Malnutrition-related hyperammonemic encephalopathy presenting with burst suppression: a case report

Abstract

Background Hyperammonemia is a common cause of metabolic encephalopathy, mainly related to hepatic cirrhosis. Numerous nonhepatic etiologies exist but they are infrequent and not well known, thus, leading to misdiagnosis and inadequate care. Electroencephalography has a proven diagnostic and prognostic role in comatose patients. Burst suppression is a preterminal pattern found in deep coma states and is rarely associated with metabolic causes. Case presentation We report the case of an 81-year-old Caucasian man presenting with rapidly progressive somnolence and mutism. Soon after his arrival in our hospital, he developed profound coma. A comprehensive diagnostic workup was unremarkable except for admission electroencephalography showing diffuse slowing of cerebral activity with an intermittent pattern of burst suppression. He was admitted to our intensive care unit for supportive care where malnutrition-related hyperammonemia was diagnosed. His clinical course was spontaneously favorable and follow-up electroencephalography demonstrated normal cerebral activity. Conclusions Nonhepatic hyperammonemia is a rare and potentially reversible cause of encephalopathy. Ammonia level measurement should be part of the diagnostic workup in patients with unexplained coma, particularly in the setting of nutritional deficiencies or nutritional supply. Detection of diffuse and nonspecific mild to moderate slowing of cerebral activity (theta-delta ranges) on electroencephalography is common. In contrast, to the best of our knowledge, burst suppression has never been described in association with hyperammonemia.

Prognostic Role of Ammonia in Critical Care Patients Without Known Hepatic Disease

“…NHH can be quite common in critically ill patients (up to 73% in a recent study) (5). NHH can occur in patients with a variety of serious conditions, such as intracranial hypertension (6) or congestive heart failure, malnutrition, infectious enterocolitis, or lung transplantation (7)(8)(9)(10)(11).…”

Multifaceted ammonia transporters

“…Uncharged ammonia is highly soluble in water and readily overcomes the intestinal and blood-brain barriers. However, the danger posed by ammonia is greatest in brain tissue, where it raises the risk of development of severe encephalopathy (Hawkes et al 2001;Gulati et al 2004;Panlaqui et al 2008;Cichoż-Lach and Michalak 2013;Leidi et al 2019). Therefore, its content in physiological conditions is regulated by a complex process of glutamine biosynthesis.…”

Methamphetamine-Associated Hyperammonemic Encephalopathy

“…The kidney also produces ammonia in proximal tubule, to buffer H+ in the urine. 4 Mild hyperammonemia can cause neuropsychiatric, irritability, headache, vomiting, ataxia, and gait abnormalities, and in severe acute cases, it can lead to rapid progression, often fatal, encephalopathy and cerebral edema. Recently, the relationship between hyperammonemia and methamphetamine intoxication, as well as contributory role of ammonia in methamphetamine-associated mental status changes, has been reported in clinical studies and some animal studies.…”

“…In healthy individuals, ammonia mainly resulted from the degradation of protein and urea by intestinal bacteria and detoxified in the liver through conversion to urea. The kidney also produces ammonia in proximal tubule, to buffer H+ in the urine 4 . Mild hyperammonemia can cause neuropsychiatric, irritability, headache, vomiting, ataxia, and gait abnormalities, and in severe acute cases, it can lead to rapid progression, often fatal, encephalopathy and cerebral edema.…”