In the last few years, medicine has started to shed some light on the rearrangements that can be processed in the brain of people who have suffered some damage to their neurons and have lost some motor or cognitive capacity. Sometimes, functions originally controlled by the damaged nerve areas that have died as a result of trauma are transferred, in an almost mysterious way, to healthy regions of the brain. This as yet little understood and rare ability to reorganize itself and to learn to get round the injury may not be exclusive to the brain.
The spinal cord – which, with the brain, makes up the central nervous system – also seems, in some measure, to show this mechanism for adapting in the face of some aggression. Evidence in this direction is starting to become more frequent in the group of some 100 paraplegics and quadriplegics who are taking part in research by bioengineer Alberto Cliquet Junior, of the University of São Paulo (USP) in São Carlos and of the State University of Campinas (Unicamp), on the use of electrical stimuli in the rehabilitation of this kind of patient.
With the help of an exam called evoked potential testing, which makes it possible to register whether an exchange of nerve impulses is taking place between the injured spinal cord and the brain. In some patients, Cliquet found that, albeit precariously, some kind of connection was re-established between the two ends of the central nervous system. This must be the reason why these paraplegics and quadriplegics began to move and to feel limbs that had been paralyzed, to stand up, and possibly to take a few steps with the help of devices and electrical stimuli applied to the muscles – a technique similar to the one used in the treatment of the actor Christopher Reeve, famous as Superman in the cinema, who became quadriplegic after a fall in an equestrian competition in 1995. “In an objective way, the test shows that the improvement reported by the patient is not just a subjective feeling”, says Cliquet. “As the neurons killed by the injury do not regenerate, the nerve stimulus, to reach the brain, must havefound an alternative path through healthy sectors of the spinal cord”.
For the time being, however, there is no way of knowing what exactly is the new route followed by the electrical impulse. “There is no examination or test capable of showing this in a dynamic way, to make clear the whole trajectory followed by the nerve impulse between the spinal cord and the brain and vice-versa”, explains Cliquet. He is developing equipment and prostheses for paraplegics and quadriplegics at USP’s electrical engineering department in São Carlos and coordinates the assistance of spinal injury victims at Unicamp’s College of Medical Sciences. The researcher does not rule out the hypothesis, put forward in international works, that the spinal cord shows a greater degree of independence with regard to thebrain than is thought. In these cases, even without succeeding in re-establishing a connection in the brain, the spinal cord, on its own, could control some of the body’s basic movements, above all the involuntary ones or reflexes.
In serious injuries at some region of the spinal cord – the largest bundle of nerves that brings and takes impulses from the brain to the rest of the body – all the parts of the body located below the damaged area are disconnected from the brain. In other words, they neither receive from nor send signals to this vital organ, thus losing their motor capacity and feeling. The more serious the injury is in the spinal cord (which is almost half a meter long, between the base of the brain to the waist), the larger the area of the body paralyzed. Quadriplegics are usually unable to moved or feel their arms, legs and trunk, while paraplegics lose control of the lower members. When the evoked potential testing is carried out on these patients – a procedure that consists of applying a slight shock in a part of the body located below the injury and seeing, with the aid of an apparatus, whether the nerve stimulus goes along the spinal cord and arrives at the brain -, the neuronal signal stops at the point wherethe injury is.
Sometimes, however, the nerve stimulus finds some alternative path through the spinal cord and reaches the brain. One of the patients in whom the evoked potential testing recently showed some gain in communication between the two ends of the central nervous system is the adwoman Julia D’Amico de Almeida Serra, aged 49, who, since August 1999, has lost control and sense of touch from the waist downwards, as the result of a medullary infarct (the death of neurons through lack of oxygen).
