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ARTICLES: S. M. Magaña, M. Matiello, S. J. Pittock, A. McKeon, V. A. Lennon, A. A. Rabinstein, E. Shuster, O. H. Kantarci, C. F. Lucchinetti, and B. G. Weinshenker Posterior reversible encephalopathy syndrome in neuromyelitis optica spectrum disorders Neurology 2009; 72: 712-717 [Abstract] [Full text] [PDF]

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Posterior reversible encephalopathy syndrome in neuromyelitis optica spectrum disorders

Shoichi Ito   (21 May 2009)

Reply from the authors

Brian G Weinshenker, Setty M. Magana, Marcelo Matiello, Alejandro A. Rabinstein   (21 May 2009)

Posterior reversible encephalopathy syndrome in neuromyelitis optica spectrum disorders 21 May 2009
Shoichi Ito, Department of Neurology, Graduate School of Medicine, Chiba University 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan Send Correspondence to journal: Re: Posterior reversible encephalopathy syndrome in neuromyelitis optica spectrum disorders sito{at}faculty.chiba-u.jp Shoichi Ito	I read the article by Magaña et al. with great interest. [1] They reported reversible encephalopathy occurring in five patients with neuromyelitis optica spectrum disorders (NMOSDs). I agree that the presented brain MRI findings are peculiar for NMOSDs but I have some concerns about the interpretation of the neuroradiologic findings as posterior reversible encephalopathy syndrome (PRES). As the authors mentioned, PRES was first described as reversible posterior leukoencephalopathy syndrome in 1996 [2], and the term PRES was first used in 2000. [3] Subsequent reports have described MRI features of PRES in conditions including hypertensive encephalopathy, drug-induced encephalopathy, and hemolytic uremic syndrome. The essential MRI findings in these reports indicate that vasogenic edema predominantly affects the parietal and occipital lobes, and occasionally involves the frontal lobes, basal ganglia, brainstem, and/or cerebellum. Vasogenic edema is characterized by an increased apparent diffusion coefficient (ADC), a mass effect on surrounding tissues, and reversibility after appropriate therapy. Whereas ADC of the lesions in the authors' patients increased, it is notable that increased ADC suggests not only vasogenic edema but also demyelination or decreased tissue density. [4] The right parietal lesion shown in Patient 41 is unlikely to be vasogenic edema, because T2 hyperintensity persisted after the disappearance of contrast enhancement. The lesion could indicate demyelination with reversible collapsed blood-brain barriers. Contrast enhancement in PRES usually shows a gyriform, leptomeningeal, or cortical enhancement pattern. Therefore, the multiple, patchy, or confluent enhancement in deep white matter shown in Patient 4 does not appear to represent PRES. [5] Furthermore, the periventricular white matter lesions in their Patient 51 should not be considered vasogenic edema, as post-treatment MRI showed shrinking lesions and dilated lateral ventricles, suggesting destruction of white matter tissues. These features are inconsistent with vasogenic edema, in which tissue volume after recovery is preserved. Moreover, the small medial thalamic lesions in Patient 1 are not necessarily indicative of vasogenic edema because various kinds of small lesions can disappear after treatment. The sequential MRI findings provided by Magaña et al. are helpful and could provide further understanding of the neuroradiologic features of NMOSDs, but the diagnosis of PRES should be carefully considered. References 1. Magaña SM, Matiello M, Pittock SJ, et al. Posterior reversible encephalopathy syndrome in neuromyelitis optica spectrum disorders. Neurology 2009;72:712-717. 2. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med 1996;334:494-500. 3. Casey SO, Sampaio RC, Michel E, Truwit CL. Posterior reversible encephalopathy syndrome: utility of fluid-attenuated inversion recovery MR imaging in the detection of cortical and subcortical lesions. AJNR Am J Neuroradiol 2000;21:1199-1206. 4. Schaefer PW, Grant PE, Gonzalez RG. Diffusion-weighted MR imaging of the brain. Radiology 2000;217:331-345. 5. McKinney AM, Short J, Truwit CL, et al. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. AJR Am J Roentgenol 2007;189:904-912. Disclosure: The author reports no disclosures.
Reply from the authors 21 May 2009
Brian G Weinshenker, Mayo Clinic 200 First St SW Rochester MN 55905, Setty M. Magana, Marcelo Matiello, Alejandro A. Rabinstein Send Correspondence to journal: Re: Reply from the authors weinb{at}mayo.edu Brian G Weinshenker, et al.	We appreciate Dr. Ito’s interest in our article describing five patients with acute reversible encephalopathy in the setting of neuromyelitis optica spectrum disorders. We understand his concern about the indiscriminate use of the term posterior reversible encephalopathy (PRES) particularly for patients 4 and 5. We also felt that patient 4, who had persistent T2 signal abnormality, and patient 5, who had evidence of destructive changes, were different than patients 1,2 and 3. These patients had symmetrical, rapidly improving MRI lesions characteristic of vasogenic edema and “pure PRES.” We comment on the distinction between these two groups of patients in the last paragraph of our Discussion. Nonetheless, the dramatic improvement in the encephalopathy in patient 4 within 1 week and in patient 5 within an undefined period suggests a reversible component of cerebral edema. However, we had much less convincing MRI data in those patients to support a major role of vasogenic edema. As we discussed, the contrast between these cases may highlight the duality of the pathogenesis of acute, encephalopathy-producing brain lesions in neuromyelitis optica. Pure vasogenic edema due to blockade of aquaporin-4 water channels may cause rapidly reversible, symmetrical, cerebral edema (cases 1-3), whereas a combination of aquaporin-4 blockade and complement-mediated aquaporin-4-directed cellular necrosis may cause both reversible edema and (MRI-evident) irreversible encephalopathy (cases 4 and 5). While the limits of PRES are not precisely defined, its apparent association with NMO may yield a clue to the underlying pathobiology of PRES. Disclosures: Dr. Matiello was supported by a postdoctoral fellowship from the National Multiple Sclerosis Society. Ms. Magana is a NIH-CTSA funded Mayo Graduate Student and is funded by Grant Number 1 TL1 RR024152-0. Dr. Weinshenker has received personal compensation or consulting fees from Novartis, Viral Logic and Caridian BCT, has received honoraria from Innovia CME, has received research support from Genzyme, the National MS Society and Guthy Jackson Charitable Foundation, has received royalty payments from a patent related to NMO antibody that has been licensed to RSRLtd. Dr. Rabinstein reports no disclosures.