Neurologic disorders in renal failure (second of two parts)

Electrochemical Skin Conductance by Sudoscan in Non-Dialysis Chronic Kidney Disease Patients

BACKGROUND

Peripheral neuropathy is prevalent among patients with chronic kidney disease (CKD). Sudoscan non-invasively detects polyneuropathy by measuring electrochemical skin conductance (ESC). We conducted a study on sudomotor function in CKD patients across various stages based on their estimated glomerular filtration rate (eGFR).

METHODS

In this cross-sectional study of 700 CKD patients, all underwent Sudoscan. Pathological ESC was defined as hands < 40 μS or feet < 50 μS. Clinical neuropathy scores including Michigan Neuropathy Screening Instrument (MNSI) and Douleur Neuropathique en 4 questionnaire (DN4) were obtained.

RESULTS

Among participants, 344 had diabetes and 356 did not. Hands and feet ESC decreased with CKD progression (median (IQR) in stage 1-2, 3, 4-5: 54.0 (39.0-68.0), 45.5 (30.0-63.0), 41.8 (26.5-60.5), p trend < 0.001; 64.5 (53.5-74.0), 60.5 (43.0-72.5), 55.0 (39.0-69.8), p trend < 0.001). Pathological hands and feet ESC increased in later CKD stages (stage 1-2, 3, 4-5: 26.6%, 40.9%, 45.7%, p trend < 0.001; 21.7%, 34.0%, 40.6%, p trend < 0.001). Positive hands and feet ESC-eGFR correlation existed irrespective of diabetes. Diabetic patients had lower hands and feet ESC than non-diabetics as CKD progressed. However, multivariate regression found no significant ESC-eGFR association. Sudoscan correlated with clinical neuropathy scores.

CONCLUSION

Pathological sudomotor function was common in non-dialysis CKD stages 4-5. Diabetic patients had worse function. Sudomotor dysfunction progressed with renal disease but eGFR was not an independent risk factor.

Effect of Erythropoietin-stimulating agent on uremic neuropathy in hemodialysis patients: a single-center open-label prospective study

Background

Uremic neuropathy is a distal sensorimotor polyneuropathy caused by uremic toxins; its severity is correlated with the degree of renal insufficiency. Erythropoietin (EPO) and erythropoietin receptors (EpoR) are produced in the peripheral nervous system. This is a single-center open-label prospective study was designed to investigate the possible effect of erythropoietin-stimulating agents (ESAs) on uremic neuropathy. Twenty-four newly diagnosed end-stage kidney disease (ESKD) patients were selected, clinical assessment, laboratory, and neurophysiological study were done at 1 and follow-up after 3 months. Patients were divided into two groups (group A received ESA and group B did not receive ESA).

Results

Eighteen patients completed the study, eight patients (44.4%) did not have symptoms but had electrophysiological findings of neuropathy (subclinical neuropathy). After 3 months of hemodialysis, patients in group A showed improvement of some electrophysiological features (ulnar MNCV; P = 0.016).

Conclusions

The use of ESA may improve uremic neuropathy in patients with newly diagnosed ESKD who have been started on hemodialysis.

Retinal Neurovascular Impairment in Non-diabetic and Non-dialytic Chronic Kidney Disease Patients

Background: Widespread neural and microvascular injuries are common in chronic kidney disease (CKD), increasing risks of neurovascular complications and mortality. Early detection of such changes helps assess the risks of neurovascular complications for CKD patients. As an extension of central nervous system, the retina provides a characteristic window to observe neurovascular alterations in CKD. This study aimed to determine the presence of retinal neurovascular impairment in different stages of CKD. Methods: One hundred fifteen non-diabetic and non-dialytic CKD patients of all stages and a control group of 35 healthy subjects were included. Retinal neural and microvascular parameters were obtained by optical coherence tomography angiography (OCTA) examination. Results: CKD 1-2 group (versus control group) had greater odds of having decreased retinal ganglion cell-inner plexiform layer thickness (GC-IPLt) (odds ratio [OR]: 0.92; 95% confidence interval [CI]: 0.86-0.98), increased ganglion cell complex-focal loss volume (GCC-FLV) (OR: 3.51; 95% CI: 1.27-9.67), and GCC-global loss volume (GCC-GLV) (OR: 2.48; 95% CI: 1.27-4.82). The presence of advanced stages of CKD (CKD 3-5 group versus CKD 1-2 group) had greater odds of having decreased retinal vessel density in superficial vascular plexus (SVP)-WholeImage (OR: 0.77, 95% CI: 0.63-0.92), SVP-ParaFovea (OR: 0.83, 95% CI: 0.71-0.97), SVP-ParaFovea (OR: 0.76, 95% CI: 0.63-0.91), deep vascular plexus (DVP)-WholeImage (OR: 0.89, 95% CI: 0.81-0.98), DVP-ParaFovea (OR: 0.88, 95% CI: 0.78-0.99), and DVP-PeriFovea (OR: 0.90, 95% CI: 0.83-0.98). Besides, stepwise multivariate linear regression among CKD patients showed that β2-microglobulin was negatively associated with GC-IPLt (β: -0.294; 95% CI: -0.469 ∼ -0.118), and parathyroid hormone was positively associated with increased GCC-FLV (β: 0.004; 95% CI: 0.002∼0.006) and GCC-GLV (β: 0.007; 95% CI: 0.004∼0.01). Urine protein to creatinine ratio was positively associated with increased GCC-FLV (β: 0.003; 95% CI: 0.001∼0.004) and GCC-GLV (β: 0.003; 95% CI: 0.001∼0.006). Conclusion: Retinal neuronal impairment is present in early stages of CKD (stages 1-2), and it is associated with accumulation of uremic toxins and higher UACR, while retinal microvascular hypoperfusion, which is associated with worse eGFR, was only observed in relatively advanced stages of CKD (stages 3-5). The results highlight the importance of monitoring retinal neurovascular impairment in different stages of CKD.

Movement Disorders and Renal Diseases

Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.

