Neurologic Rehabilitation

Clinical rehabilitation has developed in an ad hoc fashion. The first formal stroke rehabilitation method, published by Frenkel in the mid- 19th century, emerged from a program that a nonprofessional wife had developed to successfully rehabilitate her husband. Rehabilitation clinicians still rely on nontheory-related methodologies. Little has been written about the fact that rehabilitation as currently practiced has such meager carryover to real-life activities, and even little carryover from one session to another. This has had the effect of reinforcing the widespread view in the physical rehabilitation field that once a patient reaches a plateau, usually 6-12 months after a stroke, further administration of rehabilitation therapy does not have useful results. With standard rehabilitation, a study showed that there was a difference in what the stroke patients could do in the hospital stroke unit and what the patients did at home. Each activity of daily living was less well performed in the home situation in 2545% of the cases, and in 52% of the cases the chief caretaker claimed that the patient did not do two or more activities at home that the patient was capable of performing in the day hospital.

Ideally, therapy should be based on experimental findings. Carryover to real-life activities requires programs specifically developed to do so. Issues such as the nature of the interaction between behavioral and neural plasticity and the nature of rehabilitation programs that produce functional carryover should be evaluated. Programs based on conditioned responses have no carryover, whereas those based on shaping and on constraint-induced facilitation have been shown to have excellent carryover to real-life tasks.

A cat hemispherectomy model has provided some of the most reliable information on mechanisms underlying recovery of function in adult cats as well as the functional compensation in the developing animal following neonatal lesion. Forced exercise of the impaired limb was effective in reversing paw preference bias in all cases; however, the adult lesioned cats required more trials and extensive food deprivation. All cats continued improved performance indefinitely in their home cages. Thus, an impressive potential for recovery of directed purposeful movements remains after hemispherectomy, and recovery of function can be enhanced by forced exercise. Although 1 month of recovery time was needed in the adult hemispherect-omy cases, recovery time for directed self-feeding movements could be reduced with passive mobilization and treadmill walking and running immediately after the experimental surgery. This provides animal experimental evidence that supports clinical rehabilitation applications of passive movements (which prevent contractures that lead to limited limb range of motion) in the early stages following brain damage.

Another productive, widely used model is the differential effect of serial lesions versus the one-stage lesion of the same amount of tissue, from the same brain area, as the total of all the serial lesions. Many studies have shown that the functional recovery is far greater in the animals that have had serial lesions than in those that have had one-step lesions. Reorganization of function, including reorganization in brain tissue different from the eventually removed tissue, must occur between lesions. This provides firm evidence for brain plasticity and recovery of function, even in the adult animal.

In addition to motor recovery with appropriate rehabilitation, animal models have also demonstrated sensory recovery, such as cat visual recovery from ambliopia with training and the ability to regain all fine sensory functions with rehabilitation following primary somatosensory projection cortex ablations in monkeys trained in tactile discriminations prelesion. An incidental finding is that postlesion it is necessary to inhibit negative cues, and that lesion of the ipsilateral cortex can produce bilateral deficits

There are many excellent recent studies on the scientific basis of recovery of function with rehabilitation. The following are some conclusions drawn by the experimenters of these studies. Rehabilitation must be varied and must not be repetitive. Changes in the motor cortex are driven by the acquisition of new motor skills and not simply by motor use, which may indicate that the repetitive, boring activities of standard rehabilitation are virtually useless. Functional plasticity is accompanied by structural plasticity. Unmasking, multiplexing, synaptic plasticity, sprouting, and inhibition are mechanisms of functional reorganization following brain damage. Functional plasticity in intact cortex is initiated immediately after injury. Activity (rehabilitation) results in an increase in the neuropil, in dendritic arborization, in the number of synapses, and in the separation between neurons, resulting in the reduction of the number of neurons per cubic millimeter. Spontaneous motor recovery cannot be explained by substitution of function in the spared motor cortex immediately adjacent to the lesion. The retention of functional representation in tissue adjacent to the lesion requires motor training (rehabilitation), which appears to have a modulatory effect on plasticity in the surrounding tissue. Blocking the NMDA receptors may be neuroprotective in the early postinjury stage, but blocking them later may reinstate deficits. Immobilizing the good limb too soon after brain damage in a rat model can have extremely deleterious effects, both in behavioral responses and in causing a dramatic expansion of the original lesion, which suggests that either too much or too little activity can have profound negative consequences. In rats, forced disuse for 1 week has many measurable negative effects; thus, studies of the negative effect of forced bed rest in brain-damaged humans are necessary. Mild rehabilitation may improve functional outcome, whereas early moderate rehabilitation can have negative effects, including the exaggeration of infarct size. Human stroke patients had worse outcome with forced speech therapy for several weeks than with brief (15-min) conversations.

