“THE PLASTIC BRAIN”
OVERVIEW
Long gone are the days when the brain and the nervous system were thought to be concrete, and the damage done was unchangeable. Our nervous system is ‘plastic’ in that it can modify and repair its structural and functional organisation with appropriate stimulus and repeated experience. Where rehab used to focus on compensatory strategies, we are now trying to regain function through recovery.
A stroke is a cerebrovascular disease where blood supply to brain tissue is impaired and ultimately dies (Infarct) because it is deprived of oxygen and glucose. Stroke is the second leading cause of death worldwide, with up to 50% of survivors remaining chronically disabled [1]. In Australia, 55,000 people have strokes each year and the financial cost amounting to $5 billion per year [2]. Approximately 80% of strokes can be prevented [2], and with the burden of disability being so high, it’s essential that an exercise program be a part of their ongoing treatment. This allows patients to live a life as independent as possible and increase their chance of returning to work (30% of stroke survivors are of working age). The major types of stroke are;
Ischemic: Account for 80% of all cases and are caused by a blockage of blood supply.
Hemorrhagic: Account for 20% of all cases and are caused by a rupture/bleed of a cerebral vessel. Bleeding can occur in between brain tissue and the lining of the tissue (subarachnoid space). Bleeding results in swelling and extra pressure on regions of the brain, causing further injury.
TIA (Transient Ischemic Stroke): Is a mini stroke and is due to a temporary blockage of blood supply. There is a temporary loss of function to body parts represented by the area of brain that has its blood supply blocked. TIA’s resolve completely within 24 hours. 30% of people who had an Ischemic stroke had a prior TIA [3].
Hemorrhagic strokes are generally more severe and associated with higher mortality rates compared to Ischemic strokes (50% mortality vs 15% respectively) [1]. However, as recovery progresses and swelling subsides, hemorrhagic stroke survivors tend to have a better long term recovery.
signs and symptoms
The FAST test is a basic and quick way to recognise if someone is having/had a stroke;
FACE: Check their face, has one side drooped? In particular, the mouth
ARMS: Can they lift both arms?
SPEECH: Can they speak? Is it slurred? Can they understand you?
TIME: Time is key, the faster they receive help, the better the recovery
Other symptoms may be loss of vision in one eye, dizziness, headache or loss of coordination. Apart from the above mentioned screening for someone potentially having a stroke, there are many symptoms and impairments related to stroke survivors depending on the size and location of the brain infarct. Some of the common impairments and symptoms include;
Spasticity; This is an increased tendon/muscle reflex and impaired inhibitory signalling which is required for controlled, smooth muscle movement. Spasticity is also velocity dependent in that if you stretch a joint rapidly, you will feel a strong opposing force to the stretch. This is the hypersensitivity stretch reflex and lack of inhibitory control to stop the antagonist muscle.
Impaired tone; this relates to the cortical drive (motor output) to muscles. After stroke you can have very low tone (flaccid) or high tone (tight/fixed). Patients can present with high flexor or extensor tone.
Contracture; This is a permanent shortening of muscle length and is a consequence of unmanaged spasticity and tone.
Weakness; Weakness will occur on the side of the body opposite to side of the brain infarct. Distal body part such as hands and feet are the most difficult to regain strength and function in, although not impossible.
The brain controls every aspect of movement, speech, vision, thought, cognition, autonomic function and personality and hence a stroke will result in a long list of impairments with walking, balance, sight, depression, memory, incontinence and the list goes on. I will aim to look the effects of exercise on each specific impairment in future blogs. By now we understand that stroke is extremely debilitating and has a significant impact on quality of life. However, it’s not all doom and gloom as there is much we can do about it. It’s said that prevention is better than a cure and understanding risk factors allows us to make necessary changes to reduce the risk of having a stroke or recurring stroke. Risk factors can be modifiable or non-modifiable.