Autonomic Neuropathy in Hemodialysis Patients Treated with Recombinant Human Erythropoietin

Autonomic nervous system (ANS) function was evaluated in hemodialysis patients treated with recombinant human erythropoietin (rHu-EPO) before and after therapy, in an effort to evaluate the role of anemia in the genesis of autonomic dysfunction in chronic renal failure (CRF). Studies were conducted using a battery of five cardiovascular reflex tests: Valsalva maneuver, handgrip exercise, heart rate response to standing (30:15 index), post-Valsalva rise in blood pressure and postural drop in blood pressure. The patients were divided into two groups: group I consisted of 14 patients on maintenance hemodialysis treated with rHu-EPO for one year, and group II - 13 hemodialysis patients treated with rHu-EPO for two years. The results of the tests were compared before and after the correction of anemia by rHu-EPO in each group, as well as with the control group of ten healthy subjects. Data show that renal anemia is not implicated in the genesis of ANS dysfunction in hemodialysis patients, since correction of same by rHu-EPO does not improve the autonomic dysfunction.

The nature, consequences, and management of neurological disorders in chronic kidney disease

Perhaps no other organ in the body is affected as often and in as many ways as the brain is in patients with chronic kidney disease (CKD). Several factors contribute to the neurological disorders in CKD including accumulation of uremic toxins, metabolic and hemodynamic disorders, oxidative stress, inflammation, and impaired blood brain barrier among others. The neurological disorders in CKD involve both peripheral and central nervous system. The peripheral neurological symptoms of CKD are due to somatic and cranial peripheral neuropathies as well as a myopathy. The central neurological symptoms of CKD are due to the cortical predominantly cortical, or subcortical lesions. Cognitive decline, encephalopathy, cortical myoclonus, asterixis and epileptic seizures are distinct features of the cortical disorders of CKD. Diffuse white matter disease due to ischemia and hypoxia may be an important cause of subcortical encephalopathy. A special and more benign form of subcortical disorder caused by brain edema in CKD is termed posterior reversible encephalopathy. Subcortical pathology especially when it affects the basal ganglia causes a number of movement disorders including Parkinsonism, chorea and dystonia. A stimulus-sensitive reflex myoclonus is believed to originate from the medullary structures. Sleep disorder and restless leg syndrome are common in CKD and have both central and peripheral origin. This article provides an overview of the available data on the nature, prevalence, pathophysiology, consequences and treatment of neurological complications of CKD.

A Case Attributed to Cefazolin and a Review of the Literature

Generalized convulsions developed in a uremic patient who had received massive doses of cefazolin which resulted in a measured serum level of greater than 512 mcg/ml of drug after dialysis. Pathophysiologic mechanisms which could have contributed to the symptoms are discussed. Physicians prescribing cefazolin and other cephalosporins need to be aware of this potential complication of therapy and adjust doses accordingly in renal failure.

Hypertensive Encephalopathy in Cats with Reduced Renal Function

The clinical, hemodynamic, and pathologic features of hypertensive encephalopathy in two cats with reduced renal mass are described. The cats developed a progressive syndrome of lethargy, ataxia, blindness, stupor, and seizures following an abrupt increase in blood pressure associated with a surgical reduction in renal mass. The cats had severe gross brain edema, evidenced by cerebellar changes of caudal coning and cranial displacement over the corpora quadrigemina and cerebral changes of widening and flattening of the gyri. Histologically, interstitial edema was most pronounced in the cerebral white matter. Hypertensive vascular lesions were present as hyaline arteriolosclerosis in one cat and hyperplastic arteriolosclerosis in the other. Rare foci of parenchymal microhemorrhages and necrosis were also observed. Systemic hypertension (especially severe or rapidly developing) accompanied by neurologic signs and the pathologic findings of diffuse brain edema with cerebral arteriolosclerosis are consistent with an etiologic diagnosis of hypertensive encephalopathy.

Chorea due to diabetic hyperglycemia and uremia: distinct clinical and imaging features

This study was undertaken to describe the clinical and imaging characteristics of patients with chorea associated with nonketotic hyperglycemia (C-NKH) in comparison with patients with chorea associated with uremia (C-URE). We retrospectively analyzed the clinical data of consecutive 10 C-NKH and five C-URE patients who were treated between January 1, 2001 and January 31, 2013. Women were more frequently affected by C-NKH (70% vs. 30%) and C-URE (80% vs. 20%) compared with men. The C-NKH patients demonstrated T1-hyperintense and inhomogeneous lesions in the basal ganglia, whereas C-URE patients demonstrated T2-hyperintense and homogeneous lesions in the basal ganglia. The mean time for chorea resolution after treatment was significantly shorter in C-NKH patients than in C-URE patients (4.4 ± 2.6 d vs. 73.8 ± 14.2 d, respectively; P = 0.005). The clinical and imaging features are remarkably different between C-NKH and C-URE patients, suggesting distinct pathogenic mechanisms.

Psychomotor functions at various weeks of chronic renal failure in rats

In chronic renal failure there is a gradual retention of substances in the tissues and body fluids, called as uremic retention toxins, which can bring about a number of biochemical activities in the body. Chronic renal insufficiency also leads to progressive behavioural conflict. Uremic toxins can affect both the central and the peripheral nervous system. Uremic encephalopathy is also associated with problems in cognition and memory. To study the psychomotor functional disorders in rats with progressive chronic renal failure surgical nephrectomy was done by resection method. The animals were grouped into two control groups, Sham control (SC) and normal control (NC) and two uremic groups, moderate uremia (GM) and severe uremia (GS). Psychomotor analysis was done by passive avoidance and open field in these animals at 4, 8, 12, and 16 weeks. After the incubation period, the nephrectomised groups (GM and GS) showed significant changes in exploratory, locomotor and emotional behaviour when compared to the controls (NC and SC). Psychomotor changes involve poor cognition, reduced memory, reduced locomotor activity and decreased exploratory drive and emotional disturbance like increased fear during the initial stages. During the later stages a restless behaviour was noticed, associated with diminished fear.

Hemodialysis-related headache

Headache is one of the most frequently encountered neurological symptoms during hemodialysis. According to International Classification of Headache criteria dialysis-related headache was defined as the headache occurring during hemodialysis with no specific characteristic. It resolves spontaneously within 72 hours after the hemodialysis session ends. There are few studies in the literature investigating the clinical features of dialysis headache. The pathophysiology of hemodialysis-related headache is not known, but various triggering factors have been identified, including changes in blood pressure, serum sodium and magnesium levels during hemodialysis sessions, caffeine deprivation and stress. The aim of this article is to evaluate and analyze features of headache in patients undergoing hemodialysis.

