We report the first published case we are aware of: a patient with PV associated with severe multivessel stenoocclusive disease involving both the intracranial and extracranial circulations. Intracranially, the disease manifested in the typical angiographic changes associated with moyamoya syndrome. Extracranial involvement was seen in multiple large vessels off the aortic arch.
Moyamoya syndrome is a rare cause of stroke in young patients. It is due to progressive stenosis of the intracranial ICAs and their proximal branches with extensive collateralization; this latter finding produces the characteristic “puff of smoke” appearance on conventional angiogram (). The large vessel stenoocclusion is due to hyperplasia of smooth muscle cells and luminal thrombosis rather than atherosclerosis or inflammation [1
]. The underlying etiology remains unknown, but genetic, acquired, and environmental factors have all been implicated [1
]. The cooccurrence of intracranial and extracranial vessel occlusion in moyamoya has not been previously reported in English.
Polycythemia vera (PV) is a myeloproliferative disorder characterized by excess erythrocytosis, but also leukocytosis, thrombocytosis, and bone marrow hypercellularity [3
]. Although vascular complications occur in PV, including strokes, coronary artery disease, and erythromelalgia, the mechanism of thrombus formation is unclear [4
]. Various mechanisms have been postulated including hypercoagulability from thrombocytosis, venous stasis, leukocytosis, and/or platelet dysfunction [4
]. In our patient, thrombosis does not appear to account for both the multiple large vessel stenoses extracranially and concurrent intracranial moyamoya syndrome. The cause of strokes and transient ischemic attacks in our patient was likely hemodynamic and due to decreased perfusion in the setting of cerebral vessel stenosis.
The most commonly reported hematologic condition associated with moyamoya is sickle-cell anemia (SCA) [1
]. Of the myeloproliferative disorders, there are only two case reports of moyamoya associated with essential thrombocythemia (ET) and none with PV [6
]. In SCA, moyamoya is thought to be due to progressive intimal and medial wall proliferation, endothelial irritation and edema due to repeated microvascular thrombosis [8
]. Lazzaro et al. [6
] suggest that ET may lead to moyamoya vascular changes in a similar fashion due to a prothrombotic state predisposing to endothelial injury and intimal hyperplasia, ultimately leading to progressive occlusion and thrombosis. They further suggest that hematologic disorders should affect all vascular beds, rather than to be restricted intracranially, and have pathologic support for this hypothesis with demonstration of intimal thickening of the superficial temporal artery. Our case further strengthens this hypothesis due to the presence of diffuse large extracranial stenoses.
It is unlikely that our case represents a systemic vasculitis, although we have no pathology to rule this out; inflammatory markers in our patient were negative. Further, the moyamoya changes would be most unusual in this setting. We suggest that PV patients who present with transient neurologic deficits undergo noninvasive angiography in addition to standard MRI to evaluate for the presence of stenoocclusive disease involving the cerebral circulation. This may identify patients who warrant further evaluation and intervention.