Two years ago, Julia, who lives on the outskirts of Campinas, started the motor rehabilitation work advocated by Cliquet, with the use of electrical stimuli. At the beginning of the treatment, he carried out the evoked potential testing on the patient, and saw that nerve signals coming from the region below the spinal cord injury were not reaching the brain, which was totally to be expected, due to her condition as a paraplegic. Recently, a new examination found that there is some tenuous exchange of information, between the patient’s brain and spinal cord. The finding makes even more sense in the light of the advances shown by the patient after starting her rehabilitation work at Unicamp. “I started to move the toes of the left foot and my quadriceps (thigh muscle)”, says Julia. “Progress is happening, but it is slow. As, besides electro-stimulation, I am having other rehabilitation treatment, I cannot say which is bringing more results”.
This kind of tardy return of movement and feelings that was experienced by Julia and other patients, which takes place several years after the injury, is not yet clearly explained by science. According to the classic line, which still guides the majority of rehabilitation work with paraplegics, the doctors estimate that victims of spinal cord damage may show some improvement up to 12 months, at the most, after the accident. According to this more conventional view, once this period is over, the patient’s situation will merely stabilize or tend to worsen, unless he or she does some physiotherapeutic work for the maintenance of the joints. The rehabilitation techniques used by Cliquet in the treatment of spinal cord injuries, like other research carried out abroad, have checkmated this proposition.
The methodology used by the researcher fromSão Paulo is known as neuromuscular electrical stimulation, and it can be summed up in a few words: using electrodes controlled by a computer, the patient is given little shocks, in the order of milliamperes, in muscles of the paralyzed members, and this electrical stimulus leads to the muscular contraction that is necessary for movement. When the desired effect occurs, which does not always happen, the stimulus can, for example, make a paralyzed leg that used to be bent and immovable become rigid and stretch out completely. With the firmness in the lower members brought about by electrical stimulus, the patient can attempt his first steps, always with the support of a walking frame. Repeating this procedure for months, sometimes years, may restore movement and feeling in the paralyzed parts of the body of some patients. “But we don’t know why the treatment works better with some people and produces no results in others”.
Cliquet has other tests that suggest some change of the neuronal activity in paraplegics and quadriplegics who are following his alternative therapy. Magnetic resonance examinations show that the quantity of areas of the brain activated during rehabilitation work using nerve stimuli is greater than when the victims of spinal cord injuries are not submitted to this kind of treatment. It is one more indication that electrical stimulation, applied to the patient’s muscle, probably passes – Heaven knows how – through the damaged spinal cord and reaches regions of the brain not normally used by the patients. With the improvement of the motor function and the return of a few tactile sensations, the patients at Unicamp frequently need increasingly fewer stimuli to move themselves.
The fact is well illustrated by the story of Luis Carlos de Castro, who suffered a spinal cord injury at the height of his chest in a car accident in 1997. When he started rehabilitation with Cliquet’s team, two years ago, Luis needed the help of eight electrodes – four in each leg – to stand up and take a few steps, always with the support of a walking frame. Today, two electrodes in each lower limb are enough for this paraplegic to carry out the same movements. “With the work here (at Unicamp), I have also managed to regain control over my trunk, which was paralyzed before”, says Luis. Probably, the signals that used to be provided by the two electrodes suppressed, with the repetition of the rehabilitation work, have gone back to being produced by the brain, which has made the help of the artificial stimulus dispensable.
When they reach Luis’s stage – of being able to stand up and to take a few steps with the aid of electrodes and support equipment -, Cliquet’s patients are submitted to a battery of examinations at the biomechanics and rehabilitation of the motor apparatus laboratory of Unicamp’s Hospital and Clinics. They take steps on a mat covered with sensors that measure the mechanical force applied against the ground. And the movements of their joints and bone protuberances – picked out by plastic balls placed at 30 points of the body – are filmed and digitally stored, from the most different angles, by six infrared cameras. Periodically, they also carry out a control of the consumption of oxygen by the patients during the exercise, to prevent them from making an exaggerated effort that may cause heart problems.
