Abnormal Cerebral Cortical Neurons
in a Child With Maternal PKU

Syndrome
Daniel J. Lacey, MD, PhD; Kornel Terplan, MD

Abstract
A child born to a phenylketonuric (PKU) woman not on dietary treatment was microcephalic and had congenital heart and
other physical anomalies consistent with the maternal PKU syndrome. After a repeat cardiac catherization at 3 months of
age, he suffered an embolic left cerebral infarct and seizures. He was found by his mother dead in bed at 4 months of age;
general autopsy revealed Klebsiella sepsis and pneumonia. Neuropathologic studies of the right cerebral hemisphere
showed neuronal loss of the third cortical layer; Golgi studies revealed persistently immature cortical pyramidal cell somata
and dendritic spines. This is the first report of specific neuronal abnormalities in a child with the maternal PKU syndrome
and may, in part, account for the clinical features of microcephaly, mental retardation, and seizures seen in affected
children. (J Child Neurol
1987;2:201-204).

born to phenylketonuric (PKU)
mothers not on dietary restriction of phenylalanine during pregnancy have a high incidence of
microcephaly, mental retardation, and congenital
anomalies.l-4 These children have not inherited the
metabolic disease but express manifestations of the
teratogenicity of maternal hyperphenylalaninemia,
the incidence and spectrum of which relate to
maternal phenylalanine levels early in gestation.
Because more PKU women are having children,
terminating their diet prior to conception, neurodevelopmental concerns regarding the maternal 5PKU
child are becoming more frequently expressed.5
To date, pathologic reports6 of the brains of these
children have consisted of only scattered case reports
(Gilles, personal communication). Similar to the
findings reported in brains of human PKU patients
processed by conventional histologic methods, little
has been found (ie, delayed myelination) that would
correspond to the clinical features of maternal PKU.

children

Received May 20, 1986, Received revised Sept 2, 1986.
Accepted for publication Sept 11, 1986.
From the departments of Neurology and Pediatrics, State
University of New York at Buffalo, and the Brain Laboratory,
Children’s Hospital of Buffalo, Buffalo, NY.
Address correspondence to Daniel J. Lacey, MD, PhD,
Department of Neurology, Children’s Medical Center, One Children’s Plaza, Dayton, OH 45404.

Applications of the Golgi methods to the brains of
PKU patients,~ and in animal models of PKU, 8-12
have shown alterations of neuronal and dendritic
architecture that may account for the retardation and
seizures. We have recently studied the brain of a 4month-old child with the maternal PKU syndrome,
using routine and Golgi histologic techniques.
Case Report
A male infant was born to a 25-year-old PKU
woman who was off her diet for many years
until the pregnancy was confirmed in the sixth
week. She was then placed on a phenylalaninerestricted diet, but serum phenylalanine levels
were not measured throughout her pregnancy.
(Details regarding maternal history were not
available to the authors.) Delivery was at 36
weeks, birth weight was 2,900 g, and Apgar
scores were 9/9. On the third day, &dquo;dusky
spells&dquo; were noticed when the child became
agitated, and an echocardiogram diagnosed a
single ventricle. A cardiac catheterization at our
hospital at 7 days of life revealed a single
ventricle, truncus arteriosus, and total anomalous
pulmonary venous return; oxygenation was
normal. Neurologic exam was significant by the
presence of microcephaly; head circumference
was 31.3 cm. After being discharged on digoxin,
and with an interval history of poor feeding and
&dquo;blue spells&dquo; when crying, a repeat cardiac

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catheterization was performed at 3 months of
life. Results were identical to those detailed
above, with normal oxygen saturations. Within
2 hours of the procedure, right focal seizures
occurred, which were stopped by intravenous
phenobarbital. An immediate computed tomographic (CT) scan was normal, but a scan 4 days
later showed a large infarct of the left parietal
lobe. No further seizures were noted, and the
child was discharged on phenobarbital and
digoxin. One month later, at age 4 months, his
mother found him dead in bed in the early

morning.
General autopsy was performed 8 hours
later. External examination revealed microsomia
with microcephaly, micrognathia, left hydrocele,
and a right undescended testicle. Additional
diagnoses included complex congenital heart
disease, passive congestion of the liver, Klebsiella septicemia and bronchopneumonia, pneumoperitoneum, and left parietal brain softening.

tracts of the maternal PKU child from those of the

other two infants.
Golgi sections of hippocampus and cerebellum of
the child detailed above showed normal pyramidal
and Purkinje cells for age. Changes of chronic
hypoxia, most notably dendritic spine loss, were not
present on hippocampal pyramidal cells of our
patient, although spine loss was evident in the other
infant with congenital heart disease. Cortical pyramidal cells of the maternal PKU child showed
prominent perikaryal spines and dendritic spines that
were longer and thinner (ie, immature) than normal
for age (see Figures 1 and 2). These findings were not
present in brains of the two other infants who served
as controls (see Figure 3). The morphological dendritic spine alterations were primarily qualitative; spine
counts did not reveal significant differences between
controls and the maternal PKU child.

