What is the relationship between Moyamoya disease and Sickle Cell Disease (SCD)?

From the Guidelines

Moyamoya disease and Sickle Cell Disease (SCD) are associated, with up to 40% of children with SCD showing moyamoya-like changes on imaging 1.

Key Findings

• Moyamoya disease is a rare steno-occlusive disease of the arteries of the circle of Willis, which can be idiopathic (moyamoya disease) or occur in association with other conditions (moyamoya syndrome), including SCD 1.
• The pathophysiology of ischemic stroke in patients with SCD is large artery arteriopathy, believed to be caused by intimal hyperplasia related to repeated endothelial injury and inflammation, which can lead to cerebral vasculopathy or moyamoya syndrome 1.
• As many as 12% of patients with sickle cell anemia will have a clinically detected stroke by the age of 20, and most strokes in moyamoya in children are ischemic 1.

Relationship Between Moyamoya Disease and SCD

• The underlying cause of moyamoya disease is unclear, but it is likely that many different factors, both genetic and environmental, contribute to developing the arteriopathy, and SCD is one of the conditions associated with moyamoya syndrome 1.
• Moyamoya syndrome may be asymptomatic, but it can predispose a patient to both ischemic stroke and intracranial hemorrhage, and caution is advised when considering antithrombotics for secondary stroke prevention in patients with SCD 1.

Clinical Implications

• Treatment for moyamoya disease focuses on preventing progression and reducing the risk of ischemic or hemorrhagic stroke, and surgical revascularization may be considered for preventing hemorrhagic stroke 1.
• In patients with SCD, it is essential to consider the risk of hemorrhagic stroke when administering antithrombotics for secondary stroke prevention, and antithrombotics may be reasonable if there is evidence for other stroke mechanisms, such as atherosclerosis 1.

From the Research

Relationship Between Moyamoya Disease and Sickle Cell Disease (SCD)

The relationship between Moyamoya disease and Sickle Cell Disease (SCD) is complex and involves an increased risk of cerebrovascular complications. Key aspects of this relationship include:

• SCD can lead to progressive vasculopathy, increasing the risk of cerebrovascular complications, including Moyamoya syndrome (MMS) 2
• MMS is a rare disorder characterized by stenosis of the internal carotid arteries, which can occur in SCD patients due to chronic endothelial damage and inflammation 2
• The coexistence of SCD and MMS can result in severe cerebrovascular complications, presenting unique diagnostic and therapeutic challenges 2, 3

Clinical Characteristics and Management

Clinical characteristics and management of MMS in SCD patients include:

• Frequent unilateral Moyamoya syndrome, uncommon posterior cerebral artery (PCA) involvement, and moderate steno-occlusion and moyamoya vessel (MMV) scores 4
• Cerebral revascularization, in the form of extracranial-intracranial bypass, has been shown to prevent recurrent strokes in SCD patients with MMS 5
• Early detection and surgical intervention, in addition to chronic transfusion therapy (CTT), could significantly reduce stroke recurrence and improve neurocognitive outcome 5
• Medical management may be beneficial for adult SCD patients with MMS, particularly those with hypercoagulable states, such as protein S deficiency 6

Outcomes and Prognosis

Outcomes and prognosis for SCD patients with MMS include:

• Patients with SCD-associated MMS may experience recurrent cerebrovascular events and progressive neurological deficits despite maximal therapy 2
• Indirect surgical revascularization can decrease stroke risk for pediatric patients with MMS, including those with SCD 3
• SCD-associated MMS may represent a more aggressive variant of the disease, while neurofibromatosis type 1 may represent a more benign variant 3