RESUMO
Stroke constitutes a major cause of functional disability and mortality, with increasing prevalence. Thus, the timely and accurate prognosis of stroke outcomes based on clinical or radiological markers is vital for both physicians and stroke survivors. Among radiological markers, cerebral microbleeds (CMBs) constitute markers of blood leakage from pathologically fragile small vessels. In the present review, we evaluated whether CMBs affect ischemic and hemorrhagic stroke outcomes and explored the fundamental question of whether CMBs may shift the risk-benefit balance away from reperfusion therapy or antithrombotic use in acute ischemic stroke patients. A literature review of two databases (MEDLINE and Scopus) was conducted to identify all the relevant studies published between 1 January 2012 and 9 November 2022. Only full-text articles published in the English language were included. Forty-one articles were traced and included in the present review. Our findings highlight the utility of CMB assessments, not only in the prognostication of hemorrhagic complications of reperfusion therapy, but also in forecasting hemorrhagic and ischemic stroke patients' functional outcomes, thus indicating that a biomarker-based approach may aid in the provision of counseling for patients and families, improve the selection of more appropriate medical therapies, and contribute to a more accurate choice of patients for reperfusion therapy.
RESUMO
BACKGROUND: The circle of Willis provides collateral pathways to perfuse the affected vascular territories in patients with severe stenoocclusive disease of major arteries. The collateral perfusion may become insufficient in certain physiological circumstances due to failed vasodilatory reserve and intracranial steal phenomenon, so-called 'Reversed-Robinhood syndrome'. We evaluated cerebral hemodynamics and vasodilatory reserve in patients with symptomatic distal internal carotid (ICA) or middle cerebral artery (MCA) severe steno-occlusive disease. METHODS: Diagnostic transcranial Doppler (TCD) and TCD-monitoring with voluntary breath-holding according to a standard scanning protocol were performed in patients with severe ICA or MCA steno-occlusive disease. The steal phenomenon was detected as transient, spontaneous, or vasodilatory stimuli-induced velocity reductions in affected arteries at the time of velocity increase in normal vessels. Patients with exhausted vasomotor reactivity and intracranial steal phenomenon during breath-holding were further evaluated by (99)technetium(m)-hexamethyl propylene amine oxime single photon emission computed tomography (HMPAO-SPECT) with acetazolamide challenge. RESULTS: Sixteen patients (age 27-74 years, 11 men) fulfilled our TCD criteria for exhausted vasomotor reactivity and intracranial steal phenomenon during the standard vasomotor testing by breath holding. Acetazolamide-challenged HMPAO-SPECT demonstrated significant hypoperfusion in 12 patients in affected arterial territories, suggestive of failed vasodilatory reserve. A breath-holding index of ≤0.3 on TCD was associated with an abnormal HMPAO-SPECT with acetazolamide challenge. TCD findings of a breath holding index of ≤0.3 and intracranial steal during the procedure were determinants of a significant abnormality on HMPAO-SPECT with acetazolamide challenge. CONCLUSION: Multimodal evaluation of cerebral hemodynamics in symptomatic patients with severe steno-occlusive disease of the ICA or MCA is helpful in the identification and quantification of failed vasodilatory reserve. This approach may be useful in selecting patients for possible revascularization procedures.