Risk factors for dementia after critical illness in elderly Medicare beneficiaries

Introduction

Hospitalization increases the risk of a subsequent diagnosis of dementia. We aimed to identify diagnoses or events during a hospitalization requiring critical care that are associated with a subsequent dementia diagnosis in the elderly.

Methods

A cohort study of a random 5% sample of Medicare beneficiaries who received intensive care in 2005 and survived to hospital discharge, with three years of follow-up (through 2008) was conducted using Medicare claims files. We defined dementia using the International Classification of Diseases, 9th edition, clinical modification (ICD-9-CM) codes and excluded patients with any prior diagnosis of dementia or cognitive impairment in the year prior to admission. We used an extended Cox model to examine the association between diagnoses and events associated with the critical illness and a subsequent diagnosis of dementia, adjusting for known risk factors for dementia.

Results

Over the three years of follow-up, dementia was newly diagnosed in 4,519 (17.8%) of 25,368 patients who received intensive care and survived to hospital discharge. After accounting for known risk factors, having an infection (adjusted hazard ratio (AHR) = 1.25; 95% CI, 1.17 to 1.35), or a diagnosis of severe sepsis (AHR = 1.40; 95% CI, 1.28 to 1.53), acute neurologic dysfunction (AHR = 2.06; 95% CI, 1.72 to 2.46), and acute dialysis (AHR = 1.70; 95% CI, 1.30 to 2.23) were all independently associated with a subsequent diagnosis of dementia. No other measured ICU factors, such as need for mechanical ventilation, were independently associated.

Conclusions

Among ICU events, infection or severe sepsis, neurologic dysfunction, and acute dialysis were independently associated with a subsequent diagnosis of dementia. Patient prognostication, as well as future research into post-ICU cognitive decline, should focus on these higher-risk subgroups.

Relative contribution of THTR-1 and THTR-2 in thiamin uptake by pancreatic acinar cells: studies utilizing Slc19a2 and Slc19a3 knockout mouse models

Thiamin is essential for normal function of pancreatic acinar cells, and its deficiency leads to a reduction in pancreatic digestive enzymes. We have recently shown that thiamin uptake by rat pancreatic acinar cells is carrier-mediated and that both thiamin transporter (THTR)-1 and THTR-2 are expressed in these cells; little, however, is known about the relative contribution of these transporters toward total carrier-mediated thiamin uptake by these cells. We addressed this issue using a gene-specific silencing approach (siRNA) in mouse-derived pancreatic acinar 266-6 cells and Slc19a2 and Slc19a3 knockout mouse models. First we established that thiamin uptake by mouse pancreatic acinar cells is via a carrier-mediated process. We also established that these cells as well as native human pancreas express THTR-1 and THTR-2, with expression of the former (and activity of its promoter) being significantly higher than that of the latter. Using gene-specific siRNA against mouse THTR-1 and THTR-2, we observed a significant inhibition in carrier-mediated thiamin uptake by 266-6 cells in both cases. Similarly, thiamin uptake by freshly isolated primary pancreatic acinar cells of the Slc19a2 and Slc19a3 knockout mice was significantly lower than uptake by acinar cells of the respective littermates; the degree of inhibition observed in the former knockout model was greater than that of the latter. These findings demonstrate, for the first time, that both mTHTR-1 and mTHTR-2 are involved in carrier-mediated thiamin uptake by pancreatic acinar cells.

Spontaneous Intracranial Hypotension: Correlation of Imaging Findings with Clinical Features

BACKGROUND

Spontaneous intracranial hypotension (SIH) is increasingly recognized as a clinically variable and likely underdiagnosed syndrome caused by non-traumatic CSF leaks. The aim of this study was to correlate the findings of imaging studies - magnetic resonance imaging (MRI), radionuclide cisternography - with clinical features and CSF pressure in SIH in order to improve the diagnostic yield and management in patients with SIH.

METHODS

Clinical case study of 10 consecutive cases of SIH, MRI, radio-isotope cisternography.

RESULTS

5 out of 10 patients had unusual clinical symptoms of SIH(2 subdural haematomas, 1 gait ataxia, 1 tinnitus, 1 haemodialysis-associated headache). In 7 patients pachymeningeal gadolinium enhancement was detected in MRI accompanied by a reduced CSF opening pressure. In contrast, the 3 patients with normal MRI also had a normal CSF pressure. Radio-isotope cisternography was abnormal in all patients tested. There was no correlation between the severity of clinical symptoms and MRI or radionuclide cisternography findings.

CONCLUSIONS

The spectrum of clinical symptoms and imaging findings in SIH is highly variable. There- fore the diagnosis of SIH is often delayed. Radio-isotope cisternography is an important additional diagnostic method to detect CSF leaks or pathological kinetics of radio-isotope movement particularly in cases with normal MRI findings.

Developmental maturation of intestinal and renal thiamin uptake: studies in wild-type and transgenic mice carrying human THTR-1 and 2 promoters

Thiamin (B1) is an essential micronutrient for normal growth and development. Mammals obtain thiamin through intestinal absorption, while in the kidney thiamin is reabsorbed to prevent its loss in the urine, both processes are specialized, carrier-mediated and involve thiamin transporters-1 and 2 (THTR-1 and THTR-2, respectively; products of the SLC19A2 and SLC19A3 genes). Although thiamin appears to play an important role in neonatal growth, little is currently known about the possible regulation of intestinal and renal thiamin uptake during developmental maturation. We addressed these issues by examining intestinal and renal thiamin uptake and expression of THTR-1 and THTR-2 during early stages of life. We utilized wild-type mice (mice express orthologues of both thiamin transporters) and transgenic mice expressing human SLC19A2 or SLC19A3 promoter-reporter transgenes as a model system and examined carrier-mediated thiamin uptake, mTHTR-1 and 2 protein and mRNA levels and luciferase activity in suckling (13 days), weanling (25-27 days), and adult (60-65 days) mice. Carrier-mediated thiamin uptake by jejunal and renal brush border membrane vesicles (BBMV) both decreased with maturation (suckling>weanling>adult) and were associated with a reduction in mTHTR-1 and mTHTR-2 protein, mRNA levels, and the activity of human SLC19A2 and SLC19A3 promoter-reporter constructs in the intestines and kidneys of transgenic mice. These results are the first to demonstrate that intestinal and renal thiamin uptake are developmentally regulated during early stages of life, mediated through mTHTR-1 and mTHTR-2, and suggest the possible involvement of transcriptional regulatory mechanism(s) in this regulation.

