Operational ischemic penumbra

Schlaug G, Benfield A, Baird AE, Siewert B, Lovblad KO, Parker RA, Edelman RR, Warach S. The ischemic penumbra operationally defined by diffusion and perfusion MRI. Neurology 1999 53 1528-1537. 

The clinical ischemic penumbra was described in a recent review by Moustafa and Baron [1]. They provided three criteria which are listed in Table 9.1. The clinical ischemic penumbra is the hypoperfused, but viable brain that is responsible for neurological deficits that can be reversed with the resumption of normal blood flow. This operational definition has value because it provides a physiologically relevant target for therapy, and the target may be identifiable by methods including CT and MRl as described in prior chapters. An important known property of the ischemic penumbra is that it is dynamic, that is, it becomes smaller with time, and conversely, the irreversibly injured brain (infarct core) grows with time. This is illustrated in Fig. 9.1. The... 

Despite these potential issnes with absolnte thresholds, they have been applied with good resnlts in some centers - most notably for core CBV assessment [33,188-190]. Receiver operating characteristic cnrve analysis in 130 patients snspected of acnte ischemic stroke suggested that relative MTT with an optimal threshold of 145% was the CTP parameter most accurately characterizing salvageable penumbra, and absolute CBV the parameter most accurately characterizing infarct core at admission, again with an optimal threshold of 2.0 mL/100 g [187]. 

---