The syndrome of inappropriate antidiuretic hormone secretion

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the commonest form of normovolaemic or dilutional hyponatraemia. The diagnosis of SIADH should be considered if the five cardinal criteria are fulfilled (hypotonic hyponatraemia, natriuresis, urine osmolality in excess of plasma osmolality, absence of oedema and volume depletion, normal renal and adrenal function). The clinical features are principally neuro-muscular and gastro-intestinal, the severity of which is related to both the absolute serum sodium concentration and its rate of fall, particularly if greater than 0.5 mmol/1/h. The dilutional hyponatraemia of SIADH develops due to persistent detectable or elevated plasma arginine vasopressin (AVP) concentrations in the presence of continued fluid intake. Osmoregulated inhibition of thirst failures to curb fluid intake. The major groups of causes of SIADH are: (i) neoplasia, (ii) neurological diseases, (iii) lung diseases and (iv) a wide variety of drugs. Inappropriate infusion of hypotonic fluids in the post-operative state remains a common cause. Four categories of osmoregulated AVP secretion have been described: (i) erratic AVP release, (ii) reset osmostat, (iii) persistent AVP release at low plasma osmolality and (iv) normal osmoregulated AVP secretion. For symptomatic patients with chronic SIADH, the mainstay of therapy remains fluid restriction. New antagonists to the antidiuretic action of AVP offer a new therapeutic approach.

A fatal case of inappropriate ADH secretion induced by cyclophosphamide therapy

Cyclophosphamide is used extensively to treat malignancies. A 5-year-old boy with stage IV neuroblastoma is described who developed a fatal syndrome of inappropriate antidiuretic hormone (ADH) secretion after high dose cyclophosphamide therapy.

Pathogenesis of the neurotoxicity caused by anti-GD2 antibody therapy

After treatment of melanomas with anti-GD2 monoclonal antibody (MAb) (14G2a), some patients develop sensorimotor demyelinating polyneuropathy with and without the syndrome of inappropriate antidiuretic hormone (SIADH). To clarify what causes the neurotoxicity of anti-GD2 MAb, we investigated the immunohistochemical localization of GD2 in the human nervous system. Anti-GD2 MAb (14G2a) reacted with the myelin sheaths in the peripheral nerves as well as with the pituicyte cytoplasm in the posterior lobe of the pituitary gland. We assume that the binding of anti-GD2 MAb to peripheral nerve myelin and the pituicytes in the posterior pituitary causes sensorimotor demyelinating neuropathy and SIADH.

Simultaneous above and below approach to giant pituitary adenomas: surgical strategies and long-term follow-up

INTRODUCTION

Giant pituitary adenomas of excessive size, fibrous consistency or unfavorable geometric configuration may be unresectable through conventional operative approaches. We present our select case series for operative resection and long-term follow-up for these unusual tumors, employing both a staged procedure and a combined transsphenoidal-transcranial above and below approach.

METHOD

A retrospective chart review was performed on patients operated via the staged, and combined approaches by the senior author (J.N.B.). Preoperative characteristics and postoperative outcomes were reviewed. A detailed description of the operative technique and perioperative management is provided.

RESULTS

Between 1993 and 1996, two patients harboring giant pituitary adenomas underwent an intentionally staged resection, and between 1997 and 2006, nine patients harboring giant pituitary adenomas underwent surgery via a single-stage above and below approach. Nine patients (82%) presented with non-secreting adenomas and two patients (18%) presented with prolactinomas refractory to medical management. Gross total resection was achieved in six patients (55%), near total resection in 1 (9%), and subtotal removal in 4 (36%). Seven patients (64%) experienced visual improvement postoperatively and no major complications occurred. Long-term follow-up averaged 51.6 months. Panhypopituitarism was observed in four patients, partial hypopituitarism in four, persistent DI in two, and persistent SIADH in one.

