STROKE AND INTERVENTIONAL NEUROLOGY

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Ischaemic Stroke:

Stroke also commonly known as "Brain Attack" is defined as an sudden onset of neurological deficit developing as a result of sudden blockage of arterial blood supply to the brain or bleeding in the brain. Thus it is broadly divided into two categories:

Ischemic Stroke

Haemorrhagic Stroke

The WHO has defined stroke as a clinical syndrome characterized by rapidly developing symptoms and/or signs of focal, and at times global (for patients in coma), loss of cerebral function, with symptoms lasting more than 24 hours or leading to death, with no apparent cause other than that of vascular origin.

Stroke is the third leading cause of death in the United States after heart attack and cancer, and is also a major cause of functional disability affecting quality of life. The outcome of stroke is crucially dependent on the extent of the brain damage, as well as the patient's age and prestroke health status. The case fatality after a first ever stroke are 12% at 7 days, 19% at 30 days and 31% at 1 year. Haemorrhagic stroke carries a higher risk of death than ischaemic stroke.

The goal of treatment in acute stroke management is :

1) to revascularise (to reopen blocked artery) the ischemic brain by            

    means of thrombolysis

2) to salvage ischemic penumbra by neuroprotection

3) to prevent early recurrence of stroke

4) to rehabilitate the patient

 

The most crucial step in the overall management is to revascularise the ischemic zone by means of recanalization of the occluded artery which is achieved by thrombolytic therapy.

Intravenous throbolysis (with rt-PA)is now established method of treatment in ischemic stroke. The most common limiting factors for the treatment with intravenous rt-PA are

1) Time window of three hours, that means the therapy must begin with in three hours of the onset of the symptoms( including time spent on transportation, evaluation of the patient in emergency department, biochemical tests and CT scan head)

2) In various trials the benefit of intravenous agents has been limited by the hemorrhagic complications, usually occurring in patients treated late.

Selective Intra-arterial thrombolysis:

It has certain advantages and can be implied in certain stroke conditions.

1) Can be undertaken for an extended time window (anterior cerebral, middle cerebral, or internal carotid artery thromboembolic occlusions are considered for intra-arterial thrombolysis, if they present within 6 hours of symptom onset. Patients with basilar artery occlusions frequently have a fluctuating course, hence may be considered for treatment up to 24 to 48 hours from symptom onset

2) Requires less dose of the drug and hence less risk of haemorrhagic complications

3) as the drug is delivered right into the thrombus, there are high chances of recanalization

How intra-arterial thrombolysis is done:

It is done usually under local anaesthesia in neuroangiographic suit. A cerebral angiography is performed through femoral artery to identify the site of embolic occlusion of an artery. A microcatheter is then navigated to the intracranial artery and the tip of the catheter is positioned close to the thrombus under angiographic control. The drug is then infused slowly into the thrombus.

Relative contraindications to intraarterial thrombolysis include a history of recent stroke or surgery, known intracranial tumor or vascular lesion, recent prior head trauma, active or recent hemorrhage elsewhere in the body, recent myocardial infarction, hemorrhagic diathesis, etc.

References:

The National Institute of Neurological Disorders, and Stroke rt-PA Stroke Study Group. Tissue Plasminogen Activator for Acute Ischemic Stroke. New England Journal of Medicine. 1995;333:1581-1587.

CAROTID STENTING:

Primary and Secondary stroke prevention may be done by:

1- Drug treatment: antiplatelet medicines like Aspirin, Clopidogrel, and combination of Aspirin and Slow release Dipyridamol, or Oral anticoagulants depending upon the situation along with Vascular risk factors modifications

2- By Intervention:  Large vessel disease is a cause of Stroke in about 30 - 40% cases. This usually involves carotid bifurcation region commonly or other parts of Internal carotid artery, vartebral artery, Basilar artery or intracranial arteries. In these cases revascularization of a critically stenosed vessel reduces risk of stroke substantially. Revascualrization may be done both surgically (by carotid endarterectomy) or by Stent assisted angioplasty (Carotid/Vertebral/Basilar/MCA).

In the recent past advancement in neurointerventional Techniques have made Carotid Stent Angioplasty a safe and preferred approach of revascualrization.

There are various cerebral protection devices available, which theoretically help reduce the chances of embolic complication during Carotid Stenting. However, there use has not been universally approved. Many neurointerventional groups have demonstrated comparable results or even better results even without the use of these protection devices, raising a question on the neccessity for their use. Moreover, protection devices adds on asignificant extra cost to the procedure as they are quite expensive. Sometimes they psose an extra risk, though minimal, due to difuculties in thier retrival. Our experience of carotid stenting without the use of protection devices has been both satisfactory and encouraging.

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