title: Intracranial Pressure Monitoring Demonstrates that Cerebral Edema Is Not Correlated to Hyperammonemia in a Child with Ornithine Transcarbamylase Deficiency.
abstract: BACKGROUND
  Ornithine transcarbamylase deficiency (OTCD) is an inborn error of urea cycle resulting in increased plasma levels of ammonia and glutamine and cerebral edema. However, the underlying mechanism of brain cytotoxicity remains controversial. Our objective is to present an unusual acute hyperammonemic crisis suggesting a key role of brain glutamine to mediate ammonia neurotoxicity and the interest of intracerebral pressure (ICP) monitoring to maintain adequate cerebral perfusion pressure and to prevent neurological damages.
  
  
  METHODS
  A 6-year-old boy with OTCD was admitted for an acute hyperammonemic encephalopathy following viral infection. At admission, he presented vomiting, confusion, lethargy (Glasgow scale 7/15), and bilateral papilledema, suggesting cerebral edema. Plasma ammonia level was slightly increased (194 μmol/L, rr 25-50 μmol/L), contrasting with the severity of neurological deterioration and with high levels of glutamine in plasma (1,949 μmol/L, rr 335-666 μmol/L) and the brain (10-fold increase on in vivo MR spectroscopy). The patient was placed on neuroprotective treatments and respiratory support.
  
  
  RESULTS
  With a hypercaloric protein-free diet and nitrogen scavenger drugs, plasma levels of ammonia and glutamine rapidly decreased without neurological improvement. Continuous ICP monitoring showed repetitive peaks of pressure up to 60 mmHg in the first four days and was helpful to manage neuroprotective treatments. After several days, the patient progressively recovered without cognitive or motor disability.
  
  
  CONCLUSIONS
  This case report highlights the discrepancy between the severity of neurological impairment, presumably related to high level of brain glutamine, and plasma levels of ammonia or glutamine in a child with acute hyperammonemic encephalopathy related to OTCD. In this situation, continuous ICP monitoring was helpful to manage neuroprotective treatments and prevent brain damages.
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Chantreuil
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.|Inserm U930, Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, Tours, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Favrais
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.
authors.forename: Nadine
authors.initials: N
authors.lastname: Fakhri
authors.affiliation: CHRU de Tours, Médecine Pédiatrique, Tours, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Tardieu
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Roullet-Renoleau
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Perez
authors.affiliation: CHRU de Tours, Neurochirurgie Pédiatrique, Tours, France.
authors.forename: Nadine
authors.initials: N
authors.lastname: Travers
authors.affiliation: CHRU de Tours, Radiopédiatrie, Tours, France.|Inserm U930, Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, Tours, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Barantin
authors.affiliation: CHRU de Tours, Radiopédiatrie, Tours, France.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Morel
authors.affiliation: CHRU de Tours, Services de Réanimation Pédiatrique et Néonatologie, Tours, France.|Inserm U930, Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, Tours, France.
authors.forename: Elie
authors.initials: E
authors.lastname: Saliba
authors.affiliation: CHRU de Tours, Médecine Pédiatrique, Tours, France. labarthe@med.univ-tours.fr.|Inserm U1069, Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, Tours, France. labarthe@med.univ-tours.fr.
authors.forename: François
authors.initials: F
authors.lastname: Labarthe
keywords: Ammonia; Coma; Glutamine; Intracranial pressure; Metabolic brain disorder; Urea cycle disorder