CONCLUSIONS

The addition of a transcranial component to the transsphenoidal approach offers additional visualization of critical neurovascular structures during giant pituitary adenoma resection. Complications rates are similar to other series in which complex pituitary adenomas are resected by other means. The above and below approach is both safe and effective and the immediate and long-term advantages of a single-stage approach justify its utility in this select group of patients.

Prevalence and clinical demographics of cerebral salt wasting in patients with aneurysmal subarachnoid hemorrhage

Hyponatremia is a frequent complication following subarachnoid hemorrhage (SAH), and is commonly attributed either to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or cerebral salt wasting syndrome (CSW). The object of this study is to elucidate the clinical demographics and sequelae of hyponatremia due to CSW in subjects with aneurysmal SAH. Retrospective chart review of patients >18 years with aneurysmal SAH admitted between January 2004 and July 2007 was performed. Subjects with moderate to severe hyponatremia (serum sodium <130 mmol l(-1)) were divided into groups consistent with CSW and SIADH based on urine output, fluid balance, natriuresis, and response to saline infusion. Clinical demographics were compared. Of 316 subjects identified, hyponatremia (serum sodium <135 mmol l(-1)) was detected in 187 (59.2%) subjects and moderate to severe hyponatremia in 48 (15.2%). Of the latter group, 35.4% were categorized with SIADH and 22.9% with CSW. Compared to eunatremic subjects, hyponatremia was associated with significantly longer hospital stay (15.7 +/- 1.9 vs. 9.6 +/- 1.1 days, p < 0.001). Subjects with CSW had similar mortality and duration of hospital stay vs. those with SIADH. Though less common than SIADH, CSW was detected in approximately 23% of patients with history of aneurysmal SAH and was not clearly associated with enhanced morbidity and mortality compared to subjects with SIADH. Further studies regarding the pathogenesis and management, along with the medical consequences, of CSW are important.

Characterization of three vasopressin receptor 2 variants: an apparent polymorphism (V266A) and two loss-of-function mutations (R181C and M311V)

Arginine vasopressin (AVP) is released from the posterior pituitary and controls water homeostasis. AVP binding to vasopressin V2 receptors (V2Rs) located on kidney collecting duct epithelial cells triggers activation of Gs proteins, leading to increased cAMP levels, trafficking of aquaporin-2 water channels, and consequent increased water permeability and antidiuresis. Typically, loss-of-function V2R mutations cause nephrogenic diabetes insipidus (NDI), whereas gain-of-function mutations cause nephrogenic syndrome of inappropriate antidiuresis (NSIAD). Here we provide further characterization of two mutant V2Rs, R181C and M311V, reported to cause complete and partial NDI respectively, together with a V266A variant, in a patient diagnosed with NSIAD. Our data in HEK293FT cells revealed that for cAMP accumulation, AVP was about 500- or 30-fold less potent at the R181C and M311V mutants than at the wild-type receptor respectively (and about 4000- and 60-fold in COS7 cells respectively). However, in contrast to wild type V2R, the R181C mutant failed to increase inositol phosphate production, while with the M311V mutant, AVP exhibited only partial agonism in addition to a 37-fold potency decrease. Similar responses were detected in a BRET assay for β-arrestin recruitment, with the R181C receptor unresponsive to AVP, and partial agonism with a 23-fold decrease in potency observed with M311V in both HEK293FT and COS7 cells. Notably, the V266A V2R appeared functionally identical to the wild-type receptor in all assays tested, including cAMP and inositol phosphate accumulation, β-arrestin interaction, and in a BRET assay of receptor ubiquitination. Each receptor was expressed at comparable levels. Hence, the M311V V2R retains greater activity than the R181C mutant, consistent with the milder phenotype of NDI associated with this mutant. Notably, the R181C mutant appears to be a Gs protein-biased receptor incapable of signaling to inositol phosphate or recruiting β-arrestin. The etiology of NSIAD in the patient with V266A V2R remains unknown.

