Hyperammonemic encephalopathy in a patient with primary hepatic neuroendocrine carcinoma

Non-cirrhotic hyperammonaemic encephalopathy secondary to metastatic pancreatic neuroendocrine tumour treated with peptide receptor radio nucleotide therapy and transarterial chemoembolisation

Neuroendocrine tumours (NETs) are rare cancers which often carry significant morbidity and mortality, frequently related to burden of liver metastases. Hyperammonaemia and subsequent hepatic encephalopathy carries a poor prognosis and has been described in these patients. We discuss a case of a woman in her 50s with hyperammonaemic encephalopathy and a new diagnosis of pancreatic NET with hepatic metastases. She presented with a reduced conscious state a few days post commencing chemotherapy. This was considered to have a multifactorial pathophysiology: the primary driver being large volume hepatic metastases and contributed by portosystemic microshunting, sepsis, severe weight loss and malnutrition. We describe how each of these exacerbating factors was addressed and highlight the effective multimodal treatment approach consisting of sequential transarterial chemoembolisation followed by peptide receptor radio nucleotide therapy, resulting in the resolution of hyperammonaemic encephalopathy and radiological partial metabolic response.

Hyperammonemic Encephalopathy in a Patient with Pancreatic Neuroendocrine Tumor and Portosystemic Shunt

Hyperammonemia can lead to encephalopathy and may be accompanied by a diagnostic dilemma. Imaging as well as biochemical analyses are the cornerstone for identifying possible underlying causes such as severe liver disease or urea cycle defect. We report a case of a patient that presented with neurological deficits based on hyperammonemia in the presence of a large pancreatic neuroendocrine tumor (PNET) and portosystemic shunts in the liver. Prior cases are rather scarce, and the exact mechanism is not fully understood. The case illustrates the added value of a multimodality imaging approach in patients presenting with hyperammonemia-induced encephalopathy.

Molecular Basis of Hyperammonemic Encephalopathy in Fibrolamellar Hepatocellular Carcinoma

Hyperammonemic encephalopathy is a potentially fatal condition associated with fibrolamellar hepatocellular carcinoma. The mechanism involved in hyperammonemia in patients with fibrolamellar carcinoma was unclear until a possible physiopathological pathway was recently proposed. An ornithine transcarboxylase dysfunction was suggested as a result of increased ornithine decarboxylase activity induced by c-Myc overexpression. This c-Myc overexpression resulted from Aurora kinase A overexpression derived from the activity of a chimeric kinase that is the final transcript of a deletion in chromosome 19, common to all fibrolamellar carcinomas. We performed the analysis of the expression of all enzymes involved and tested for the mutation in chromosome 19 in fresh frozen samples of fibrolamellar hepatocellular carcinoma, non-tumor liver, and hepatic adenomatosis. The specific DNAJB-PRKACA fusion protein that results from the recurrent mutation on chromosome 19 common to all fibrolamellar carcinoma was detected only in the fibrolamellar carcinoma sample. Fibrolamellar carcinoma and adenomyomatosis samples presented increased expression of Aurora kinase A, c-MYC, and ornithine decarboxylase when compared to normal liver, while ornithine transcarbamylase was decreased. The proposed physiopathological pathway is correct and that overexpression of c-Myc may also be responsible for hyperammonemia in patients with other types of rapidly growing hepatomas. This gives further evidence to apply new and adequate treatment to this severe complication.

Marked improvement in hyperammonaemic encephalopathy from multimodal treatment of metastatic neuroendocrine tumour

Gastroenteropancreatic neuroendocrine tumours (GEPNETs) are a heterogenous group of tumours which are rising in incidence. Morbidity and mortality related to these tumours is dependent on the location of metastatic spread. Hyperammonaemia and subsequent encephalopathy has previously been described in GEPNET and is typically associated with a poor prognosis. We describe a case of a 55-year-old woman with hyperammonaemic encephalopathy and a new diagnosis of GEPNET. Given the poor prognosis and the outcomes in this patient group we feel this case highlights the benefit of a multimodality treatment approach including peptide receptor radionucleotide therapy and transarterial chemoembolisation.

Hyperammonemic Encephalopathy Associated With Fibrolamellar Hepatocellular Carcinoma: Case Report, Literature Review, and Proposed Treatment Algorithm

We report a case of a 31-year-old man with metastatic fibrolamellar hepatocellular carcinoma (FLHCC) treated with gemcitabine and oxaliplatin complicated by hyperammonemic encephalopathy biochemically consistent with acquired ornithine transcarbamylase deficiency. Awareness of FLHCC-associated hyperammonemic encephalopathy and a pathophysiology-based management approach can optimize patient outcome and prevent serious complications. A discussion of the management, literature review, and proposed treatment algorithm of this rare metabolic complication are presented.

IMPLICATIONS FOR PRACTICE

Pathophysiology-guided management of cancer-associated hyperammonemic encephalopathy can improve patient outcome and prevent life-threatening complications. Community and academic oncologists should be aware of this serious metabolic complication of cancer and be familiar with its management.

Hyperammonemic encephalopathy in an adenocarcinoma patient managed with carglumic acid

Hyperammonemic encephalopathy (he) is a rare complication of malignancy and chemotherapy. Although the cause of he is unclear, a functional arginine deficiency secondary to increased catabolism has been suggested as a possible mechanism. Either that deficiency or an undetermined metabolite could lead to inhibition of N-acetylglutamate synthase (nags), a urea cycle enzyme, resulting in hyperammonemia. We present a case of chemotherapy-induced he in a patient with no underlying primary urea cycle disorder. The patient had a successful trial of carglumic acid (a synthetic analog of the product of nags), which suggests that, at least in some cases, he can be treated by overcoming proximal inhibition of the urea cycle. Further, our case is the first in the literature to exclude genetic defects and disorders of the proximal urea cycle, suggesting that hyperammonemia in these patients is probably secondary to chemotherapy.

Reversing Hyperammonemia in Neuroendocrine Tumors

Ammonia is a neurotoxin that is normally cleared by the intact liver and if not, hyperammonemia results in hepatic encephalopathy. Hyperammonemia may be owing to primary or secondary causes. Early diagnosis is important to prevent permanent brain damage. Advanced malignancy involving the liver is associated with hyperammonemia as a result of abnormality of the portal venous system or massive hepatic tumor burdon. Neuroendocrine tumors are an example of a malignant process that frequently involves the liver but despite this, may still have a relatively good prognosis, and are often characterized by chronic manageable symptoms and slow progression. Hyperammonemia in neuroendocrine tumor would represent a potentially reversible but ongoing process associated with an indolent malignancy. We present 2 cases that are examples of this diagnosis and discuss the diagnostic and management issues that may arise.