Contrast nephropathy may be partly mediated by autonomic dysfunction: renal failure considered as a modern maladaptation of the prehistoric trauma response

The mechanism behind iodinated radiocontrast nephropathy remains elusive. Direct oxidative damage is the prevailing hypothesis, but the apparent protective effect of iodine against oxidation contradicts this view. We propose that autonomic dysfunction participates in the pathogenesis of radiocontrast nephropathy and may account for other contrast-associated reactions previously attributed to allergy. Iodine, through its effects on thyroid function and chemoreceptor response to metabolic acidosis, may induce hyperadrenergia and consequently diminish renovascular flow and urine output. The renal response to adrenergia likely served an adaptive function during prehistoric evolution when trauma was a dominant source of hypovolemia and adrenergia, but the response may behave maladaptively today as evolutionarily nai ve triggers for adrenergia have emerged. Autonomic dysfunction can further impair renal function by deranging renovascular autoregulation and inducing oxidative reperfusion injury as a secondary phenomenon. Many other causes of acute renal failure such as drug toxicity, surgery, hospitalization, and diabetes may operate through hyperadrenergia, impaired renovascular autoregulation, and oxidative reperfusion injury. Dialysis, a volume reduction therapy for renal failure, can counterintuitively worsen renal dysfunction by exacerbating adrenergia, which may explain its association with accelerated atherosclerosis, inflammation, and cancer. Other examples of vicious cycles that perpetuate renal dysfunction may include renal artery stenosis, carotid stenosis, and atherosclerosis as well as the cardio-renal, hepato-renal, and pulmonary-renal syndromes. The benefits of hydration and bicarbonate in protecting renal function may operate in part through baroreceptor- and chemoreceptor-mediated reduction of sympathovagal ratio, respectively. New treatment paradigms for renal failure including pharmacologic and electro-mechanical therapies are envisioned based on autonomic remodeling, reduced sympathovagal ratio, and neuromodulation of pathways typically associated with trauma such as renin, angiotensin, vasopressin, and aldosterone.

Renal (uremic) encephalopathy in a goat

Renal encephalopathy was diagnosed in a 2-year-old male boar goat with a history of chronic weight loss and ataxia. Histopathological examination of the brain revealed a striking myelin vacuolation distributed mainly in two patterns: (i) along the junction of the neocortex and corona radiata, and (ii) in the bundles of the internal capsule as it dissects through the basal nuclei. The kidneys had diffuse severe tubular and glomerular necrosis and degeneration. The neural lesions are consistent with renal (uremic) encephalopathy. To the authors' knowledge, this is the first report of renal encephalopathy in a goat.

Adaptive regulation of intestinal thiamin uptake: molecular mechanism using wild-type and transgenic mice carrying hTHTR-1 and -2 promoters

Thiamin participates in metabolic pathways contributing to normal cellular functions, growth, and development. The molecular mechanism of the human intestinal thiamin absorption process involves the thiamin transporters-1 (hTHTR-1) and -2 (hTHTR-2), products of the SLC19A2 and SLC19A3 genes. Little is known about adaptive regulation of the intestinal thiamin uptake process or the molecular mechanism(s) involved during thiamin deficiency. In these studies, we addressed these issues using wild-type mice and transgenic animals carrying the promoters of the hTHTR-1 and -2. We show that, in thiamin deficiency, a significant and specific upregulation in intestinal carrier-mediated thiamin uptake occurs and that this increase is associated with an induction in protein and mRNA levels of mTHTR-2 but not mTHTR-1; in addition, an increase in the activity of the SLC19A3, but not the SLC19A2, promoter was observed in the intestine of transgenic mice. Similar findings were detected in the kidney; however, expression of both thiamin transporters and activity of both human promoters were upregulated in this organ in thiamin deficiency. We also examined the effect of thiamin deficiency on the level of expression of mTHTR-1 and mTHTR-2 messages and activity of the human promoters in the heart and brain of transgenic mice and found an increase in mTHTR-1 mRNA and a rise in activity of the SLC19A2 promoter in thiamin-deficient mice. These results show that the intestinal and renal thiamin uptake processes are adaptively upregulated during dietary thiamin deficiency, that expression of mTHTR-1 and mTHTR-2 is regulated in a tissue-specific manner, and that this upregulation is mediated via transcriptional regulatory mechanism(s).

Characterization of the 5'-regulatory region of the human thiamin transporter SLC19A3: in vitro and in vivo studies

Transcriptional regulation of expression of the human thiamin transporter-2 (the product of the SLC19A3 gene) is unknown. In this study, we cloned the 5'-regulatory region of the human SLC19A3 gene (2,016 bp), identified the minimal promoter region required for basal activity, demonstrated a critical role for specific cis-regulatory elements in determining the promoter activity, and confirmed activity and physiological relevance of the cloned SLC19A3 promoter in vivo. With the use of transiently transfected human intestinal epithelial Caco-2 cells and 5'-deletion analysis, the minimal promoter region required for basal activity of the SLC19A3 promoter was found to be encoded in a sequence between -77 and +59 by using the start of transcription initiation as position 1. This minimal region was found to contain a number of putative cis-regulatory elements, with a critical role for a stimulating protein-1 (SP1)/GC-box binding site (at position -48/-45 bp) established by means of mutational analysis. With the use of EMSA and supershift assays, the binding of SP1 and SP3 to the minimal promoter region was also demonstrated. In transiently transfected Drosophila SL2 cells, both SP1 and SP3 transactivated the SLC19A3 minimal promoter in a dose-dependent manner and in combination demonstrated an additive stimulatory effect. Functionality of the full-length SLC19A3 promoter was confirmed in vivo in transgenic mice expressing the promoter-luciferase reporter gene. These studies report the first characterization of the SLC19A3 promoter in vitro and in vivo and demonstrate the importance of an SP1 cis-regulatory element in regulating promoter activity of this important human gene.

