[Central pontine myelinolysis developed during alcohol withdrawal in a chronic alcoholic with hyperosmolar hyperglycemic state]

We present a 46-year-old man with central pontine myelinolysis (CPM). He had been diagnosed with diabetes mellitus and chronic pancreatitis. He had drunk more than 1.2 l of Japanese sake daily for 20 years and more. He developed slight reduction of consciousness, dysarthria and truncal ataxia 7 days after he stopped drinking. The laboratory data on admission showed hyperosmolar hyperglycemic state, according to the following findings; glucose 1,058 mg/dl, serum osmolality 328 mOsm/l and serum sodium 119 mEq/l. According as administration of acetic Ringer's solution and insulin injection, the laboratory data 14 hours after admission showed glucose 235 mg/dl, serum osmolality 290 mOsm/l and serum sodium 131 mEq/l. The initial diffusion weighted images (DWI) on MRI revealed a small high signal intensity spot in the pons. The second DWI after 14 days revealed a trident-shaped hyperintensity in the pons that was compatible with CPM. His symptoms showed no remarkable changes, but susceptibility weighted images of MRI after 4 months revealed low signal intensity area in the CPM lesion that indicated pontine hemorrhage. We speculate that marked fluctuation of serum osmotic pressure associated with the rapid change of the serum glucose had a significant role in the pathogenesis of the present case. Therefore, we recommend gradual correction of serum glucose and serum osmolality to maintain less than 12 mEq/l/day as correction of chronic hyponatremia in to prevent and ameliorate pathologic condition of CPM.

A study of the pathogenesis and prevention of central pontine myelinolysis in a rat model

The development of central pontine myelinolysis was studied in rats. Severe hyponatraemia was induced using vasopressin tannate and 2.5% dextrose in water and then rapidly corrected with hypertonic saline alone, hypertonic saline and dexamethasone simultaneously, or hypertonic saline plus dexamethasone 24 h later. The permeability of the blood-brain barrier was evaluated using the extravasation of Evans blue dye and the expression of inducible nitric oxide synthase (iNOS) in the brain was examined using Western blot analysis. Histological sections were examined for demyelinating lesions. In rats receiving hypertonic saline alone, Evans blue dye content and expression of iNOS began to increase 6 and 3 h, respectively, after rapid correction of hyponatraemia and demyelinating lesions were seen. When dexamethasone was given simultaneously with hypertonic saline, these increases were inhibited and demyelinating lesions were absent. These effects were lost if dexamethasone injection was delayed. Disruption of the blood-brain barrier and increased iNOS expression may be involved in the pathogenesis of central pontine myelinolysis, and early treatment with dexamethasone may help prevent the development of central pontine myelinolysis.

[Central pontine and extrapontine myelinolysis (review)]

The paper addresses the etiopathogenetic, clinical and therapeutical peculiarities of central pontine and extrapontine myelinosis. The causes of these disorders are analyzed. A role of the inadequate correction of hyponatremia, especially in alcoholism, in the genesis of myelinosis is emphasized. Neurological disorders in such patients are reviewed with highlighting the clinical and prognostic heterogeneity of central pontine and extrapontine myelinosis. The author suggests the recommendations on patient management and perfect correction of hyponatremia.

[Prevention of central pontine myelinolysis in rats by early treatment with dexamethasone]

OBJECTIVE

To explore the effect and mechanism of dexamethasone (DEX) in the prevention of central pontine myelinolysis (CPM) in rats.

METHODS

Hyponatremia was induced in rat by subcutaneous injection of Vasopressin Tannate and intraperitoneal injection of 2.5% dextrose in water for 3 d, the rats of Group A received a bolus of 1 mol/L NaCl (2 ml/kg) and DEX (5 mg/kg) simultaneously at the 4th day; the rats of Group B were treated with DEX after 24 h of the injection of 1 mol/L NaCl; the rats in Group C received a bolus of 1 mol/L NaCl and saline simultaneously; Group D was the control group. The demyelinative lesions were evaluated by myelin staining. The Evans blue (EB) contents of brain were detected to evaluate the blood-brain-barrier permeability after rapid correction of hyponatremia. The expression of inducible nitric oxide synthase (iNOS) in brains was evaluated by Western blotting.

RESULT

CPM was induced successfully in rats. The EB contents of Group A, B and C had no significant difference at 0 h after injection of hypertonic saline compared with Group D. The EB contents of Group C began to increase significantly at 6 h after injection of hypertonic saline, peaked at 24 h; the expression of iNOS in brains began to increase after 3 h after the rapid correction of hyponatremia. The rate of morbidity in Group C was 66.7%. The demyelinative lesions were rarely seen in Group A, the EB contents of brain decreased significantly compared with Group C at the same time point (P<0.05), the iNOS expression was also inhibited. DEX could not prevent the attack of CPM at Group B, the rate of morbidity (75%) had no significant difference compared with Group C (P>0.05).

