The Influence of Research into Neuroplasticity on Post-stroke Rehabilitation of the Upper Limb
Improved acute care after stroke has increased the number of those who survive. As a result there are more stroke survivors who require rehabilitation to enable them to lead self sufficient and productive lives either at work and/or during their leisure time. Once a patient has been medically stabilised assessment and rehabilitation can begin. Initially this will focus on helping them to return home. A stroke can affect many functions in an individual such as speech, language, difficulties swallowing, loss of movement, or cognitive and sensory impairments. Therefore immediate intervention needs to address those issues which prevent stroke survivors from returning to their own community however, this still leaves many with long term impairments. For example it is estimated that between 30%-60% of stroke survivors do not have full arm function after stroke.
A stroke interrupts the motor pathway that runs from the brain through the spinal cord to the muscles. This reduces the brain’s ability to control the muscle’s movements. If there is a complete loss of communication between the brain and the muscle the result will be paralysis. Paralysis usually affects a group of muscles in the same region. These muscles can then have a low tone whereby they are flaccid and flabby or an abnormally high tone which increases with movement where they are tight and spastic.
In functional terms the upper limb needs to be able to reach, mainly using the shoulder and elbow joints and grasp and release using the fingers. Stroke survivors who suffer from paralysis, commonly in the form of hemiplegia, therefore lose function in the upper limb including the hand and so find it hard to be self sufficient and take part in all everyday activities.
There is much current research into neuroplasticity of the brain. This gives great hope to stroke survivors. Neuroplasticity is the ability of the neurons in the brain to change and reorganize themselves as a result of the stimuli they receive. This is an ongoing process throughout life. The brain creates a cortical map in response to the sensory and motor responses it receives. Current research supports the idea that it is through Neoroplasticity that the brain is able to recruit healthy cells to take on some of the tasks performed by those that have been damaged through trauma such as stroke. As this is a continuous process there is no time limit as to how long this can start or continue. However there is a negative side to this. It is on the use it or lose it principle. When a limb is no longer used there is little or no stimuli to the brain and as a result the area of the cortical map representing that part of the body is reduced.
It is often easier for stroke survivors to use their non affected hand in Activities of Daily Living (ADL) and as a result Neuroplasticity informs the brain that that hand no longer exists. This is less of a problem with an affected lower limb because both legs need to be used in standing or walking just a few steps. Standing and walking are basic functional activities and need to be achieved for a stroke survivor to return home.
Impairments are a result of neurological deficits resulting from a stroke and are determined primarily by the site and extent of the stroke. Initially neurological recovery arises as a result of the reduction of oedema and return of circulation.( Lo 1986). Cerebral haemorrhages tend to be associated with more oedema which may take longer to subside but may in turn be associated with a more dramatic recovery. (Nudo)
Functional brain imaging has enabled researchers to visualise and evaluate recovery within the brain following a stroke. Functional MRT, PET, and transcranial magnetic stimulation have all been used to assess motor activation after a stroke. (Thirumala et al.2002).
Based on research by, Bury and Jones2002 and Cramer 2003 Teasal et al in the EBRS review concludes that: “ In humans, following stroke recovery, motor activity in the affected hand results in recruitment of the cortical areas along the infarct rim, secondary motor areas in the contralateral hemisphere and ipsilateral hemisphere motor areas. The predominant pattern seen is increased activation of secondary (surrounding) cortical regions of the affected limb.”
Constraint Induced Movement Therapy CIMT is a treatment whereby the less affected limb is immobilised often in a mitt or a sling. The reasoning behind continuing to use the affected limb is to prevent “learned non-use” as well as to promote movement through ADL (Activities of Daily Living). Taub et al 1999 describes CIMT as “being designed to overcome learned non-use by promoting cortical reorganisation “ Often the non affected limb will be constrained for between 5-7 hours a day on weekdays for approximately though not always two weeks. In practise this is often too great a commitment for stroke survivors to adhere to and so a modified less intense version has been devised known as mCIMT or modified CIMT. This will involve structured functional practice sessions combined with restricted use of the less affected arm.
The largest study of CIMT was the rigorously conducted Extremity Constraint Induced Therapy Evaluation trial (EXCITE) It showed the benefits of CIMT and involved 222 recruits. with moderate disability. The results were promising, showing significant gains that were maintained over a period of twenty four months afterwards. However the trial found that only 6.3% of patients screened were eligible and it remains uncertain if those with more severe impairments would have benefited from this therapy.