Modifiable;
Hypertension is the strongest risk factor after age. 3-4 times more likely
Diabetes, high blood cholesterol, cardiovascular disease, atrial fibrillation, physical inactivity, smoking, alcohol consumption and stress
The INTERSTROKE study found that these risk factors accounted for 90% of all strokes. Therefore stroke is highly preventable through exercise and lifestyle modification [1].
Non-Modifiable;
Age is the strongest determinant of stroke as the risk doubles for every decade after 55 years old [1]
Women have a higher lifetime risk factor
Genetic factors and family history of stroke
treatment
Recovery can be classified into 3 general categories, acute phase;
Acute Phase; (0 - 2 weeks) - can be up to 1 month in the acute ward. This is within the acute ward of the hospital. They are being treated for immediate complications of the stroke and needs to being within hours of the first symptoms. They can be given clot dissolving medication or have surgery for clot removal. In hemorrhagic strokes, the first hours are used to control blood pressure, reverse effects of blood thinning medication, reduce bleeding/swelling and repair ruptured aneurysms. As soon as patients are medically stable, they will begin rehabilitation, usually 48 hours after admission.
Sub-Acute Phase; (2 weeks - 6 months) - patients have been discharged from the acute ward to the rehab ward. They rehab team, including allied health professionals, neurologist, nurses and social worker will come up with a discharge plan and goals relating to the functional prognosis. Patients usually spend up to 3 months maximum in the rehab ward and therefore discharged into the community with minimal outpatient follow up to take advantage of the spontaneous recovery window. They will be provided medication for prevention of secondary strokes. In addition to physical rehab (walking, standing, transfers), they will be given botox, baclofen, stretching and serial casting to prevent contractures due to spasticity and high tone.
Chronic Phase; (> 6 months) - Patient has been discharged into the community, either back to their home or a nursing home. They are followed up every 6-12 months by the GP and Neurologist for review of condition and medication. Patients may have regular botox for spasticity management. Typically, they are finished as an outpatient and very inactive. They will be extremely deconditioned and deteriorate in function. Exercise programming is essential in this phase to reduce risk factors for secondary stroke and other comorbidities. Exercise is also important in this stage to enhance recovery and promote neuroplastic changes within the brain.
exercise
We will have a look at the impact exercise has on recovery. Research has shown that 20 consecutive days of bed rest (seen in the acute ward) reduces aerobic capacity (VO2max) by 25% and reduces capillaries in trained muscles by 20%. In stroke, the first mechanism of recovery is from early spontaneous recovery (first 2 weeks - 6 months). This process involves resolution of local swelling, toxins and recovery of partially damaged neurons. Exercise has been shown to enhance these effects. The second mechanism of recovery is based on neuroplasticity, which is the amazing ability of our brain to modify and repair its structural and functional organisation. It is widely accepted that exercise promotes neuroplasticity. Aerobic exercise (AE) is critical across all stages of recovery and is unfortunately underutilised.
AEROBIC EXERCISE:
Aerobic capacity is measured as the persons maximum ability to supply oxygen to tissue (VO2max). Stroke patients have a drastically reduced VO2max of about 15 ml.kg.min-1 (50% lower than age matched norms) [5]. This means patients fatigue much quicker, have reduced walking endurance and will struggle to get through intensive rehab programs. Also, the minimum VO2 cost of normal daily activity is between 10 and 17.5 ml.kg.min-1, therefore stroke patients will be working at maximal intensity just to complete basic daily functions. Improving a stroke patient’s aerobic fitness will be the difference between being independent in the community vs being dependent. AE has shown to improve VO2max, increase brain blood flow by 25 - 30% during exercise, increase mitochondria in skeletal muscle up to 50%, improve left ventricular volume, improve blood pressure, arterial stiffness and max cardiac output, promote the growth of new arteries and capillaries and reducing the risk of comorbidities such as diabetes and heart disease.
