help in the push toward the affected (paretic) side, resulting in an abnormal lateral tilt of the body axis. The third is that, when a care provider tries to realign the patient's body to an upright posture, the patient spontaneously pushes back against the attempt, feeling this normal posture to be off balance. The pusher syndrome is present in 10.4% of patients with acute stroke and hemiparesis, and may increase the time needed for physical rehabilitation. The Copenhagen Stroke Study found that patients who presented with ipsilateral pushing took an average of 3.6 additional weeks to reach the same functional outcome, as measured by the Barthel Index, compared with acute-stroke and hemiparesis patients who did not engage in ipsilateral pushing. Pushing behaviour demonstrates that these patients' perception of their body posture in relation to gravity has been altered. They experience their body as oriented "upright" when the body is actually tilted to the side of the brain lesion. At the same time, their processing of visual and vestibular inputs when determining the subjective visual vertical seems to be normal. When they are sitting, the pushing presents as a strong lateral lean toward the affected side. When they stand up, the pushing creates a highly unstable situation as they are unable to support their body weight on the weakened lower extremity. The resulting increased risk of falls must be addressed with therapy aimed at correcting their altered proprioceptive perception of vertical. Pusher syndrome is sometimes confused with hemispatial neglect, and the two terms are sometimes (incorrectly) used interchangeably. Some older theories suggested that hemispatial neglect is what leads to pusher syndrome. However, hemispatial neglect occurs mostly when there is a right-hemisphere lesion, and one study found that pusher syndrome is also present in patients with left hemisphere lesions (which generally also lead to aphasia). Neglect and aphasia are not the cause of pusher syndrome, although both are highly correlated with it (possibly because the brain structures associated with these syndromes are close to each other). Physical therapists treating patients with pusher syndrome focus on motor learning strategies that reduce its ill effects, such as the use of verbal cues, consistent feedback, and practice correcting orientation and shifting weight, for example sitting with their stronger side next to a wall and repeatedly leaning towards the wall, thus gradually re-training the brain to recognize true vertical. A physical-therapy approach for patients with pusher syndrome debuted in 2003 suggests that the visual control of vertical upright orientation, which is undisturbed in these patients, is the most important intervention. In sequential order, treatment is designed to enable 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.
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