Compared with the feats of other superior mammals, which, even with serious damage to spinal cord, relearn to walk in an almost normal fashion, the progress shown by human beings with injuries to this organ does not come as a complete surprise. Incats, for example, the spinal cord seems to have neuron circuitry that is so sophisticated and versatile that cats with severe paraplegia are capable of standing up and even of taking steps. Science has been trying to understand this ability ever since 1910, when the English neurophysiologist (and winner of the Nobel Prize for Medicine in 1932), Charles Sherrington, of Oxford University, found that cats with their spinal cord completely damaged were able to walk again, if they were properly exercised. Regardless of having found alternative access routes to take signals to the brain and to bring them back, the spinal cord in these cats, by itself, has the capacity to control some kinds of movement of the body, including those involved in walking. It is capable ofcoordinating certain acts and feelings, even though being completely disconnected from the brain. This is something that runs counter to one of the dogmas of neurology.
In the light of these findings and of a series of later studies with animals, over the last few decades some scientists have begun to research in depth the hypothesis that the neuronal circuitry of the spinal cord of injured persons may also reorganize its routes for nerve connections with the brain – or even work in a manner that is more or less independent of this organ. After all, if injured cats can walk again when they are trained to do so, perhaps a paraplegic, to a greater or lesser degree, can (re)acquire this capacity. In several parts of the world, from the 80’s onwards, reports have multiplied on paraplegics who have gained movement and the tactile sense after being submitted to intensive work with physiotherapy, with or without the help of drugs or slight electrical stimuli.
Amongst Cliquet’s patients at Unicamp, there have been at least two cases of paraplegics who have gone back to walking in an almost normal manner, with the assistance of electrical stimuli. “One of them went back to walking so naturally that it was impossible to notice that he was a paraplegic one day”, says the researcher. For good measure, another benefit experienced by some patients submitted to rehabilitation with electrical stimuli was a reduction in the levels of osteoporosis, the progressive loss of bone loss. In paraplegics, decalcification of the bones is fundamentally a result of the non-usage of the parts of the body affected by the injury. With the use of electrostimulation and, in some cases, of low intensity ultrasound waves, the problem, which increases the risk of fractures, can be brought down in these individuals.
A good deal of the equipment used on the paraplegics and quadriplegics attended in Unicamp’s Hospital and Clinics came out of projects run at the Biocybernetics and Rehabilitation Engineering Laboratory (Labciber) of USP’s School of Engineering in São Carlos, also headed up by Alberto Cliquet Junior. The most recent products developed by the bioengineers are prototypes of instrumented walking sticks and crutches, equipment that is fitted with sensors capable of measuring the force applied by the hands of the paraplegics to this kind of support. The information picked up by these apparatuses is sent to a computer, where it is stored and processed. The walking stick and the crutches may be useful for doctors and physiotherapists to assess the clinical condition of their patients. “The force that an individual applies to the stick or to the crutches to remain in balance is directly proportional to the degree of his injury”, explains Cliquet.
In a more ambitious venture, the researchers from USP are working on the creation of a prosthesis for the upper members, called the Hand of São Carlos. The first prototype of this artificial joint, which from the outside will have the appearance of a human hand and should be ready a year and a half from now, will be capable of carrying out a few basic tasks. “The prosthesis has to open and close the hand in at least three different ways”, explains Fransérgio Leite da Cunha, one of the engineers who is taking part in the development of the Hand of São Carlos. Only three of the fingers of the artificial hand will be capable of carrying out movements (the thumb, the index finger and the middle finger). The other two, with just an esthetic function, will remain immobile.
The prosthesis for the hand will have sensors of force, temperature and slip. “This will make it possible for the user to measure the force used to hold objects, to recognize the heat or cold coming from things, and also to notice when something is slipping from his fingers”, Cunha says. If the research at Labciber reaches its objectives, the Hand of São Carlos will be able to be controlled by any healthy part of the handicapped person, such as the voice or muscles in the body that have been preserved.
Cliquet’s team recently began to research into the possibility of transforming one of the fingers of the artificial hand (possibly the forefinger) into a useful artifact for surgery carried out at a distanced. The researchers’ idea is to turn the finger into a sort of electronic scalpel, which will be able to be controlled via the Internet from any part of the globe. “The American space agency, NASA, is researching into this technology and we, together with the University of Dundee, in Scotland, we will be going firmly into this area”, Cliquet guarantees.