Astrocytes are an early target in osmotic demyelination syndrome

Case report: Acute severe hyponatremia-induced seizures in a newborn: a community-acquired case and literature review

Severe neonatal hyponatremia represents a critical electrolyte imbalance with potentially severe neurological outcomes, a condition rarely documented in community-acquired, full-term newborns. This report underscores a unique case of a 23-day-old, previously healthy, full-term male neonate experiencing severe hyponatremia that precipitated seizures, underscoring the urgency of prompt recognition and intervention. The neonate presented with symptoms including vomiting, groaning, chills, fixed staring, and limb tremors. Critical findings upon admission encompassed hypothermia, hypotension, tachycardia, and tachypnea accompanied by significant weight loss. The clinical presentation was marked by dehydration, lethargy, weak crying, a fixed gaze, irregular breathing, and coarse lung sounds, yet a distended abdomen, hypertonic limb movements, and recurrent seizures were observed. Immediate interventions included establishing IV access, rewarming, mechanical ventilation, seizure management, volume expansion, dopamine for circulatory support, and initiation of empirical antibiotics. Diagnostic evaluations revealed a sodium ion concentration of 105.9 mmol/L, while amplitude-integrated electroencephalography (aEEG) detected pronounced seizure activity characterized by a lack of sleep-wake rhythmicity, noticeable elevation in both the lower and upper amplitude margins, and a sustained decrease in the lower margin voltage dropping below 5 μV, presenting as sharp or serrated waveforms. The management strategy entailed rapid electrolyte normalization using hypertonic saline and sodium bicarbonate, anticonvulsant therapy, and comprehensive supportive care, with continuous aEEG monitoring until the cessation of seizures. Remarkably, by the third day, the neonate's condition had stabilized, allowing for discharge in good health 10 days post-admission. At a 16-month follow-up, the child exhibited no adverse neurological outcomes and demonstrated favorable growth and development. Our extensive review on the etiology, clinical manifestations, aEEG monitoring, characteristics of seizures induced by severe neonatal hyponatremia, treatment approaches, and the prognosis for seizures triggered by severe hyponatremia aims to deepen the understanding and enhance clinical management of this complex condition. It stresses the importance of early detection, accurate diagnosis, and customized treatment protocols to improve outcomes for affected neonates. Additionally, this review accentuates the indispensable role of aEEG monitoring in managing neonates at elevated risk for seizures. Yet, the safety and efficacy of swiftly administering hypertonic saline for correcting severe hyponatremia-induced seizures necessitate further investigation through medical research.

Thalamic Neuron Resilience during Osmotic Demyelination Syndrome (ODS) Is Revealed by Primary Cilium Outgrowth and ADP-ribosylation factor-like protein 13B Labeling in Axon Initial Segment

A murine osmotic demyelinating syndrome (ODS) model was developed through chronic hyponatremia, induced by desmopressin subcutaneous implants, followed by precipitous sodium restoration. The thalamic ventral posterolateral (VPL) and ventral posteromedial (VPM) relay nuclei were the most demyelinated regions where neuroglial damage could be evidenced without immune response. This report showed that following chronic hyponatremia, 12 h and 48 h time lapses after rebalancing osmolarity, amid the ODS-degraded outskirts, some resilient neuronal cell bodies built up primary cilium and axon hillock regions that extended into axon initial segments (AIS) where ADP-ribosylation factor-like protein 13B (ARL13B)-immunolabeled rod-like shape content was revealed. These AIS-labeled shaft lengths appeared proportional with the distance of neuronal cell bodies away from the ODS damaged epicenter and time lapses after correction of hyponatremia. Fine structure examination verified these neuron abundant transcriptions and translation regions marked by the ARL13B labeling associated with cell neurotubules and their complex cytoskeletal macromolecular architecture. This necessitated energetic transport to organize and restore those AIS away from the damaged ODS core demyelinated zone in the murine model. These labeled structures could substantiate how thalamic neuron resilience occurred as possible steps of a healing course out of ODS.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Osmotic demyelination syndrome: novel risk factors and proposed pathophysiology

BACKGROUND

Osmotic demyelination syndrome (ODS) is non-inflammatory demyelination in response to an osmotic challenge. It can be pontine or extrapontine in presentation.

AIMS

To retrospectively review cases involving ODS and define the spectrum of causes, risk factors, clinical and radiological presentations, and functional outcomes.

RESULTS

The study utilised data from 15 patients with a mean age of 53.6 years. Malnutrition (9; 60%) and chronic alcoholism (10; 66.7%) were the most common associated disorders. Two (13.3%) patients had severe hyponatraemia (<120 mmol/L). The average highest single-day change was 5.1 mmol/L. Radiologically, 14 (93.3%) had pontine and 6 (40%) had extra-pontine lesions. Hypokalaemia (14; 93.3%) and hypophosphataemia (9; 60%) were commonly associated. Common clinical manifestations include altered consciousness/encephalopathy (9; 60%), dysphagia (4; 26.7%) and limb weakness (4; 26.7%). At 3 months, two (14.3%) had died and six (40%) were functionally independent (modified Rankin scale 0-2).

CONCLUSION

We found that ODS occurred despite appropriate correction rates of hyponatraemia. Factors such as malnutrition, chronic alcoholism, hypokalaemia and hypophosphataemia are thought to play a role in its pathogenesis. Approximately half of the patients survived and became functionally independent.

Fructose: A New Variable to Consider in SIADH and the Hyponatremia Associated With Long-Distance Running?

Fructose has recently been proposed to stimulate vasopressin secretion in humans. Fructose-induced vasopressin secretion is not only postulated to result from ingestion of fructose-containing drinks but may also occur from endogenous fructose production via activation of the polyol pathway. This raises the question of whether fructose might be involved in some cases of vasopressin-induced hyponatremia, especially in situations where the cause is not fully known such as in the syndrome of inappropriate secretion of diuretic hormone (SIADH) and exercise-associated hyponatremia, which has been observed in marathon runners. Here we discuss the new science of fructose and vasopressin, and how it may play a role in some of these conditions, as well as in the complications associated with rapid treatment (such as the osmotic demyelination syndrome). Studies to test the role of fructose could provide new pathophysiologic insights as well as novel potential treatment strategies for these common conditions.

