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  • Title: The dynamics of brain concentrations of phenylalanine and its clinical significance in patients with phenylketonuria determined by in vivo 1H magnetic resonance spectroscopy.
    Author: Pietz J, Kreis R, Boesch C, Penzien J, Rating D, Herschkowitz N.
    Journal: Pediatr Res; 1995 Nov; 38(5):657-63. PubMed ID: 8552430.
    Abstract:
    Cerebral concentrations of phenylalanine (PHE) were measured by means of quantitative in vivo 1H MR spectroscopy in 8 adult patients treated early for phenylketonuria type I. A 1.5-Tesla routine magnetic resonance scanner, localization sequence with short echo time (20 ms), and a fully automated data processing scheme were used. Baseline plasma PHE concentrations were 1.04 (0.70-1.39) mmol/L PHE with concurrent brain PHE concentrations of 0.27 (0.13-0.41) mmol/kg of wet weight resulting in a plasma/brain ratio of 4.12. Plasma and brain concentrations correlated significantly (Kendall tau b = 0.91, p < 0.01). During an oral load with a single dose of 100 mg L-PHE per kg of body weight in four patients, plasma levels steeply increased. Concurrent brain PHE increase was less steep, was significantly delayed, and still continued up to 20 h postload. Despite the proven rise in plasma and brain concentrations of PHE, neuropsychologic examinations revealed no impairment of attentional and fine motor abilities from preload up to 20 h postload.
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