Introduction to Stroke

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Introduction

Stroke is the leading cause of acquired adult disability worldwide and the second most common cause of death after coronary heart disease. Stroke is expensive in terms of acute and ongoing care costs. Stroke is fatal in about 10%. Stroke affects all ages. Indeed, many strokes are preventable with very treatable risk factors - Hypertension, Anticoagulation for AF, Lipid-lowering, Alcohol reduction and smoking cessation. Before the development of interventional strategies, the usual treatment for stroke consisted of stabilisation, observation, and rehabilitation. However many patients were simply neglected with an attitude of futility. In the past 10-20 years, there have been considerable advances in diagnosis and the treatment of those with acute stroke. This has been brought about by improvements in <a href="imaging.php">imaging</a> and effective clinical pathways allowing near-immediate access to potentially life-changing therapies. Accurate diagnosis by those familiar with stroke and its myriad causes is key. Stroke care is multidisciplinary and involves a team of skilled medical, nursing and therapy professionals and carers to optimise outcomes. However early recognition pre-hospital is key. Lastly, the best stroke management is to prevent stroke. That is where much of our work must focus on reducing stroke risks. </ul>

Primary stroke subtypes include

Primary stroke subtypes include Ischaemic Stroke and Intracerebral haemorrhage and Subarachnoid haemorrhage and each stroke subtype has differing aetiologies, outcomes, and management strategies. There is increased awareness of the importance of occult stroke - that which is found on imaging but without a clear history. It is important to note that diagnosing stroke itself is not difficult, it is the underlying aetiology that often proves to be the most difficult part of the job and avoiding both under and overtreatment.


Definition

Before the modern era of the past 20 years with nearly ubiquitous access to brain imaging the diagnosis of stroke had to be clinical other than for those who died when it could be made at post-mortem. A good practical definition of stroke eludes us and I am always reminded of the quotation from an American chief justice who stated about another topic - "I can't define it, but I know it when I see it". by Justice Potter Stewart. The difficulties are that a clinically based diagnosis does not suffice as some patients with modern imaging have evidence of prior episodes of possibly subclinical areas of either small bleeds or infarcts which only come to light later. Many patients are unaware that they have had an ischaemic or even haemorrhagic brain injury. An imaging-based diagnosis may be enough as not all patients can have an MRI due to metallic fragments, body habitus, personal reference or simple choice as well as affordability and access. Any time-based differentiation between TIA and Stroke, especially at 24 hrs, will end up labelling patients as having had TIAs when there is obvious infarction or haemorrhage on imaging. The current definition by the World Health Organization (WHO) as "rapidly developing clinical signs of focal (at times global) disturbance of cerebral function, lasting more than 24 hours or leading to death with no apparent cause other than that of vascular origin." The definition therefore is a mixed function which could be stated as sort of mathematical equation where the P(Stroke) = P(likelihood of stroke based on a priori risk) + P(likelihood of stroke based on clinical findings) + P(likelihood of stroke based on imaging reaching a certain threshold of certainty).

Basic Pathological Types

Pathologically imaging can help us separate stroke into one of several types. The binary separation is into Ischaemic (no blood on CT at presentation but CT or MRI findings later if needed) and haemorrhagic (blood on CT at presentation). In the USA and Europe, approximately 87% of strokes are ischaemic, with the remaining 13% occurring as a result of haemorrhage. In contrast developing countries especially in Asia, there is a larger proportion of strokes are due to intracerebral haemorrhage.

Clinical Classification: Bamford classification / Oxford Stroke Classification

There are many ways of classifying stroke clinically but the most useful and most commonly accepted method is the Oxford Stroke Classification, also known as the Bamford classification. The Bamford classification divides people with stroke into four different categories, according to the symptoms and signs with which they present. This classification is useful for understanding the likely underlying pathology, which in turn gives information on treatments likely to be useful and the prognosis. It is a relatively simple, robust, bedside classification using clinical information.

