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  • 2.1 Stroke & Spasticity
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Stroke & Spasticity

Stroke

A stroke is a potentially life-threatening event in which parts of the brain are deprived of oxygen. There are two types of stroke:  

1. The most common type of stroke is a blockage. This is called an ischaemic stroke, which happens when a clot blocks an artery that carries blood to the brain. It may be caused by:

• a cerebral thrombosis, when a blood clot (thrombus) forms in a main artery to the brain;
• a cerebral embolism, when a blockage caused by a blood clot, air bubble or fat globule (embolism) forms in a blood vessel somewhere else in the body and is carried in the bloodstream to the brain; or
• a blockage in the tiny blood vessels deep within the brain (lacunar stroke).

2. The second type of stroke is a bleed, when a blood vessel bursts, causing bleeding (haemorrhage) into the brain. This is called a haemorrhagic stroke. It may be caused by:

• an intracerebral haemorrhage, when a blood vessel bursts within the brain; or
• a subarachnoid haemorrhage, when a blood vessel on the surface of the brain bleeds into the area between the brain and the skull (subarachnoid space).

(Stroke Association 2010)

Spasticity

Spasticity was defined by Lance as follows (Lance 1980):

"Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (‘muscle tone’) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one component of the upper motor neuron syndrome."

In the United Kingdom, approximately 100,000 people have a first-time stroke every year, and an additional 30,000 have a repeated stroke. Stroke afflicts almost 2,000 out of every 1 million people per year worldwide. Almost 40% of people who have a stroke continue to have spasticity one year later. The prevalence of post-stroke spasticity is 0.2%, that is 200 per 100,000 inhabitants (WHO MONICA Project, Stegmayr 1997; www.wemove.org/spa).

Etiology

The cause of spasticity is actually an injury to a part of the central nervous system (the brain or spinal cord) that controls voluntary movements. Such an injury is often associated with one of the following diseases:

• stroke (blockage or bleeding from a blood vessel in the brain)
• head or spinal cord injury
• multiple sclerosis
• brain damage caused by oxygen deficiency
• spasticity acquired in early childhood, i.e., cerebral palsy (CP)
• encephalitis (infection of the brain) or meningitis (infection of the covering of the brain and spinal cord)

The damage in the central nervous system causes a change in the balance of excitatory and inhibitory input to alpha motor neurons. This imbalance leads to increased activity (excitability) in the muscles. The severity of muscle spasticity partly depends on the site of the upper motor neuron lesion. Spasticity tends to be less severe with lesions above the brain stem than with lesions in the brain stem (these are usually fatal) or spinal cord. (www.wemove.org/spa/spa)