HILTON HEAD—Posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS) can cause severe irreversible neurologic injury if left untreated, according to an overview presented at Vanderbilt University's 37th Annual Contemporary Clinical Neurology Symposium.
Imaging plays a crucial role in the diagnosis of PRES and RCVS, which were defined fairly recently. The two conditions share certain features, and their pathologies are not well understood.
Anecdotal evidence suggests that the number of patients presenting with PRES and RCVS is increasing. “We need to do better at recognizing and treating these disorders urgently to prevent permanent neurologic injury,” said Anne O’Duffy, MD. Neurologists should study the diseases closely to understand them better, she added.
PRES Associated With Hypertension
The first description of PRES was a series of 15 patients published in 1996, said Dr. O’Duffy, Assistant Professor of Neurology at the Vanderbilt Stroke Center in Nashville. The clinical presentation varies and may include seizures, altered consciousness, headaches, and visual abnormalities. PRES can develop in association with various conditions, but the main physiologic abnormality is thought to be cerebral vasogenic edema. PRES typically is reversible when the cause is identified and removed.
The incidence of PRES is unknown. It has been reported in individuals between ages 4 and 90, but the mean age range is from 39 to 47. PRES affects significantly more females than males. The typical patient has poorly treated hypertension, and PRES manifests itself as a sudden and marked elevation of blood pressure. PRES also can be related to bone marrow transplantation, cancer chemotherapy agents, antirejection drugs, and chronic renal failure.
Seizures occur in the majority of patients with PRES, and status epilepticus occurs in approximately 13% of patients. Visual symptoms of blurred vision, hemianopsia, visual hallucinations and cortical blindness may be present. Although between 67% and 80% of patients have acute hypertension, the level of blood pressure does not correlate with disease severity. Between 35% and 40% of patients with PRES require mechanical ventilation for three to seven days. Patients’ mean length of hospital stay is 20 days.
MRI is superior to CT in identifying PRES, said Dr. O’Duffy. The typical MRI finding is FLAIR white matter lesions that often are symmetric and are predominantly posterior. Lesions also may appear in a holohemispheric watershed pattern or in the superior frontal sulcus. About half of patients with PRES have MRI contrast enhancement, 10% to 23% have cerebral infarctions, and 5% to 17% have intraparenchymal or subarachnoid hemorrhage.
The pathophysiology of PRES is controversial, and investigators have proposed two contradictory hypotheses. One explanation is that impaired autoregulation causes increased cerebral blood flow, and the other is that endothelial dysfunction results in cerebral hypoperfusion. In either hypothesis, perfusion abnormalities lead to blood–brain barrier dysfunction and vasogenic edema.
When a patient has a diagnosis of PRES, a neurologist should evaluate him or her for associated organ problems. “You’re really trying to identify the trigger and deal with it,” said Dr. O’Duffy. Managing problems such as high blood pressure, seizures, and electrolyte disturbances is important in PRES. If PRES is related to a hypertensive emergency, the treating physician should decrease mean arterial pressure by 20% to 25% in the first several hours and aim to reduce blood pressure to less than 160/100 mm Hg within the first six hours.
Calcium-Channel Blockers Effective for RCVS
RCVS has been known by several names since the late 1980s, including Call–Fleming syndrome, postpartum angiopathy, migrainous vasospasm, and drug-induced arteritis or angiopathy. The hallmark of RCVS is a thunderclap headache, which has a sudden onset, reaches maximal intensity in less than a minute, and can last for 10 days. For migraineurs, a thunderclap headache is distinct from a typical migraine. To diagnose primary thunderclap headache, a neurologist must rule out other entities such as subarachnoid hemorrhage, venous sinus thrombosis, cervical artery dissection, and pituitary apoplexy. Neurologists should strongly consider a diagnosis of RCVS for a patient with repeated thunderclap headaches during a period of several days to a week, said Dr. O’Duffy. Conditions associated with RCVS include pregnancy, puerperium, exposure to vasoactive drugs, blood products, pheochromocytoma, unruptured aneurysms, and post carotid endarterectomy syndrome.
The largest series of adults with RCVS includes 139 cases with a mean age of 42.5. Approximately 81% of cases were female, and 85% of them had thunderclap headache. Patients with RCVS may be more likely to have migraine than the average population. Initial imaging of the brain often is normal, but patients subsequently may develop hemorrhages, which are typically small subarachnoid hemorrhages on the cortical surface, and infarcts, which are typically in a symmetric, arterial watershed distribution. Approximately 90% of patients with RCVS have a good clinical outcome.