JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Osmotic Demyelination Syndrome Revisited: Review with Neuroimaging
Krystle Barhaghi, MD, Olga Molchanova-Cook, MD, Michael Rosenburg, MD, Banks Deal, MD, Enrique Palacios, MD, Jeremy Nguyen, MD, Cynthia Hanemann, MD
Osmotic demyelination syndrome (ODS) is a general term that has become commonplace in the practice of medicine, encompassing both central pontine myelinolysis and extrapontine myelinolysis. Historically ODS arises as a serious complication of rapid correction of hyponatremia, yet its manifestations seem to be influenced by a multifactorial process. Further understanding of this rare demyelinating disease has elucidated the significant role of other electrolyte disturbances and the presence of chronic comorbidities as disease risk factors. This reviewdiscusses the current research regarding the pathophysiology, clinical manifestations, neuroimaging features, patient management, and prognosis of osmotic demyelination syndrome. We hope that this review will further endorse and aid in the proper diagnosis of ODS and its suitable management through the understanding of clinical and imaging correlations and outcomes, and the comorbid factors that may predispose the development of ODS in certain patient populations.
INTRODUCTION
to respond to a rapid increase in extracellular sodium. The end result is cellular dehydration and cell death that is characterized by non-inflammatory demyelinating lesions in the central nervous system, especially in the most metabolically sensitive oligodendrocytes of the pons, but including extrapontine areas aswell. 3 However, themajority of patients receiving rapid sodium correction do not develop ODS, which suggests the existence of other factors and conditions that may predispose certain patient populations to this phenomenon, most notably chronic alcoholics and those with preexisting liver disease. 3 Diabetics with hypokalemia are also prone to ODS due to their impaired glucose utilization and the stress placed on the cell membrane pump, resulting in apoptosis and cellular dysfunction. 5 In a case report describing four diabetic patients with CPM by Ichikawa et al., authors concluded that comorbidities such as diabetes, hypertension, renal failure, and viral hepatitis, play a significant role in facilitating the development of pontine lesions when compared to patients without these risk factors. 6 The overall nutritional status of the patient has also been implicated as a major factor and determinant in the development of ODS. If the patient’s abilities to adequately generate organic osmoles as well as provide the energy substrates needed to maintain cellular metabolism are impaired, metabolic stress placed on these CNS cells can ultimately trigger apoptosis. 5 The chronicity of the state of hyponatremia also plays a major role. More acute processes involving hyponatremia, which include marathon runners and those who may have ingested MDMA (street drug ‘Ecstasy’), can be corrected more rapidly without significant risk of developing ODS, as the cells have not had sufficient time to osmotically adjust their cellular components. Many new cases have been reported linking osmotic demyelination to the development and correction of other metabolic derangements, including hypophosphatemia (especially in pediatric patients), 7 postpartum hypernatremia, 8 and metabolic abnormalities associated with refeeding syndrome. 9 However, correction of hyponatremia remains
Historically, centralpontinemyelinolysis (CPM)wasfirstdescribed by Adams at al. in 1959 as a distinctive pattern of demyelination limited to the central pons, found inpatientswith clinical findings of pseudobulbar paralysis and quadriparesis occurring on a background of alcoholism and malnutrition. 1 Later, it was noted that this myelinolysis syndrome can also affect areas outside the pons, so-called extrapontine myelinolysis (EPM). It was believed to be an exclusive disease of alcoholics and the malnourished until the 1970s, when it was found to be linked to the rapid rate of sodium correction in the hyponatremic patient. 2 Osmotic demyelination syndrome (ODS) is a more general term that has become commonplace in the practice of medicine, and encompasses both pontine and extrapontine myelinolysis. Further understanding of this rare demyelinating disease has elucidated the significant role of other electrolyte disturbances and the presence of chronic comorbidities including renal failure, diabetes, liver disease, and cancer as disease risk factors, however, rapid correction of hyponatremia remains the most common cause. 3,4 This review discusses the pathophysiology, clinical manifestations, neuroimaging features, patient management, and prognosis of ODS.
PATHOPHYSIOLOGY
Although poorly understood, there are several mechanisms and theories that have been proposed to explain the unique pathophysiology involving ODS. Most notably and historically the rate of rapid correction of sodium in a hospitalized chronic hyponatremic patient has been implicated as the major cause. As our knowledge and technology have increased, so too has our understanding, leading to the development of new theories, and the discovery of factors that may contribute to this process. The original osmotic hypothesis refers to the decreased ability of braincells,whichhaveadaptedtoachronicstateofhyponatremia,
J La State Med Soc VOL 169 JULY/AUGUST 2017 89
Made with FlippingBook Digital Publishing Software