CONCLUSION

Early treatment with DEX can protect blood-brain-barrier and inhibit the expression of iNOS to prevent the attack of CPM.

Mechanisms and therapy of osmotic demyelination

Central pontine myelinolysis (CPM) is a rare but serious demyelinative disease that is associated with rapid correction of chronic hyponatremia. Disruption of the blood-brain barrier (BBB) following a rapid increase in serum sodium concentration is considered to play a critical role in the pathogenesis of osmotic demyelination. We investigated the protective effect of dexamethasone (DEX) on osmotic demyelination in rats. After rapid correction of chronic hyponatremia, rats displayed serious neurologic impairments and demyelinative lesions were observed in various brain regions. Conversely, DEX-treated rats exhibited minimal neurologic impairments and demyelinative lesions were rarely seen in the brain. A marked extravasation of endogenous immunoglobulin G and Evans blue dye were observed in the brains of rats that did not receive DEX, indicating disruption of the BBB, but this was not observed in DEX-treated rats. These results indicate that DEX is effective in preventing osmotic demyelination by inhibiting BBB disruption, and suggest that DEX might be useful for the prevention of CPM in clinical practice.

Protective effect of dexamethasone on osmotic-induced demyelination in rats

Central pontine myelinolysis (CPM) is a serious demyelination disease commonly associated with the rapid correction of hyponatremia. Although its pathogenesis remains unclear, the disruption of the blood-brain barrier (BBB) as a consequence of a rapid increase in serum sodium concentration is considered to play a critical role. Since glucocorticoids are known to influence BBB permeability and prevent its disruption as a result of hypertension or hyperosmolarity, we investigated whether dexamethasone (DEX) could protect against osmotic demyelination in an animal model of CPM. Hyponatremia was induced in rats by liquid diet feeding and dDAVP infusion. Seven days later, the animals' hyponatremia was rapidly corrected by injecting a bolus of hypertonic saline intraperitoneally. Rats subjected to this treatment displayed serious neurological impairment and 77% died within 5 days of rapid correction of their hyponatremia; demyelinative lesions were observed in various brain regions in these animals. On the other hand, rats that were treated with DEX (2 mg/kg, 0 and 6 h after hypertonic saline injection) exhibited minimal neurological impairment and all were alive after 5 days. Demyelinative lesions were rarely seen in the brains of DEX-treated rats. A marked extravasation of endogenous IgG was observed in the demyelinative lesions in the brains of rats that did not receive DEX, indicating disruption of the BBB, but was not observed in DEX-treated rats. Furthermore, Evans blue injection revealed a significant reduction in staining in the brains of DEX-treated rats (P < 0.05). These results indicate that early DEX treatment can prevent the BBB disruption that is caused by the rapid correction of hyponatremia and its associative demyelinative changes, and suggest that DEX might be effective in preventing CPM.

Central pontine myelinolysis

Central pontine myelinolysis (CPM) is a demyelinating disease of the pons often associated with demyelination of other areas of the central nervous system (CNS). The term 'osmotic demyelinization syndrome' is used for pontine and extrapontine myelinolysis. In this paper, we are concerned with CPM although the extrapontine one is based on the same pathogenesis. Both share the diagnostic methods, and their prevention and therapy are the same. The etiology and pathogenesis of this disorder are unclear and will be discussed. However, almost all cases of CPM are related to severe diseases. Chronic alcoholism is still the most common underlying condition of CPM patients. In the literature, 174 cases of CPM have been reported in alcoholics since 1986, which is equivalent to an incidence of 39.4%. Likewise, 95 cases of CPM following the correction of hyponatremia have been documented since 1986 (21.5%). The role of hyponatremia and its correction will be outlined in the discussion of the pathogenesis of CPM. The third largest group of CPM cases are liver transplant patients (17.4%), with the development of CPM being attributed to the immunosuppressive agent cyclosporine in particular. Depending on the involvement of other CNS structures, the clinical picture can vary considerably. The large-scale introduction of magnetic resonance imaging has increasingly facilitated the antemortem diagnosis of CPM, although the radiological findings lag behind and do not necessarily correlate with the clinical picture. As yet, there is no specific therapy of choice. A number of therapeutic approaches have been tested and although they have not been compared with regard to their rate of success, they have all led to a substantial improvement in the prognosis of CPM.

