Evidence-Base Medicine Stroke Int 韓孟志、蘇熙淵

Issue 1 What is the imaging modality of choice for the detection of intracranial hemorrhage?

Angiography: DSA gold standard for vascular anomaly(84%) ICH NECT T1WI T2WI Hyperacute (intracellular oxy-Hgb) Hyperdense Isointense Hyperintense Acute (intra deoxy-Hgb) Hypointense Subacute-early (intra met-Hgb) Isodense Subacute-late (extra met-Hgb) Chronic-early (extra met-Hgb, hemosiderin,ferritin) Hypodense Chronic-late (Hemosiderin) Angiography: DSA gold standard for vascular anomaly(84%)

Image recommendation Initial Dx: NECT Staging/workup: MRI, MRA, MRV Angiography: no clear cause; young, normtensive, stable, surgical candidates Diagnostic Imaging, p:I4-58;Blaser etc.

MRI for early detection of hemorrhage typically the first diagnostic study susp stroke widespread access ; speed of acquisition. MRI for early detection of hemorrhage Gradient-echo images can also show the presence of old hemorrhages MRI is more sensitive than CT for the early diagnosis of brain infarction, Overview of the evaluation of stroke – 2006 UpToDate; Louis R Caplan, MD 3a

CT of the head is the imaging procedure of choice in the initial evaluation of suspected ICH Angiography should be considered for all patients without a clear cause of hemorrhage who are surgical candidates, particularly young, normotensive patients who are clinically stable MRI and MRA are helpful and may obviate the need for contrast cerebral angiography in selected patients. Guidelines for the Management of Spontaneous Intracerebral Hemorrhage, Joseph P ,etc. (Stroke. 1999;30:905-915.) 3a

MRI may be as accurate as CT for the detection of acute hemorrhage in patients presenting with acute focal stroke symptoms and is more accurate than CT for the detection of chronic intracerebral hemorrhage Comparison of MRI and CT for detection of acute intracerebral hemorrhage. JAMA. 2004 Oct 20;292(15):1823-30. ) Kidwell CS, Chalela JA, Saver JL, 4

New evidence suggests that MR imaging alone may be adequate to identify hemorrhagic stroke in the acute setting, and that MR imaging is superior to CT for identification of chronic microbleeds and hemorrhagic conversion of infarction. Hemorrhagic stroke. (Neuroimaging Clin N Am. 2005 May;15(2):259-72), Smith EE, Rosand J,Greenberg SM.

Issue 2 What are the imaging modalities of choice for the identification of brain ischemia and the exclusion of stroke mimics?

Image recommendation Acute: MR+T2, DWI Subacute: MR+ DWI, T2, T1C+ Chronic: CT or MRI Diagnostic Imaging, p:I4-76~84;Blaser etc.

Perfusion and diffusion MRI together with MR angiography (MRA) are very helpful for the acute evaluation of patients with ischemic stroke. MRI and MRA are the recommended techniques for screening cerebral aneurysms and for the diagnosis of cerebral venous thrombosis and arterial dissection. EFNS guideline on neuroimaging in acute stroke. Report of an EFNS task force. Masdeu JC etc. European Federation of Neurological Societies (EFNS)

MR imaging More sensitive and specific than CT for detection of acute cerebral ischemia within the first few hours Depicting the pathologic entity (stroke and mimics) Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

Diffusion-weighted MRI DWI represents a major advance in the early diagnosis of acute ischemic stroke DWI can be normal in the ischemic brain regions. A sensitive and specific measure of normal rCBF is a necessary complement to a negative DWI F.S.Buonanno, et al. Neurology 1999;52;1784-1791

Low CBF may occur in patients with migrainous aura, or postictal cortical depression. Best use DWI in concert with MRI bases rMTT/rCBF maps as a clinically valuable indicator: requires further systematic study. F.S.Buonanno, et al. Neurology 1999;52;1784-1791

Issue 3 What imaging modality should be used for the determination of tissue viability the ischemic penumbra?

