[The possible causes of serious central nervous system complications occurring after liver transplantation]

OBJECTIVE

To study the classification, possible causes, cure and prevention measures of serious central nervous system (CNS) complications occurring early following liver transplantation.

METHODS

The clinical material records of 347 patients undergoing the orthotopic liver transplantation from July 2001 to July 2006 were analyzed retrospectively. The perioperation risk factors of CNS complications, which might be the primary liver disease, serum sodium level, magnesium level, fluctuation degree of plasma osmolality and serum sodium, function of blood clotting, etc. , were analyzed between patients with serious CNS complications and without neurological complications.

RESULTS

A total of 71 (20. 46%) neurological symptoms appeared in 347 postoperative patients who included 6 cases (1. 73%) with serious CNS complications such as cerebral edema, cerebral hemorrhage and central pontine myelinolysis, and of 6 cases, 5 patients died. The morbidity of early serious complications of CNS was higher in patients with decompensate cirrhosis and/or hypersplenism. Compared with the group of no neurological complications, two patients with cerebral hemorrhage suffered from preoperative hypersplenism and worse dysfunction of blood clotting (P<0. 05); patients with developed CPM and cerebral oedema had serious hyponatremia history before operation, and intensely fluctuated plasma osmolality showed before and after operation.

CONCLUSION

The onset of serious complications of CNS in recipients of liver transplantation may be intimately related to the primary liver disease, and be associated with chronic hyponatremia, rapid correction of serum sodium concentration, intense increase of plasma osmolality and no prompt rectification of the function of blood clotting during perioperation.

Early treatment of premature infants with steroids: neurological sequelae

(1) For more than 30 years premature infants with respiratory disorders have been routinely prescribed a steroid during the first days of life. (2) A number of immediate adverse effects have been described, and studies in which infants were monitored until they were 3 years old have raised concerns about neurological sequelae. (3) 146 children who participated in a randomised placebo-controlled trial of systemic steroid therapy in the early postnatal period were monitored until they were eight years old. (4) Mean height was lower in the dexamethasone group than among placebo-treated controls (121 cm to 122 cm, depending on gender, versus 124 cm to 126 cm), and mean cranial circumference was also smaller (49.8 cm versus 50.6 cm). (5) Scores for various motor and cognitive tests, as well as some school examinations, were lower in children exposed to dexamethasone. (6) Disabilities were more frequent in the group exposed to dexamethasone (28 of 72 children versus 16 of 74 controls; p <0.05). (7) These data confirm the neurological adverse effects of prolonged treatment of premature infants with systemic steroids in the early postnatal period. Such steroid regimen should no longer be used in this setting.

Toll-like receptors as targets for inflammation, development and repair in the central nervous system

Toll-like receptors (TLRs) that play key roles in inflammation are also widely expressed in the CNS. While they are well known to activate inflammatory responses to microbial products, TLRs fulfill additional roles in the absence of infection. Emerging evidence suggests that several TLRs play a role in CNS development during fetal life and in repair during adult life. This review discusses the available data on the expression and function of individual TLR family members in the CNS and clarifies why TLRs deserve close scrutiny as a novel group of therapeutic targets for CNS disorders.

BCG vaccination confers poor protection against M. tuberculosis HN878-induced central nervous system disease

Using a rabbit model of tuberculous meningitis (TBM), we compared the protective efficacy of Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccination against central nervous system infection with the virulent M. tuberculosis clinical isolate HN878 and the laboratory strain H37Rv. Although BCG clearly provided protection against infection with either challenge strain, protection against disease manifestations was significantly poorer in rabbits infected with HN878. BCG was less efficient in protecting against HN878 dissemination to the liver and spleen and against HN878-induced inflammation, loss of body weight, lung and brain pathology, and signs of disease. We suggest that the efficacy of newly developed vaccines should be tested in animal models not only against challenge with M. tuberculosis H37Rv but also with different clinical isolates including the highly virulent strains of the W-Beijing family.

Novel strategies for protection and repair of the central nervous system

Clinical possibilities in many neurological conditions are limited by our current inability to correct structural damage to the nervous system, and treatments to prevent damage are also limited. Current research has produced promising treatments that promote neuroprotection, plasticity, axon regeneration, remyelination and cell replacement. As these treatments go through clinical trials and enter the clinic, the treatment of several neurological conditions will change greatly.

Erythropoietin protects the central nervous system during prolonged hypothermic circulatory arrest: An experimental study in a canine model

OBJECTIVE

Current data suggest that erythropoietin protects the brain and the spinal cord from ischemic and traumatic injury. In this study, we determined whether erythropoietin protects the central nervous system during prolonged hypothermic circulatory arrest in an experimental canine model.