Oral Urea Supplementation in the Treatment of Acute Hyponatremia among Hospitalized Adults: A Systematic Review

Hyponatremia is the most common electrolyte disturbance among hospitalized adults. Oral urea is currently recommended in Europe in the treatment of chronic hyponatremia; no published systematic review investigating oral urea for acute hyponatremia among hospitalized adults exists. An oral urea supplement became available in the United States in 2016. This was a systematic review investigating the use of oral urea in the treatment of acute hyponatremia among hospitalized adults. Pubmed, CINAHL, Scopus, Web of Science, and Cochrane databases were searched for studies published between 1998 and 2021. Risk of bias was assessed using the ROBINS-I tool; strength of the evidence was assessed using GRADE criteria. Changes in serum sodium and measures of safety and tolerance were reported. Eight studies were identified that met inclusion criteria, which included a total of 296 patients. Seven studies were retrospective. All studies found an increase in serum sodium levels associated with oral urea supplementation. Side effects were minimal; one patient discontinued urea due to a side effect (dysgeusia). Urea dose/duration varied among the studies. Based on the serious risk of bias and GRADE criteria, the strength of the evidence was considered low. Oral urea supplementation was associated with increases in serum sodium concentrations among hospitalized adults with hyponatremia, and appears to be safe and well tolerated in this population. Prospective controlled trials are needed to establish the efficacy, comparative effectiveness, and potential cost savings of this therapy.Key teaching pointsHyponatremia is associated with negative clinical outcomes among hospitalized adults.Oral urea is now available in the United States, and is currently recommended in Europe to treat chronic hyponatremia.This systematic review shows that oral urea supplementation may be associated with increases in serum sodium levels among hospitalized adults with hyponatremia, and appears safe and well-tolerated; however, the studies reviewed here are at high risk of bias and the available evidence is of low quality, making any recommendation drawn from this data weak.Prospective controlled trials are needed to establish the efficacy, comparative effectiveness, and potential cost savings of oral urea supplementation for hyponatremia.

Adaptation of the Brain to Hyponatremia and Its Clinical Implications

Hyponatremia is the most common electrolyte disorder, occurring in up to 25% of hospitalized patients. Hypo-osmotic hyponatremia when severe and left untreated invariably results in cell swelling, which can lead to fatal consequences, especially in the central nervous system. The brain is particularly vulnerable to the consequences of decreased extracellular osmolarity; because of being encased in the rigid skull, it cannot withstand persistent swelling. Moreover, serum sodium is the major determinant of extracellular ionic balance, which in turn governs crucial brain functions such as the excitability of neurons. For these reasons, the human brain has developed specific ways to adapt to hyponatremia and prevent brain edema. On the other hand, it is well known that rapid correction of chronic and severe hyponatremia can lead to brain demyelination, a condition known as osmotic demyelination syndrome. In this paper, we will discuss the mechanisms of brain adaptation to acute and chronic hyponatremia and the neurological symptoms of these conditions as well as the pathophysiology and prevention of osmotic demyelination syndrome.

Case report: Recovery and sequential imaging of a patient with osmotic demyelination syndrome

A 4-year-old neutered-male Australian Shepherd was presented to an emergency and referral hospital for an acute onset of neurologic signs and abnormal mentation. Seven days prior, the patient had been diagnosed with hypoadrenocorticism and was treated accordingly at another hospital. Based on recent clinical history, the neurologic signs were consistent with thalamic and brainstem deficits and suspected to be caused by osmotic demyelination syndrome secondary to rapid correction of hyponatremia. A brain MRI confirmed lesions consistent with osmotic demyelination syndrome. The patient's clinical signs initially worsened, and he required intensive nursing care with multimodal sedation, close monitoring of electrolytes and tailored fluid therapy. The patient recovered and was discharged on day seven of hospitalization. Four and a half months later, re-evaluation of the patient showed complete resolution of the neurological deficits with a now unremarkable neurological exam, and follow-up MRI revealed still present, yet improved bilateral thalamic lesions. This is the first known veterinary case report of sequential brain imaging of a dog that has recovered from osmotic demyelination syndrome. In humans, patients can have evidence of near to full clinical recovery, yet imaging findings may still be abnormal several months after recovery. This report details similar imaging findings in a canine with improved clinical signs, despite persistent lesions on brain MRI. Prognosis of canines with osmotic demyelination syndrome may be better than previously perceived, despite the severity of clinical signs and brain lesions apparent on MRI.

Astrocytes as Context for the Involvement of Myelin and Nodes of Ranvier in the Pathophysiology of Depression and Stress-Related Disorders

Astrocytes, despite some shared features as glial cells supporting neuronal function in gray and white matter, participate and adapt their morphology and neurochemistry in a plethora of distinct regulatory tasks in specific neural environments. In the white matter, a large proportion of the processes branching from the astrocytes' cell bodies establish contacts with oligodendrocytes and the myelin they form, while the tips of many astrocyte branches closely associate with nodes of Ranvier. Stability of myelin has been shown to greatly depend on astrocyte-to-oligodendrocyte communication, while the integrity of action potentials that regenerate at nodes of Ranvier has been shown to depend on extracellular matrix components heavily contributed by astrocytes. Several lines of evidence are starting to show that in human subjects with affective disorders and in animal models of chronic stress there are significant changes in myelin components, white matter astrocytes and nodes of Ranvier that have direct relevance to connectivity alterations in those disorders. Some of these changes involve the expression of connexins supporting astrocyte-to-oligodendrocyte gap junctions, extracellular matrix components produced by astrocytes around nodes of Ranvier, specific types of astrocyte glutamate transporters, and neurotrophic factors secreted by astrocytes that are involved in the development and plasticity of myelin. Future studies should further examine the mechanisms responsible for those changes in white matter astrocytes, their putative contribution to pathological connectivity in affective disorders, and the possibility of leveraging that knowledge to design new therapies for psychiatric disorders.

Life-Threatening Hyponatremia Secondary to Chronic Kratom Use: A Case Presentation

Hyponatremia is defined as a serum sodium concentration of less than 135 mEq/L. Severe hyponatremia is defined as a serum sodium concentration of less than 125 mEq/L and is a life-threatening complication that must be managed promptly to avoid irreversible neurological damage. One particular cause of hyponatremia is the ingestion of recreational drugs, such as 3,4-Methylenedioxymethamphetamine (MDMA), also known as Ecstasy. Another drug with limited understanding of its adverse effects on specific individuals and is widely available to purchase legally is Kratom (Mitragyna speciosa). Here, we present the case of severe hyponatremia secondary to the ingestion of Kratom. Kratom is believed to act on various pain-modulating receptors and may explain its role in causing hyponatremia. Unfortunately, Kratom remains poorly understood and underreported. Our case illustrates the need for further in-depth studies to determine the complete toxic profile of Kratom, providing awareness to clinicians in anticipation of severe complications that may develop.

