Data for this review were identified by searches of PubMed, and many articles were also identified through searches of the extensive files of the authors. The search terms “ischaemic penumbra”, “penumbra review”, and “neuroimaging” were used. Only papers published in English were reviewed.
ReviewNeuroimaging, the ischaemic penumbra, and selection of patients for acute stroke therapy
Section snippets
CT
Without CT, the introduction of thrombolysis as the first successful form of acute stroke therapy would not have been possible. Indeed, one possible explanation for the unsuccessful outcome of the early trials of thrombolysis with streptokinase in the pre-CT era was the inability of the investigators to distinguish reliably between cerebral haemorrhage and infarction.9 CT can exclude cerebral haemorrhage with almost complete sensitivity and specificity.
More recently, CT has been used to detect
What is the ischaemic penumbra and how is it best imaged?
The ischaemic penumbra is functionally impaired but potentially viable tissue that (normally) surrounds an area of recent cerebral infarction.2, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 Since the original definition proposed by Astrup and co-workers3 in a baboon model of cerebral ischaemia, in which blood flow was measured by the hydrogen electrode technique and tissue function by somatosensory evoked potentials, various ways of identifying the penumbra have been developed.39, 41, 42 Baron
Duration and temporal and spatial progression of the penumbra
The duration of the penumbra in human beingss is still uncertain. Heiss and colleagues80 suggested that beyond 6 h, 20% or less of penumbra remained. Hence, there is a need to focus most efforts at tissue salvage within the first 6 h after stroke onset. By contrast, Furlan and co-workers81 used PET with oxygen and water techniques and found that a mean of 30% of tissue was penumbral when scanned 7–17 h after stroke onset. Their findings were confirmed in a study by Read and colleagues51 with 18
Where to now?
Despite the advances in imaging technology over the past 20 years, we seem to be at the beginning of its effective use in translational stroke research.103 Various exciting developments have occurred including the introduction of magnetic resonance spectroscopy: for example, a neurochemical fingerprint of ischaemic tissue, which reflects its viability, can be obtained.104, 105 Work by our group has shown that spectroscopic changes in lesion concentrations of lactate and N-acetylaspartate
Search strategy and selection criteria
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