Water channelopathies beyond NMOSD: a pathophysiological discussion on two real-world clinical cases

Address for correspondence: Gustavo Figueira (email: [e-mail]).

Abstract

Background: The functions of water channels have been clarified since the 1950s, and their disorders are now well recognized as autoimmune, toxic or vascular. Neuromyelitis optica remains as one of the most significant neurological water channelopathies, involving immune attack of a well-defined autoantibody to water channels not only on the optic nerves and spinal cord but also on the brain. On the other hand, a more diffuse pattern of dysfunction triggered by toxicity and/or vascular insult targeting the structures of water channel evolves acutely as an encephalopathy syndrome, potentially but not always reversible.

Objectives: We herein present two cases of posterior reversible encephalopathy syndrome (PRES), its different pathophysiological mechanisms, and the possible correlations to NMOSD management.

Methods: In the first case, a patient with hypertensive renal disease on hemodialysis was admitted to the ER on a hypertensive crisis and with generalized convulsive epileptic status. In the second case, a woman with bilateral nephrectomy and renal transplantation, immunosuppression with tacrolimus and steroids, was also admitted to the ER with a generalized convulsive epileptic status.

Results: Both patients shared comorbidities. They were admitted to the ICU due to acute encephalopathy, and they had good outcomes after proper management. The first patient showed parieto-occipital cortical linear areas of hyperintense signal on T2W/FLAIR with patches of diffusion restriction, while the second exhibited a holohemispheric watershed pattern involving cortical and periventricular areas with hyperintense signal on T2W/FLAIR and no diffusion restriction.

Conclusion: We present two hypotheses for PRES pathophysiology: the hemodynamic hypothesis, in which rapid increase in blood pressure leads to hyperperfusion, breakdown of autoregulation, vascular leakage, and vasogenic edema; and the neurotoxicity hypothesis, which suggests endothelial dysfunction due to endogenous or exogenous toxins, also leading to vascular leakage and vasogenic edema. We finally discuss the possible implication of PRES on NMOSD patients, some of whom have undergone rituximab treatment, as well as a possible role of anti-aquaporin 4 antibody on its mechanism.

 

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Publikationsverlauf

Artikel online veröffentlicht:
02. Oktober 2024