Approach to the Patient: Hyponatremia and the Syndrome of Inappropriate Antidiuresis (SIAD)

Hyponatremia is the most common electrolyte disturbance seen in clinical practice, affecting up to 30% of acute hospital admissions, and is associated with significant adverse clinical outcomes. Acute or severe symptomatic hyponatremia carries a high risk of neurological morbidity and mortality. In contrast, chronic hyponatremia is associated with significant morbidity including increased risk of falls, osteoporosis, fractures, gait instability, and cognitive decline; prolonged hospital admissions; and etiology-specific increase in mortality. In this Approach to the Patient, we review and compare the current recommendations, guidelines, and literature for diagnosis and treatment options for both acute and chronic hyponatremia, illustrated by 2 case studies. Particular focus is concentrated on the diagnosis and management of the syndrome of inappropriate antidiuresis. An understanding of the pathophysiology of hyponatremia, along with a synthesis of the duration of hyponatremia, biochemical severity, symptomatology, and blood volume status, forms the structure to guide the appropriate and timely management of hyponatremia. We present 2 illustrative cases that represent common presentations with hyponatremia and discuss the approach to management of these and other causes of hyponatremia.

The Blood–Brain Barrier—A Key Player in Multiple Sclerosis Disease Mechanisms

Over the past decade, multiple sclerosis (MS), a chronic neuroinflammatory disease with severe personal and social consequences, has undergone a steady increase in incidence and prevalence rates worldwide. Despite ongoing research and the development of several novel therapies, MS pathology remains incompletely understood, and the prospect for a curative treatment continues to be unpromising in the near future. A sustained research effort, however, should contribute to a deeper understanding of underlying disease mechanisms, which will undoubtedly yield improved results in drug development. In recent years, the blood–brain barrier (BBB) has increasingly become the focus of many studies as it appears to be involved in both MS disease onset and progression. More specifically, neurovascular unit damage is believed to be involved in the critical process of CNS immune cell penetration, which subsequently favors the development of a CNS-specific immune response, leading to the classical pathological and clinical hallmarks of MS. The aim of the current narrative review is to merge the relevant evidence on the role of the BBB in MS pathology in a comprehensive and succinct manner. Firstly, the physiological structure and functions of the BBB as a component of the more complex neurovascular unit are presented. Subsequently, the authors review the specific alteration of the BBB encountered in different stages of MS, focusing on both the modifications of BBB cells in neuroinflammation and the CNS penetration of immune cells. Finally, the currently accepted theories on neurodegeneration in MS are summarized.

Astroglia in the Vulnerability and Maintenance of Alcohol Use Disorders

Changes induced in the morphology and the multiplicity of functional roles played by astrocytes in brain regions critical to the establishment and maintenance of alcohol abuse suggest that they make an important contribution to the vulnerability to alcohol use disorders. The understanding of the relevant mechanisms accounting for that contribution is complicated by the fact that alcohol itself acts directly on astrocytes altering their metabolism, gene expression, and plasticity, so that the ultimate result is a complex interaction of various cellular pathways, including intracellular calcium regulation, neuroimmune responses, and regulation of neurotransmitter and gliotransmitter release and uptake. The recent years have seen a steady increase in the characterization of several of the relevant mechanisms, but much remains to be done for a full understanding of the astrocytes' contribution to the vulnerability to alcohol dependence and abuse and for using that knowledge in designing effective therapies for AUDs.

Osmotic Demyelination Syndrome: Clinical, Neuroimaging Characteristics, and Outcomes in a Series of 18 Cases

Objective

To investigate the etiology, clinical as well as neuroimaging characteristics, and outcomes after proper treatment in a series of 18 patients with osmotic demyelination syndrome.

Methods

Medical records, including video records, of 18 patients with osmotic demyelination syndrome were retrospectively examined. Demographic and clinical information, imaging results, plans of management, and outcomes during the follow-up period were collected and analyzed.

Results

Eighteen patients, including 10 males and 8 females, were included in the present study. The mean age at diagnosis of CNS insult was 47.4 ± 13.3 years (ranged from 30 to 78 years). Etiologies included rapidly corrected hyponatremia (50%), alcoholism (27.8%), and others. Neurological manifestations included encephalopathy (61.1%), dysphonia (50%), extrapyramidal symptoms (38.9%), and seizures (22.2%). Neuroimaging results showed that 6 patients (33.3%) had central pontine myelinolysis, 5 (27.8%) had extrapontine myelinolysis, and 7 (38.9%) had both. After treatment, 12 patients showed improvement and the other 6 did not. Among these patients, those who showed symptoms of encephalopathy had a favorable outcome. The majority of those who presented with mental retardation, seizures, and no other symptoms recovered better than their counterparts who had other symptoms. Nine out of 11 patients with pseudobulbar paralysis and/or extrapyramidal symptoms showed improvement, but the other 2 did not show improvement. Five patients who did not improve after treatment during admission were followed up for 1-3 months with rehabilitation training recommended, and it was found that 3 showed significant improvement after training, and the other 2 did not respond to this training.

Conclusions

Osmotic demyelination syndrome is a complex disease entity due to a variety of etiologies, manifesting with symptoms involving diverse systems of the brain. Early identification and removal/correction of conditions leading to osmotic demyelination syndrome are the key to prevent and/or manage this disease.

Amelioration of clinical course and demyelination in the cuprizone mouse model in relation to ketogenic diet

Ketogenic diet (KD) is defined as a high-fat, low-carbohydrate diet with appropriate amounts of protein, which has broad neuroprotective effects. However, the mechanisms of ameliorating the demyelination and of the neuroprotective effects of KD have not yet been completely elucidated. Therefore, the present study investigated the protection mechanism of KD treatment in the cuprizone (bis-cyclohexanone oxalydihydrazone, CPZ)-induced demyelination mice model, with special emphasis on neuroinflammation. After the KD treatment, an increased ketone body level in the blood of mice was detected, and a significant increase in the distance traveled within the central area was observed in the open field test, which reflected the increased exploration and decreased anxiety of mice that received CPZ. The results of Luxol fast blue and myelin basic protein (MBP) immunohistochemistry staining for the evaluation of the myelin content within the corpus callosum revealed a noticeable increase in the number of myelinated fibers and myelin score after KD administration in these animals. Concomitant, the protein expressions of glial fibrillary acidic protein (GFAP, an astrocyte marker), ionized calcium-binding adaptor molecule 1 (Iba-1, a microglial marker), CD68 (an activated microglia marker) and CD16/32 (a M1 microglial marker) were down-regulated, while the expression of oligodendrocyte lineage transcription factor 2 (OLIG2, an oligodendrocyte precursor cells marker) was up-regulated by the KD treatment. In addition, the KD treatment not only reduced the level of the C-X-C motif chemokine 10 (CXCL10), which is correlated to the recruitment of activated microglia, but also inhibited the production of proinflammatory cytokines, including interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α), which are closely correlated to the M1 phenotype microglia. It is noteworthy, that the expression levels of histone deacetylase 3 (HADC3) and nod-like receptor pyrin domain containing 3 (NLRP3) significantly decreased after KD administration. In conclusion, these data demonstrate that KD decreased the reactive astrocytes and activated the microglia in the corpus callosum, and that KD inhibited the HADC3 and NLRP3 inflammasome signaling pathway in CPZ-treated mice. This suggests that the inhibition of the HADC3 and NLRP3 signaling pathway may be a novel mechanism by which KD exerts its protective actions for the treatment of demyelinating diseases.

