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Brain MRI changes in phenylketonuria. Associations with dietary status

A J Thompson1, S Tillotson, I Smith

  • 1Institute of Neurology, University College, London, UK.

Brain : a Journal of Neurology
|August 1, 1993
PubMed

Insights

Phenylketonuria (PKU) patients, even with early treatment, often show MRI-detected white matter changes. High phenylalanine levels and treatment withdrawal are linked to these brain abnormalities, suggesting a lifelong risk.

Area of Science:

  • Neurology
  • Biochemistry
  • Medical Imaging

Background:

  • Neonatal screening and early dietary treatment for phenylketonuria (PKU) have reduced neurological dysfunction.
  • Subtle neurological impairment and white matter abnormalities on MRI persist in some early-treated PKU subjects.
  • The frequency and relationship of white matter changes to dietary management in PKU remain unclear.

Purpose of the Study:

  • To investigate the frequency and characteristics of MRI-detected white matter abnormalities in individuals with phenylketonuria.
  • To determine the association between these abnormalities and factors like phenylalanine levels and dietary treatment adherence.

Main Methods:

  • Magnetic Resonance Imaging (MRI) was used to examine brain structure in 34 subjects with phenylketonuria (aged 8-33 years).
  • Subjects included those detected by neonatal screening and those missed by the program.
  • Dietary phenylalanine intake and phenylalanine concentrations were assessed.

Main Results:

  • Twenty-five of 34 subjects showed abnormalities on MRI.
  • In early-diagnosed subjects, MRI change severity correlated significantly with phenylalanine levels and time since dietary treatment withdrawal.
  • These findings align with animal studies showing phenylalanine's dose-dependent effect on myelin turnover.

Conclusions:

  • White matter abnormalities are common in phenylketonuria, even with early treatment.
  • Elevated phenylalanine levels and treatment cessation are linked to these changes, indicating a potential lifelong risk to myelin.
  • Phenylalanine's impact on myelin suggests ongoing neurotoxicity in PKU.

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