Classification of Stroke
In 2013, the American Heart Association and American Stroke Association (AHA/ASA) published an expert consensus statement updating the definition of stroke. This statement was endorsed and/or affirmed by the following organizations:
American Association of Neurological Surgeons Congress of Neurological Surgeons
American Academy of Neurology
The AHA/ASA classification broadly characterizes stroke into the following four broad subtypes
:
Central nervous system (CNS) infarction (including ischemic stroke and silent infarction)
Intracerebral hemorrhage (ICH)
Subarachnoid hemorrhage (SAH)
Stroke caused by cerebral venous thrombosis
CNS infarction is defined as brain, spinal cord, or retinal cell death attributable to ischemia, based on one of the following:
Pathological, imaging, or other objective evidence of cerebral, spinal cord, or retinal focal ischemic injury in a defined vascular distribution,
or
Clinical evidence of cerebral, spinal cord, or retinal focal ischemic injury based on symptoms persisting ≥24 hours or until death, and other etiologies excluded
Stroke caused by intracerebral hemorrhage is defined as rapidly developing clinical signs of neurological dysfunction attributable to a focal collection of blood within the brain parenchyma or ventricular system. The bleeding is not caused by trauma
Stroke caused by subarachnoid hemorrhage is defined as rapidly developing signs of neurological dysfunction and/or headache because of bleeding into the subarachnoid space (the space between the arachnoid membrane and the pia mater of the brain or spinal cord). The bleeding is not caused by trauma.
Stroke caused by cerebral venous thrombosis is defined as infarction or hemorrhage in the brain, spinal cord, or retina because of thrombosis of a cerebral venous structure. Symptoms or signs caused by reversible edema without infarction or hemorrhage do not qualify as stroke.
Not all strokes will fit into one of those four categories. Stroke, not otherwise specified is defined as an episode of acute neurological dysfunction presumed to be caused by ischemia or hemorrhage, and persisting ≥24 hours or until death, but lacking sufficient evidence to be classified as one of the above.
AHA/ASA recommends against the use of the term “hemorrhagic stroke” because it may refer to both hemorrhage that occurs after CNS infarction or primary ICH or SAH. Instead, the statement suggests that hemorrhagic infarctions, which are characterized by a lack of mass effect, should be considered CNS infarctions, while parenchymal hemorrhages, which are characterized by the presence of mass effect should be considered ICHs.
The International Classification of Diseases (ICD) 10th revision along with its clinical modification (ICD-10-CM) published in 2015, classifies cerebrovascular disorders chiefly into the following categories:
Transient ischemic attack (TIA)
Cerebral infarction
ICH
SAH
Cerebral thrombosis with infarction