Effect of alcohol on the central nervous system to develop neurological disorder: pathophysiological and lifestyle modulation can be potential therapeutic options for alcohol-induced neurotoxication

The central nervous system (CNS) is the major target for adverse effects of alcohol and extensively promotes the development of a significant number of neurological diseases such as stroke, brain tumor, multiple sclerosis (MS), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). Excessive alcohol consumption causes severe neuro-immunological changes in the internal organs including irreversible brain injury and it also reacts with the defense mechanism of the blood-brain barrier (BBB) which in turn leads to changes in the configuration of the tight junction of endothelial cells and white matter thickness of the brain. Neuronal injury associated with malnutrition and oxidative stress-related BBB dysfunction may cause neuronal degeneration and demyelination in patients with alcohol use disorder (AUD); however, the underlying mechanism still remains unknown. To address this question, studies need to be performed on the contributing mechanisms of alcohol on pathological relationships of neurodegeneration that cause permanent neuronal damage. Moreover, alcohol-induced molecular changes of white matter with conduction disturbance in neurotransmission are a likely cause of myelin defect or axonal loss which correlates with cognitive dysfunctions in AUD. To extend our current knowledge in developing a neuroprotective environment, we need to explore the pathophysiology of ethanol (EtOH) metabolism and its effect on the CNS. Recent epidemiological studies and experimental animal research have revealed the association between excessive alcohol consumption and neurodegeneration. This review supports an interdisciplinary treatment protocol to protect the nervous system and to improve the cognitive outcomes of patients who suffer from alcohol-related neurodegeneration as well as clarify the pathological involvement of alcohol in causing other major neurological disorders.

Relationship between Hyponatremia and Peripheral Neuropathy in Patients with Diabetes

OBJECTIVES

Hyponatremia is a common complication of diabetes. However, the relationship between serum sodium level and diabetic peripheral neuropathy (DPN) is unknown. This study was aimed at investigating the relationship between low serum sodium level and DPN in Chinese patients with type 2 diabetes mellitus.

METHODS

A retrospective study was performed on 1928 patients with type 2 diabetes between 2010 and 2018. The multivariate test was used to analyze the relationship between the serum sodium level and the nerve conduction function. A restricted cubic spline was used to flexibly model and visualize the relationship between the serum sodium level and DPN, followed by logistic regression with adjustment.

RESULTS

As the serum sodium level increased, the prevalence of DPN had a reverse J-curve distribution with the serum sodium levels (69.6%, 53.7%, 49.6%, 43.9%, and 49.7%; P = 0.001). Significant differences existed between the serum sodium level and the motor nerve conduction velocity, sensory nerve conduction velocity, part of compound muscle action potential, and sensory nerve action potential of the participants. Compared with hyponatremia, the higher serum sodium level was a relative lower risk factor for DPN after adjusting for several potential confounders (OR = 0.430, 95%CI = 0.220-0.841; OR = 0.386, 95%CI = 0.198-0.755; OR = 0.297, 95%CI = 0.152-0.580; OR = 0.376, 95%CI = 0.190-0.743; all P < 0.05). Compared with low-normal serum sodium groups, the high-normal serum sodium level was also a risk factor for DPN (OR = 0.690, 95%CI = 0.526-0.905, P = 0.007). This relationship was particularly apparent in male participants, those aged <65 years, those with a duration of diabetes of <10 years, and those with a urinary albumin - to - creatinine ratio (UACR) < 30 mg/g.

CONCLUSIONS

Low serum sodium levels were independently associated with DPN, even within the normal range of the serum sodium. We should pay more attention to avoid the low serum sodium level in patients with type 2 diabetes mellitus.

Lack of astrocytes hinders parenchymal oligodendrocyte precursor cells from reaching a myelinating state in osmolyte-induced demyelination

Demyelinated lesions in human pons observed after osmotic shifts in serum have been referred to as central pontine myelinolysis (CPM). Astrocytic damage, which is prominent in neuroinflammatory diseases like neuromyelitis optica (NMO) and multiple sclerosis (MS), is considered the primary event during formation of CPM lesions. Although more data on the effects of astrocyte-derived factors on oligodendrocyte precursor cells (OPCs) and remyelination are emerging, still little is known about remyelination of lesions with primary astrocytic loss. In autopsy tissue from patients with CPM as well as in an experimental model, we were able to characterize OPC activation and differentiation. Injections of the thymidine-analogue BrdU traced the maturation of OPCs activated in early astrocyte-depleted lesions. We observed rapid activation of the parenchymal NG2⁺ OPC reservoir in experimental astrocyte-depleted demyelinated lesions, leading to extensive OPC proliferation. One week after lesion initiation, most parenchyma-derived OPCs expressed breast carcinoma amplified sequence-1 (BCAS1), indicating the transition into a pre-myelinating state. Cells derived from this early parenchymal response often presented a dysfunctional morphology with condensed cytoplasm and few extending processes, and were only sparsely detected among myelin-producing or mature oligodendrocytes. Correspondingly, early stages of human CPM lesions also showed reduced astrocyte numbers and non-myelinating BCAS1⁺ oligodendrocytes with dysfunctional morphology. In the rat model, neural stem cells (NSCs) located in the subventricular zone (SVZ) were activated while the lesion was already partially repopulated with OPCs, giving rise to nestin⁺ progenitors that generated oligodendroglial lineage cells in the lesion, which was successively repopulated with astrocytes and remyelinated. These nestin⁺ stem cell-derived progenitors were absent in human CPM cases, which may have contributed to the inefficient lesion repair. The present study points to the importance of astrocyte-oligodendrocyte interactions for remyelination, highlighting the necessity to further determine the impact of astrocyte dysfunction on remyelination inefficiency in demyelinating disorders including MS.

Central pontine myelinolysis during treatment of hyperglycemic hyperosmolar syndrome: a case report

Background

Central pontine myelinolysis (CPM) is a non-inflammatory demyelinating lesion of the pons. CPM and extrapontine demyelination (EPM) are together termed osmotic demyelination syndrome (ODS), a known and serious complication of acute correction of hyponatremia. Conversely, hyperglycemic hyperosmolarity syndrome (HHS) develops in patients with type 2 diabetes who still have some insulin secretory ability due to infection, non-compliance with treatment, drugs, and coexisting diseases, and is often accompanied by ketosis. HHS represents a life-threatening endocrine emergency (mortality rate, 10–50%) associated with marked hyperglycemia and severe dehydration. HHS may develop ODS, and some cases have been associated with hypernatremia.

