Unlocking the Mystery: How Brain Blood Vessel Differences Impact Stroke Treatment
"New research reveals the crucial role of specific protein variations in intracranial atherosclerosis and moyamoya disease, paving the way for more targeted therapies."
The human brain relies on a complex network of blood vessels to function correctly. When these vessels become narrowed or blocked, it can lead to severe conditions like stroke. Intracranial atherosclerosis (ICAD) and moyamoya disease (MMD) are two such conditions, both characterized by narrowed arteries in the brain, but they differ significantly in how the body attempts to compensate by forming new blood vessels (collaterals). Understanding these differences at a molecular level is crucial for developing better treatments.
Vascular endothelial growth factor (VEGF) is a protein that plays a vital role in stimulating the growth of new blood vessels. However, not all VEGF is created equal. VEGF-A165, a specific form of VEGF, exists in two versions: one that promotes blood vessel growth (VEGF-A165a) and one that inhibits it (VEGF-A165b). The balance between these two versions can significantly impact how well the brain can compensate for blocked arteries.
Recent research has delved into the differing roles of VEGF-A165a and VEGF-A165b in ICAD and MMD, revealing key distinctions that could revolutionize treatment strategies. This article breaks down the study's findings, explaining how these protein variations influence the conditions and what this means for future therapies.
The Burden of Intracranial Atherosclerosis
Symptomatic intracranial atherosclerotic stenosis (sICAS) is typically defined as an ischemic stroke or transient ischemic attack associated with 50% to 99% stenosis of a relevant intracranial artery. Multiple sources describe sICAS or intracranial atherosclerotic disease as one of the most common or leading causes of ischemic stroke worldwide. The reported first-year recurrence rate for non-ICAS strokes is 5%, which the cited reviews compare with the one-year stroke rate in patients with sICAS. Risk factors reported for intracranial atherosclerotic disease include hypertension, diabetes mellitus, hyperlipidemia, metabolic syndrome, sedentary lifestyle, smoking, older age, and Asian or Black race.
From Thrombolysis to Mechanical Thrombectomy
The cited historical review of intracranial atherosclerosis covers developments in its history, surgery, therapy, lifestyle management, stroke prevention, and thrombolytic treatment. Acute stroke care later expanded from systemic thrombolysis to endovascular treatment using intra-arterial tPA and, subsequently, mechanical thrombectomy. The push for endovascular therapy was driven partly by the desire to extend the acute-treatment window beyond 4.5 hours. The history of this transition was described as rocky, reflecting the challenges involved in establishing effective endovascular treatment.
VEGF-A165a/b Ratio: A Key Differentiator in Brain Blood Vessel Diseases
A new study compared the levels of VEGF-A165a and VEGF-A165b in patients with ICAD and MMD. The results showed a significantly higher baseline ratio of VEGF-A165a to VEGF-A165b in MMD patients compared to those with ICAD. This suggests that MMD is characterized by a greater natural tendency to promote blood vessel growth, which aligns with its known propensity for collateral formation.
- Surgical Intervention: In ICAD patients, surgical revascularization led to a rapid increase in the VEGF-A165a/b ratio within one week. This indicates that surgery can effectively stimulate blood vessel growth in ICAD.
- Medical Management: Intensive medical management in ICAD patients also increased the VEGF-A165a/b ratio, but at a slower pace, peaking after three months. This suggests that lifestyle modifications and medication can gradually shift the balance towards promoting blood vessel growth.
- MMD Response: Surgical intervention did not significantly alter the VEGF-A165a/b ratio in MMD patients, possibly because their baseline ratio is already high.
Genetics and Collateral Vessel Biology
A Chinese familial case report involving a heterozygous c.14429G>a variant in RNF213 emphasized the potential value of genetic screening for family members suspected of having moyamoya disease. The reported biological factors under investigation include VEGF expression, VEGF-A165 isoforms, VEGF-antagonizing cytokines, vascular-stabilizing factors, HIF-1 alpha, TGF-beta1, and bFGF. A separate study specifically examined differential expression of VEGF-A165 isoforms between intracranial atherosclerosis and moyamoya disease. Another report stated that surgical bypass can increase VEGF-A165 a/b ratios in both moyamoya disease and intracranial atherosclerotic disease.
