ABSTRACT
The characterization of potentially reversible versus irreversible loss of function is based on the concept of the ischemic penumbra.1 Until recently, only positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging could approximately define ischemia and penumbra thresholds. This is, however, not feasible for emergency services for broad populations, where imaging in an acute setting is confined to computed tomography (CT) and also increasingly magnetic resonance imaging (MRI). Only the advent of new imaging techniques such as novel MRI sequences and continuing improvement of imaging hardware allows improvement in diagnostic yield. An adequate therapy demands an adequate diagnostic workup first. For readers interested in a more detailed coverage of this topic, including the basics of the novel imaging techniques presented in this overview, two textbooks are now available, both published in 2003.2,3
The underlying rationale for the introduction and application of thrombolytic agents is the lysis of a thrombus and subsequent re-establishment of cerebral blood flow by cerebrovascular recanalization.4,5 The local delivery of thrombolytic agents, at or
within the thrombus (intra-arterial thrombolysis), has the advantage of providing a higher concentration of the particular thrombolytic agent where it is needed while minimizing the concentration systemically. Hence, local intra-arterial thrombolysis has the potential for greater efficacy with higher arterial recanalization rates and greater safety with lower risk of hemorrhage. The technique involves performing a cerebral arteriogram, localizing the occluding clot, navigating a microcatheter to the site of the clot, and administering the lytic agent at or inside the clot with or without mechanical destruction of the thrombus.