Electrophysiological abnormalities in upper extremities after brachiocephalic A-V fistulas construction in predialysis patients

BACKGROUND

Peripheral neuropathy is considered a common complication in patients suffering from advanced chronic kidney disease (CKD). Superimposed peripheral multiple neuropathies may complicate arteriovenous (A-V) fistulas construction.

AIM

To evaluate, prospectively, the influence of brachiocephalic A-V fistulas construction on the peripheral nerves of the same extremity and to characterize the patients at risk for developing ischemic and neurological complications.

PATIENTS AND METHODS

Twenty patients suffering from advanced CKD were enrolled in the study: 10 diabetic and 10 non-diabetic patients. All patients underwent electrophysiological evaluation one week before, 3 weeks and 3 months after surgery. Median, ulnar and radial nerves were studied.

RESULTS

In non-diabetic patients MNCV was normal before and after surgery, but were significantly lower and reduced progressively and significantly after surgery in diabetic patients (p< or =0.02). In both non-diabetic and diabetic patients SNCV was reduced, but were significantly lower in diabetic patients before and after surgery (p< or =0.03). In diabetic patients it reduced progressively and significantly after surgery (p<0.01). Thirty percent of patients developed local edema and significant decrease of CMAP of median nerve three weeks after surgery (p=0.02) with complete resolution at three months.

CONCLUSION

Diabetic uremic patients are at increased risk to develop disabling neurological complications after the construction of A-V fistulas. Diabetes was the only predictive risk factor for developing these complications. Prevention requires careful preoperative electrophysiological evaluation and postoperative follow-up.

Inducible brain COX-2 facilitates the recurrence of hippocampal seizures in mouse rapid kindling

Brain cyclooxygenase-2 (COX-2), the rate-limiting enzyme in prostaglandin synthesis, is rapidly and transiently induced by convulsions in hippocampal and cortical neurons. Therefore, we examined the effects of COX-2 on the 'rapid kindling' development in COX-2 knockout mice and in mice treated with nimesulide, a COX-2-selective inhibitor. Rapid kindling development was examined based on the incidence of hippocampal EEG seizures and behavioral seizures following repetitive electrical stimulation of the perforant path at an interval of 40 s, and on the total afterdischarge (AD) duration induced by 50 stimulations. In addition, we measured COX-2 mRNA expression by in situ hybridization and PGE2 concentration using enzyme immunoassay following rapid kindling stimulation. The results suggested that brain COX-2 mRNA levels were markedly increased in the hippocampal neurons and the concentration of PGE2 was elevated significantly, and that the incidence of AD and seizure behavior induction and the total AD duration were significantly decreased under conditions of COX-2 deficiency. Therefore, we concluded that inducible COX-2 facilitates the recurrence of hippocampal seizures.

Central pontine and extrapontine myelinolysis owing to disequilibrium syndrome

Neurologic disorders can be seen in patients with end-stage renal failure owing to complications of hemodialysis or peritoneal dialysis. The disequilibrium syndrome can be seen, usually soon after or toward the end of dialysis. We report a patient with central pontine and extrapontine myelinolysis owing to disequilibrium syndrome. The patient had depressed consciousness, agitation, tremor, stupor and hyperactive deep tendon reflexes toward the end of the second peritoneal dialysis. A brain computed tomographic (CT) scan showed hypodense lesions in pontine and extrapontine locations without radiocontrast medium enhancement After 2 days, the patient had only minimal memory deficits. A control brain CT scan 1 week later showed a decrease of the lesions in central pontine and extrapontine locations. Central pontine and extrapontine myelinolysis should be suspected and investigated in the acute neurologic disorders of dialysis patients.

Headache and hemodialysis: a prospective study

OBJECTIVE

To determine the prevalence and clinical characteristics of headache in patients undergoing hemodialysis and to compare the prevalence of headache prior to and following the beginning of a hemodialysis program.

BACKGROUND

About 70% of patients receiving hemodialysis complain of headache. Despite this, headaches have not been well studied in this group of patients.

METHODS

We evaluated a series of patients with chronic renal failure who attended 3 hemodialysis services in a Brazilian town from January of 1998 to December of 1999. Patients with headache were prospectively followed and classified according to the International Headache Society criteria. The headaches were also categorized according to their temporal profile relative to hemodialysis.

RESULTS

Headache was reported by 87 (70.7%) of the 123 patients studied. Prior to beginning dialysis, 48% had migraine, 19% had episodic tension-type headache, and 8% had both. Headache related to arterial hypertension was the second most frequent headache diagnosis in these patients (25.4%). Fifty patients (57.5%) experienced headache during the session of hemodialysis. Thirty-four were classified as dialysis headache, 7 were classified as migraine, 7 as episodic tension-type headache, and 2 were unclassified. Twenty-four patients (27.6%) reported dramatic improvement of their headaches after the beginning of the dialysis program.

CONCLUSIONS

Headache is common in patients undergoing hemodialysis. Classification of such headaches according to the International Headache society criteria may be difficult.

Cellular and molecular aspects of thiamin uptake by human liver cells: studies with cultured HepG2 cells

The liver is an important site for thiamin metabolism, utilization, and storage. Little is known about the mechanism of thiamin uptake by the human liver. In this study, we examined cellular and molecular aspects of the human liver thiamin uptake process using the human-derived liver HepG2 cells as a model system. Our studies showed that the initial rate of thiamin uptake to be: (1) Na(+)-independent and occurs with no detectable metabolic alterations in the transported substrate, (2) highly pH-dependent with diminished uptake upon decreasing incubation buffer pH from 8.0 to 5.0, (3) higher following cell acidification compared to unacidified control cells, (4) saturable as a function of concentration with an apparent K(m) of 7.7+/-1.6 microM, (5) inhibited by the thiamin structural analogues oxythiamin and amprolium but not by the unrelated organic cations tetraethylammonium (TEA) and N-methylnicotinamide (NMN), and (6) inhibited in a concentration-dependent manner by the membrane transport inhibitor amiloride. Both of the recently cloned human thiamin transporters, i.e., SLC19A2 and SLC19A3, were found to be expressed in liver HepG2 cells with the former being the predominant form. High promoter activity of the predominant form, i.e., SLC19A2, was detected in HepG2 cells, and the minimal region of the SLC19A2 promoter required for its basal activity in these cells was found to be encoded in a sequence between -356 and -36 and has multiple putative cis-regulatory elements. Mutation of a number of these putative cis-elements diminished promoter activity of the SLC19A2 minimal region. These results show the involvement of a specialized carrier-mediated mechanism for thiamin uptake by human liver HepG2 cells. In addition, SLC19A2 was found to be the predominant thiamin uptake carrier expressed in these cells and its promoter displays a high level of activity in them.

