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Letters Central-Variant Posterior Reversible Encephalopathy Syndrome: More Than Meets the Eye We read with great interest the article by McKinney et al. [1] in the September 2013 issue of the AJR. The article justified the increased incidence of central-variant of posterior reversible encephalopathy syndrome (PRES) because of improving awareness of imaging patterns of PRES. We regard central-variant PRES as one of the varied presentations that have been increasingly described in the past 10 years. However, PRES is more than meets the eye. Such variants may not only reflect intrinsic associations but also correlate well with the potential pathogenesis involved in particular risk factors or causes. Isolated brainstem or pons involvement of PRES has been well described and has usually been seen in patients suffering from hypertension or chronic kidney disease [2]. Clinical manifestations of brainstem-type PRES are similar to but not the same as those of classic PRES. The lack of clinical signs is also characteristic of this condition. Despite massive brainstem involvement, patients generally have minor or no focal neurologic dysfunction, showing a relatively benign course. Thus, there is no positive association between clinical symptoms and signs and the severity of radiologic findings: “clinicoradiologic dissociation” [3]. No clear explanation has been suggested for the prominence of brainstem or basal ganglia involvement with the absence of a hemispheric lesion. Although the brainstem is invulnerable in hypertensive conditions, an unexpected extremely rapid increase in blood pressure may induce brainstem insults.
Therefore, unlike in classic PRES, hypertension may play a key role in the development of vasogenic edema in central-variant PRES. Relatively mild acceleration of hypertension would produce edema in supratentorial white matter with little or no subtentorial involvement. More severe and longer-lasting malignant hypertension is unlikely to cause predominantly subtentorial edema rather than supratentorial lesions. Hypertension is believed to be the most important risk factor for accelerating atherosclerosis and incurring cerebrovascular disease. As shown by McKinney et al. [1], both patient 3 and patient 4 presented with speech difficulties and residual lesions both in supra- and subtentorial edema regions. It is difficult to identify whether these residual lesions contribute to edema itself. We believe these lesions probably result from intrinsic arteriolosclerosis rather than as microhemorrhage clinging to vasogenic edema of PRES. And cerebral lacuna would also coexist in these regions, supplied by perforating arteries. Moreover, McKinney et al. accepted time intervals for follow-up that were too long (9 and 4 months, respectively) beyond the commonly accepted time of 1–2 weeks, which would unavoidably include cases that were not PRES. Central-variant PRES has been more frequently observed in patients with hemolysis, elevated liver enzymes, and low platelets syndrome in pregnancy-related vascular encephalopathy; MRI findings showed more lesions in the brainstem, basal ganglia, and thalamus than those in the cerebral hemispheres [4]. Patients with chronic kidney disease might also develop PRES with a mild elevation of blood pressure because of elec-
trolyte imbalance and urinary protein loss. PRES can also be induced by cyclosporine medication and is completely reversible after rapid withdrawal. This finding should be suspected in every patient presenting with neurologic symptoms who is undergoing immunosuppressive therapy. Physicians should be alert to the possible causes of PRES to reduce morbidity by rapid diagnosis and treatment. Bo Gao Yantai Yuhuangding Hospital, Qingdao University Shandong, China Cui Lv Yantai City Yantaishan Hospital, Shandong, China DOI:10.2214/AJR.14.12671 WEB—This is a web exclusive article.
