Can a computed tomography (CT) perfusion scan be negative in a patient with suspected lacunae infarction, particularly those with risk factors such as hypertension, diabetes, and atherosclerosis?

Can CT Perfusion Be Negative with Lacunar Infarction?

Yes, CT perfusion can frequently be negative in patients with lacunar infarction, with sensitivity ranging from 0% to only 62.5% across studies, making it an unreliable tool for excluding this diagnosis. 1

Key Evidence on CT Perfusion Performance in Lacunar Stroke

The most recent systematic review examining CT perfusion (CTP) in lacunar stroke demonstrates poor and inconsistent diagnostic performance 1:

• Sensitivity ranges from 0% to 62.5%, meaning CTP fails to detect perfusion deficits in a substantial proportion of confirmed lacunar infarcts 1
• Specificity ranges from 20% to 100%, showing high variability 1
• CTP does not allow reasonable exclusion of lacunar infarct when no perfusion deficit is found 1

In a prospective study of patients with lacunar syndrome, CTP detected the symptomatic lesion in only 62% of patients with DWI-confirmed lacunar infarcts, compared to 19% detection on non-contrast CT 2. This means 38% of confirmed lacunar infarcts showed no perfusion abnormality on CTP 2.

Why CT Perfusion Fails in Lacunar Infarction

Pathophysiological Considerations

Lacunar infarcts result from occlusion of small penetrating arteries supplying deep brain structures (basal ganglia, internal capsule, thalamus, pons), measuring <1.5 cm in diameter 3, 4, 5. The pathophysiology is more complex than simple large vessel occlusion 1:

• Small vessel disease mechanisms include lipohyalinosis and microatheroma affecting penetrating arterioles, not large vessel occlusion 6
• The perfusion deficit may be below the detection threshold of CTP technology given the small size of affected vessels and tissue 2, 1
• Collateral circulation through adjacent penetrating vessels may maintain perfusion parameters within normal ranges despite infarction 2

Technical Limitations

Multiple technical factors contribute to poor CTP performance 1:

• Variable scanner technology (16 to 320 detector rows) affects spatial resolution 1
• Different post-processing software and perfusion maps yield inconsistent results 1
• Infratentorial lesions are particularly poorly detected compared to supratentorial locations 2

Clinical Implications for Your Patient

When to Suspect Lacunar Infarction Despite Negative CTP

In patients with hypertension, diabetes, and atherosclerosis presenting with acute neurological deficits, you should maintain high clinical suspicion for lacunar infarction even with negative CTP 3, 4:

• Classic lacunar syndromes (pure motor hemiparesis, pure sensory syndrome, sensorimotor stroke, ataxic hemiparesis, dysarthria-clumsy hand) strongly suggest lacunar infarction regardless of CTP findings 5, 7
• Risk factor profile matters: 68% of lacunar infarct patients have hypertension, 37% have diabetes 6
• The absence of cortical signs (no aphasia, neglect, or visual field defects) supports lacunar localization 5

Recommended Diagnostic Approach

MRI with diffusion-weighted imaging (DWI) is the gold standard for detecting lacunar infarcts and should be obtained when clinical suspicion exists despite negative CTP 4, 2:

• DWI sequences detect acute ischemic lesions that CTP misses 4, 2
• MRI with T2 FLAIR distinguishes lacunar infarcts from perivascular spaces 3, 8
• MRI is superior to CT for detecting small subcortical infarcts 5

Critical Pitfall to Avoid

Do not use negative CTP to exclude lacunar infarction in patients with appropriate clinical syndromes and vascular risk factors 1. The American College of Radiology guidelines emphasize that while CT can detect stroke mimics, it is relatively insensitive for acute infarcts, particularly small ones 3.

Additional Diagnostic Considerations

Despite the traditional teaching that lacunar infarcts result purely from small vessel disease, comprehensive evaluation remains essential 6:

• 23% of lacunar infarct patients have carotid atherosclerotic plaque as a potential embolic source 6
• 18% are at high risk for cardioembolism 6
• Even among patients without hypertension or diabetes, 32% have possible carotid or cardiac etiology 6

Therefore, vascular imaging (CTA or MRA) and cardiac evaluation (echocardiography, rhythm monitoring) should be performed even when lacunar infarction is suspected 5, 6.

Long-Term Significance

The detection of lacunar infarcts has important prognostic implications beyond the acute presentation 4:

• Subclinical lacunar infarcts confer approximately 4-fold increased risk of future symptomatic stroke 4
• They are associated with 2-fold increased risk of dementia during long-term follow-up 4
• Multiple lacunar infarcts indicate subcortical ischemic vascular dementia risk 4, 8
• Aggressive vascular risk factor management is crucial for secondary prevention 4