Case presentation

The patient was an 87-year-old woman with hyperglycemia, dehydration, malnutrition, and potential thrombus formation during long-term bed rest. HHS was suspected to have developed due to progression of hyperglycemia and dehydration caused by pneumonia. Furthermore, ketoacidosis developed from ketosis and prerenal renal failure associated with circulating hypovolemia shock, which was also associated with disseminated intravascular coagulation. Treatment was started with continuous intravenous injection of fast-acting insulin and low-sodium replacement fluid. In addition, ceftriaxone sodium hydrate, heparin sodium, thrombomodulin α, human serum albumin, and dopamine hydrochloride were administered. Blood glucose, serum sodium, serum osmolality, and general condition (including vital, infection/inflammatory findings, and disseminated intravascular coagulation) improved promptly, but improvements in disturbance of consciousness were poor. Diffusion-weighted imaging of the brain 72 h after starting treatment showed no obvious abnormalities, but high-intensity signals in the midline of the pons became apparent 30 days later, leading to definitive diagnosis of CPM.

Conclusions

Fluctuation of osmotic pressure by treatment from hyperosmolarity due to hyperglycemia and hypernatremia in the presence of risk factors such as malnutrition, severe illness, and metabolic disorders may be a cause of CPM onset. When treating HHS with risk factors, the possibility of progression to ODS needs to be kept in mind.

Cuprizone-Induced Demyelination in Mouse Hippocampus Is Alleviated by Ketogenic Diet

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Recently, ketogenic diet (KD) supplementation has attracted great interest. Therefore, we established the cuprizone (CPZ)-induced demyelination mouse model to investigate the possible neuroprotective effect of KD on the hippocampus of mice. We found that KD significantly elevated the level of serum β-hydroxybutyric acid, improved behavioral and motor abnormalities, and impaired the spatial learning and memory of CPZ-induced demyelination mice. Meanwhile, KD lessened the hippocampal demyelination by enhancing the expression of mature oligodendrocytes (OLs), which was revealed by the elevated expression of MBP and CNPase, as well as the luxol fast blue-staining intensity. Furthermore, KD inhibits the activation of microglia (especially M1-like microglia) and reactive astrocytes. Interestingly, KD attenuated the CPZ-induced oxidative stress by decreasing the malondialdehyde (MDA) content and restoring the glutathione (GSH) levels. In addition, the double immunofluorescence staining revealed that KD enhanced the expression of SIRT1 in astrocytes, microglia, and mature oligodendrocytes. Concomitantly, Western blot demonstrated that KD increased the expression of SIRT1, phosphorylated-AKT, mTOR, and PPAR-γ. In conclusion, KD exerted a neuroprotective effect on CPZ-induced demyelination mice, and this activity was associated with the modulation of the SIRT1/PPAR-γ and SIRT1/P-Akt/mTOR pathways.

Multifocal Necrotizing Leukoencephalopathy: Expanding the Clinicopathologic Spectrum

Multifocal necrotizing leukoencephalopathy (MNL) is a rare condition typically described in patients undergoing chemotherapy or with HIV/AIDS. As a pathologic entity, it is characterized by multiple small foci of necrosis typically within white matter of the pons and occasionally in other areas. Herein we describe findings in 6 patients with MNL, 5 diagnosed at postmortem examination and 1 by surgical biopsy. Histopathologic features were characteristic, with generally small foci of necrosis, most frequently within the pontine base, although larger lesions were seen in the frontal white matter and basal ganglia. Axonal swellings, occasional dystrophic calcification and minimal microglial activity or reactive responses were common. Glial fibrillary acidic protein immunoreactivity was absent or markedly reduced within the lesions although it remained well defined in the surrounding areas. The underlying clinical circumstances ranged from HIV/AIDS, hematologic malignancy, chemotherapy for malignancies to postcardiac transplant, the latter reported for the first time. A significant common thread identified in our cases was altered immune status. A second common factor, which has also been previously implicated, was the presence of significant ongoing infection or sepsis. The role of concurrent inflammatory processes, specifically proinflammatory cytokine release in the context of these complex clinical scenarios is discussed with possible pathogenetic considerations.

Astrocyte and Oligodendrocyte Cross-Talk in the Central Nervous System

Over the last decade knowledge of the role of astrocytes in central nervous system (CNS) neuroinflammatory diseases has changed dramatically. Rather than playing a merely passive role in response to damage it is clear that astrocytes actively maintain CNS homeostasis by influencing pH, ion and water balance, the plasticity of neurotransmitters and synapses, cerebral blood flow, and are important immune cells. During disease astrocytes become reactive and hypertrophic, a response that was long considered to be pathogenic. However, recent studies reveal that astrocytes also have a strong tissue regenerative role. Whilst most astrocyte research focuses on modulating neuronal function and synaptic transmission little is known about the cross-talk between astrocytes and oligodendrocytes, the myelinating cells of the CNS. This communication occurs via direct cell-cell contact as well as via secreted cytokines, chemokines, exosomes, and signalling molecules. Additionally, this cross-talk is important for glial development, triggering disease onset and progression, as well as stimulating regeneration and repair. Its critical role in homeostasis is most evident when this communication fails. Here, we review emerging evidence of astrocyte-oligodendrocyte communication in health and disease. Understanding the pathways involved in this cross-talk will reveal important insights into the pathogenesis and treatment of CNS diseases.

Role of Risk Factors in Developing Osmotic Demyelination Syndrome During Correction of Hyponatremia: A Case Study

This case report describes a 57-year-old man who presented first with lethargy and dysarthria due to hyponatremia resulting from poor intake and diuretics. One week after discharge, he returned with confusion, ataxia and dysphagia, and he ultimately turned out to have developed an osmotic demyelination syndrome (ODS). In his first hospital admission, his serum sodium was corrected without new neurological symptoms occurring. In retrospect, he had several risk factors for the development of ODS during the correction of hyponatremia. The serum sodium correction rate only briefly exceeded the recommended limits. This case underlines that (1) extra awareness of the serum sodium correction rate is warranted in patients with risk factors, (2) factors other than sodium can play an important role in the development of ODS and (3) that the manifestations of ODS can be delayed substantially after an incident of osmotic stress.

Osmotic Demyelination: From an Oligodendrocyte to an Astrocyte Perspective

Osmotic demyelination syndrome (ODS) is a disorder of the central myelin that is often associated with a precipitous rise of serum sodium. Remarkably, while the myelin and oligodendrocytes of specific brain areas degenerate during the disease, neighboring neurons and axons appear unspoiled, and neuroinflammation appears only once demyelination is well established. In addition to blood‒brain barrier breakdown and microglia activation, astrocyte death is among one of the earliest events during ODS pathology. This review will focus on various aspects of biochemical, molecular and cellular aspects of oligodendrocyte and astrocyte changes in ODS-susceptible brain regions, with an emphasis on the crosstalk between those two glial cells. Emerging evidence pointing to the initiating role of astrocytes in region-specific degeneration are discussed.