Neurologic manifestations of renal disease

Mortality and morbidity from kidney disease and the spectrum of renal-associated neurologic disease have changed markedly since the introduction of renal dialysis and with the advent of renal transplantation. This article includes historical studies of the neurologic complications of acute uremia, now fairly uncommon, and recent literature regarding neurologic side effects associated with dialysis and renal transplantation.

[Drug resistant status epilepticus]

Refractory epileptic state (RES) is defined by severe seizures that are resistant to antiepileptic drug treatment. Diagnostic errors such as pseudo-seizures and encephalopathies with triphasic waves must be distinguished at an early stage from cases of RES. The latter are symptomatic of a focal brain lesion or severe systemic disease, most frequently metabolic in origin. The treatment of such conditions is aimed at correction of the underlying cause. A nosographic issue that is still a subject of discussion and which requires further study, i.e., PLEDS, will also be discussed in this article.

Transport of thiamine in human intestine: mechanism and regulation in intestinal epithelial cell model Caco-2

The present study examined the intestinal uptake of thiamine (vitamin B(1)) using the human-derived intestinal epithelial cells Caco-2 as an in vitro model system. Thiamine uptake was found to be 1) temperature and energy dependent and occurred with minimal metabolic alteration; 2) pH sensitive; 3) Na(+) independent; 4) saturable as a function of concentration with an apparent Michaelis-Menten constant of 3.18 +/- 0.56 microM and maximal velocity of 13.37 +/- 0.94 pmol. mg protein(-1). 3 min(-1); 5) inhibited by the thiamine structural analogs amprolium and oxythiamine, but not by unrelated organic cations tetraethylammonium, N-methylnicotinamide, and choline; and 6) inhibited in a competitive manner by amiloride with an inhibition constant of 0.2 mM. The role of specific protein kinase-mediated pathways in the regulation of thiamine uptake by Caco-2 cells was also examined using specific modulators of these pathways. The results showed possible involvement of a Ca(2+)/calmodulin (CaM)-mediated pathway in the regulation of thiamine uptake. No role for protein kinase C- and protein tyrosine kinase-mediated pathways in the regulation of thiamine uptake was evident. These results demonstrate the involvement of a carrier-mediated system for thiamine uptake by Caco-2 intestinal epithelial cells. This system is Na(+) independent and is different from the transport systems of organic cations. Furthermore, a CaM-mediated pathway appears to play a role in regulating thiamine uptake in these cells.

Behavioural deficits during the acute phase of mild renal failure in mice

Partially nephrectomized (NX) and sham-operated mice were biochemically and behaviourally compared, 10 days, 1 month and 1 year post-surgery. Plasma urea and creatinine concentrations were mildly increased in all NX groups, but creatinine clearance was significantly decreased, 10 days post-surgery only. NX mice showed lower body weights and reduced growth. Wire suspension and rotarod indicated unaffected motor functions, but NX mice did show reduced ambulation and swimming velocity, 10 days post-surgery. Hidden-platform water maze indicated a spatial learning impairment in NX mice, 10 days post-surgery, which could not be entirely reduced to motor incapacity. The acute behavioural deficits in these mildly uremic mice may relate to analogous symptoms in uraemic encephalopathy, a poorly understood brain syndrome occurring in uraemic patients.

Wernicke's encephalopathy associated with hemodialysis: report of two cases and review of the literature

Two rare cases of Wernicke's encephalopathy (WE) in non-alcoholic patients on hemodialysis (HD) are reported. They presented with the clinical triad of WE (ophthalmoplegia, ataxia and disturbance of consciousness) and intravenous administration of thiamine led to complete elimination of these manifestations. Reduced plasma thiamine levels prior to the administration confirmed the diagnosis of WE. Interestingly, a reduction in plasma thiamine levels by about half was seen in one of the patients on HD, suggesting that thiamine, a water-soluble vitamin, can be depleted with HD. In the literature, nine HD-dependent patients have been reported to develop WE, seven of whom were diagnosed postmortem. Their premortem diagnoses included uremic encephalopathy, dysequilibrium syndrome and dialysis dementia, which can often complicate HD and present symptoms similar to those of WE. We therefore emphasize that WE, even though a rare complication, should be suspected in all patients on HD who present with at least one of the clinical triad of WE.

Neurology and the kidney

Renal failure is relatively common, but except in association with spina bifida or paraplegia it is unlikely to occur as a result of disease of the CNS. Renal failure, however, commonly affects the nervous system. The effects of kidney failure on the nervous system are more pronounced when failure is acute. In addition to the important problems related to renal failure there are both acquired and genetically determined diseases which may affect the kidney and the brain. Those acquired diseases include the vasculitides, the paraproteinaemias, and various granulomatous conditions (considered in other chapters of Neurology and Medicine). In two of the most commonly encountered genetically determined diseases, Von Hippel-Lindau disease and polycystic kidney disease, location of pathogenic mutations will provide improved screening programmes and, possibly, allow therapeutic intervention. Uraemia may affect both the central and peripheral nervous systems. Whereas the clinical features of uraemia are well documented, the pathophysiology is less well understood and probably multifactorial. Uraemic encephalopathy, which classically fluctuates, is associated with problems in cognition and memory and may progress to delirium, convulsions, and coma. The encephalopathy may initially worsen with periods of dialysis and almost certainly relates to altered metabolic states in association with ionic changes and possibly impaired synaptic function. Renal failure may affect the peripheral nervous system, resulting in a neuropathy which shows a predilection for large diameter axons. This may be reversed by dialysis and transplantation. The myopathy seen in renal failure, often associated with bone pain and tenderness, is similar to that encountered in primary hyperparathyroidism and osteomalacia. Dialysis itself is associated with neurological syndromes including the dysequilibrium syndrome, subdural haematoma, and Wernicke's encephalopathy. Dialysis dementia, which was prevalent during the 1970s, has reduced in frequency with the use of aluminium free dialysate. With the introduction of transplantation and the concomitant use of powerful immunosuppressive drugs, the pattern of neurological problems encountered in renal replacement therapy has shifted. Five per cent of patients develop nerve injuries during renal transplantation, and up to 40% of patients experience neurological side effects from cyclosporine. Furthermore, CNS infections, often fungal in type, have been reported in up to 45% of transplant patients coming to postmortem. The nature of the involvement of neurologists with their nephrology colleagues is therefore evolving.