Small cell carcinoma of the prostate expressing prostate-specific antigen and showing syndrome of inappropriate secretion of antidiuretic hormone: an autopsy case report

An autopsy case of primary small cell carcinoma (SCC) of the prostate in a 68-year-old man is reported. The patient was admitted to hospital because of a bloody stool and suspected rectal cancer. However, a diagnosis of prostate cancer was made on the basis of a digital rectal examination, the serum level of prostate-specific antigen, and a needle biopsy of the prostate. The patient also experienced a syndrome of inappropriate secretion of antidiuretic hormone. He died 29 days after admission. At autopsy, the tumor had invaded the rectum, bladder and pelvic peritoneum. Metastases to the heart, vertebrae and lymph nodes were observed. Microscopically, the tumor was composed of small round cells that showed a solid growth pattern. Rosette formations were observed. Immunohistochemically, the tumor cells were positive for a prostatic epithelial marker and neuroendocrine markers. A high level of antidiuretic hormone was detected in the tumor tissue. To our knowledge, this is the first reported case of SCC of the prostate in which both a prostatic epithelial marker and neuroendocrine markers have been found in the same tumor. This finding supports the hypothesis that SCC of the prostate originates from a multipotential stem cell of the prostatic epithelium.

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) in patients with limited stage small cell lung cancer

A few series in the literature were published before 1987 on syndrome of inappropriate antidiuretic hormone secretion (SIADH) in small cell lung cancer (SCLC). This study examines the outcome in more recent era. From 1981-1998, there were 1417 new cases of SCLC diagnosed in the provincial registry, of which 244 were of limited stage (LS). A chart review and statistical analyses were performed using Mann-Whitney test, chi-square test and Kaplan-Meier method. Fourteen LS patients (group A) had SIADH at presentation. Group B consisted of 230 LS patients without SIADH. There were more patients with poorer performance status (ECOG 2-4) in group A than B (28.6% versus 7.8%, P=0.03). Otherwise, sex, age at diagnosis, nodal spread, pleural effusion, bronchial obstruction, superior vena cava obstruction, performance status, weight loss, and lactic dehydrogenase at presentation, were comparable between the two groups. Treatments given, e.g., extent of surgical resection (if performed, whether complete/incomplete), total number of chemotherapy cycles, radiotherapy doses, were comparable (P>0.05). The response to chemo-radiation was not significantly different (P=0.7). Five-year overall survival (8% versus 19%, P=0.08), and cause-specific survival (16% versus 20%, P=0.13) showed that group A patients had a worse outcome, though of borderline significance. Symptoms related to SIADH included: weakness, 4 patients; tiredness, 3; change in level of consciousness, 1; seizure, 1. The range of lowest sodium level was 110-129. Two patients also had paraneoplastic myopathy. SIADH resolved in 12 patients at 1.6-44.7 weeks (median: 4.3). Among the 14 patients who initially presented with SIADH and recurred later, 10 had recurrence of SIADH at the time of tumor recurrence. Serum sodium was useful for post-treatment surveillance in SCLC patients who presented with SIADH, with 71% (10/14) developing SIADH again at the time of recurrence. SIADH is a poor prognostic factor for LS SCLC.

Treatment of symptomatic hyponatremia with hypertonic saline: a real-life observational study

OBJECTIVE

Treatment of symptomatic hyponatremia is not well established. The European guidelines recommend bolus-wise administration of 150 mL of 3% hypertonic saline. This recommendation is, however, based on low level of evidence.

DESIGN

Observational study.

METHODS

Sixty-two consecutive hyponatremic patients admitted to the emergency department or intensive care unit of the University Hospital Wuerzburg were divided in subgroups according to treatment (150 mL bolus of 3% hypertonic saline or conventional treatment) and symptom severity. Treatment target was defined as an increase in serum sodium by 5-10 mEq/L within first 24 h and maximum 8 mEq/L during subsequent 24 h.

