Ischaemic Stroke

What Is An Ischaemic Stroke?

 

An Ischaemic Stroke occurs when there is a blood clot in one of the blood vessels of neck or brain which blocks of the blood supply to a part of brain.

 

It is important to note that despite the lack of blood supply that part of the brain does not immediately die; instead it remains in a state of shock but still viable and is still able to recover for up to a period of 4.5 – 6 hours. If within this time period the blood supply to the brain can be restored (Treatments are available at specialist centres) then the damage and brain death can be limited and reversed to certain extent.

 

Aetiology of Ischaemic Stroke

 

Thrombotic (Cerebral Small Vessel Disease): When the clot forms in one of the smaller blood vessels of brain and blocks the blood supply a thrombotic or lacunar stroke will result. These generally will only affect the power or sensation in arms and legs and has excellent recovery potentials in the short term. As much as 90% patients will gain independence again. Blood pressure is the main aetiology behind cerebral small vessel disease and lacunar strokes.

 

Large Vessel Atheroembolism: The clot forms in one of the larger blood vessels in neck or brain and then disperses or propagates further into the brain thus blocking the blood supply to a larger area of brain. These strokes are larger and in addition to power and sensation can affect higher brain functions, most commonly understanding and output of speech. Prognosis is variable depending on severity of disabilities, and between 10% to 90% patients regain independence. In addition to blood pressure, high cholesterol, diabetes, smoking are important risk factors.

 

Cardiac Embolism: The clot forms in the heart and then disperses into the brain blocking a blood vessel and affecting a large area of brain. AF is the largest killer in this type of stroke, but certain other heart valve diseases and heart failure also confers some risk. By far this kind of stroke carries the worst prognosis both in terms of mortality and morbidity.

 

Rarer Causes:

  • Infections like HIV, syphilis and TB has been associated with causing strokes.
  • Use of drugs like cocaine and cannabis can affect blood vessel wall and cause strokes.
  • Inflammation of Brain blood vessels called CNS vasculitis or angitis can cause strokes. This can happen in conjunction with other systemic rheumatological disease (SLE, Sjogren’s syndrome etc.) or on its own independently.
  • Genetic causes: There are certain genetic diseases which can affect small blood vessels of the brain and mostly cause recurrent small strokes in deep areas of the brain.  Mitochondrial dysfunctions (MELAS), CADASIL and Fabry’s disease are relatively more common amongst this rare diseases.

 

What Are The Risk Factors For Ischaemic Stroke?

Non Modifiable:

  • Age
  • Gender – Males are more likely to suffer from stoke than females.

Modifiable:

  • Smoking
  • Diabetes Mellitus
  • Obesity
  • High Blood Pressure
  • High Cholesterol
  • Heart Disease (Angina, heart attack, heart valve problems)
  • Atrial Fibrillation (irregular heart rhythm)
  • Obstructive Sleep Apnoea

What Are The Symptoms Of Ischaemic Stroke?

Recognising stroke early is of paramount importance as there is only a short time window where the treatment is effective and brain damage can be reversed. FAST is a very common assessment tool designed for lay bystanders to recognise stroke early. It involves quick assessment of facial asymmetry, power of arms, and speech within the ability of a layperson.

 

Symptoms of Ischaemic Stroke

 

Facial Movements

  • Ask patient to show teeth, Is there an unequal smile or grimace,
  • Note which side does not move well

 

Arm Movements

  • Lift the patient’s arms together to 90º if sitting, 45º if supine and ask them to hold the position for 5 seconds before letting go, does one arm drift down or fall rapidly?
  • If one arm drifts down or falls, note whether it is the patient’s left or right.

 

Speech

  • Listen for NEW disturbance of speech, or slurred speech.
  • Listen for word-finding difficulties with hesitations. This can be confirmed by
  • Asking the patient to name common objects like a cup, key or watch. IS THIS NORMAL FOR THEM

Time

  • Time to ring an ambulance

Investigations & Treatment Of Ischaemic Stroke

Below are the investigations conducted for Ischaemic Stroke

  • Brain Scan: Doctors usually ask for a CT scan of brain. On special circumstances when there is confusion over diagnosis a MRI scan can be advised.