References 1. McKinney AM, Jagadeesan BD, Truwit CL. Central-variant posterior reversible encephalopathy syndrome: brainstem or basal ganglia involvement lacking cortical or subcortical cerebral edema. AJR 2013; 201:631–638 2. Gao B, Liang H, Liu FL, et al. Isolated pons involvement in posterior reversible encephalopathy syndrome in a patient with chronic renal insufficiency: case report and literature review. Clin Neuroradiol 2012; 22:341–344 3. Shintani S, Hino T, Ishihara S, et al. Reversible brainstem hypertensive encephalopathy (RBHE): clinicoradiologic dissociation. Clin Neurol Neurosurg 2008; 110:1047–1053 4. Okada T, Kanagaki M, Yamamoto A, et al. Magnetic resonance imaging of vascular encephalopathy related to pregnancy. Neurol Med Chir (Tokyo) 2013; 53:520–525
AJR 2014; 203:W454 0361–803X/14/2034–W454 © American Roentgen Ray Society
W454
AJR:203, October 2014
Letters Central-Variant Posterior Reversible Encephalopathy Syndrome: More Than Meets the Eye We read with great interest the article by McKinney et al. [1] in the September 2013 issue of the AJR. The article justified the increased incidence of central-variant of posterior reversible encephalopathy syndrome (PRES) because of improving awareness of imaging patterns of PRES. We regard central-variant PRES as one of the varied presentations that have been increasingly described in the past 10 years. However, PRES is more than meets the eye. Such variants may not only reflect intrinsic associations but also correlate well with the potential pathogenesis involved in particular risk factors or causes. Isolated brainstem or pons involvement of PRES has been well described and has usually been seen in patients suffering from hypertension or chronic kidney disease [2]. Clinical manifestations of brainstem-type PRES are similar to but not the same as those of classic PRES. The lack of clinical signs is also characteristic of this condition. Despite massive brainstem involvement, patients generally have minor or no focal neurologic dysfunction, showing a relatively benign course. Thus, there is no positive association between clinical symptoms and signs and the severity of radiologic findings: “clinicoradiologic dissociation” [3]. No clear explanation has been suggested for the prominence of brainstem or basal ganglia involvement with the absence of a hemispheric lesion. Although the brainstem is invulnerable in hypertensive conditions, an unexpected extremely rapid increase in blood pressure may induce brainstem insults.
Therefore, unlike in classic PRES, hypertension may play a key role in the development of vasogenic edema in central-variant PRES. Relatively mild acceleration of hypertension would produce edema in supratentorial white matter with little or no subtentorial involvement. More severe and longer-lasting malignant hypertension is unlikely to cause predominantly subtentorial edema rather than supratentorial lesions. Hypertension is believed to be the most important risk factor for accelerating atherosclerosis and incurring cerebrovascular disease. As shown by McKinney et al. [1], both patient 3 and patient 4 presented with speech difficulties and residual lesions both in supra- and subtentorial edema regions. It is difficult to identify whether these residual lesions contribute to edema itself. We believe these lesions probably result from intrinsic arteriolosclerosis rather than as microhemorrhage clinging to vasogenic edema of PRES. And cerebral lacuna would also coexist in these regions, supplied by perforating arteries. Moreover, McKinney et al. accepted time intervals for follow-up that were too long (9 and 4 months, respectively) beyond the commonly accepted time of 1–2 weeks, which would unavoidably include cases that were not PRES. Central-variant PRES has been more frequently observed in patients with hemolysis, elevated liver enzymes, and low platelets syndrome in pregnancy-related vascular encephalopathy; MRI findings showed more lesions in the brainstem, basal ganglia, and thalamus than those in the cerebral hemispheres [4]. Patients with chronic kidney disease might also develop PRES with a mild elevation of blood pressure because of elec-
trolyte imbalance and urinary protein loss. PRES can also be induced by cyclosporine medication and is completely reversible after rapid withdrawal. This finding should be suspected in every patient presenting with neurologic symptoms who is undergoing immunosuppressive therapy. Physicians should be alert to the possible causes of PRES to reduce morbidity by rapid diagnosis and treatment. Bo Gao Yantai Yuhuangding Hospital, Qingdao University Shandong, China Cui Lv Yantai City Yantaishan Hospital, Shandong, China DOI:10.2214/AJR.14.12671 WEB—This is a web exclusive article.
References 1. McKinney AM, Jagadeesan BD, Truwit CL. Central-variant posterior reversible encephalopathy syndrome: brainstem or basal ganglia involvement lacking cortical or subcortical cerebral edema. AJR 2013; 201:631–638 2. Gao B, Liang H, Liu FL, et al. Isolated pons involvement in posterior reversible encephalopathy syndrome in a patient with chronic renal insufficiency: case report and literature review. Clin Neuroradiol 2012; 22:341–344 3. Shintani S, Hino T, Ishihara S, et al. Reversible brainstem hypertensive encephalopathy (RBHE): clinicoradiologic dissociation. Clin Neurol Neurosurg 2008; 110:1047–1053 4. Okada T, Kanagaki M, Yamamoto A, et al. Magnetic resonance imaging of vascular encephalopathy related to pregnancy. Neurol Med Chir (Tokyo) 2013; 53:520–525
AJR 2014; 203:W454 0361–803X/14/2034–W454 © American Roentgen Ray Society
W454
AJR:203, October 2014