RESULTS

Thirty-three out of sixty-two patients (53%) were presented with moderate symptoms and 29/62 (47%) with severe symptoms. Thirty-six were treated with hypertonic saline and 26 conventionally. In the hypertonic saline group, serum sodium increased from 116 ± 7 to 123 ± 6 (24 h) and 127 ± 6 mEq/L (48 h) and from 121 ± 6 to 126 ± 5 and 129 ± 4 mEq/L in the conventional group, respectively. Overcorrection at 24 h occurred more frequent in patients with severe symptoms than with moderate symptoms (38% vs 6%, P < 0.05). Diuresis correlated positively with the degree of sodium overcorrection at 24 h (r = 0.6, P < 0.01). Conventional therapies exposed patients to higher degrees of sodium fluctuations and an increased risk for insufficient sodium correction at 24 h compared to hypertonic saline (RR: 2.8, 95% CI: 1.4-5.5).

CONCLUSION

Sodium increase was more constant with hypertonic saline, but overcorrection rate was high, especially in severely symptomatic patients. Reducing bolus-volume and reevaluation before repeating bolus infusion might prevent overcorrection. Symptoms caused by hypovolemia can be misinterpreted as severely symptomatic hyponatremia and diuresis should be monitored.

Low sodium excretion in SIADH patients with low diuresis

It is well known that during low diuresis or low effective circulating volume, salt excretion is low. The aim of this study was to find out whether salt excretion, expressed as either urinary sodium concentration (UNa) or fractional sodium excretion (FENa), and the combined use of FENa and fractional urea excretion (FEurea) still differentiate between hyponatremic SIADH and hyponatremic salt depletion (SD) patients when diuresis is low. The relationships between UNa, FENa and diuresis, indirectly estimated by the urinary to plasma creatinine ratio (U/P creat), were studied in 42 hyponatremic SIADH patients, 21 hyponatremic SD patients and 66 normonatremic controls (CO) of similar age and sex ratio. There was no significant relationship between UNa and U/P creat either in SIADH or in SD or CO patients. FENa and U/P creat were inversely correlated, both in CO (r = -0.72; p < 0.001) and in SIADH (r = -0.68; p < 0.001). SIADH and SD patients can be fairly well differentiated from one another using FENa and U/P creat. Even with high U/P creat values, SIADH patients, despite a sharp decrease in their FENa values, presented still higher FENa values than SD patients did (mean FENa = 0.3 +/- 0.2% in SIADH and 0.1 +/- 0.04% in SD; p < 0.05). However, FENa values of SIADH patients with low diuresis (mean FENa = 0.3 +/- 0.2% for a mean U/P creat = 191 +/- 40) are indistinguishable from those of SD patients with normal urine volumes (mean FENa = 0.2 +/- 0.2% for a mean U/P creat = 92 +/- 30). The combined use of FENa and FEurea remains a reliable way to discriminate SD patients and SIADH patients, as far as the differential limit value for FENa is narrowed to a value of 0.15%, for hyponatremic patients with U/P creat >140.

CONCLUSION

In SIADH, FENa values are lower than 0.5%, as soon as U/P creat exceeds a value of 180. In SD patients with U/P creat values exceeding 140, FENa is lower than 0.15% and FEurea lower than 45%.

Optic chiasm glioma associated with inappropriate secretion of antidiuretic hormone, cerebral ischemia, nonobstructive hydrocephalus and chronic ascites following ventriculoperitoneal shunting

An optic chiasm glioma may cause loss of vision, endocrine disturbances, hydrocephalus and cerebral ischemia due to its proximity to the pituitary, hypothalamus, III ventricle and internal carotids. A 3-month-old infant with optic chiasm glioma developed hypopituitarism and inappropriate secretion of antidiuretic hormone with plasma hypo-osmolality. The cerebrospinal fluid (CSF) protein concentration was markedly elevated. The impairment of fluid absorption via arachnoid villi and peritoneum by the high protein content, and reversed osmotic gradient between protein-rich CSF and hypo-osmolar plasma may have contributed to both nonobstructive hydrocephalus and recurrent ascites following ventriculoperitoneal shunting. Cerebral ischemia from carotid compression may have led to cerebral atrophy.