A review of the causes of central pontine myelinosis: yet another apoptotic illness?

One of the well recognized stimuli for central pontine myelinosis (CPM) is the rapid correction of chronic hyponatraemia. Conventionally this has been perceived to lead to pontine glial cell swelling through osmosis and eventually to cell death. However, although a purely osmotic argument has been central to any patho-physiological understanding of CPM, there are deficiencies in this approach that do not account for why certain individuals develop CPM with relatively mild osmotic insults. Here we review the varying aetiologies of CPM and propose a novel hypothesis for CPM causation by suggesting that individuals predisposed to CPM have inadequate energy provision as well as other factors that result in a pro-apoptotic drive, which renders them susceptible to brain injury from diverse causes. In CPM, the precipitant of brain injury appears to be osmotic stress. Furthermore, this model suggests a number of therapeutic interventions that may prevent or at least mitigate the consequences of CPM.

Azotemia (48 h) decreases the risk of brain damage in rats after correction of chronic hyponatremia

Brain myelinolysis complicates excessive correction of chronic hyponatremia in man. Myelinolysis appear in rats for correction levels deltaSNa) > 20 mEq/l/24 h. We previously showed in rats that when chronic hyponatremia was corrected with urea, the incidence and the severity of brain lesions were significantly reduced compared to hypertonic saline. In man, hyponatremia is frequently associated with azotemia and hemo-dialysis usually corrects rapidly the serum sodium (SNa) but only few patients apparently develop demyelination. We hypothesize that uremic state protects brain against myelinolysis. This hypothesis was evaluated in rats developing azotemia by administration of mercuric chloride (HgCl2, 1.5 mg/kg). Severe (SNa < 120 mEq/l) hyponatremia (3 days) was induced by S.C. AVP and i.p. 2.5% D-glucose for 3 days. HgCl2 was injected on day 2. Hyponatremia was corrected on day 4 by i.p. injections of 5% NaCl in order to obtain a correction level largely above the toxic threshold for brain (deltaSNA approximately 30 mEq/l/24 h). Surviving rats were decapitated on day 10 for brain analysis. In the group with renal failure (Group I, n = 15, urea 59 mmol/l) the outcome was remarkably favourable with only three rats (3/15) dying before day 10 and only one of them (1/3) presenting myelinolysis-related neurologic symptoms. The 12 other rats (80%) survived in Group I without symptoms and brain analysis was normal in all of them despite large correction level (deltaSNa: 32 mEq/l/24 h). On the contrary in nine rats in which HgCl, did not produce significant azotemia (control 1, n = 9, urea: 11 mmol/l), all the rats developed severe neurologic symptoms and eight of them died before day 10. Similar catastrophic outcome was observed in the non-azotemic controls (control 2, no HgCl2 administration, n = 15, urea: 5 mmol/l). All of them developed myelinolysis-related neurologic symptoms and only four of them survived with severe brain lesions (survival 12/15 in Group I vs. 5/24 in pooled controls 1 and 2, p < 0.001). In conclusion, we showed for the first time that chronic hyponatremic rats with azotemia (48 h) tolerated large increases in SNa (approximately 30 mEq/l/24 h) without significant brain damage.

Therapeutic relowering of the serum sodium in a patient after excessive correction of hyponatremia

BACKGROUND

Inappropriate correction of chronic hyponatremia could lead to major neuropathological sequelae. In man, the risk of brain myelinolysis increases strikingly when correction of the serum sodium exceeds 10-15 mEq/l/24 h. No treatment is actually available for this iatrogenic brain injury. However, recent experimental data showed that rapid reinduction of the hyponatremia greatly reduces the incidence of brain damage and death in case of serum sodium overshooting.

SUBJECTS AND METHODS

We tested this rescue manoeuver in a 71-year-old woman with nausea, confusion and severe (SNa 106 mEq/l) chronic hyponatremia related to thiazides. It was associated with hypokalemia (SK: 3.2 mEq/l).

RESULTS

Treatment with isotonic saline produced inappropriately high SNa correction level of +21 mEq/l after the first 24 h. After initial improvement, the neurological status deteriorated after 72 h. Rapid reinduction of the hyponatremia was then ordered. Administration of hypotonic fluids (by oral and i.v. route) combined with dDAVP induced a prompt decline in the SNa (-16 mEq/l/14 h) with a final gradient of correction of deltaSNa +9 mEq/l. This manoeuver was well tolerated without untoward effects. The natremia then progressively normalized and the patient completely recovered without neurological sequelae.

CONCLUSION

Hypotonic fluids may be safely administered to decrease the natremia after excessive correction of hyponatremia for potential prevention of myelinolysis.