SUMMARY: CTP has a growing role in evaluating stroke. It can be performed immediately following NCCT and has advantages of accessibility and speed. Differentiation of salvageable ischemic penumbra from unsalvageable core infarct may help identify patients most likely to benefit from thrombectomy or thrombolysis. Still, CTP interpretation can be complex. We review normal and ischemic perfusion patterns followed by an illustrative series of technical/diagnostic challenges of CTP interpretation in the setting of acute stroke syndromes.ABBREVIATIONS: ACA ϭ anterior cerebral artery; AIF ϭ arterial input function; ASPECTS ϭ Alberta Stroke Program Early CT Score; CBF ϭ cerebral blood flow; CBV ϭ cerebral blood volume; CTA ϭ CT angiography; CTP ϭ CT perfusion; DWI ϭ diffusion-weighted imaging; ICA ϭ internal carotid artery; MCA ϭ middle cerebral artery; MTT ϭ mean transit time; NCCT ϭ noncontrast CT; PET ϭ positron-emission tomography; SPECT ϭ single-photon emission CT; TTP ϭ time to peak; VOF ϭ venous output function
Perfusion CT has proven to be a valuable tool in the diagnosis of acute ischemic stroke. The knowledge provided by these cases will allow the reader not only to confidently identify the presence of acute ischemic stroke, but also to recognize the common pitfalls and limitations of perfusion CT in this setting.
Erdheim-Chester disease is a rare form of non-Langerhans histiocytosis presenting in the 5th through 7th decades of life. Osseous manifestations include symmetrical sclerosis of the long bones and, rarely, the spine. Central nervous system disease commonly affects the white matter tracts as well as the orbits, but epidural disease is rare. To the best of the authors' knowledge, simultaneous epidural and skeletal spine disease has not been reported. The MR imaging characteristics of skeletal spine disease have also not been reported. The authors describe the case of an 87-year-old man with both epidural and skeletal spine disease. The clinical characteristics, imaging manifestations, and the histological features are discussed.
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