Syndrome of inappropriate secretion of antidiuretic hormone associated with multiple sclerosis

A 63-year-old man who developed episodes of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) twice in the course of multiple sclerosis (MS) is reported. SIADH in this patient occurred only during the administration of antibiotics (sulbactam/cefoperazone, SBT/CPZ). At autopsy, demyelinating lesions in the optic nerves, cervical and thoracic spinal cord, and areas adjacent to the lateral ventricles were observed. Destruction and loss of neuronal cells were found in the supraoptic nuclei. Lymphocytic infiltration was observed in the area adjacent to the supraoptic nuclei. Destruction and swelling of axons and reactive astrocytic gliosis were observed in the hypothalamus. SIADH associated with MS is rare and the histological findings in such a case have not yet been reported. It is suggested that the development of SIADH in MS may be related to the damage in the supraoptic nuclei of the hypothalamus.

Histopathological study of kidney abnormalities in an experimental SIADH rat model and its application to the evaluation of the pharmacologic profile of VP-343, a selective vasopressin V2 receptor antagonist

The aim of this work was to investigate histopathologically the relationship between the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and kidney abnormalities and the therapeutic efficacy of VP-343 ((N-[4-[[(2S,3aR)-2-hydroxy-2,3,3a,4-tetrahydropyrrolo[1,2-alqunoxalin-5(1H)-yl]phenyl]-4'-methyl[1,1'-biphenyl]-2-carboxamide], a selective vasopressin V2 receptor antagonist, in an experimental SIADH rat model. In the model, which was prepared by continuously administering 1-desamino-8-D-arginine vasopressin (DDAVP), histopathologic abnormalities, such as dilatation of tubules, basophilic changes in tubules, inflammatory cell infiltration, and mineralization were found in the kidney, accompanied by significant increases in the relative weight of the kidney, lung, liver, adrenal gland, and heart. VP-343 was shown to be effective in protecting the kidney from the histopathologic abnormalities and to normalize the relative weight of the kidney and several common pathophysiologic features, such as hyponatremia, hyposmolarity of plasma, hyperosmolarity of urea, and oligurea, as described previously. These results demonstrate the occurrence of histopathologic abnormalities in the kidney and the efficacy of VP-343 in improving abnormalities in the DDAVP-induced SIADH rat model.

Syndrome of inappropriate secretion of antidiuretic hormone caused by vincristine therapy: a case report of the neuropathology

The syndrome of inappropriate secretion of antidiuretic hormone is a rare but well-recognized neurotoxic side effect of vincristine therapy. The first neuropathological report of a case is presented. A 6-month-old boy with skin leukemia developed inappropriate secretion of antidiuretic hormone caused by vincristine. Postmortem examination revealed axonal spheroids in the ansa lenticularis and the area surrounded by the substantia innominata, amygdala and supraoptic nucleus. The lesion was confined to that area and the neurosecretory neurons were intact with well preserved neurophysin. The pathological findings suggest that these fibers play a role in the development of inappropriate secretion of antidiuretic hormone caused by vincristine therapy.

Severe hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with fluoxetine: case report

Hyponatremia is a significant complication of treatment with serotonin selective reuptake inhibitors (SSRI). We describe a case of a 53-year-old woman that was started on fluoxetine 20 mg/day for depression. Nine days later, the patient started with weakness, nausea, progressing to confusion, inapetence and vomit. Three hours later she became unresponsive and had a generalized seizure. She was brought to our emergency service. On admission, the patient was normovolemic, without focal motor deficits, but had mild generalized muscle rigidity and Babinski's sign bilaterally. Serum sodium was 105 mmol/L, serum osmolality, 220 mmol/L, and urinary osmolality, 400 mmol/L. The other laboratory exams, chest X-ray, cerebrospinal fluid and cranium tomography were normal. She was found to have fluoxetine-induced SIADH and it was descontinued. We started the hyponatremia correction and, in 5 days, the mental status of the patient gradually returned to a normal baseline, paralleling the resolution of her hyponatremia, without recurrence. Hyponatremia and SIADH should be considered if a patient experiences deterioration in his or her clinical condition while taking SSRI. The use of SSRI antidepressants should be remembered in the differential diagnosis of drug-induced hyponatremia.