Taub al 2003 noted that Constraint Induced Movement Therapy “produces a variable outcome that depends on the severity of the stroke” For stoke survivors with the lowest motor functioning CIMT does improve movement at the shoulder and elbows. Because these people have little or no ability to move their fingers there is no adequate motor basis for carrying out training of hand function. This is immensely frustrating because grasping and releasing are functions that we need to perform everyday tasks. Hands constantly send information to the brain as a result of the signals they receive. As the brain responds to this it constantly adapts to the changes experienced. The hand and the plastic brain are functionally linked together. Thus a hand which is impaired by stroke and has limited movement is unable to send the usual amount of stimuli to the brain and the representation of the hand within the cortical map is reduced.
Timing for this therapy is also important. Although it was designed to combat learned non use there has been research into animals suggesting that very early intervention in the acute phase could cause damage. It is has been suggested by Grotta et all that most benefit will be gained by employing this therapy during the chronic phase.
Work that has been done with amputees using Mirror Visual Feedback (MVF) has been found beneficial to stoke survivors with chronic regional pain syndrome and hemiparesis following a stroke. In this therapy a mirror is placed vertically in the saggital plane and the patient is able to see the reflection of their good limb moving. V.S Ramachandran hypothesizes that these results suggest a change in the way we think about neurorehabilitation because firstly there appears to be a tremendous latent plasticity even in the adult brain. Secondly the brain can be thought of as a set of complex interacting networks that are in a state of dynamic equilibribrium with the brain’s environment” both concepts can be used in a clinical context to provide rehabilitation.
Mental imaging has also shown to have some use in stroke rehabilitation. In 2004 Liu and others compared the effects of mental imaging with functional training. Over a three week period patients were divided into two groups. In the first group Liu had patients mentally rehearse tasks such as washing dishes, preparing tea and folding laundry. The second functionally training group practised the task having the therapist demonstrate first. By the end of the study there was no significant difference in the way the two groups performed the task. Encouraging results were also reported by Page et al 2005. Patients with severe stroke received 30 minutes therapy sessions twice a week over a period of six weeks. They had an intervention which consisted of either mental practice of ADL activities or sessions which focussed on relaxation techniques. Patients in the mental practice group showed an increase in the amount of use in their affected upper limb and the quality of their movement improved to a greater degree.
Robotic therapies show promise for helping provide safe and intensive rehabilitation to patients who have mild to severe motor impairment. Robotic devices themselves are varied and many studies have chosen patients with either mild moderate or severe stroke so comparison and overall evaluation can be somewhat difficult to assess. A recent review of robot-aided therapy on recovery of the hemiparetic arm was carried out by (Prange et al. 2006). The authors looked at results from 8 studies evaluating the MIT-Manus, MIME, and ARM Guide and concluded that robotic devices improved both short and long term motor function of the paretic shoulder and elbow more than could be achieved through therapy on its own. In the EBRS review 2008 Teasel R et al review data on robotic interventions and conclude that; “ There is strong evidence that sensimotor training with robotic devices improves upper extremity functional outcomes and motor outcomes of the shoulder and elbow. There is strong evidence that robotic devices do not improve motor outcomes of the wrist and hand”.
The upper limb, including the hand and the fingers constantly performs sequences of varied types of movement in the simplest of everyday activities. Turning a door handle, dressing, making a cup of tea is normally carried out with no thought as to the movement required from the shoulder elbow wrist and finger joints. Carrying heavy objects reaching out to high shelf, turning a handle, writing etc make appropriate use of muscles and develop neuroplasticity in the brain. For a stroke survivor these prove to be an enormous challenge requiring rehabilitation and planning.
The challenges a stroke survivor faces needs to be considered. Although each stroke is different and individual to that person there are some common features that will be experienced to a greater or lesser degree. So as to be able to complete everyday tasks a stroke survivor needs to be able to both reach as well as grasp and release and object. This in turn may well lead to further more complex upper limb movements For example picking up and then using a comb. In addition to being able to reach, grasp, release and turn, the upper limb also needs to be able to lift and therefore needs to have strength to perform everyday activities.