METHODS

Ten adult beagle dogs were randomly and intravenously injected with either 5000 U/kg recombinant human erythropoietin or normal saline. Each dog was then subjected to a cardiopulmonary bypass and 120 minutes of deep hypothermic circulatory arrest (18 degrees C). The level of tau proteins in the cerebrospinal fluid, a modified marker of neurologic deficit in dogs, and the histopathologic characteristics of the brains and spinal cords were then examined.

RESULTS

The level of tau proteins was significantly lower in the erythropoietin-treated group than in the untreated group at 6 hours (20 +/- 12 vs 144 +/- 54 pg/mL; P = .036) and 12 hours (64 +/- 35 vs 478 +/- 103 pg/mL; P = .01) after the operation. The total Neurologic Deficit Score was 59 +/- 31 (0, normal; 500, brain death) in the erythropoietin-treated group, compared with 376 +/- 30 in the untreated group (P = .0117). Histopathologic examination revealed that ischemic neuronal changes and apoptosis in the hippocampus CA1 were significantly lower in the erythropoietin-treated group (P < .01 and P = .028, respectively).

CONCLUSIONS

This study showed that erythropoietin protected the central nervous system during prolonged hypothermic circulatory arrest, partly by preventing both necrosis (ischemic neuronal changes) and apoptosis.

Overview of safety pharmacology

Safety pharmacology assesses the potential risks of novel pharmaceuticals for human use. ICH S7A guidelines recommend a core battery of studies on three vital systems: central nervous system (CNS), cardiovascular (CV) and respiratory. Primary CNS studies look for effects on general behavior, locomotion, neuromuscular coordination, the convulsive threshold, and vigilance. The primary CV test battery evaluates proarrhythmic risk using in vitro approaches (hERG channel and Purkinje fiber assays) and in vivo measurements in conscious animals via telemetry. Comprehensive cardiac risk assessment also includes full hemodynamic evaluation, most suitably conducted in the anesthetized large animal. Basic respiratory function can be approached via whole-body plethysmography in conscious animals where sensitivity to respiratory-depressant effects can be enhanced by exposure to increased CO(2). Other aspects of safety pharmacology studies discussed are the timing of studies, ethical and animal welfare issues, and statistical evaluation.

Effects of statins beyond lipid lowering: Potential for clinical benefits

BACKGROUND

The role of statin drugs in the reduction of serum lipids has been well documented. More recently, evidence suggesting that statins may positively impact many organ systems and disease states independent of lipid reduction has emerged. The term "pleiotropic effects" has been used to refer to these properties. We reviewed the evidence exploring such potential effects.

METHODS

A search of the MEDLINE database was conducted for articles published between 1985 to 2005 on the pleiotropic and the lipid-lowering independent effects of statin drugs. The search terms "statin", "HMG-CoA reductase inhibitor", "pleiotropic effects", and "inflammation" were used. English language articles were selected for inclusion along with selected cross-references.

RESULTS

Numerous animal and clinical studies support the presence of a spectrum of beneficial effects for statins that are independent of their lipid-lowering properties. These effects are mediated by a variety of mechanisms and they suggest that the therapeutic role of statins may expand.

CONCLUSION

Statins have shown great promise beyond their lipid-lowering effects. Ongoing and future studies will help to further clarify the potential clinical impact of these "pleiotropic effects".

Application of Physiologically Based Pharmacokinetic Modeling in Setting Acute Exposure Guideline Levels for Methylene Chloride

Acute exposure guideline levels (AEGLs) are derived to protect the human population from adverse health effects in case of single exposure due to an accidental release of chemicals into the atmosphere. AEGLs are set at three different levels of increasing toxicity for exposure durations ranging from 10 min to 8 h. In the AEGL setting for methylene chloride, specific additional topics had to be addressed. This included a change of relevant toxicity endpoint within the 10-min to 8-h exposure time range from central nervous system depression caused by the parent compound to formation of carboxyhemoglobin (COHb) via biotransformation to carbon monoxide. Additionally, the biotransformation of methylene chloride includes both a saturable step as well as genetic polymorphism of the glutathione transferase involved. Physiologically based pharmacokinetic modeling was considered to be the appropriate tool to address all these topics in an adequate way. Two available PBPK models were combined and extended with additional algorithms for the estimation of the maximum COHb levels. The model was validated and verified with data obtained from volunteer studies. It was concluded that all the mentioned topics could be adequately accounted for by the PBPK model. The AEGL values as calculated with the model were substantiated by experimental data with volunteers and are concluded to be practically applicable.