Ganglioglioma of the neurohypophysis

The normal infundibulum and neurohypophysis consist entirely of neuronal processes, the neuronal cell bodies of which lie within the supraoptic and paraventricular nuclei of the hypothalamus and supportive glial cells or pituicytes. The finding of neurons within the neurohypophysis is exceedingly rare, as are ganglion cell tumors at this site. In this paper, we report a ganglion cell tumor of the neurohypophysis found incidentally at autopsy. Despite chronic hypertension and the finding of some vasopressin immunoreactivity in lesional neurons, the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was excluded on the basis of normal serum sodium levels. The morphologic and immunohistochemical features of the tumor are presented, cytogenetic considerations are discussed, and literature regarding neuronal lesions of the pituitary gland is reviewed.

Neuropsychiatric systemic lupus erythematosus and the syndrome of inappropriate secretion of antidiuretic hormone: a case report with very late onset systemic lupus erythematosus

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with neuropsychiatric lupus (NP-SLE) is rare. We report a case of SIADH associated with the new onset of SLE in an 88-yr-old female. The unique features of this case include the extreme age of onset of SLE presenting with neuropsychiatric manifestations and positive antiribosomal P antibody titres. Both the NP manifestations of SLE and SIADH were highly correlated with the SLE disease activity. This case illustrates a novel presentation of NP-SLE with SIADH which may develop due to antibody-mediated hypothalamic dysfunction.

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in a patient with multiple sclerosis

Association of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) with multiple sclerosis (MG) is very rare, although many other disorder of the nervous system have been reported to be associated with this syndrome; there is only one case report in the literature. We describe here a patient with the syndrome associated with MS. A 62-year-old women had a variety of neurologic symptoms, where clinical course was typical of MS. Transient episodes of hyponatremia and disturbance of consciousness occurred repeatedly with deterioration of MS. The concentration of antidiuretic hormone (ADH) was high whereas the plasma osmolality was low in the presence of concentrated urine, during the episodes of hyponatremia. Urinary Na excretions exceeded 20 mEq/day. Computed tomography and magnetic resonance imaging revealed lesions in the brain, especially in the periventricular region. The hypothalamus and pituitary appeared normal by these imaging methods. Since the periventricular region surrounds and may be functionally connected to the hypothalamus which plays the central role in the regulation of ADH secretion, it was concluded that association of SIADH and MS in this patient was not coincidental, and that demyelinating processes in the periventricular region exerted an abnormal influence on ADH secretion resulting in SIADH. Contribution of other mechanisms as increased intrathoracic pressure, however, could not be excluded completely.

A Rare Case of Combined Syndrome of Inappropriate Antidiuretic Hormone Secretion and Fanconi Syndrome in an Elderly Woman

An 83-year-old Japanese woman was admitted to our hospital with severe hyponatremia (sodium, 108 mEq/L [108 mmol/L]), hypokalemia, hypochloridemia, hypocalcemia, hypophosphatemia, and hypouricemia. Despite low plasma osmolarity (232 mOsm/kg [232 mmol/kg]), urine osmolarity (320 mOsm/kg) was greater than that of plasma, and she had increased urinary sodium excretion (88 mEq/L [88 mmol/L]) and an unsuppressed high plasma level of antidiuretic hormone (ADH; 5.5 pg/mL [5.1 pmol/L]). These findings indicated that she had syndrome of inappropriate ADH secretion (SIADH). In addition, she had a generalized reabsorption defect of the proximal tubules, including decreased tubular reabsorption of phosphate, increased fractional excretion of uric acid, glycosuria despite a normal blood glucose level, and panaminoaciduria. Thus, combined SIADH and Fanconi syndrome was diagnosed. The cause was thought to be the antidepressant paroxetine, which is a selective serotonin reuptake inhibitor (SSRI). Several of the abnormal values resolved within 1 week after discontinuation of this drug. Although the precise mechanism responsible was not elucidated, we report an extremely rare case of combined SIADH and Fanconi syndrome, probably caused by short-term SSRI therapy.

