The outcome of PKU: the relevance of

neuroimaging and neurophysiological examinations

Vincenzo Leuzzi

vincenzo.leuzzi@uniroma1.it

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

Woodman, 2010

Woodman, 2010

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)

WMA severity and mental functioning

■ 4.875 vs ■ 3.812; p=0.13

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 ?

“…it is much more important

to know what kind of patient

has a disease than to know

what kind of disease the

patient has “

Caleb H. Parry, M.D. 1755-1822