Neurologic and psychiatric complications of antiretroviral agents

Advances in highly active antiretroviral therapy (HAART) aim to improve the efficacy of HIV drugs as well as the quality of life in HIV-infected patients. Neurologic and psychologic disturbances that occur because of HIV disease and therapy are of great concern, and because they can overlap and are often difficult to distinguish, their pathogenesis is not clearly understood. Furthermore, these complications can lead to decreased adherence, thereby interfering with treatment outcomes. Antiretrovirals, including nonnucleoside reverse transcriptase inhibitors, can penetrate the central nervous system (CNS) and suppress viral replication, but they can also exacerbate CNS side effects and neuropsychiatric symptoms. When deciding which HAART drug combination is most appropriate for a patient, clinicians must consider the individual's risk of CNS complications together with the efficacy of the specific HAART regimen.

Oligodendrocyte progenitor cell (OPC) transplantation is unlikely to offer a means of preventing X-irradiation induced damage in the CNS

Oligodendrocyte lineage cells [oligodendrocytes and their parent cells, the oligodendrocyte progenitor cells (OPCs)] are depleted by X-irradiation and progenitor cell transplantation has been proposed as a therapeutic strategy to counteract radiation induced myelopathy. Previous studies have demonstrated that oligodendrocyte progenitor cell (OPC) depletion is a prerequisite for establishing transplanted OPCs in normal tissue. One can therefore predict that the extent and timing of OPC depletion and regeneration following X-irradiation will be crucial factors in determining the feasibility of this therapeutic approach. To address this issue, we have examined the time course of OPC depletion and regeneration following a range of X-irradiation doses (5 to 40 Gy), and its relationship to establishing transplanted OPCs in X-irradiated tissue. Doses above 10 Gy resulted in rapid death of OPCs. With doses up to 20 Gy, surviving X-irradiated OPCs were capable of robust regeneration, restoring normal densities within 6 weeks. Transplanted OPCs could only be established in tissue that had been exposed to > or =20 Gy. Since 20 Gy is close to the ED50 for radiation necrosis, our findings demonstrate the limitation of OPC replacement strategies.

Menopause and disorders of the central nervous system

The cessation of ovarian estrogen production occurring around the time of menopause has the potential to influence central nervous system function, as well as a number of neurological disorders that affect women during midlife and old age, including memory loss and mild cognitive impairment, ischemic stroke, Parkinson's disease, and Alzheimer's disease. During midlife, there is observational evidence that episodic memory is not substantially affected by natural menopause or by use of estrogen-containing hormone therapy, but short-term clinical trial evidence suggests hormone therapy might benefit verbal memory after surgical menopause. Clinical trial data indicate that hormone therapy does not reduce, and may increase, stroke incidence. Parkinson's disease and Alzheimer's disease are the 2 most common neurodegenerative illnesses. Estrogen influences dopaminergic pathways within the central nervous system. However, available observational evidence is limited and inconclusive regarding any role of hormone therapy in influencing risk or symptoms of Parkinson's disease, a disorder of dopaminergic neurons. Finally, clinical trial data indicate that hormone therapy should not be initiated in the late postmenopause with the goal of improving memory, preventing cognitive decline, reducing dementia risk, or improving Alzheimer's disease symptoms. An important priority for clinical investigation is to determine whether hormone therapy used during the menopausal transition and early postmenopause has long-term effects on cognition or dementia risk. The critical window hypothesis as applied to Alzheimer's disease conjectures that effects of early hormone therapy might differ from those of hormone therapy initiated in the late postmenopause, but convincing evidence is yet to be obtained.

Prophylactic activation of neuroprotective stress response pathways by dietary and behavioral manipulations

It is well established that when most types of cells, including neurons, are exposed to a mild stress they increase their ability to resist more severe stress. This "preconditioning" phenomenon involves up-regulation of genes that encode cytoprotective proteins such as heat-shock proteins and growth factors. We found that a similar beneficial cellular stress response can be induced in neurons throughout the brain by a "meal-skipping" dietary restriction (DR) regimen in rats and mice. DR is effective in protecting neurons and improving functional outcome in models of stroke, Alzheimer's, Parkinson's and Huntington's diseases. DR induces an increase in the levels of brain-derived neurotrophic factor (BDNF) and heat-shock proteins in neurons. DR also stimulates neurogenesis in the hippocampus, and BDNF plays a role in this effect of DR. Physical exercise and environmental enrichment are two other manipulations that have been shown to induce BDNF expression in the brain, presumably because it is a mild cellular stress. When taken together with epidemiological and clinical studies in humans, the data from animal studies suggest that it may be possible to reduce the risk for age-related neurodegenerative disorders through dietary and behavioral modifications that act by promoting neuronal plasticity and survival.

