Editing Transient ischemic attack (section)

== Pathogenesis ==
There are three major mechanisms of ischemia in the brain: [[embolism]] traveling to the brain, in situ thrombotic occlusion in the [[Circle of Willis|intracranial vessels]] supplying the parenchyma of the brain, and [[stenosis]] of vessels leading to poor perfusion secondary to flow-limiting diameter.<ref name=":11" /><ref name=":10" /> Globally, the vessel most commonly affected is the [[middle cerebral artery]].<ref name=":11" /> Embolisms can originate from multiple parts of the body.

Common mechanisms of stroke and TIA:<ref name=":11" />
{| class="wikitable"
!Stroke mechanism
!Frequency
!Pattern of infarcts
!Number of infarcts
|-
|In situ thrombotic occlusion
|Uncommon
|Large subcortical; Sometimes with borderzone; Rarely, whole territory; Sometimes enlarging
|Single
|-
|Artery to artery embolism
|Common
|Small cortical and subcortical
|Multiple
|-
|Impaired clearance of emboli
|Common
|Small, scattered, alongside the borderzone region
|Multiple
|-
|Branch occlusive disease
|Common
|Small subcortical, lacune-like
|Single
|-
|Hemodynamic
|Uncommon
|Borderzone; may be without lesion
|Multiple; None
|}