Can a cerebellar infarct in a patient with an old hematoma be ischemic in origin if Susceptibility-Weighted Imaging (SWI) does not show blooming?

Can a Cerebellar Infarct Be Ischemic Without SWI Blooming?

Yes, a cerebellar infarct can absolutely be ischemic in origin even when SWI does not show blooming artifact, as the absence of blooming does not exclude ischemic stroke—it simply indicates the absence of detectable hemorrhagic transformation, intravascular thrombus, or paramagnetic blood products at the time of imaging. 1, 2

Understanding SWI in Acute Ischemic Stroke

SWI is highly sensitive for detecting paramagnetic substances (blood products, calcium, iron) but serves multiple distinct roles in stroke evaluation:

What SWI Blooming Indicates

• Intravascular thrombus: The "blooming" or hypointense signal within an artery (the "dark artery sign") suggests acute thromboembolism, seen in approximately 85% of cases when thrombus is present 1, 3
• Hemorrhagic transformation: SWI detects both macroscopic hemorrhage and petechial microbleeds that may not be visible on conventional sequences 2
• Pre-existing microbleeds: Important for treatment decisions regarding thrombolysis 1

What Absence of Blooming Means

The lack of SWI blooming does not exclude ischemic infarction because:

• Pure ischemic infarcts without hemorrhagic transformation will not show blooming artifact—they remain ischemic without blood product deposition 4, 2
• Distal emboli or small vessel occlusions may not produce detectable blooming if the thrombus is small or has already fragmented 3
• Timing matters: Early imaging may precede hemorrhagic transformation, which occurs in 15-43% of ischemic strokes but develops over hours to days 4

Diagnostic Approach for Your Patient

Primary Diagnostic Sequence

MRI with DWI remains the gold standard for diagnosing acute ischemic cerebellar infarction, not SWI 5:

• DWI is 77% sensitive within the first 3 hours versus CT at only 16% 5
• DWI directly demonstrates cytotoxic edema from ischemia regardless of hemorrhagic transformation 5
• SWI is complementary, not primary, for stroke diagnosis 1, 2

Interpreting the Old Hematoma

In a patient with a known old hematoma:

• The old hematoma will show blooming on SWI due to hemosiderin deposition 5, 1
• A new cerebellar infarct without blooming suggests pure ischemic stroke without hemorrhagic transformation 2
• This pattern actually provides reassurance that the new event is ischemic rather than a new hemorrhage 1

Additional SWI Findings to Assess

Even without blooming in the infarct itself, look for:

• Prominent cortical veins in the ischemic territory (seen in 14/62 patients with acute infarct), indicating venous congestion and impaired perfusion 2
• Asymmetric hypointense cortical veins as a surrogate marker of tissue perfusion status 1
• These findings support ischemic pathophysiology even without arterial thrombus blooming 1, 2

Clinical Implications

Management Priorities

For cerebellar infarction specifically, immediate admission to intensive care or stroke unit with early neurosurgical consultation is essential, regardless of SWI findings, as cerebellar infarcts carry risk of brainstem compression and obstructive hydrocephalus 6:

• Monitor closely for deterioration: decreased consciousness, new brainstem signs, fourth ventricular compression 6
• The presence or absence of SWI blooming does not change this management algorithm 6

Common Pitfall to Avoid

Do not rely on SWI blooming as a requirement for diagnosing ischemic stroke—this is a fundamental misunderstanding of the sequence's role 1, 2:

• SWI adds value by detecting hemorrhage, thrombus, and venous changes, but DWI remains the primary sequence for identifying acute ischemia 5, 1
• In one series, SWI detected unsuspected hemorrhage in 22/62 patients with acute infarct, but the infarcts themselves were diagnosed on DWI 2

When to Suspect Alternative Diagnoses

Consider arterial dissection if clinical suspicion exists, as SWI shows blooming in only 5/7 cases of posterior inferior cerebellar artery dissection, while conventional MRI may be negative 7:

• T1-weighted imaging with fat suppression may show intramural hematoma in 76-91% of dissections 5
• Catheter angiography remains the gold standard when dissection is suspected but not confirmed 5, 7

Bottom Line

The cerebellar infarct is ischemic based on DWI findings, not SWI blooming. The absence of blooming simply indicates no hemorrhagic transformation or detectable intravascular thrombus at the imaging time point—it does not negate the ischemic diagnosis established by restricted diffusion on DWI 5, 1, 2. Focus management on the established cerebellar infarction protocol with intensive monitoring and early neurosurgical involvement 6.