Uraemic pruritus is not related to plasma histamine concentrations

Pruritus is a common symptom in uraemic patients and its aetiology is poorly understood, although several factors have been implicated, including high histamine plasma levels. The aim of the study was to evaluate plasma levels of histamine in patients on maintenance haemodialysis in relation to the presence of itching (35 pruritic patients = group A; 50 non-pruritic patients = group B). Furthermore, we compared the values obtained with those of a healthy control group (64 subjects). We observed increased plasma histamine levels in uraemic patients compared with healthy controls. However, no relationship was found between plasma histamine values and itching because groups A and B showed overlapping values and there was no correlation between the intensity of pruritus and plasma histamine concentrations in group A patients. In conclusion, we suggest that there is no evidence for plasma histamine playing a significant part in uraemic pruritus.

The spectrum of epilepsy in sickle cell anemia

In a study population of 152 patients seen at Thomas Jefferson University Hospital's sickle cell center between 1981 and 1992, 21 patients with seizures were identified. Clinical charts, electroencephalograms and neuroradiological studies were reviewed retrospectively. Seventeen patients with epilepsy were identified. Eleven had generalized tonic-clonic, 2 had partial, and 4 had poorly characterized seizures. CT/MRI evaluation was focally abnormal in 6 patients, 4 of whom had cortical lesions. Atrophy was noted in 3 patients, while imaging studies were normal in 6 patients. The EEGs demonstrated focal epileptiform discharges in 9 patients, generalized slowing in 5 patients, and was normal in 3 patients. Four patients had generalized seizures only with meperidine administration, all of whom had nonfocal EEG and radiological studies. We concluded that (1) epilepsy is more common in sickle cell patients than in the general population; (2) the majority of our epileptic sickle cell patients have nonfocal CT or MRI studies but demonstrate focal EEG abnormalities; and (3) meperidine administration is associated with generalized seizures in sickle cell patients.

Retinal oscillatory potential abnormalities in patients with chronic renal failure, before and after dialytic treatment

Nineteen patients with chronic renal failure were studied, oscillatory potentials (OPs) being recorded shortly before and after dialytic treatment. Mean values of either onset latency (O1 latency) and duration of the complex (O1-N4 inter-peak latency) were found to be significantly longer in patients than in controls (p < 0.001). Most of the patients (12) showed a pathological prolongation of latency (> 2.5 SD). Amplitude changes also affected OPs, but earlier components were reduced to a lesser degree than the later ones, as shown by statistical analysis. Moreover, seven patients showed an almost complete loss of O3 and O4 peaks. Latency changes may be transiently reversed by dialysis, suggesting a functional impairment of the retinal response; the loss of later components is a more persistent abnormality probably related with a structural damage.

Relief of pruritus and decreases in plasma histamine concentrations during erythropoietin therapy in patients with uremia

BACKGROUND

The pathophysiologic aspects of pruritus in patients with chronic renal insufficiency are poorly understood, and there is no universally effective treatment. The improvement of pruritus in several patients receiving erythropoietin therapy raised the possibility that erythropoietin affects uremic pruritus directly.

METHODS

We undertook a 10-week placebo-controlled, double-blind, crossover study in a group of patients receiving hemodialysis who had severe pruritus, to investigate the effects of recombinant human erythropoietin on their pruritus and plasma histamine levels. Twenty patients with uremia, of whom 10 had severe pruritus and 10 did not, received erythropoietin (36 units per kilogram of body weight three times weekly) and placebo in random order, each for five weeks. The severity of pruritus was scored weekly, and plasma histamine levels were measured at the beginning and end of each five-week period.

RESULTS

Eight of the 10 patients with pruritus had marked reductions in their pruritus scores during erythropoietin therapy. The mean (+/- SE) pruritus score decreased from 25 +/- 3 to 6 +/- 1 in these patients. The pruritus returned within one week after the discontinuation of therapy. The improvement was not related to the change in hemoglobin level. These eight patients were successfully treated again with low doses of erythropoietin (18 units per kilogram three times weekly), and the effect has persisted for six months. The patients with pruritus had elevated plasma histamine concentrations (20.7 +/- 2.7 nmol per liter), as compared with the patients without pruritus (4.2 +/- 0.6 nmol per liter; P less than 0.001) and normal subjects (2.1 +/- 0.2 nmol per liter; P less than 0.001). Therapy with erythropoietin induced a decrease in plasma histamine concentrations in both groups of patients with uremia, and recurrences of pruritus after the discontinuation of erythropoietin were accompanied by increases in plasma histamine concentrations.

CONCLUSIONS

Erythropoietin therapy lowers plasma histamine concentrations in patients with uremia and can result in marked improvement of pruritus.

Neurologic complications in chronic renal failure: a retrospective study

We have retrospectively examined 324 patients with chronic renal failure and evaluated the probable underlying causes of neurologic complications, laboratory data and therapeutic interventions. The common neurologic problems in our patients were alterations in consciousness (40.7%) and convulsions (35.1%). When BUN concentration was above 135 mg/dl and creatinine clearance was below 8 m/min/1.73 m2, alteration of consciousness was observed and when BUN concentration was 200 mg/dl and creatinine clearance was below 7 m/min/1.73 m2, abnormal convulsives appeared. Changes in deep tendon reflexes and pathologic reflexes were associated with hypertension. All of the patients with cortical atrophy using computerized cranial tomography aluminum hydroxide at least for 18 months, and six of them had hemodialysis. Fourteen patients who underwent dialysis developed convulsions and were thought to have disequilibrium syndrome. These findings are consistent with the suggestion that the metabolic and biochemical derangements associated with CRF may be particularly detrimental to the still developing CNS of the child.