Intravascular large B-cell lymphoma with preceding syndrome of inappropriate secretion of antidiuretic hormone

Intravascular large B-cell lymphoma (IVL) is a rare subtype of B-cell lymphoma presenting with neurological and dermatological lesions in addition to generalized symptoms such as fever and malaise. It may also be associated with variable manifestations of affected organs due to extranodal progression predominantly in the lumen of the small vessels. Here, we report a case of IVL with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) as the sole manifestation at the initial presentation. The present case suggests that hormonal disturbances may progress in advance in IVL, before generalized symptoms develop.

Two cases of MND/ALS developing the syndrome of inappropriate secretion of antidiuretic hormone

We report 2 autopsy-proven cases of motor neuron disease/amyotrophic lateral sclerosis (MND/ALS), who developed the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) prior to the respiratory failure. With respect to the underlying mechanisms of SIADH in the cases, we considered two factors; 1) dysfunction of the feedback system in ADH secretion via intrathoracic volume receptors caused by changes in intrathoracic circulation, and 2) primarily functional abnormalities in the limbic system which could influence hypothalamic osmoreceptors. It appears that SIADH can be followed by an exacerbation of respiratory dysfunction in MND/ALS.

Disseminated varicella-zoster virus infection with the syndrome of inappropriate antidiuretic hormone

A patient with non-Hodgkin's lymphoma who was previously treated with chemotherapy and radiotherapy was seen with intestinal pseudoobstruction due to paralytic ileus associated with herpes zoster (varicella zoster) infection. The infection was accompanied by a polydermatomal rash with typical morphologic characteristics, followed by cutaneous dissemination and the syndrome of inappropriate antidiuretic hormone (SIADH), as well as myotomal paresis. The diagnosis was supported by cytology and by culture of the virus from the CSF. The isolation of the virus from the CSF, coupled with abnormalities of the patient's mental status and CSF, indicate that meningoencephalitis occurred and probably accounted for the SIADH. The patient had a spontaneous and complete recovery. To our knowledge, this is the first report of SIADH associated with herpes zoster infection.

Vasopressin escape and memory impairment in a model of chronic syndrome of inappropriate secretion of antidiuretic hormone in mice

Recently, chronic hyponatremia, even mild, has shown to be associated with poor quality of life and high mortality. The mechanism by which hyponatremia contributes to those symptoms, however, remains to be elucidated. Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a primary cause of hyponatremia. Appropriate animal models are crucial for investigating the pathophysiology of SIADH. A rat model of SIADH has been generally used and mouse models have been rarely used. In this study, we developed a mouse model of chronic SIADH in which stable and sustained hyponatremia occurred after 3-week continuous infusion of the vasopressin V2 receptor agonist 1-desamino-8-D-arginine vasopressin (dDAVP) and liquid diet feeding to produce chronic water loading. Weight gain in chronic SIADH mice at week 2 and 3 after starting dDAVP injection was similar to that of control mice, suggesting that the animals adapted to chronic hyponatremia and grew up normally. AQP2 expression in the kidney, which reflects the renal action of vasopressin, was decreased in dDAVP-infused water-loaded mice as compared with control mice that received the same dDAVP infusion but were fed pelleted chow. These results suggest that "vasopressin escape" occurred, which is an important process for limiting potentially fatal severe hyponatremia. Behavioral analyses using the contextual and cued fear conditioning test and T-maze test demonstrated cognitive impairment, especially working memory impairment, in chronic SIADH mice, which was partially restored after correcting hyponatremia. Our results suggest that vasopressin escape occurred in chronic SIADH mice and that chronic hyponatremia contributed to their memory impairment.