A CT scan can be used to further classify the type of stroke into intracranial haemorrhage or infarction. Clinical examination cannot do this reliably, so the CT scan is useful - but it does not make the diagnosis of stroke nor rule it out should the CT scan be normal. NB: A stroke diagnosed clinically as a Lacunar stroke (LACS) can be then reclassified as either Infarct (LACI) or haemorrhage (LACH) on the basis of imaging.



TypeAbbreviationFindings
Lacunar StrokeLACS (LACI/LACH) Motor and/or sensory and/or ataxia deficit only
Partial anterior circulationPACS (PACI/PACH) 2 of following: motor or sensory deficit; higher cortical dysfunction; hemianopia
Total anterior circulationTACS (TACI/TACH) All of: motor or sensory; cortical; hemianopia
Posterior circulationPOCS (POCI/POCH) Isolated hemianopia; brainstem signs; cerebellar ataxia



Classifying by Types of Stroke

Basic Causes of Stroke with my subcategories

Ischaemic Stroke (TOAST trial classification)

Large Artery Ischaemic stroke : Thrombotic

  • Atherosclerosis
  • Dissection
  • Vasculitis
  • Fibromuscular dysplasia
  • Fabry disease
  • Sickle cell disease
  • Moyamoya disease
  • Migraine
  • Postpartum angiopathy
  • Herpes Zoster

Cardioembolic stroke: Embolic

  • Atrial Fibrillation
  • LV Thrombus
  • Valvular heart disease
  • Paradoxical embolism - PFO, ASD
  • Endocarditis
  • Dilated cardiomyopathy
  • Atrial myxoma
  • Fat embolism
  • Air embolism

Small-artery occlusion (or Lacunar Stroke: Thrombotic

  • Hypertension and Charcot-Bouchard aneurysm
  • CADASIL, MELAS, Fabry's disease
  • Radiation angiopathy
  • Small vessel vasculitis
  • Cerebral amyloid angiopathy

Other determined aetiology

  • Embolism from Aorta
  • Venous thrombosis
  • Procoagulant disorders
  • Polcythmaeia vera
  • Thombocythaemia
  • Leukaemia

Undetermined aetiology - so called Cryptogenic stroke

Haemorrhagic Stroke

Intracerebral Haemorrhage

  • Hypertension
  • Cerebral amyloid angiopathy
  • Vascular lesions - aneurysms, AVMS, Cavernomas
  • Anticoagulation
  • Others - see below

Subarachnoid Haemorrhage

  • Saccular aneurysms
  • Arteriovenous malformations
  • RCVS
  • Amyloid angiopathy

Summary of Investigations of Stroke

This is a brief list of potential investigations. All patients with suspected stroke should have an initial blood glucose to exclude hypoglycaemia mimicking stroke, a non-contrast CT and if on warfarin an INR. The remainder of investigations depends on what is found in the history and examination and CT scan.

  • Blood: FBC, U&E, ESR in all
  • Non contrast CT in all
  • ECG in all. CXR in those with symptoms or smokers.
  • MRI, MRA, MRV where indicated
  • Carotid Doppler - where symptomatic disease suspected and candidate for intervention
  • Vasculitis screen - expert advice
  • Thrombophilia screen - venous stroke

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Management of Stroke

  • Current management has changed dramatically over 10-20 years and continues to do so. It is composed now of several steps in the stroke pathway.
  • Early recognition in the community by educating the public and first resonders - e.g. FAST
  • Early recognition by Emergency Department teams e.g. ROSIER
  • Urgent Travel only to centres offering Hyperacute care providing
    • Early exert diagnosis and Imaging with non contrast CT
    • Thrombolysis and/ or Thrombectomy for Ischaemic strokes.
    • Reversal of anticoagulation for Haemorrhagic strokes with coagulopathy
    • Care on a Multidisciplinary Stroke unit with early expert assessment.
    • Hemicraniectomy for Malignant MCA syndrome
    • Neurosurgery for Haemorrhage or Hydrocephalus
    • Appropriate anticoagulation for AF or other embolic source
    • Early expert rehabilitation 7 days per week
    • Early supported discharge home if appropriate
  • Community based rehab and follow up
  • Ongoing tests as needed

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