Background: Disturbances of microcirculation playa significant role in the development and progression of both acute and chronic cerebrovascular diseases (CVD) and may be associated with different hemogram abnormalities. One of the reasons of the prothrombogenic state of the endothelium is the increase in the number of blood corpuscles leading to (non Ph) myeloproliferative disorders (MPD) including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PM). Materials and Methods: The study included 167 patients: 102 patients with Ph-MPD and the control group comprising 65 patients with CVD. According to MPD subtype, the patients were divided into three groups: patients with ET (37%, n = 38, male/female 7/31, age 52 +/- 7 years), those with PV (40%, n = 41, male/female 20/21, age 50 +/- 6 years) and those with PM (23%, n = 23, male/female 5/18, age 54 +/- 4 years). Results: In 79% (n = 81) of cases in the study group (with Ph-MPD), patients had chronic CVD, with the most frequently identified symptoms being asthenia (92%) and headache (72%). Headache in Ph-MPD patients was more frequently (86%) associated with PM, while in patients with PV and ET it was equally distributed (70%). Neurological symptoms in 53% of cases were associated with focal changes of the brain on MRI localized in the subcortical area of the frontal and parietal lobes. Twenty-one (21%) patients suffered an acute cerebrovascular accident, 8 of them had thrombotic occlusion of one of the internal carotid arteries leading to hemispheric infarcts. Endothelial function (as measured by flow-dependent dilation of the brachial artery) was severely impaired in all study groups (median 5% with normal cut-off at 10%), the lowest degree of vasodilator activity being specific for patients with a history of stroke (p = 0.011). Conclusion: Patients suffering from MPD had asymptomatic focal changes in the brain in the absence of concomitant vascular disease (hypertension, atherosclerotic vascular disease, heart rhythm disorders) in 50% of cases. MPD, while remaining un- or underdiagnosed, presents a major concern in the cerebrovascular setting. A large number of thrombotic strokes occurring in patients with ET underline the necessity of early diagnostics and preventive therapy in these patients. (C) 2016 The Author(s) Published by S Karger AG, Basel