Dietary salt promotes ischemic brain injury and is associated with parenchymal migrasome formation

Sodium chloride promotes vascular fibrosis, arterial hypertension, pro-inflammatory immune cell polarization and endothelial dysfunction, all of which might influence outcomes following stroke. But despite enormous translational relevance, the functional importance of sodium chloride in the pathophysiology of acute ischemic stroke is still unclear. In the current study, we show that high-salt diet leads to significantly worse functional outcomes, increased infarct volumes, and a loss of astrocytes and cortical neurons in acute ischemic stroke. While analyzing the underlying pathologic processes, we identified the migrasome as a novel, sodium chloride-driven pathomechanism in acute ischemic stroke. The migrasome was previously described in vitro as a migrating organelle, which incorporates and dispatches cytosol of surrounding cells and plays a role in intercellular signaling, whereas a pathophysiological meaning has not been elaborated. We here confirm previously reported characteristics of the migrasome in vivo. Immunohistochemistry, electron microscopy and proteomic analyses further demonstrate that the migrasome incorporates and dispatches cytosol of surrounding neurons following stroke. The clinical relevance of these findings is emphasized by neuropathological examinations, which detected migrasome formation in infarcted brain parenchyma of human stroke patients. In summary, we demonstrate that high-salt diet aggravates stroke outcomes, and we characterize the migrasome as a novel mechanism in acute stroke pathophysiology.

Tongue fasciculations with denervation pattern in osmotic demyelination syndrome: a case report of diagnostic dilemma

Background

The pathogenesis of osmotic demyelination syndrome is not completely understood and usually occurs with severe and prolonged hyponatremia, particularly with rapid correction. It can occur even in normonatremic patients, especially who have risk factors like alcoholism, malnutrition and liver disease. Bilateral tongue fasciculations with denervation pattern in electromyogram is a manifestation of damage to the hypoglossal nucleus or hypoglossal nerves. Tongue fasciculations were reported rarely in some cases of osmotic demyelination syndrome, but the exact mechanism is not explained.

Case presentation

A 32-year-old Sri Lankan male, with a history of daily alcohol consumption and binge drinking, presented with progressive difficulty in walking, dysphagia, dysarthria and drooling of saliva and alteration of consciousness. On examination he was akinetic and rigid resembling Parkinsonism with a positive Babinski sign. Clinical features were diagnostic of osmotic demyelination syndrome and MRI showed abnormal signal intensity within the central pons and basal ganglia. He also had tongue fasciculations. The electromyogram showed denervation pattern in the tongue with normal findings in the limbs. Medulla and bilateral hypoglossal nerves were normal in MRI.

Conclusion

We were unable to explain the exact mechanism for the denervation of the tongue, which resulted in fasciculations in this chronic alcoholic patient who developed osmotic demyelination syndrome. The hypoglossal nuclei are located in the dorsal medulla and radiologically undetected myelinolysis of the medulla is a possibility. Hypoglossal nerve damage caused by methanol or other toxic substances that can contaminate regular ethyl alcohol is another possibility, as it is known to cause neurological and radiological features similar to osmotic demyelination syndrome with long-term exposure. So these toxic substances might play a role in chronic alcoholic patients with central pontine myelinolysis.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3287-8) contains supplementary material, which is available to authorized users.

Treatment response in osmotic demyelination syndrome presenting as severe parkinsonism, ptosis and gaze palsy

Osmotic demyelination syndrome commonly affects the pons and infrequently involves the extrapontine region. We report a patient with severe hyponatraemia who developed osmotic demyelination syndrome as a consequence of rapid sodium correction. The condition manifested as acute severe parkinsonism, bilateral ptosis and gaze impairment. MRI revealed typical features of central pontine and extrapontine myelinolysis. The patient improved gradually after treatment with a combination of levodopa, intravenous immunoglobulin and dexamethasone. However, it is important to emphasise that the improvement of neurological symptoms is not necessarily causal with these experimental therapies.

The Dilemma of Inadvertent Pontine Demyelinosis: A Review of Literature

Osmotic demyelination syndrome is classically associated with a swift adjustment of previously low serum sodium levels which lead to cellular dehydration and subsequent neurological insult. We also review the epidemiology, different postulations to explain the underlying pathophysiology, current diagnostic modalities, subsequent therapeutic interventions used to manage this phenomenon, and the resultant prognosis of this ailment.

Pharmacological management of hyponatremia

INTRODUCTION

Hyponatremia is the most common electrolyte disorder with a prevalence of up to 30% in hospitalized patients. Furthermore, it is associated with increased morbidity and mortality.

AREAS COVERED

This review discusses the efficacy and side effects of the currently available treatment options for hyponatremia and the differences in the pharmacological approach between the European and USA guidelines. Additionally, the authors provide their expert perspectives on current treatment strategies and what they expect from this field in the future.

EXPERT OPINION

Several pharmacological options are available for the treatment of hyponatremia, but data from trials examining and comparing these treatments are missing. Regarding chronic hyponatremia, the role of vaptans should be further analyzed, focusing on comparisons with other active treatments on patient-relevant outcomes and not only on serum sodium concentration. Clinicians should be cautious to an overly rapid increase in serum sodium levels with all available treatment strategies. Finally, it is important to ascertain whether correction of serum sodium levels improves mortality in hyponatremic patients.

Astroglial Modulation of Hydromineral Balance and Cerebral Edema

Maintenance of hydromineral balance (HB) is an essential condition for life activity at cellular, tissue, organ and system levels. This activity has been considered as a function of the osmotic regulatory system that focuses on hypothalamic vasopressin (VP) neurons, which can reflexively release VP into the brain and blood to meet the demand of HB. Recently, astrocytes have emerged as an essential component of the osmotic regulatory system in addition to functioning as a regulator of the HB at cellular and tissue levels. Astrocytes express all the components of osmoreceptors, including aquaporins, molecules of the extracellular matrix, integrins and transient receptor potential channels, with an operational dynamic range allowing them to detect and respond to osmotic changes, perhaps more efficiently than neurons. The resultant responses, i.e., astroglial morphological and functional plasticity in the supraoptic and paraventricular nuclei, can be conveyed, physically and chemically, to adjacent VP neurons, thereby influencing HB at the system level. In addition, astrocytes, particularly those in the circumventricular organs, are involved not only in VP-mediated osmotic regulation, but also in regulation of other osmolality-modulating hormones, including natriuretic peptides and angiotensin. Thus, astrocytes play a role in local/brain and systemic HB. The adaptive astrocytic reactions to osmotic challenges are associated with signaling events related to the expression of glial fibrillary acidic protein and aquaporin 4 to promote cell survival and repair. However, prolonged osmotic stress can initiate inflammatory and apoptotic signaling processes, leading to glial dysfunction and a variety of brain diseases. Among many diseases of brain injury and hydromineral disorders, cytotoxic and osmotic cerebral edemas are the most common pathological manifestation. Hyponatremia is the most common cause of osmotic cerebral edema. Overly fast correction of hyponatremia could lead to central pontine myelinolysis. Ischemic stroke exemplifies cytotoxic cerebral edema. In this review, we summarize and analyze the osmosensory functions of astrocytes and their implications in cerebral edema.

