Intracranial Collaterals in Acute Stroke and Clinical Outcome
Condition: Collateral Circulation, Any Site
Study type: Observational

Summary: 
      Assessment of the evolution of intracranial collaterals and its relationship with functional
      outcomes in acute ischemic stroke (AIS) patients treated with IV tissue plasminogen activator
      (tPA).
    

Detailed description: 
      Intracranial collaterals Assessment in acute ischemic stroke In clinical practice, infarct
      growth does not always progress to involve the full extent of the vascular territory, even if
      the affected intracranial artery fails to recanalize. The presence and recruitment of various
      collateral channels are believed to be responsible for this phenomenon in acute ischemic
      stroke (AIS). These collaterals may also play an important role in influencing the safety and
      efficacy of acute revascularization approaches. Although blood supply from the leptomeningeal
      collaterals may temporarily maintain the ischemic penumbra, the persistence and effectiveness
      of this alternative circulatory supply is erratic and unpredictable. Some collaterals may
      disappear over time (collateral failure); this is one of the mechanisms responsible for
      clinical deterioration following initial improvement.

      Conversely, dramatic resolution of initial neurologic deficits may be seen though the
      occluded intracranial artery did not recanalize, often attributable to the rapid improvement
      of cerebral perfusion via effective collateral pathways (collateral recruitment). Therefore,
      the temporal behavior of intracranial collaterals may play an important role in determining
      the functional outcome in AIS patients.

      CT angiography (CTA) of the brain is acutely performed in AIS patients before or immediately
      after administering IV tissue plasminogen activator (tPA) The Alberta Stroke Program Early CT
      (ASPECTS) leptomeningeal collaterals score on CT-angiography helps in prognosticating
      functional outcome in acute ischemic stroke (AIS) patients treated with intravenous
      thrombolysis. Leptomeningeal collaterals in AIS are dynamic, especially during the first few
      hours or days of AIS.

      In animals, 3 different types of collaterals have been identified: transient collaterals that
      could be seen immediately after the stroke and last less than 90 minutes; impermanent
      collaterals that disappear after 90-150 minutes; and persistent collaterals, which can be
      seen for longer periods.

      Patients with good collateral flow demonstrated less hypo perfused tissue and less infarct
      growth within the penumbra zone than those with poor collateral . A relationship is found
      between good early collaterals on pretreatment imaging and smaller infarct volume with better
      outcomes.

      The initial state of the collateral circulation on the pretreatment CTA also has bearing on
      the clinical effect of the collateral recruitment on the day 2 CTA.

      However, collateral recruitment with poor pretreatment collaterals was associated with poor
      functional outcome at 3 months and a higher risk of intracranial hemorrhage.

      One plausible mechanism that delayed collateral recruitment lead to worse outcomes could be
      related to the maximal vasodilation in the ischemic area and how collateral recruitment in
      the adjacent regions may trigger a steal-like phenomenon with resultant expansion of the
      ischemic core. Another possible mechanism could be related to failed autoregulation in the
      affected vascular territory, leading to increased hyper perfusion damage with a higher chance
      of bleeding.
    

Intervention name(s): Actilyse
Intervention type(s): Drug
Intervention description(s): thrombolytic therapy
Other intervention name(s): Alteplase
Intervention MeSH terms: Tissue Plasminogen Activator
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        All patients with acute ischemic stroke within 4.5 hours - legible for receiving IV r TPA-
        admitted to Neurology department of Asyut University within 1 year (2017-2018)