Electroencephalographic abnormalities in liver transplant recipients: practical considerations and review

New Methods of Testing and Brain Imaging in Hepatic Encephalopathy: A Review

The diagnosis of hepatic encephalopathy is predominantly clinical, and the tests available assist in the diagnosis only by excluding other causes. Covert hepatic encephalopathy, which is defined as abnormal performance on psychometric tests when standard neurologic examination is completely normal, has gained widespread attention in recent years due to its effect on quality of life. This review focuses on the tests available to aid in the diagnosis of this significant complication of liver disease, and discusses the complex pathophysiologic mechanisms identified through new imaging techniques and their significance toward development of new therapeutic targets for this condition.

Neurologic aspects of multiple organ transplantation

Complex multiorgan failure may require simultaneous transplantation of several organs, including heart-lung, kidney-pancreas, or multivisceral transplantation. Solid organ transplantation can also be combined with hematopoietic stem cell transplantation to modulate immunologic response to a solid organ allograft. Combined multiorgan transplantation may offer a lower rate of allograft rejection and lower immunosuppression needs. In recent years, intestinal and multivisceral transplantations became viable as a rescue treatment for patients with irreversible intestinal failure who can no longer tolerate total parenteral nutrition with 70% survival after 5 years which is comparable to other types of solid organ allografts. Post-transplant neurologic complications were reported in up to 86% of allograft recipients and greatly overlap in intestinal and multivisceral allograft recipients, without a significant effect on the outcome of transplantation. Other common organ combinations in multiorgan transplantation include kidney-pancreas, which is mostly used for patients with renal failure and uncontrolled diabetes, and heart-lung for patients with congenital heart disease and idiopathic pulmonary arterial hypertension. Kidney-pancreas transplantation frequently results in an improvement of diabetic complications, including diabetic neuropathy. Heart-lung allograft recipients have very similar clinical course and spectrum of neurologic complications to lung transplant recipients. At this time there are no reports of an increased risk of graft-versus-host disease with combined transplantation of solid organ allograft and hematopoietic stem cells. Chronic immunosuppression and complex toxic-metabolic disturbances after multiorgan transplantation create a permissive environment for development of a wide spectrum of neurologic complications which largely resemble complications after transplantations of individual components of complex multiorgan allografts.

Cerebral protective effect of nicorandil premedication on patients undergoing liver transplantation

BACKGROUND

Neurological injury is a common complication in the early period after liver transplantation, posing an enormous obstacle to treatment efficiency and patient survival. Nicorandil is a mitochondrial ATP-sensitive potassium channel (mitoKATP) opener. It has been reported to be effective in reducing brain injury in recent studies. However, it is still unclear whether nicorandil has cerebral protective effect in patients undergoing liver transplantation.

METHODS

Fifty patients scheduled for liver transplantation were randomly divided into a nicorandil group (group N) (n=25), in which patients received 10 mg nicorandil through a nasogastric tube 30 minutes before induction of anesthesia, and a control group (group C) (n=25) who received 10 mL normal saline. The Mini-Mental State Examination (MMSE) was performed before anesthesia (day 0), and on days 3 and 7 after surgery. Blood samples were obtained before induction of anesthesia (T1), and at 12 (T2) and 36 hours (T3) after surgery for determination of serum neuron-specific enolase (NSE) and S100β protein (S100β) concentrations.

RESULTS

During surgery, 5 patients in each group were eliminated due to severe reperfusion or renal insufficiency. Therefore, 20 patients remained in each group. The MMSE scores after operation were significantly lower than those before operation in group C. However, there was no difference at days 3 and 7 compared with day 0 in group N. Serum NSE concentrations after surgery were significantly higher than baseline (at T1) in both groups, except at T3 in group N. Serum S100β concentration after surgery was significantly higher than baseline (at T1) in both groups. The MMSE scores at days 3 and 7 in group N were significantly higher than those in group C. The concentrations of serum NSE and S100β at T2 and T3 in group N were significantly lower than those in group C.

CONCLUSIONS

Oral nicorandil, as a premedication before liver transplantation, improves postoperative MMSE scores. It also attenuates the increase of NSE and S100β in blood, indicating its cerebral protective effect.

Methods for diagnosing hepatic encephalopathy in patients with cirrhosis: a multidimensional approach

There is no "gold standard" for diagnosing hepatic encephalopathy in patients with cirrhosis. In consequence, the presence of this condition, unless floridly overt, is often missed. As a result, the majority of patients are denied the benefits of treatment. There are a number of individual techniques, which access different aspects of cerebral function that can be used, singly or in combination, to provide diagnostic information in this condition, including mental state assessment, psychometric testing, electroencephalography, sensory and cognitive evoked potentials, and neuroimaging. These have been variously applied to the study of hepatic encephalopathy but fundamental differences in the essential aims of the studies, as well as differences in the patient populations and the acquisition and analysis of the data, have made comparisons difficult. Thus, there is no clear consensus as to the sensitivity, specificity, or validity of these tests when used alone or in combination. There are, however, a number of additional methods that could be used to analyze the electrophysiological data, and a number of alternative evoked potentials that could be measured to provide better diagnostic information. In addition, there are a number of techniques, such as critical flicker frequency and smooth pursuit eye movements, which have not yet been applied systematically in this condition and which may provide useful diagnostic information. Clearly the methods for assessing hepatic encephalopathy need to be reviewed, newer methods for analyzing the electrophysiological data and newer techniques for assessing alternative aspects of cerebral function need to be explored for their diagnostic utility. This process should aim at developing a multidimensional diagnostic tool.

Epileptiform abnormalities in hepatic encephalopathy

Epileptiform abnormalities are uncommon in patients with hepatic encephalopathy. A review of EEGs in patients with hepatic encephalopathy over a 10-year period identified 18 (15%) with epileptiform abnormalities. Thirteen patients had interictal discharges consisting of focal spike and sharp wave discharges, bilateral independent discharges, and generalized spike and wave discharges. A total of 10 patients had electrographic seizure discharges, focal in 6 and generalized in 5 (some patients had more than one abnormality). Twelve patients had clinical seizures, partial in four and generalized in eight. Neuroimaging failed to provide an etiology for the generation of epileptiform discharges in most patients, including those with focal abnormalities. Most patients with epileptiform discharges died or deteriorated. We conclude that epileptiform can be seen in patients with hepatic encephalopathy, and when present imply a poor prognosis.

Seizures after orthotopic liver transplantation

Orthotopic liver transplantation is the accepted treatment for endstage liver disease. In the US alone, more than 3000 patients receive liver transplants yearly distributed through more than 100 liver transplant programmes. Neurological complications occur in up to 47% of these patients. Among them, seizures are one of the most common. They tend to occur during the first few weeks after transplantation. Generalized seizures are the most frequently encountered. Their aetiology is usually multifactorial requiring a comprehensive diagnostic and therapeutic approach. Seizures must be differentiated from a variety of behavioural and movement disorders. In this review article, the frequency and time of occurrence of seizures, their types and aetiology, diagnostic approaches and treatment are discussed.