Why Standard Thrombectomy May Fail in ICAD
Intracranial atherosclerosis is described as a major cause of stroke worldwide, and one cited review reports that approximately 12% of White patients with a history of acute ischemic stroke or transient ischemic attack have some form of ICAS detected on routine screening in predominantly older adults. The cited thrombectomy analysis argues that devices are designed around an embolic mechanism. Consequently, those devices are not expected to be effective for reperfusion of intracranial atherosclerotic disease-related large-vessel occlusion in the same way they are for embolic occlusion. This mechanistic mismatch is a central limitation of applying standard thrombectomy assumptions to ICAD-related occlusions.
Comparing Endovascular and Medical Strategies
The cited systematic reviews compare endovascular therapy with conventional or best medical treatment for symptomatic intracranial atherosclerotic stenosis, which is associated with high recurrence rates despite medical management. One 2025 source reports that ICAS has a nearly twofold higher prevalence among Asian than non-Asian populations and that stroke recurrence can affect up to one-third of high-risk patients within one year. A 2026 review cautions that documented ethnic differences in the pathological features of intracranial atherosclerosis and treatment responses make it unsafe to generalize findings to non-Asian populations. These sources support comparing treatment strategies alongside population and disease-pattern differences rather than assuming uniform results.
Personalized Stroke Treatment: A Future Shaped by Protein Understanding
The research sheds light on the complex interplay of proteins and blood vessel health in the brain. By understanding the specific roles of VEGF-A165a and VEGF-A165b in ICAD and MMD, doctors can move closer to personalized stroke treatments that target the underlying molecular mechanisms of each condition.
Treatment Must Reflect the Occlusion Mechanism
ICAD is identified as a major cause of large-vessel occlusion stroke and as a source of unique challenges for endovascular treatment. The cited outcomes study compares angiographic and clinical results after endovascular treatment in ICAD-related and non-ICAD large-vessel occlusions. A 2022 practice advisory specifically reviewed treatments intended to reduce recurrent stroke or death in patients with symptomatic intracranial atherosclerotic arterial stenosis. Together, these sources frame treatment selection around both the underlying arterial disease and the risk of recurrent events.
A Disproportionate Global Burden
Atherosclerotic disease affecting the extracranial and intracranial cerebral arteries is described as a major cause of ischemic stroke. The World Stroke Organization source reports that it is the presumable cause of approximately 25% of all ischemic strokes. It also identifies atherosclerotic disease as the leading cause of stroke among individuals of Asian ancestry, accounting for 33% of all strokes in that population. The source cautions that this figure may underestimate the true burden of large-artery disease.
Early Experience With the CREDO heal Stent
Early real-world experience with the fibrin-heparin coated CREDO heal stent addresses symptomatic intracranial atherosclerotic disease, particularly in Asian populations, where the condition is described as a major cause of ischemic stroke and transient ischemic attack. The retrospective observational case series included patients with symptomatic intracranial stenosis of at least 70% who were receiving best medical therapy and had experienced at least one qualifying ischemic event. Its primary safety endpoint was stroke, intracranial hemorrhage, or death within 30 days. Secondary endpoints included technical success, making the study relevant to both procedural feasibility and patient safety.
Future studies should focus on confirming these findings in larger patient groups and exploring how other factors, such as genetics and lifestyle, influence the VEGF-A165a/b ratio. Further research into how Insulin Growth Factor (IGF) affects levels of VEGF could lead to better long-term medical treatment.
Ultimately, this research paves the way for more effective therapies that promote blood vessel growth in ICAD and MMD, improving outcomes for individuals at risk of stroke and other cerebrovascular diseases. By targeting the VEGF-A165a/b ratio, scientists and clinicians can unlock new possibilities for preventing and treating these debilitating conditions.