Molecular Neuropathology of Astrocytes and Oligodendrocytes in Alcohol Use Disorders

Postmortem studies reveal structural and molecular alterations of astrocytes and oligodendrocytes in both the gray and white matter (GM and WM) of the prefrontal cortex (PFC) in human subjects with chronic alcohol abuse or dependence. These glial cellular changes appear to parallel and may largely explain structural and functional alterations detected using neuroimaging techniques in subjects with alcohol use disorders (AUDs). Moreover, due to the crucial roles of astrocytes and oligodendrocytes in neurotransmission and signal conduction, these cells are very likely major players in the molecular mechanisms underpinning alcoholism-related connectivity disturbances between the PFC and relevant interconnecting brain regions. The glia-mediated etiology of alcohol-related brain damage is likely multifactorial since metabolic, hormonal, hepatic and hemodynamic factors as well as direct actions of ethanol or its metabolites have the potential to disrupt distinct aspects of glial neurobiology. Studies in animal models of alcoholism and postmortem human brains have identified astrocyte markers altered in response to significant exposures to ethanol or during alcohol withdrawal, such as gap-junction proteins, glutamate transporters or enzymes related to glutamate and gamma-aminobutyric acid (GABA) metabolism. Changes in these proteins and their regulatory pathways would not only cause GM neuronal dysfunction, but also disturbances in the ability of WM axons to convey impulses. In addition, alcoholism alters the expression of astrocyte and myelin proteins and of oligodendrocyte transcription factors important for the maintenance and plasticity of myelin sheaths in WM and GM. These changes are concomitant with epigenetic DNA and histone modifications as well as alterations in regulatory microRNAs (miRNAs) that likely cause profound disturbances of gene expression and protein translation. Knowledge is also available about interactions between astrocytes and oligodendrocytes not only at the Nodes of Ranvier (NR), but also in gap junction-based astrocyte-oligodendrocyte contacts and other forms of cell-to-cell communication now understood to be critical for the maintenance and formation of myelin. Close interactions between astrocytes and oligodendrocytes also suggest that therapies for alcoholism based on a specific glial cell type pathology will require a better understanding of molecular interactions between different cell types, as well as considering the possibility of using combined molecular approaches for more effective therapies.

Chloride imbalance is involved in the pathogenesis of optic neuritis in neuromyelitis optica

Chloride imbalance between the serum and the cerebrospinal fluid (CSF) has been recently shown to exist in the acute phase of neuromyelitis optica (NMO). In this report, we studied the relation between the quotient of chloride (Q_Cl) and the severity of optic neuritis (ON) in NMO patients. There was a positive correlation (R = 0.67; p < 0.05) between Q_Cl and the length of ON-lesion. The visual prognosis also showed a positive correlation with Q_Cl in the acute phase (R = 0.58; p < 0.05). These results support the theory that chloride imbalance between serum and CSF may trigger the ON in NMO spectrum disorders.

Serum sodium and chloride are inversely associated with dyskinesia in Parkinson's disease patients

OBJECTIVE

We aim to report and evaluate the associations between serum sodium and chloride and dyskinesia in patients with Parkinson's disease. One hundred and two patients with Parkinson's disease were enrolled in this study.

METHODS

Patients' serum electrolytes including sodium, calcium, potassium, magnesium, and chloride were measured. Other demographic information was collected, and Unified Parkinson's disease rating scale and Hoehn and Yahr stage scale were also performed.

RESULTS

Patients with dyskinesia tended to have longer duration of disease, higher daily levodopa-equivalent dose, and Hoehn-Yahr stage, with lower serum sodium than those without dyskinesia. Spearman correlation analyses showed that serum sodium inversely correlated with duration of disease (r = -.218, p = .028), and positively correlated with serum chloride levels (r = .565, p < .001). Univariate logistic regression analysis found that duration of disease, daily levodopa-equivalent dose, serum sodium, and serum chloride were associated with dyskinesia in Parkinson's disease patients (p < .05 for all). After adjusting for age, sex, age at onset of Parkinson's disease, medical history, and other covariates, serum sodium and chloride were still associated with dyskinesia, with corresponding Odd ratios 0.783 (95% confidence intervals, 0.642-0.955) and 0.796 (95% confidence intervals, 0.652-0.972), respectively.

CONCLUSION

Our findings indicated that serum sodium and chloride levels were inversely associated with dyskinesia in patients with Parkinson's disease. Further studies with large samples and range of serum sodium and chloride are needed.

Prednisone alleviates demyelination through regulation of the NLRP3 inflammasome in a C57BL/6 mouse model of cuprizone-induced demyelination

Myelin abnormalities, oligodendrocyte damage, and concomitant glia activation are common in demyelinating diseases of the central nervous system (CNS). Increasing evidence has demonstrated that the inflammatory response triggers demyelination and gliosis in demyelinating disorders. Numerous clinical interventions, including those used to treat multiple sclerosis (MS), have confirmed prednisone (PDN) as a powerful anti-inflammatory drug that reduces the inflammatory response and promotes tissue repair in multiple inflammation sites. However, the underlying mechanism of PDN in ameliorating myelin damage is not well understood. In our study, a cuprizone (CPZ)-induced demyelinated mouse model was used to explore the mechanism of the protection provided by PDN. Open-field tests showed that CPZ-treated mice exhibited significantly increased anxiety and decreased exploration. However, PDN improved emotional behavior, as evidenced by an increase in the total distance traveled, and central distance traveled as well as the mean amount of time spent in the central area. CPZ-induced demyelination was observed to be alleviated in PDN-treated mice based on luxol fast blue (LFB) staining and myelin basic protein (MBP) expression analyses. In addition, PDN reduced astrocyte and microglia activation in the corpus callosum. Furthermore, we demonstrated that PDN inhibited the Nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome signaling pathway and related inflammatory cytokines and chemokines, including TNF-α, CCL8, CXCL10 and CXCL16. PDN also reduced the serum corticosterone levels in the CPZ-treated mice. Taken together, these results suggest that inhibition of the NLRP3 signaling pathway may be a novel mechanism by which PDN exerts its protective actions in demyelinating diseases.

