Expanding Role of Proton Magnetic Resonance Spectroscopy: Timely Diagnosis and Treatment Initiation in Partial Ornithine Transcarbamylase Deficiency

Abstract

We report the case of a 3-year-old male patient who presented with a 3-day history of altered mental status, emesis, and abdominal pain in the setting of a viral illness. A rapid screening revealed a high ammonia level and after reviewing his proton magnetic resonance spectroscopy (1H MRS) which showed the classic triad of high glutamate, low choline, and myoinositol, a diagnosis of ornithine transcarbamylase deficiency (OTCD) was made within 6 hours of presentation. Therapy with sodium phenylbutyrate and sodium benzoate was initiated and patient was discharged after 3 days with no neurologic disability. Biochemical and molecular testing eventually confirmed the diagnosis. 1H MRS is a practical and fast neuroimaging modality that can aid in diagnosis of OTCD and enables faster initiation of treatment in acute settings.

Dysregulation of Astrocytic Glutamine Transport in Acute Hyperammonemic Brain Edema

“…Importantly, biochemical changes of different osmotically active substances in the brain are frequently observed even before the onset of clinical symptoms ( Larsen, 2002 ). Studies performed by proton magnetic resonance spectroscopy ( 1 H MRS) in symptomatic patients with severe ornithine transcarbamylase deficiency showed that a significantly elevated level of glutamine was accompanied by a simultaneous decrease in myo-inositol and choline, which is considered compensatory in nature ( Gropman et al, 2009 ; Sen et al, 2021 ). However, at a very high concentration of ammonia, osmoregulation may be insufficient to compensate for the rapid cerebral glutamine increase.…”