Many of these conclusions challenge several dogmas of rehabilitation; however, especially since they are based on experimental findings, they should lead to further studies and, undoubtedly, to changes in the practice of clinical rehabilitation. Clinical studies have rarely used prospective randomized methods. One such study, carried out at the Karolinska Institutet in Huddinge (Stockholm), revealed that for patients for whom early stroke rehabilitation was possible, home rehabilitation was effective. However, well-documented individual case studies demonstrating unusual recovery are valuable, especially since they indicate what is possible and they may suggest effective rehabilitation approaches. In one such study, an elderly stroke patient with extensive brain damage (that was documented on autopsy 7 years later) followed a home rehabilitation program and recovered an extrodinary degree of function and returned to fulltime work.

Little emphasis has been placed on late rehabilitation programs, possibly because late recovery has not generally been expected. However, reports of late recovery are not new; it was discussed in an article in the Journal of the American Medical Association in 1915, and many such reports have emerged from the treatment of war injuries. A case report of late recovery in a quadriplegic patient noted that since most quadriplegic patients are discharged 4 or 5 months postinjury, many patients have not achieved full motor recovery at discharge. It is possible that in many other cases of central nervous system damage the late recovery of function goes unnoticed since the patients have been discharged.

In addition to neural factors, learned nonuse has been demonstrated in human stroke patients. Although both lower extremities are almost always used as soon as possible in the recovery phase following the stroke since both are necessary for gait, the affected upper extremity is often not used, possibly because many tasks can be performed with one hand, leading to the development of learned nonuse. Behavioral training provided even years after the lesion that could involve as few as 3 days of restraint of the normal limb, thus forcing the use of the affected limb, can reverse the learned nonuse, converting a useless limb into a limb capable of extensive movement. It had previously been shown that forced use of the paretic upper extremity of monkeys with experimentally produced hemiplegia (unilateral cortical area 4 ablation) produced significant recovery of function.

A sensory substitution model of late brain rehabilitation has been developed based on the consideration that a major sensory loss, such as blindness, removes a large part of the input to the brain and, similar to an actual lesion, induces a major reorganization of the brain. Tactile vision substitution systems (TVSS's) have been developed to deliver visual information from a TV camera to arrays of stimulators in contact with the skin of one of several parts of the body, including the abdomen, back, thigh, forehead, fingertip, and tongue. Mediated by the tactile receptors, images transduced from the camera are encoded as neural pulse trains. In this manner, the brain is able to recreate "visual" images that originate in a TV camera. Indeed, after sufficient training with the TVSS, subjects who were blind since early infancy reported experiencing the images in space instead of on the skin. They learned to make perceptual judgments using visual means of analysis, such as perspective, parallax, looming, and zooming, and to make depth judgments. They have been able to perform complex perception and "eye"-hand coordination tasks, including facial recognition, accurate judgment of speed and direction of a rolling ball with more than 95% accuracy in batting the ball as it rolls over a table edge, and complex inspection-assembly tasks. The results have been interpreted as demonstrating the capacity of the brain to reorganize even when the training (rehabilitation) of congenitally blind persons is initiated in adulthood.

Another post-acute program was developed for persons with long-standing facial paralysis due to facial nerve damage during the removal of an acoustic neuroma who had undergone a VII-XII cranial nerve anastomosis (connecting part of the tongue nerve to innervate the facial muscles). In this model, it is clear that the facial muscles are innervated by nerve fibers from structures genetically programmed to move tongue muscles. However, with appropriate rehabilitation, persons recover spontaneous and voluntary bilateral facial symmetrical movements, and they learn to inhibit dyskinetic movements, even many years after the causitive event. The study was designed to evaluate brain plasticity in a human model in which the extent of the lesion is definitely known and in which, due to the complete loss of connectivity from the brain regions genetically programmed to control facial movements, another system (in this case, the brain regions that had previously controlled tongue movements) could be demonstrated to have reorganized to obtain the functional recovery.

Motivating therapy is effective. An example is the ingenious approach taken by a research group in France to obtain eye movement control in children with cerebral palsy who had eye coordination deficits. They noted, as had others before them, that watching a pendulum aided in the training, but they found that the children refused to watch because they found it too boring. They developed a fascinating functional pendulum by projecting children's movies (Snow White and Lassie) at a galvanometer-controlled mirror, which reflected the image to the back side of a projection screen. The children sat in front of the screen with their heads fixed so that to follow the pendular movements of the image they had to use eye movements. They underwent 6 hr a week of intense therapy (three movies) and within 1 month improved to the point that they could learn to read.

A comparable approach was taken in the early 1970s with the early electronic pong games, which could be connected to home TV sets. One of the joystick controls was replaced with a device used in the clinic for hemiparetic persons to train arm movements. Instead of meaningless exercise, the arm could control a paddle (paddle size and ball speed were varied according to the capabilities of individual patients) allowing participation in a highly motivating game.

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