on a neurological level, AE increases blood levels of BDNF and other neurotrophic factors responsible for neuroplasticity. Types of AE such as treadmill walking and cycling also promote neuroplasticity as they allow for high repetitions and intensity required to stimulate the brain for plastic changes. A systematic review found that AE 24-48 hours post stroke reduced lesion volume, decreased inflammation and increased neurogenesis [6]. Observational studies looking at physical activity levels of stroke patients during hospital inpatient stay were standing or waling only 23% of the time and sitting or in bed 76% of the time! AE should also be used as neural primer before and after skill acquisition and motor relearning training as it enhances BNDF levels, brain blood blow and activation of neural pathways, all of which enhance the environment required for retention of skill.
RESISTANCE TRAINING
One of the main symptoms of stroke survivors is muscle weakness and paresis. Progressive resistance training (PRT) and functional strength training is extremely effective at improving strength in stroke patients. Resistance Training (RT) is essential for improving health and well-being by reducing the risk of comorbidities and secondary stroke. However, RT is more that, it’s essential as part of rehab and needs to be specific to the functional goals and deficits of the patient. Cross talk is the ability for the limb on one side of the body to get stronger by doing resistance training on the non affected limb. research has shown strength gains of up to 11% in the affected arm by only training the non affected arm. Improving lower limb strength will improve the ability to stand, transfer, climb stairs, push and pull open doors, open jars and much more.
Interestingly, lower limb strength programs have been inconclusive in showing improvements to walking capacity, speed and quality. This is because strength programs usually focus on knee extensors (quadriceps) and knee flexors (hamstrings) when these muscles are not the primary muscles required for forward propulsion and acceleration during walking. Furthermore, it is muscle power more than strength that is relevant for forward propulsion in walking and running. RT programs need to focus on plantar flexors (calf), hip flexors and extensors when created a lower limb strength program.
For neuroplasticity and functional changes to occur, we need to be practicing specific functional tasks at higher intensity with 1000’s of reps. However, adding AE and RT will enhance the outcome and will be the catalyst for actual physiological changes at the impairment level and treat the disease at the source of injury instead of just treating the symptoms.
Overall, an exercise program for stroke patients must focus on skill acquisition and motor relearning with components of aerobic, resistance and balance training. The minimum exercise guidelines for stroke patients are Aerobic exercise for 20-60 min at 55-80% of max heart rate for 3-5 days/week. Resistance exercise at 50-80% 1RM, 1-3 sets of 10-15 reps for 2-3 days/week [4]. Although, higher intensity and volume of exercise will yield better results and is optimal for neuroplastic change. Stroke patients are a high risk population group and it is ESSENTIAL you consult with an allied health professional who specialises in neurological rehab PRIOR to starting an exercise program.
Overall, treatment can significantly improve your symptoms and quality of life. A combination of medicine and exercise is the gold standard for treatment. I hope you have learnt something from this information and it helps direct you to a path of you improving your life. If you would like to learn more or speak to an Exercise Physiologist that specialises in neurological rehabilitation you can reach out to us via our website, Facebook, email or phone. Please click on the ‘contact’ tab for all our information.
[1] E. S. Donkor. Stroke in the 21st Century: A Snapshot of the Burden, Epidemiology and Quality of life. Stroke Research and Treatment, 2018.
[2] http://www.strokefoundation.org.au
[3] http://www.brainfoundation.org.au/disorders/stroke
[4] S. A. Billinger et al. Physical Activity and Exercise Recommendations for Stroke Survivors. Stroke, 45 (8), pg 2532 - 2553.
[5] O. Stoller et al. Cardiopulmonary Exercise Testing Early after Stroke using Feedback - Controlled Robotics-Assisted Treadmill Exercise. Journal of Neuroengineering and Rehabilitation, 2014, 11, pg 145.
[6] M. W. Austin et al. Aerobic Exercise Effects on Neuroprotection and Brain Repair Following a Stroke: A Systematic Review and Perspective. Neuroscience Research, 2014, 87, pg 8 - 15.