For example, reaching for a heavy book on a shelf carrying it back to a chair and then turning the pages to read. The simple solution may be to use the non affected upper limb, but this would be a compensation strategy and although useful simply avoids rehabilitation in the affected limb. Until a stroke survivor has regained sufficient movement in all upper limb areas i.e. shoulder, elbow, wrist, and fingers as well as strength their ability to complete everyday activities will be compromised. Post stroke fatigue, the need to complete upper limb tasks quickly and help from others can make it easier for a stroke survivor to avoid using the affected upper limb thereby further reduce strength, further contracture and promote learned non use. In addition other rehabilitations such as standing and taking a few steps may need to take precedence and consequently a stroke survivor can have very little flexion and extension in the wrist and fingers.
The hand has a hundred touch receptors for every one on the torso. However after a stroke, the brain maps for an affected hand, particularly the motor and sensory ones, register shrinkage by about a half so the stroke survivor has about half the neurons to work on. This would be lessened if it was at all possible to continue to use the hand.
However it is possible to regain function in the hand long after a stroke. This can be a long and slow process, whereby a stroke survivor needs to be highly motivated and commit to regular practise of task training. So as to recognise the small incremental steps that have been made a stroke survivor may well need to keep a diary recording their achievements however small so as to celebrate success and continue their motivation.
The stroke survivor will often need to manage spasticity, a process by which as a result of neurological injury the upper limb draws into the body through flexion and so prevent further injury to itself by flailing about.
With spasticity comes the need to combat this automatic response. Just to make things harder for stroke survivors as soon as the affected and contracted limb is required to move into extension so as to undertake an everyday task it responds by drawing further into flexion. So fingers which need to extend prior to grasping or release afterwards are further immobilised. Functional training which works the affected hand and not simply using passive stretching can reverse this and start to rewire the brain.
The problems restoring movement to the hand may lead to the conclusion that the hand is more affected by a stroke than the shoulder, and that movement in the upper limb becomes more restricted as one moves away from the trunk. Recent studies by Beebe and Lang (2008) have shown that this is not so. They set out to find whether was “A proximal to distal gradient in motor deficits in nine segments of the affected upper extremity (shoulder, elbow, forearm, wrist and the five fingers). They also wanted to know which upper extremity made the greatest contribution to hand function. A total of thirty-three subjects were tested on average 18.6 days after their stroke. AROM (Active Range Of Motion ) was tested for all nine areas. They found that the AROM was reduced in all nine areas and there was no evidence of proximal to distal gradient in AROM values. They also found that strength was reduced equally across all areas. They found that hand function was not reduced more than shoulder function and that loss of hand function was due to loss of ability to move many segments of the upper extremity and not just the distal ones.
Research continues on hand mobility post stroke. (Lang et al 2009). report that difficulties with grasp relate to post- stoke difficulties with the finger and thumb extension required to grasp an object. Having discovered that grasping was not relatively more disrupted than reaching in people with acute hemiparesis, Lang Wagner et al (2006) looked at the recovery of reach versus grasp. They found that both reach speed and grasp speed improved over time. Initially there was a greater deficit in accuracy during reach than in grasp but after 90 days these had become the same. However initially there was a greater deficit in grasp than reach as far as efficiency was concerned, an efficient movement being defined “as a movement directly to the target without extraneous or abnormally circuitous movements”. Efficiency in grasp did not improve over a 90 day period. The authors hypothesised that “
In chronic hemiparesis, purposeful movements requiring distal control may be more impaired than purposeful movements requiring proximal control, not because of the initial lesion, but because over the course of recovery, spared componenents of the descending motor system may be able to compensate for the accuracy deficits in reaching (proximal control ) but not the efficiency deficits in grasping (distal control).
So, modern research is beginning to demonstrate that to have full use of the upper limb a stroke survivor needs to be able to move the shoulder , elbow and hand, that initially post stroke impairments are evenly distributed along the nine segments of the upper limb and that neuroplasticity needs to be engaged positively. The need to rehabilitate the wrist and fingers at the same time as the shoulder is being better understood.
Beebe and Lang (2008) state that “the ability to move your wrist and hand is equally important for hand function as the ability to move your shoulder”. Tyson et al have concluded that the practise of therapists withholding treatment to restore movement in the fingers until shoulder impairments have been resolved needs to be reconsidered. Stroke survivors often have many impairments to address. Neuroplasticity has the potential to overcome some of these as the brain adapts and reorganises itself after the damage caused by injury. Research has shown that by carefully planned rehabilitation learned non use can be avoided and new neural pathways can be created and employed.
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