Continuation vs discontinuation of low-phenylalanine diet in PKU adolescents

Schmidt, H; Mahle, Marlene; Michel, Ute; Pietz, Joachim

doi:10.1007/bf00442050

Cited by 23 publications

(13 citation statements)

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“…by disturbing synapse development [25,26]. It is uncertain if the MRI abnormalities are related to minor neuropsychological deficits observed in early treated adolescent PKU patients, who have been without dietary treatment for several years [31,46,57,60]. Further MR examinations should therefore be integrated in carefully controlled clinical trials including detailed neuropsychological tests, to further evaluate this possible relationship [35,42].…”

Section: Discussionmentioning

confidence: 99%

White matter abnormalities in patients with treated hyperphenylalaninaemia: Magnetic resonance relaxometry and proton spectroscopy findings

et al. 1993

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In order to further clarify the pathogenesis and clinical significance of MRI white matter abnormalities in treated hyperphenylalaninaemia (HPA), ten patients (seven type I HPA, two type II and one type III) underwent T2 relaxometry (n = 8) and/or 1H spectroscopy (n = 7) in addition to conventional MR spin-echo imaging at 1.5 T. Two patients with severe MRI abnormalities had repeat examinations during and after a 6- to 8-month period of strict diet control. The clinical evaluation included a detailed neurological examination. In nine out of ten patients visual evoked potentials (VEP) were obtained parallel to the MR examination. MR imaging demonstrated typical symmetrical areas of prolonged T2 relaxation time predominantly in the posterior periventricular white matter in all but one of type I and II patients. There was no consistent relationship between MRI findings and time of diagnosis/initiation of therapy, IQ or visual evoked potential changes. MRI abnormalities tended to be more severe in patients with poor dietary control and high current plasma phenylalanine levels, whereas a normal MRI was found only in patients with plasma phenylalanine levels continuously below 0.36 mmol/l. There was marked regression of MRI abnormalities already after 3 months of strict diet control. T2 relaxometry showed a bi-exponential behaviour of T2 in the affected white matter, with a slow component of about 200-450 ms, indicating an increase in free (extracellular) water. 1H spectroscopy revealed no signs of severe neuronal damage. We conclude, that the observed white matter changes in treated HPA probably represent reversible structural myelin changes rather than permanent demyelination.

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Section: Discussionmentioning

confidence: 99%

White matter abnormalities in patients with treated hyperphenylalaninaemia: Magnetic resonance relaxometry and proton spectroscopy findings

et al. 1993

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“…In another study, while no decrease of IQ can be seen in con-$40 nection with the increasing blood phenylalanine (Phe) levels, it was concluded that the quality of dietary control in later childhood and adolescence was important for intellectual outcome [13]. Nevertheless, after 8-10 years, when previous effects are allowed for, it becomes more difficult to demonstrate any independant influence of the Phe control on measures of general ability [11,14].…”

Section: Abbreviationsmentioning

confidence: 98%

Long-term follow up of patients with classical phenylketonuria after diet relaxation at 5 years of age

et al. 1996

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The age for discontinuing dietary treatment of phenylketonuria (PKU) has been a worldwide source of controversy for many years. It is the reason we report here the results of a prospective, controlled study in which the diet was relaxed at 5 years of age in 31 so far well-treated children with classical PKU. The increase of phenylalanine (Phe) plasma levels to about 1500 mumol/l (25 mg/dl) after relaxing the diet was not associated with any significant decline of intellectual performance as measured by the Wechsler scores. Paired comparisons at 7-8 years and 11-13 years of age (n = 12) have shown WISC scores of 102.6 +/- 16.2 and 104.8 +/- 16, respectively, which were not significantly different. Similarly, paired comparisons at 9-10 years and 14-16 years (n = 6) did not demonstrate a significant loss of IQ points (107.7 +/- 13 vs 104.8 +/- 18). Of course, it is possible to argue that we should have observed an increase in IQ with increasing age in our patients and that the absence of deterioration cannot be considered by itself as a good result. Nevertheless, it cannot be excluded that the subtle but global intellectual impairments that have been documented in early-treated subjects are, to a very substantial degree, determined in the pre-school years, long before there is any question of stopping or relaxing the diet.

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“…For many years, discontinuation or at least dietary relaxation in the adolescent patient was considered safe [17]. However recent data suggesting subclinical deficits in adolescent and adult patients, in whom dietary treatment was discontinued, question this policy [18,26,32,34].…”

Section: ]mentioning

confidence: 99%

Disturbed myelination in patients with treated hyperphenylalaninaemia: evaluation with magnetic resonance imaging

et al. 1991

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Cranial magnetic resonance imaging (MRI) was performed in nine treated adolescents with hyperphenylalaninaemia (HPA) in order to analyse possible changes in myelination. Three patients suffered from type I HPA, four from type II and two from type III (persistent HPA). Images were obtained with a 1.5 T unit using spin-echo-sequences. In all patients with type I or type II HPA, abnormal findings in the cerebral white matter were demonstrated including band-like and/or confluent patchy areas of high signal intensity predominantly in the peritrigonal region, with anterior and posterior periventricular extension and/or involvement of the subcortical white matter. The extent of MRI changes did not correlate with the initiation, duration or quality of dietary treatment. There was also no consistent relationship between electrophysiological changes and white matter abnormalities on MRI. Our findings suggest a disturbance of myelination in patients with treated HPA. These results correspond well with earlier neuropathological and biochemical studies in untreated patients.

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Continuation vs discontinuation of low-phenylalanine diet in PKU adolescents

Cited by 23 publications

References 1 publication

White matter abnormalities in patients with treated hyperphenylalaninaemia: Magnetic resonance relaxometry and proton spectroscopy findings

White matter abnormalities in patients with treated hyperphenylalaninaemia: Magnetic resonance relaxometry and proton spectroscopy findings

Long-term follow up of patients with classical phenylketonuria after diet relaxation at 5 years of age

Disturbed myelination in patients with treated hyperphenylalaninaemia: evaluation with magnetic resonance imaging

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