 

  • Vascular (blood vessel) Imaging: This is done to image the blood vessels of neck and brain to identify any clots or cholesterol deposits. The various modalities available are Carotid Doppler, CT Angiogram and MR Angiogram.

 

  • Blood Tests: These should include routine blood tests and specific ones to screen for diabetes and high cholesterol.

 

  • ECG: This is a heart tracing and will identify heart problems including Atrial fibrillation.

 

  • Echocardiogram: This is a heart scan that can identify any problem with the structure of the heart including any defects of heart valves.

 

  • Prolonged Cardiac Monitoring: This is an important modality to pick up Atrial Fibrillation an important rhythm abnormality of heart which is associated with a very high stroke risk.

Treatment For Ischaemic Stroke

Emergency treatment of Ischaemic stroke:

 

  • Emergency treatment aimed removing the block in the blood vessel and restoring the blood supply to brain can restrict brain damage. Typically this treatment can be provided up to a maximum of 6 hours from stroke onset.

 

  • Intravenous Thrombolysis: A specific clot bursting drug called lteplase can be used to unblock the blood vessel and restore blood supply to brain. Typically 30 – 35% of patients benefit in terms of reduced morbidity when treated with this drug within 4.5 hours from Stroke onset. 

 

  • Intra Arterial Thrombectomy: In addition to giving the clot bursting drug in some circumstances, especially when a clot can be identified in one of the bigger blood vessel of neck or brain, the clot can be extracted or removed mechanically. The procedure will often need administration of general anaesthesia and needs to be done typically within 6 hours of the stroke onset.

 

  • Antiplatelet Therapy: The risk of stroke recurrence can be reduced by early initialisation of blood thinning medication like Aspirin or Clopidogrel.

 

  • Swallowing Assessment: The muscles of swallowing get affected after a stroke and therefore it is common for food and drink to go into lungs and cause a pneumonia. Formal swallowing assessment should be carried out in all stroke patients to determine the risk of pneumonia and correct consistency of food and drink should be given to aid their swallow. This significantly reduces the risk of post stroke pneumonia.

 

  • Early Mobilisation: Contrary to common belief early mobilisation after a stroke prevents many complications like pneumonia, clot in leg or lung and disuse atrophy in muscles.

 

  • Decompressive Hemicraniectomy: On occasions after a large stroke the swelling in brain tissue can cause severe pressure over other parts of brain leading to a life-threatening complication called “Malignant MCA Syndrome”. Neurosurgical treatment called Decompressive Hemicraniectomy can save up to 50% lives in such situation.

 

  • Specialist Stroke Unit Care: Admission and coordinated care in a dedicated Stroke Unit has shown to have significant benefit in the care of stroke patients. This model fares much better than when care is provided with the stroke patients scattered over different wards causing disjointed care

 

Long Term Treatment of Ischaemic Stroke 

 

  • Antiplatelet Therapy: Blood thinning medication called Clopidogrel is recommended to be continued long term to reduce the risk of recurrence.

 

  • Anticoagulation: In cases where Stroke is suspected to be due to Cardiac embolism (Clot originating in heart, Atrial Fibrillation) the blood needs to be thinned with much stronger medicines of the warfarin group. These are called anticoagulants. While warfarin was the age old trusted member of this group new medicines called novel oral anticoagulants have emerged over the last 10 years. They are as effective as warfarin.

 

  • Diabetes Mellitus: All patients should be screened for this and managed with medicines if diagnosed.

 

  • Cholesterol: All patients should be screened for high cholesterol and started on statins if appropriate.

 

  • Blood Pressure: All patients should be screened and treated for high blood pressure.

 

  • Smoking Cessation: All smokers should be given counselling and help to stop smoking.

 

  • Feeding: Nutrition after stroke is extremely important to ensure a positive influence on rehabilitation outcome. If the patient is shown to have high risk of pneumonia with oral feeding a feeding tube through nose (Nasogastric tube) can be used temporarily. If it is deemed that safe swallow cannot be established by 4 weeks the Nasogastric tube is replaced by a PEG tube. This is directly put in through abdomen into patients stomach.

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