Table 2.
Differential diagnosis of Acute-Onset Slurred Speech and Weakness.
| Diagnosis | Catheter Angiography | CT Angiography | MR Perfusion + DWI | MR Perfusion + DWI + SWI |
|---|---|---|---|---|
| Occlusive Carotid Artery Dissection | Vascular wall abnormality with arterial filling defect, classically flame shaped, and absent distal vessels | Filling defect in the affected vessel, classically flame shaped, with distal hypodensity |
Reversible ischemia: DWI/PWI mismatch; restriction of cerebral blood flow, cerebral blood volume, and increase time to peak flow in the area of reversible ischemia without diffusion restriction Irreversible ischemia: No DWI/PWI mismatch; restriction of cerebral blood flow, cerebral blood volume, and increase time to peak flow in the area of reversible ischemia with diffusion restriction |
Stage I hemodynamic failure: DWI/PWI mismatch without increased prominence of the venous vasculature Stage II hemodynamic failure (misery perfusion): Increased prominence of the venous vasculature in the area of DWI/PWI mismatch Irreversible ischemia: Diffusion restriction with decreased blood flow (no DWI/PWI mismatch), and prominence of the venous vasculature on SWI |
| Non-Hemodynamically Significant (<50–70% Occlusive) Carotid Artery Dissection† | Vascular wall abnormality with arterial filling defect and normally visualized vessels distally | Vascular wall abnormality in the affected vessel with distal contrast opacification | Normal cerebral blood flow, cerebral blood volume, and time to peak flow, without diffusion restriction | No diffusion restriction or decreased cerebral blood flow |
| Acute intracranial vasculature thromboembolic occlusion | No vascular wall abnormality proximally, with arterial filling defect with absent distal vessels at the site of thromboembolic occlusion. |
Early (<1hr): normal findings Late (>1hr): CT Angiogram: hypodense findings in the distribution of the affected vessel Noncontrast CT: Hyperdense lesion in affected artery representing acute thrombus |
Decreased cerebral blood flow, variable cerebral blood volume, and increased time to peak flow on PWI, with diffusion restriction in the area of the infarct and DWI/PWI mismatch in the at-risk tissue of the penumbra |
Stage I hemodynamic failure: DWI/PWI mismatch without increased prominence of the venous vasculature Stage II hemodynamic failure (misery perfusion): Increased prominence of the venous vasculature in the area of DWI/PWI mismatch Irreversible ischemia: Diffusion restriction with decreased blood flow (no DWI/PWI mismatch), and prominence of the venous vasculature on SWI |
†
This assumes poor collateral flow in the setting of an incomplete circle of Willis. In the setting of adequate collateral flow, no change in perfusion parameters or diffusion characteristics will be seen on MRI.