Kulkarni S*, Mali K**, Warke H***.
(* Junior Resident, ** Assistant Professor, *** Associate Professor, Department of Obstetrics and Gynecology, Seth G S Medical College and K E M Hospital, Mumbai, India.)
PRES is considered as an entity with multifactorial etiologies, mostly associated with acute hypertension. Although more than 70% of patients with PRES are hypertensive, a significant proportion have normal or only mildly raised blood pressure.[1, 2] Breakdown in cerebral autoregulation due to uncontrolled hypertension leads to hyperperfusion and cerebral vessel damage resulting in interstitial extravasation of proteins and fluids causing vasogenic edema. Irreversible damage is seen at mean arterial pressures above 200 mm of Hg. An alternative theory is that PRES is a result of a systemic inflammatory state causing endothelial dysfunction. This is supported by the observation that PRES is usually associated with a systemic inflammatory process such as sepsis, eclampsia, transplantation and autoimmune disease. However, why some cases of PRES occur without any underlying inflammation cannot be explained. Besides preeclampsia and hypertension, PRES is associated with various conditions like renal failure, immunosuppressive therapy, post-transplantation, antineoplastic drugs and some autoimmune diseases like systemic lupus erythromatosus, systemic sclerosis, Wegener’s granulomatosis and polyarteritis nodosa. Cases usually present with complaints of headaches, visual disturbances in the background of high blood pressure and a characteristic radiologic picture. Severity of clinical presentation varies from visual disturbance like blurring of vision to focal neurological deficit such as cortical blindness. Seizures could be generalized tonic clonic or status epilepticus. Rarely, severe neurological presentations leading to coma maybe seen. Clinical symptoms and neuroradiological findings are typically indistinguishable among the cases of PRES regardless of the underlying cause. Typical MRI findings in PRES are bilateral white-matter abnormalities in vascular watershed areas in the posterior regions of both cerebral hemispheres, affecting mostly the occipital and parietal lobes. Posterior circulation is considered more susceptible to involvement owing to the reduced amount of sympathetic innervation as compared to the anterior circulation. Rapid identification and removal of trigger and aggressive management mostly results in reversal of MRI changes and improved general condition within few days to weeks. Another syndrome being increasingly identified is reversible cerebral vasoconstriction syndrome, characterised by severe thunderclap headaches with or without symptoms and segmental constriction of cerebral arteries that resolves within three months. It is supposedly due to a transient disturbance in the control of cerebrovascular tone. Stroke can occur a few days after initial imaging. Calcium channel blocker nimodipine seems to reduce thunderclap headaches within 48 hours of administration but has no proven effect on hemorrhagic and ischemic complications. This has to be ruled out in cases with pre monitory symptoms of headache. HELLP syndrome is a life threatening condition that can potentially complicate pregnancy in the third trimester and is named by three main features of hemolysis, elevated liver enzymes and low platelet counts. Pathophysiology of HELLP syndrome is not well defined and it is considered as a variant of severe preeclampsia by some. Defective placental vascular remodelling during the 16-22 weeks of pregnancy results in inadequate placental perfusion. The hypoxic placenta releases various placental factors which cause endothelial and placental dysfunction by preventing them from binding endothelial cell receptors. The result is hypertension, proteinuria and increased platelet activation and aggregation. Further decrease in platelet counts due to activation of coagulation cascade and microangiopathic hemolysis and multiorgan microvascular injury including liver necrosis contribute to the development of HELLP.
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Kulkarni S, Mali K, Warke H. Posterior Reversible Encephalopathy Syndrome (PRES) Associated With Eclampsia And HELLP Syndrome. JPGO 2019. Vol. 6. No. 8. Available from:https://www.jpgo.org/2019/08/posterior-reversible-encephalopathy.html