CT perfusion image Measure the following perfusion parameter: (1)cerebral blood volume, (2)cerebral blood flow, (3)mean transit time, (4)time to peak enhancement

CT perfusion image penumbra Infarcted tissue Increased mean transit time with moderately decreased cerebral blood flow(>60%) and normal/increased cerebral volume(80~100%) Increased mean transit time with markedly reduced cerebral blood flow (>30%) and moderately reduced cerebral volume (>60%) Infarcted tissue Severely decreased cerebral blood flow (<30%) and cerebral volume (<40%) with increased mean transient time

Diffusion-weighted MRI Areas of cytotoxic edema  restricted motion of water molecule. Higher rate of diffusion  greater loss of signals Patients with hyperacute stroke ischemic tissues appears bright in comparison with normal brain tissue.

Perfusion-weighted MRI Maps of the mean transit time the largest area of abnormality Mean cerebral blood volume underestimation of the final infarcted size Mismatch between initial cerebral blood flow maps and diffusion-weighted MRI  predicted a further extension of the infarct.

Diffusion and perfusion weighted MRI Region shows both diffusion and perfusion abnormality: irreversibly infarcted tissue. Only perfusion abnormality and normal diffusion: viable ischemic tissue

Diffusion and perfusion weighted MRI Lesion on the diffusion-weighted images < on the perfusion-weighted images: penumbra The same size on diffusion and perfusion weighted images: irreversibly infarcted tissue Lesion on the diffusion-weighted images > on the perfusion-weighted images or only on diffusion-weighted images: early reperfusion of ischemic tissue Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

Issue 2 What are the imaging modalities of choice for the identification of brain ischemia and the exclusion of stroke mimics?

MR imaging More sensitive and specific than CT for detection of acute cerebral ischemia within the first few hours Depicting the pathologic entity (stroke and mimics) Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95

Diffusion-weighted MRI DWI represents a major advance in the early diagnosis of acute ischemic stroke DWI can be normal in the ischemic brain regions. A sensitive and specific measure of normal rCBF is a necessary complement to a negative DWI F.S.Buonanno, et al. Neurology 1999;52;1784-1791

Low CBF may occur in patients with migrainous aura, or postictal cortical depression. Best use DWI in concert with MRI bases rMTT/rCBF maps as a clinically valuable indicator: requires further systematic study. F.S.Buonanno, et al. Neurology 1999;52;1784-1791

Issue 3 What imaging modality should be used for the determination of tissue viability the ischemic penumbra?

CT perfusion image Measure the following perfusion parameter: (1)cerebral blood volume, (2)cerebral blood flow, (3)mean transit time, (4)time to peak enhancement

CT perfusion image penumbra Infarcted tissue Increased mean transit time with moderately decreased cerebral blood flow(>60%) and normal/increased cerebral volume(80~100%) Increased mean transit time with markedly reduced cerebral blood flow (>30%) and moderately reduced cerebral volume (>60%) Infarcted tissue Severely decreased cerebral blood flow (<30%) and cerebral volume (<40%) with increased mean transient time

Diffusion-weighted MRI Areas of cytotoxic edema  restricted motion of water molecule. Higher rate of diffusion  greater loss of signals Patients with hyperacute stroke ischemic tissues appears bright in comparison with normal brain tissue.

Perfusion-weighted MRI Maps of the mean transit time the largest area of abnormality Mean cerebral blood volume underestimation of the final infarcted size Mismatch between initial cerebral blood flow maps and diffusion-weighted MRI  predicted a further extension of the infarct.

Diffusion and perfusion weighted MRI Region shows both diffusion and perfusion abnormality: irreversibly infarcted tissue. Only perfusion abnormality and normal diffusion: viable ischemic tissue

Diffusion and perfusion weighted MRI Lesion on the diffusion-weighted images < on the perfusion-weighted images: penumbra The same size on diffusion and perfusion weighted images: irreversibly infarcted tissue Lesion on the diffusion-weighted images > on the perfusion-weighted images or only on diffusion-weighted images: early reperfusion of ischemic tissue Ashok Srinivasan,MD, et al; Radiographics 2006; 26; S75-S95