Prevention of the Osmotic Demyelination Syndrome After Liver Transplantation: A Multidisciplinary Perspective

The osmotic demyelination syndrome (ODS) is a serious neurologic condition that occurs in the setting of rapid correction of hyponatremia. It presents with protean manifestations, from encephalopathy to the "locked-in" syndrome. ODS can complicate liver transplantation (LT), and its incidence may increase with the inclusion of serum sodium as a factor in the Mayo End-Stage Liver Disease score. A comprehensive understanding of risk factors for the development of ODS in the setting of LT, along with recommendations to mitigate the risk of ODS, are necessary. The literature to date on ODS in the setting of LT was reviewed. Major risk factors for the development of ODS include severe pretransplant hyponatremia (serum sodium [SNa] < 125 mEq/L), the magnitude of change in SNa pre- versus posttransplant, higher positive intraoperative fluid balance, and the presence of postoperative hemorrhagic complications. Strategies to reduce the risk of ODS include correcting hyponatremia pretransplant via fluid restriction and/or ensuring an appropriate rate of increase from the preoperative SNa via close attention to fluid and electrolyte management both during and after surgery. Multidisciplinary management involving transplant hepatology, nephrology, neurology, surgery, and anesthesiology/critical care is key to performing LT safely in patients with hyponatremia.

Hyponatremia and the Brain

Hyponatremia is defined by low serum sodium concentration and is the most common electrolyte disorder encountered in clinical practice. Serum sodium is the main determinant of plasma osmolality, which, in turn, affects cell volume. In the presence of low extracellular osmolality, cells will swell if the adaptation mechanisms involved in the cell volume maintenance are inadequate. The most dramatic effects of hyponatremia on the brain are seen when serum sodium concentration decreases in a short period, allowing little or no adaptation. The brain is constrained inside a nonextensible envelope; thus, brain swelling carries a significant morbidity because of the compression of brain parenchyma over the rigid skull. Serum sodium concentration is an important determinant of several biological pathways in the nervous system, and recent studies have suggested that hyponatremia carries a significant risk of neurological impairment even in the absence of brain edema. The brain can also be affected by the treatment of hyponatremia, which, if not undertaken cautiously, could lead to osmotic demyelination syndrome, a rare demyelinating brain disorder that occurs after rapid correction of severe hyponatremia. This review summarizes the pathophysiology of brain complications of hyponatremia and its treatment.

Osmotic demyelination syndrome in type 1 diabetes in the absence of dyselectrolytaemia: an overlooked complication?

Central pontine myelinolysis (CPM) is a demyelinating disorder of central nervous system which involves central portion of the pons and sometimes extrapontine areas also. It is commonly reported in settings of hyponatraemia or its rapid correction, but in the last few years it has also been reported in patients with diabetes in the absence of electrolyte disturbances or correction of serum osmolality. Here we report a case of a 20-year-old female patient, with a known history of type 1 diabetes mellitus, who presented with acute onset spastic quadriparesis with dysarthria and mild ataxia which evolved over 2 weeks. Her MRI brain showed well-defined, bilateral symmetric hyperintense lesion involving central pons showing area of diffusion restriction which was consistent with CPM. Patient was treated conservatively and improved over a period of few weeks. To diagnose more number of cases, we should not overlook CPM in patients with diabetes.

Osmotic Stress-Induced Defective Glial Proteostasis Contributes to Brain Demyelination after Hyponatremia Treatment

Adequate protein folding is necessary for normal cell function and a tightly regulated process that requires proper intracellular ionic strength. In many cell types, imbalance between protein synthesis and degradation can induce endoplasmic reticulum (ER) stress, which if sustained, can in turn lead to cell death. In nematodes, osmotic stress induces massive protein aggregation coupled with unfolded protein response and ER stress. In clinical practice, patients sustaining rapid correction of chronic hyponatremia are at risk of osmotic demyelination syndrome. The intense osmotic stress sustained by brain cells is believed to be the major risk factor for demyelination resulting from astrocyte death, which leads to microglial activation, blood-brain barrier opening, and later, myelin damage. Here, using a rat model of osmotic demyelination, we showed that rapid correction of chronic hyponatremia induces severe alterations in proteostasis characterized by diffuse protein aggregation and ubiquitination. Abrupt correction of hyponatremia resulted in vigorous activation of both the unfolded protein response and ER stress accompanied by increased autophagic activity and apoptosis. Immunofluorescence revealed that most of these processes occurred in astrocytes within regions previously shown to be demyelinated in later stages of this syndrome. These results identify osmotic stress as a potent protein aggregation stimuli in mammalian brain and further suggest that osmotic demyelination might be a consequence of proteostasis failure on severe osmotic stress.

Neurologic manifestations of major electrolyte abnormalities

The brain operates in an extraordinarily intricate environment which demands precise regulation of electrolytes. Tight control over their concentrations and gradients across cellular compartments is essential and when these relationships are disturbed neurologic manifestations may develop. Perturbations of sodium are the electrolyte disturbances that most often lead to neurologic manifestations. Alterations in extracellular fluid sodium concentrations produce water shifts that lead to brain swelling or shrinkage. If marked or rapid they can result in profound changes in brain function which are proportional to the degree of cerebral edema or contraction. Adaptive mechanisms quickly respond to changes in cell size by either increasing or decreasing intracellular osmoles in order to restore size to normal. Unless cerebral edema has been severe or prolonged, correction of sodium disturbances usually restores function to normal. If the rate of correction is too rapid or overcorrection occurs, however, new neurologic manifestations may appear as a result of osmotic demyelination syndrome. Disturbances of magnesium, phosphate and calcium all may contribute to alterations in sensorium. Hypomagnesemia and hypocalcemia can lead to weakness, muscle spasms, and tetany; the weakness from hypophosphatemia and hypomagnesemia can impair respiratory function. Seizures can be seen in cases with very low concentrations of sodium, magnesium, calcium, and phosphate.

Physiopathology, clinical diagnosis, and treatment of hyponatremia

Hyponatremia is the commonest electrolyte disorder encountered in clinical practice. It develops when the mechanisms regulating water and electrolyte handling are impaired, which in many instances occur in the setting of concurrent diseases such as heart failure, liver failure, renal failure etc… Hyponatremia as an electrolyte disorder has several specificities: when profound it can be quickly fatal and when moderate it carries a high risk of mortality and morbidity, but at the same time incorrect treatment of profound hyponatremia can lead to debilitating neurological disease and it remains unclear if treatment of moderate hyponatremia is associated with a decrease in mortality and morbidity. A proper diagnosis is the keystone for an adequate treatment for hyponatremia and in the last few years many diagnosis algorithms have been developed to aid in the evaluation of the hyponatremic patient. Also because of the availability of vasopressin receptor antagonists and the advances made in the research regarding complications associated with hyponatremia treatment, new treatment recommendations have been published recently by several panels. This review will discuss the physiopathology, epidemiology, and clinical manifestations of hyponatremia and also the diagnosis and the treatment of this disorder with special emphasis on the complication from overly rapid correction of hyponatremia.