Principles, uses, and complications of hemodialysis

Hemodialysis replaces missing renal function, and it does so incompletely. Current technology provides for reliable and flexible treatment strategies guided by patient's well-being and careful evaluation of plasma urea concentrations. Hemodialysis is indicated in many medical emergencies, notably fluid overload and hyperkalemia, and all types of renal failure. Hemodialysis requires a sizable effort and a significant commitment of time by both patients and professionals and is not suited for every patient with renal insufficiency. Notable treatment-related side effects include cramps, hypotension, problems with blood access, and reactions to dialyzer membrane materials. Far from treating underlying disease, hemodialysis extends life and permits the expression of much progressive multisystem disease. Cardiovascular disease is the most common comorbid condition and cause of early mortality.

Utility of laboratory studies in the emergency department patient with a new-onset seizure

Extensive laboratory testing is often performed in the emergency department evaluation of the new-onset seizure patient. To determine the utility of such testing, a prospective study of patients with a new-onset seizure presenting to the ED of an inner-city, university-affiliated teaching hospital was done. One hundred thirty-six patients were entered into the study between October 1984 and January 1988. All patients had uniform data collection performed. Pertinent historical information and physical examination findings were recorded on a standardized form before laboratory abnormality was a sole or contributory cause of the seizure disorder. These included four patients with hypoglycemia, four with hyperglycemia, two with hypocalcemia, and one with hypomagnesemia. Only two cases (hypoglycemia) were not suspected on the basis of findings on the history or physical examination. In ED patients, the incidence of a new-onset seizure due to a correctable metabolic disturbance is low. We conclude that, with the exception of the serum glucose, the extensive ED laboratory workup often done for the evaluation of a new-onset seizure is unnecessary. Further test ordering should be directed by the medical history and physical examination.

Convulsions in children undergoing renal transplantation

We reviewed the records of 154 children who received 207 renal transplants for end-stage renal disease from 1965 to 1987, and discovered that 48 (31%) had had convulsive seizures, some before transplant surgery, others only after transplant, and some during both before and after transplantation. The majority of children had minimal long-term problems, and 60% of the children had only a single convulsion. In six of the patients, convulsions were a manifestation of more serious underlying conditions that produced significant morbidity. Seizures of differing clinical type occurred, with hypertension being the most significant etiologic factor. In children with renal failure, there are minimal symptoms heralding the hypertensive encephalopathy. Rapid resolution without recurrence of seizures after control of hypertension is a major sign that hypertension was the cause and that the long-term prognosis is good.

Psychiatric aspects of renal transplantation

Despite the growth of heart, liver and bone marrow transplantation, the kidney continues to be the organ most frequently transplanted. Over the years psychiatrists have been active in attempting to understand the adaptational tasks of organ donors and recipients and in evaluating and treating transplant patients. A body of knowledge with regard to renal transplantation has developed. What follows is an update of psychiatric aspects of renal transplantation.

Optic neuropathy in uremia

We examined three patients who developed optic neuropathies while undergoing chronic hemodialysis. One patient developed severe bilateral deterioration of vision, but recovered totally four weeks after discontinuing deferoxamine chelation therapy. Another patient had bilateral visual loss associated with chronic papilledema of idiopathic increased intracranial pressure. A third showed atypically severe consecutive anterior ischemic optic neuropathy. The latter two patients showed little improvement with high-dose intravenous methylprednisolone therapy combined with more vigorous hemodialysis. These cases, in addition to those previously described, underscore the heterogeneity of optic nerve disease in patients with uremia.

Non surgical treatment of subdural hematoma in a hemodialysis patient

The development of subdural hematoma in the course of hemodialysis treatment has been well documented in the literature. We report a case of a subdural hematoma in a patient on hemodialysis, in whom surgery was contraindicated, due to her concurrent use of anticoagulants. Good recovery was achieved by steroid treatment. Although surgical removal constitutes the essential therapeutic approach for subdural hematoma, we emphasize the importance of medical management in special cases where surgery is contraindicated.

Patchy cerebral white matter edema in chronic renal failure

Bilateral patchy cerebral white matter edema was observed in two children with chronic renal failure. Uremia in one case and hypertension or hyponatremia in the other appeared to be the cause of the neurological and radiological findings.

Visual evoked potential changes following renal transplantation

We have followed a group of 18 uremic patients through living-related donor renal transplantation (RTX) using pattern-reversal VEPs. Recordings were made prior to and 10 weeks after surgery at high, medium and low spatial frequencies. Prior to RTX, mean latency of the P100 component of the VEP was 107 msec. Individual values did not correlate with blood urea nitrogen or creatinine. Patients requiring hemodialysis did not differ from non-dialyzed patients. Ten weeks after RTX P100 latencies were significantly shortened while N75 latencies were unchanged. Several diabetic patients exhibited the appearance of previously unrecorded wave forms. P100 latency increased significantly with increasing spatial frequency before and after transplantation. Diabetic patients demonstrated a consistent increase in P100 amplitude while non-diabetic patients demonstrated a consistent decrease in P100 amplitude after RTX. The data indicate that renal transplantation has beneficial effects on the central nervous system of uremic patients not seen with chronic hemodialysis and that these effects may be quantitatively measured using the VEP. The data further suggest that electrophysiological effects of uremia and diabetes may be additive, but reversible after RTX. Alterations in the uremic and diabetic VEP may be related to retinal or more proximal central nervous system structures.

F-wave study in patients with chronic renal failure on regular haemodialysis

Motor nerve conduction along the entire length of ulnar and tibialis posterior nerves was studied in 30 uraemic patients and in 20 control subjects. The M and F latencies, MNCV (between the stimulus sites), FWCV (between the spinal cord and the stimulus sites) and F-ratio (conduction time ratio of proximal to distal segment) were assessed to evaluate the conduction in the proximal versus the distal nerve segment. In the uraemic patients, the slowing of nerve conduction involved both segments of the tested nerves to the same extent. In fact, the F-ratio did not show any significant difference between the two groups; in only one patient was its value lower than the normal limit in the tibialis posterior nerve.