The outcome of PKU: the relevance of
neuroimaging and neurophysiological examinations
Vincenzo Leuzzi
Department of Pediatrics and Pediatric Neurology and Psychiatry
The aims of the neuroimaging and
neurophysiologic examination in PKU
a) to explore neuro-physiologic/-anatomic background of
clinical features (neurological status IQ, Executive
Functions, etc)
b) to identify a set of neuro-anatomic/-physiologic alterations
which anticipates the clinical outcome (normal/abnormal IQ,
EFs, etc)
c) to identify a set of neuro-anatomic/-physiologic preclinical
alterations reflecting the individual vulnerability to Phe
Reference Neurophysiol test
Korinthenberg et al, Neuropediatrics 1988;19:175-178 PR-VEP, BAEP
Giovannini et al, J Inher Metab Dis 1988;11:416-421 PR-VEP
Ludolph et al, Acta Neurol Scand 1992;85:243-248 NCV, BAEP, PR-VEP, SEP, MEP
Lou et al, J Inher Metab Dis 1992: 15:687-695 PR-VEP
Leuzzi et al, J Clin Neurophysiol 1994;11:1-5 BAEP, SEP, PR-VEP
Cleary et al, Lancet, 1994;344:87-90 NCV, PR-VEP, SEP, MEP
Jones et al, J Neurol Neurosurg Psych 1995; 59:260-265 PR-VEP
Ludolph et al, Eur J Pediatr 1996;155:S64-S68 NCV, BAEP, PR-VEP, SEP, MEP
Pietz et al, Radiology 1996;201:413-420 PR-VEP
Leuzzi et al, J Inher Metab Dis 1998:21:351-364 PR-VEP (different spatial frequencies
and visual contrast)
McDonnell et al, Eur Neurol 1998;39:38-43 PR-VEP, SEP,
Röricht et al, J Neurol 1999;246:21-30 focal TMS
Signal transmission in CNS: transversal studies
Ref. age (yrs) altered/exam
ined
%
Korinthemberg et al,
1993
16.2±2.8 9/25 36
Giovannini 1988 5-16 0/14 0
Ludolph et al 1992 13-24 7/22 31
Lou et al 1992 13.5-20 0/16 0
Cleary et al 1994 10-50 8/48 16
Jones et al 1994 7.5-31 23/36 64
7-14
> 14
1/9
22/27
11
81
Leuzzi et al 1994 6.5-17 3/22 13
Ullrich et al, 1994 20-32 0/9 0
Pietz et al 1996 12-33 7/51 18
Ludolph et al 1996 13-29 9/33 27
Leuzzi et al 1998 9-22.6 17-23/42 (eyes) 40-54
McDonnel, 1998 > 18 14/22 64
VEP alterations in PKU patients
VEP alterations in PKU patients: Critical points
Most of pts older than 10
Feeble or no discriminating power for early vs late treated pts (Leuzzi 1994, Jones
1995, Ludolph, 1996, Leuzzi 1998)
Conflicting results
• No association with historical and concurrent quality of dietary control (QDC) (Ludolph 1992, Ludolph, 1996)
• Association with historical QDC (Korinthenberg et al 1988, Leuzzi 1994)
• Association with recent and/or concurrent QDC (Giovannini 1988)
• Phe threshold effect: ≈ 900 μM (Leuzzi 1998), 1200 μM (Jones 1996)
• IQ and VEP
• no association (Leuzzi, 1994)
• association with VEP amplitude (Jones, 1996)
Remarks: different experimental designs, selection criteria, ages,
biochemical control and outcome measures.
