Evaluation of New Neuroinflammation Markers in Subarachnoid Haemorrhage Patients: a Pilot Study

Subarachnoid hemorrhage (SAH) consists of blood extravasation into the space between arachnoid and pia mater. Bleeding is a consequence of cerebral aneurysm rupture in most cases. It particularly affects females with an average age of 55 years. Despite incidence being only 9 cases out of 1000 people per year, young age and high mortality and morbidity lead to loosing several years of healthy life. As a matter of fact, patients that survived cerebral aneurysm rupture suffer from cognitive deficits, behavior disorders and are unable to come back to their former productivity level and jobs. Therapy priorities are: preventing rebleeding, with endovascular treatment (when possible) or neurosurgical aneurism clipping; preventing complications associated with blood extravasation into subarachnoid pace, such as acute hydrocephalus treatment (that occurs in 20% of patients), by ventricular external drainage positioning, and delayed cerebral ischemia, mainly due to vasospasm, by endovenous administration of nimodipine; optimal perfusion pressure maintenance. Under a pathophysiological point of view, after early mechanical damage, caused by aneurysm rupture (due to tissue destruction consequent to hemorrhage mass effect, acute hydrocephalus, herniation or a possible intraparenchymal hematoma) a subacute damage could be developed from three to fourteen days post haemorrhage, because of delayed cerebral ischemia. Mainly responsible for this event are vasospasm, that complicates 20-30% of SAH, microcirculation dysfunction and microthromboembolism. Secondary damage pathogenesis is not clear, but inflammation and endothelial apoptosis are shown to be involved in vasospasm development. Moreover, some studies demonstrate that patients with acute neurological dysfunction have a grater risk of organ failure, especially for lungs and kidneys.

Osteopontin (OPN) is a secreted extracellular matrix glycoprotein that plays several roles in physiological and pathological processes, such as tissue remodelling, fibrosis, cellular migration, apoptosis inhibition and inflammation. Endogenous OPN is thought to fulfil a protective activity over ischemic damage both in brain and other organs, including kidney. Besides, recombinant OPN administration markedly decreases ischemic area in a focal cerebral ischemia model, by an antiapoptotic action. Recent in vivo studies on animal models of SAH demonstrated that OPN plays a major role; its administration attenuates cerebral damage decreasing metalloproteinase 9 and inhibiting inducible nitric oxide synthase. Treatment with OPN seems to prevent vasospasm as well, inducing an endogenous mitogen-activated protein (MAP) inhibitor, i.e. MAP kinase phosphatase 1, and reducing smooth muscle cells and endothelial cells apoptosis. A further research field in this area concerns microparticles, that is mediators released by platelets, leucocytes, erythrocyte and endothelial cells. Contrary to what it used to be thought, they do not represent a form of waste material from apoptotic coagulation cells and recent studies show their paracrine ad regulatory activity. In ischemic stroke endothelial microparticles levels directly relate to clinical severity and ischemic area extension. In typical parenchymal haemorrhage microparticles levels are higher both in blood and in liquor and associated with worse clinical outcome. In SAH increased microparticles levels has been demonstrated, especially in the day of the bleeding, and microparticles levels change based on type. On the other hand, data disagree among papers about types involved in fluctuations and their time course: Lackner et al. evaluated 20 SAH patients (Fisher II, III and IV) in their first fifteen days from bleeding and found higher blood levels of platelet, endothelial, erythrocyte and leukocyte microparticles in comparison to healthy controls [28]. Moreover, endothelial type positive for cluster of differentiation (CD) 105 and CD 62 markers were particularly increased in patient affected by vasospasm, documented with doppler. Vasospasm associated ischemia, also present especially high levels of platelet CD 41 positive microparticles. Notwithstanding disability grade at the time of discharge, microparticles levels are higher in comparison to full recovered patients (n=11). More recently, Sanborn et al. study on 22 SAH patients with massive blood spreading (Fisher III and IV) confirms microparticles elevation levels in these patients. Elevation of endothelial and platelet microparticles levels is verified as well, while no correlation is found with evidence of vasospasm, in both ultrasound (mean velocity higher than 125 cm/s in anterior circulation or higher than100 cm/s in posterior circulation, in addition to a Lindegaard ratio higher than 3) and angiography.

Published data are not unanimous on neither the correlation between vasospasm and CT scan evidence of ischemia nor with disability.

The primary endpoint of the study is to evaluate:

1. the correlation between OPN and microparticles levels and vasospasm development/ischemic lesion at the CT-scan, and subsequently with medium and long-term patients outcome.