CD4+ T-cell reconstitution reduces cytomegalovirus in the immunocompromised brain

Cytomegalovirus (CMV) infection is the most common opportunistic infection of the central nervous system in patients with human immunodeficiency virus or AIDS or on immunosuppressive drug therapy. Despite medical management, infection may be refractory to treatment and continues to cause significant morbidity and mortality. We investigated adoptive transfer as an approach to treat and prevent neurotropic CMV infection in an adult immunodeficient mouse model. SCID mice were challenged with intracranial murine CMV (MCMV) and reconstituted with MCMV- or vesicular stomatitis virus (VSV)-sensitized splenocytes, T cells, or T-cell subsets. T cells labeled with vital dye or that constitutively generated green fluorescent protein (GFP) were identified in the brain as early as 3 days following peripheral transfer. Regardless of specificity, activated T cells localized to regions of the brain containing CMV, however, only those specific for CMV were effective at clearing virus. Reconstitution with unsorted MCMV-immune splenocytes, enriched T-cell fractions, or CD4(+) cells significantly reduced virus levels in the brain within 7 days and also prevented clinical disease, in significant contrast with mice given VSV-immune unsorted splenocytes, MCMV-immune CD8(+) T cells, and SCID control mice. Results suggest CMV-immune T cells (particularly CD4(+)) rapidly cross the blood-brain barrier, congregate at sites of specific CMV infection, and functionally eliminate acute CMV within the brain. In addition, when CMV-immune splenocytes were administered prior to a peripheral CMV challenge, CMV entry into the immunocompromised brain was prevented. Systemic adoptive transfer may be a rapid and effective approach to preventing CMV entrance into the brain and for reducing neurotropic infection.

Cannabinoids and neuroprotection in CNS inflammatory disease

The current failure of potent immunosuppressive agents to control progressive disease in multiple sclerosis has moved a focus from immunotherapy towards the need for neuroprotection. There is increasing evidence for cannabinoid-mediated control of symptoms, which is being more supported by the underlying biology. However there is accumulating evidence in vitro and in vivo to support the hypothesis that the cannabinoid system can limit the neurodegenerative possesses that drive progressive disease, and may provide a new avenue for disease control.

Cranio-cervical stabilization of traumatic atlanto-occipital dislocation with minimal resultant neurological deficit

Our purpose is to describe a case of atlanto-occipital dislocation and discuss treatment approaches to minimize subsequent neurological deficits. Traumatic atlanto-occipital dislocation, has traditionally been considered rare and lethal, due to resulting high levels of spinal cord injury. Outcomes are generally expected to be poor. However, recent case reports indicate that survival is increasing. Of patients who survive cranio-cervical dislocation, many endure resulting neurological deficits. We present a rare case of a 23-year-old male, who sustained an atlanto-occipital dislocation in a motor vehicle accident. The patient presented with a Glasgow Coma Scale (GCS) of 11T. Lateral C-spine x-ray and thin-section slices CT delineated a C1 ring fracture on the left side with approximately 1 cm anterior and superior subluxation of the occipital condyles of the cranium in reference to C1. The patient was completely awake, alert, and was following commands. The patient underwent a cranio-cervical stabilization from occiput to C3, using lateral mas screws (C1-C3) and transarticular screws (C2-C3). The Vertex (Medtronics) system used included longitudinal bars connected to the lateral mas plating system, which was subsequently used to place screws within the keel of the occipital bone. Motor strength and sensation remained intact following surgery. One-week post-operation, the patient was ambulating 140 feet, conversationally appropriate, and had a GCS of 15. This case illustrates the possibility for neurosurgical intervention of cranio-cervical dislocations to achieve optimal outcome and demonstrates that survival from this injury is not only conceivable, but recovery of function is also possible.

Nanotechnology approaches for the regeneration and neuroprotection of the central nervous system

Nanotechnology is the science and engineering concerned with the design, synthesis, and characterization of materials and devices that have a functional organization in at least 1 dimension on the nanometer (ie, one-billionth of a meter) scale. The ability to manipulate and control engineered self-assembling (ie, self-organizing) substrates at these scales produces macroscopic physical and/or chemical properties in the bulk material not possessed by the constituent building block molecules alone. This in turn results in a degree of functional integration between the engineered substrates and cellular or physiological systems not previously attainable. Applied nanotechnology aimed at the regeneration and neuroprotection of the central nervous system (CNS) will significantly benefit from basic nanotechnology research conducted in parallel with advances in cell biology, neurophysiology, and neuropathology. Ultimately the goal is to develop novel technologies that directly or indirectly aid in providing neuroprotection and/or a permissive environment and active signaling cues for guided axon growth. In some cases, it is expected that the neurosurgeon will be required to administer these substrates to the patient. As such, in order for nanotechnology applications directed toward neurological disorders to develop to their fullest potential, it will be important for neuroscientists, neurosurgeons, and neurologists to participate and contribute to the scientific process alongside physical science and engineering colleagues. This review will focus on emerging clinical applications aimed at the regeneration and neuroprotection of the injured CNS, and discuss other platform technologies that have a significant potential for being adapted for clinical neuroscience applications.