EPs - Longitudinal studies
Pueschel et al, J Men Def Res 1983;27:61-67
Cardona et al, EEG and Clin Neurophysiol 1991; 80:8-15
Ullrich et al, J Inher Metab Dis 1994;17:349-352
Lou et al, Acta Paediatr 1994;83:1312-14
Ullrich et al, 1996, Eur J Pediatr 155:S74-S77
Beblo et al, Neurology;2001;57:1488-1491
Agostoni et al, Arch Dis Child 2003;88:582-58
EPs: Longitudinal studies
Postnatal delayed maturation of BAEP (I-V interpeak latency ) and F-VEP (N1 and
P2 latencies) during the 1st year of life; no correlation with biochemical/clinical
parameters (Cardona et al 1991)
Postnatal delayed maturation of BAEP and F-VEP
age of diet onset 42.25±52.47
IDC-3-12 487±21.48
DQ 12 mo 95.8±13.3
Cardona et al 1991
EPs: Longitudinal studies
Postnatal delayed maturation of BAEP (I-V interpeak latency ) and F-VEP (N1 and P2
latencies) during the 1st year of life; no correlation with biochemical/clinical parameters
(Cardona et al 1991)
No variations of VEP, SEP, and BAEP after diet discontinuation at the age of 5
(Pueschel et al, 1983)
No variation of VEP after 2 yrs of free diet and supplementation with Tyr, Trp, and
essential amino acids (Lou et al, 1994)
VEP P100 latency, sustained attention, and frontal lobe functions were not affected
by 4 weeks of L-DOPA/Carbidopa administration (Ulrrich et al, 1994, 1996)
No variation of F-VEP and BAEP after an oral PHE loading test (180 mg/Kg bw/72
hrs) at the age of 6, 12, and 18 months (Leuzzi et al, unpublished data)
VEP improved in PKU patients (but not in controls) under omega-3 LC-PUFA
supplementation (Beblo 2001, Agostoni, 2003)
Event-related potentials - ERPs
aims: to explore the neural networks potentially
involved in cognitive processing of information and their
susceptibility to the biochemical alterations of PKU
methods: to assess latency and amplitude of (early and)
late evoked components associated with different
sensorial and active discriminative tasks
Event-related potentials in PKU
(Auditory) stimulus discrimination (P300) (Leuzzi et al 2000)
(Visual) stimulus discrimination (P300) (Henderson et al 2000)
Early sensory processing and inhibitory functions (visual Go-
Nogo task in adults with PKU (Wiersema et al 2005, Moyle et al
2006)
Visual selective processing task: stimulus encoding and target
selection/detection (de Sonneville et al 2010)
Ref
age
(yrs)
patients
Biochemic
al control (Phe mM)
H (historical)
C (closer or
concurrent )
Task and
ERPs
RESULTS
(A: amplitude L: Latency)
INTERPRETATION
on/off
diet
scre/
non-
scre
Leuzzi et al
2000
7-22 9/15 11/4 C on diet 259-
765
C off diet
1088-1805
auditory
discriminative
P300
• non-evocable in late treated and off diet pts
• A and L in early detected PKU on
diet
•IQ is lower in patients with non-evocable
P300
prefrontal cortex
involvement
Henderson
et al 2000
5-14 22/0 22/0 H 230-460
C 56-624 visual
discriminative
P300 (N170,
P100)
normal ( L N170 /P100)
impairment of early
sensory processing
Wiersema
et al 2005
7-12 7/0 7/0 H 264±187
C 297±165 fast and slow
Go/noGo choice
P300
• A and L in fast (+) and slow (++)
operating conditions (Go/No-Go choice)
• accuracy in fast and slow operating
conditions
• no correlation with quality of dietary
control
problems with the
inhibition of pre-
potent response
Moyle et al
2006
26 (IQR
25-30)
0/9 9/0 H
688±80.9
C
1000±258.45
Go/noGo choice
P100, N170, N2 • normal RT and accuracy
• A of P100 and N170
• no diff between Go-N2 and No-Go N2 A
impairment of early
sensory processing
and
inhibitory functions
de
Soneville et
al 2010
11.8±1.
8
42/0 42/0 C 477±253
H 16 pts
232±101
H 26 pts
672±191
orientation and
spatial
frequency
discrimination
P100, N170
N90, P180
N280
P425 (P300)
normal early sensory components, RT, P300,
A N90
no modulation of P180 A as function of the
stimulus + N90 in PKU with Phe > 360
Accuracy: PKU Phe H > 360
Accuracy increase with the age in PKU
H Phe N90, P180, N280
concurrent Phe N90, P180, N280
altered target
detection
impairment of
selective attention ?
H Phe influences
selective attention
components
EP and ERP in PKU: conclusions
The time resolution is the main advantage of EP and ERP studies
Lack of knowledge on neurophysiological background of EP and ERP alterations and of
their relevance on the outcome of the disease
The linkage between ERP and IQ remains to be explored: are ERP alterations expressed
by the IQ or do reflect an adjunctive disorder ?
Non longitudinal data available: are EP and/or ERP transient (maturational) or
persistent (lesion) alterations?
What the consequences (if any) of EP and/or ERP alterations in the real life ?
Future perspectives:
a)longitudinal studies
b)integrated neuropsychological and neurophysiological studies
c)assessment of the sensitivity of EP and ERP to the biochemical alterations of PKU.
WM alterations (WMA) and
neurological deterioration in PKU
patients
• Neurological deterioration in adult PKU. Villasana et al, J Inher Met Dis,
1989:451-457.
• Neurological deterioration in young adults with phenylketonuria. Thompson et al, Lancet 1990;336:602-605.
• Unexpected white matter changes in an early treated PKU case and improvement after diet treatment. Battistini et al, Funct Neurol
1991;6:177-180.
• Spasticity and white matter abnormality in adult phenylketonuria. McCombe et al, JNNP 1992;55:359-361.
“Neurological deterioration in young
adults with phenylketonuria“
• 11 pts
• Diagnosis: scr/non-scr 7/4
• Age at onset (yrs) 12-28
• In/out diet 2/9
• Gap diet stopping-disease onset 8 mo-16 yrs
• Previous learning/mental disorders 7/11
• Previous neurological disorders 3/11
Presentation
• Brisk reflexes 9/11
• Spastic parapesis/quadriparesis 4/11
• Mental deterioration 4/11
• Behavioural disorders 4/11
• Intention tremor, ataxia 4/11
• Epilepsy 3/11
• Dystonia 1/11
• Dorsal column sensory loss 1/11
• CSF (4/11): HVA, 5-HIAA, MHPG (2/2)
WMA and neurological deterioration:
clinical follow-up
Ref. Case no Clinical and MRI outcome
Thompson
et al, 1990 2,5,6,7
diet therapy: clinical improvement in 3/4 cases (in 2 for more years);
MRI improvement in 1/2 (2 months after starting therapy)
Battistini
et al, 1991 1
diet therapy: VEP, BAEP, and WM abnormalities regression (in a
few months)
Weglage et
al, 1993 1 diet therapy: clinical and MRI improvement (in 8 weeks)
McCombe
et al, 1992 1
diet therapy (Phe 1960 930 microM): clinical improvement
B12 supplementation: almost total normalization in 6 months (Phe
values 1760-2410)
MRI abnormalities unchanged .
WMA in PKU without neurological
deterioration • Pearsen et al, Radiology 1990, 177:437-440.
• Bick et al, Eur J Pediatr, 1991;150:185-189.
• Shaw et al, AJNR, 1991;12:403-406.
• Lou et al, J Inher Metab Dis, 1992;15:687-695.
• Leuzzi et al, Neuroped, 1993;24::302-306.
• Weaglage et al, J Inher metab Dis, 1993;16:1047-148.
• Thompson et al, Brain;1993:116:811-821.
• Bick et al, 1993;152:1012-1020.
• Lou et al, Acta Paediatr,1994;83:1312-14.
• Ulrich et al, Neuroped, 1994;25:278-279.
• Toft et al, I Inher Metab Dis, 1994;17:575-583.
• Cleary et al, Lancet, 1994;344:87-90.
• Leuzzi et al, J Inher Metab Dis, 1995:18:624-634.
• Pietz et al, Radiology 1996;201:413-420.
• Anderson et al, Dev Med Child Neurol 2004;46:230-238
• Leuzzi et al, J Inher Metab Dis, 2007;30:209-16.
WMA in PKU without neurological
deterioration: summary
Patients: 344
Age range (yrs): 0.9-49
</> 11 yrs: 42/185 (available data for 227/344)
Type
PKU (Phe > 600 µM): 332
Hphe (Phe< 600 µM): 12
Early/late detected 286/58
On/out diet: 135/209
Mental Dev
normal/abnormal 128/59 (available data for 187/344)
WM MRI
normal/abnormal 28 (8.2%) / 316 (91.8%)
Patient subgroups WM MRI score
Phe
(M) =
Strict diet (5) 400 (70-800)
5 0 0
Low protein diet (21) 1000 (830-1100)
5 5 11
No diet variation (15) 1300 (1000-1500)
4 1 10
Variation of WMA under different Phe
restriction
• 41 PKU patients (40 early treated) age
• 14 yrs: diet discontinuation
• 14-49 yrs: brain WM alterations in 41/41 (Phe 1100-1800 M)
• brain MRI 3-12 months later:
Cleary et al, 1995
MRI Phe (p>0.0002)
MRI Phe at the time of
the scan (p< 0001)
5 10 15 20 25 30 35 40
Age (yrs)
0
1
2
3
4
5
6
7
8
9
WM
MR
I sc
ore
WMA and age in PKU patents (r .4667, p< 0.01)
Leuzzi et al, 2007
WM
sco
re
WMA and age (non-screening subjects) (r 0.7713; p<0.005)
12 14 16 18 20 22 24 26 28 30 32 34 36
Age (yrs)
1
2
3
4
5
6
7
8
WM
T2 s
core
WM
sco
re
ID/DOB Age
(yrs/mo)
WM
MRI s
Blood PHE
(M)
CA
07/09/1985
14/4 6 1270
20/5 6 1300
23 6 1470
FF
13/03/1984
16/4 6 1169
18/8 6 1226
MN
13/04/1980
19/2 6 656
22 6 611
MMT
06/10/1987
12 1 401
14/11 1 649
StSe
08/02/1985
13/1 6 843
17/5 6 837
AS
15/09/1987
10/4 5 903
13/4 6 774
CM
07/09/1977
13/10 4 1350
20/6 8 1870
26/3 8 1354
PF
07/10/1982
15/11 4 709
20/4 6 499
23/1 6 571
SS
25/01/1987
14/9 2 1278
18/4 3 1340
20 3 1450
WMA score in
subsequent
exams
WM score:
08= normalmax
severity
Blood Phe values as function of the age WM involvement as function of the age
Leuzzi & Walter, unpublished
Variation of WMA severity in subsequent exams
100 early detected PKU subjects (age 19.1±7.42 yrs, range 6.4-52.1)
329 MRI scans (2 to 6 for each pt)
Phe
mM
% o
f m
axim
um
sco
re
Factors influencing WMA severity in
subsequent exams
a) Age of the patient at the first examination: higher variations of the
score until the age of 30; lower variations over the age of 30
b) Time gap between the two subsequent examinations: > gap > WM
score (or < improvement);
c) The value of concurrent Phe at the “final” examination: > blood
Phe > WM score (or < improvement)
d) Females shows a major vulnerability than males (< WM
improvement or > WM worsening)
100 early detected PKU subjects (age 19.1±7.42 yrs, range 6.4-52.1)
329 MRI scans (2 to 6 for each pt)
The clinical significance of WMA
non-significant influence of WMA on IQ (Pearsen 1990, Bick 1993,
Leuzzi 1993,Wegleage 1995, Pietz 1996, Cleary 1994, Leuzzi 1995, Leuzzi 2007)
The clinical significance of WMA
non-significant influence of WMAs on IQ (Pearsen 1990, Bick 1993, Leuzzi
1993,Wegleage 1995, Pietz 1996, Cleary 1994, Leuzzi 1995, Leuzzi 2007)
(Anderson 2004)
severe WMA impairment in IQ, divided attention, processing speed, verbal an
visual learning, mental flexibility, reading, and arithmetic
mild WMA impairment in IQ, reading and arithmetic performances
no WMA impairment in IQ and processing speed
Concl: WMAs result in compromised neural transmission
Neurophysiological studies and
WMA in PKU
• 77 PKU pts aged 10-48 (70/7 early/late treated; 19/58 on/out diet)
• MEP (55 pts): CMCT in 3/55 pts
• PR-VEP (48 pts): P100 latency in 8/48 pts
• SEP (46 pts): normal 46/47 pts
• MSNC (56 pts): NV 6/56 pts
Conclusion: “we were unable to show any relationship
between the severity of neurophysiological abnormalities
and severity of MRI changes”
Cleary et al, 1994
WMA and PKU: conclusions
• WMA occurs in a high percentage of PKU patients;
• WMA emerges at the end of the first decade of life and later stabilizes;
• WMA is not associated with unequivocal variations of the clinical status;
• WMA is not associated with unequivocal signs of myelin impairment or neural
transmission derangement;
• WMA is correlated with: lifetime and concurrent Phe level, age (with a marked
interindividual variability), and sex;
• WMA can be partially reversed by lowering blood Phe (with a marked
interindividual variability)
• WMA emergence and vanishing are slow processes (lasting months)
Neuroimaging and neurophysiologic
examination in PKU: conclusions
a) clinical examination remains the most sensitive and reliable
tool in predicting (and reflecting) the result of the treatment
in PKU;
b) neuroimaging and neurophysiologic tools have so far
furnished a scarce contribution for the comprehension of the
background of mental disorders in pts with PKU
Neuroimaging and neurophysiologic
examination in PKU: future topics
a) to explore neuro-anatomic/-physiologic background of clinical
features (neurological status IQ, Executive Functions, etc)
b) to identify a set of neuro-anatomic/-physiologic alterations
which anticipates the clinical outcome (normal/abnormal IQ,
EFs, etc)
c) to identify a set of neuro-anatomic/-physiologic preclinical
alterations reflecting the individual vulnerability to Phe
Blood Phe and intellectual phenotype in
untreated phenylketonuria patients
SJ Ramus et al., 1999
individual
vulnerability to
Phe
F/13 yrs
neonatal screening: Phe 240 μM
PAH genotype: T380M/D151E
infancy: psychomotor delay, motor difficulties,
hypersalivation, aggressiveness
> 5 yrs: episodes of ataxia gait and limb rigidity
11 yrs: mental retardation, ataxia,
hypersalivation
clinical improvement with neurotransmitter
treatment
Koch et al JIMD, 2002
How to detect individual vulnerability in early treated PKU patients ?
To what extension does the individual vulnerability affect the outcome of
PKU ?