Neuropathologic Methods and Results
Brain weight was 540 g (expected 620 g) with normal
development. No visible brain swelling or herniation
was present. As mentioned above, left parietal brain
softening and a slightly yellowish discoloration were
evident. Fresh blocks were taken from the right
frontal cortex, right occipital cortex, right hippocampus, basal ganglia, midbrain, pons, medulla, and
spinal cord. These were embedded in celloidin and
stained by Nissl, H & E, and Weil-Weigert methods.
Blocks were also obtained from the right middle
frontal gyrus, hippocampus, and cerebellum for
Golgi-Cox and rapid Golgi methods. All blocks were
sectioned coronally (celloidin-embedded material at
20 j~m and Golgi blocks at 90 j~m. These slides were
compared to those of comparable areas from a normal
4-month-old infant who was a crib death and a 5month-old who had similar congenital cardiac anomalies.
The cellular stains showed neuronal loss in the
third cortical layer, especially of the central and
parieto-occipital gyri. Betz cells in these regions were
hypoplastic with only minimal enlargement of their
perikarya. No other significant changes were found
in any of the other regions examined. Specifically,
areas usually affected by chronic hypoxia, ie, hippocampus and cerebellum, were normal. WeilWeigert myelin stains of brain sections from our
patient were qualitatively similar to those from the
two control brains. In particular, it was not possible
to differentiate blinded slides of the optic chiasm and

FIGURE 1
Cortical pyramidal cell of maternal PKU child, rapid Golgi
stain. Prominent perikaryal spines are present. Magnification x 1,000.

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FIGURE 2

Cortical pyramidal cell dendritic shaft of maternal PKU
child, rapid Golgi stain. Abnormally long and thin dendritic
spines are evident. Magnification x 1,000.

FIGURE 3
Dendritic shaft of cortical pyramidal cell from age-matched
infant with congenital heart disease, rapid Golgi stain.
Dendritic spines have normal numbers and morphology.

Magnification x 1,000.
Discussion
The major findings in the brain of this child with
maternal PKU syndrome include neuronal loss in the
third cortical layer, normal myelination for age, and
cortical pyramidal cells with persistently immature
perikaryal and dendritic spines. Because this report
details the findings of only one case, and the
literature contains only a few isolated postmortem
examinations, conclusions regarding the pathologic
substrates of the clinical features of the maternal PKU
syndrome remain tenuous. Golgi studies in a few
patients with PKU have shown reduced cortical
synaptic densities, lack of maturation of pyramidal
cell dendritic arborization, and reduced numbers of
dendritic spines.~~l3 The hypomyelination reported in
human PKU patients was not present in our patient.
Two factors that may bear upon the interpretation
of the pathologic data are the interval between death
and autopsy, and the possibility of chronic hypoxia in

this child with complex congenital heart disease.
Postmortem examination was performed approximately 8 hours after death was discovered. Although
this interval clearly did not create difficulty for the
gross and routine microscopic analysis of the brain,
Golgi staining can be profoundly affected by delays in
fixation of 6 hours of more. 14 The autolytic, degenerative neuronal changes in humans consist of shrunken
perikarya, beaded dendritic shafts, reduced density
of dendritic spines, and incomplete impregnation.
Some autolytic changes were found in our Golgi
material, but the overall quality of the sections was
satisfactory, according to the criteria of Williams et
al.l4 Only well-impregnated and stained neurons
were studied, and our Golgi results do not mimic
those from suboptimally fixed and impregnated
human brains.
The possibility of chronic hypoxic-ischemic central nervous system injury affecting our results seems

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unlikely. Although the child became dusky or cyanotic when agitated, repeated cardiac catheterizations
showed normal oxygenation. Also, routine microscopic examination of the brain did not show evidence
of chronic hypoxic-ischemic neuronal injury, eg, to
the hippocampus and cerebellum. Finally, although

2. Lenke RR,

dendritic alterations to the brain in human neonates
and infants with hypoxia and ischemia have not been
adequately studied, our unreported Golgi observations in these children are not similar to those of the
maternal PKU child. Rather, asphyxiated infants
have reduced numbers of short, stubby dendritic

220.
5. Committee on Genetics, American Academy of Pediatrics:
Maternal phenylketonuria. Pediatrics 1985;76:313-314.
6. Smith I, Erdohazi M, Macartney EJ, et al: Fetal damage despite
low-phenylalanine diet after conception in a phenylketonuric
woman. Lancet 1979;1:17-19.
7. Bauman ML, Kemper ThL: Morphologic and histoanatomic
observations of the brain in untreated human phenylketonuria. Acta Neuropathol 1982;58:55-63.
8. Nigman MP, Yagnik P: The effect of hyperphenylalaninemia
on rat neocortex: A Golgi study. Ann Neurol 1979;6:183.
9. Wen GY, Wisniewski HM, Shek JW, et al: Neuropathology of
phenylacetate poisoning in rats: An experimental model of
phenylketonuria. Ann Neurol 1980;7:557-566.
10. Robain O, Wen GY, Wisniewski HM, et al: Purkinje cell
dendritic development in experimental phenylketonuria. A
quantitative analysis. Acta Neuropathol 1981;53:107-112.
11. Lacey DJ: Hippocampal dendritic abnormalities in a rat model
of phenylketonuria (PKU). Ann Neurol 1984;16:577-580.
12. Lacey DJ: Normalization of dendritic spine numbers in rat
hippocampus after termination of phenylacetate injections
(PKU model). Brain Res 1985;329:354-355.
13. Williams RS, Hauser SL, Purpura DP, et al: Autism and mental
retardation. Neuropathologic studies performed in four persons with autistic features. Arch Neurol 1980;37:749-753.
14. Williams RS, Ferrante RJ, Caviness VS: The Golgi rapid
method in clinical neuropathology: The morphologic consequences of suboptimal fixation. J Neuropathol Exp Neurol

spines.
The perikaryal spines and long, thin dendritic
spines in our patient probably represent delayed
maturational changes from fetal to postnatal life. 15
This dendritic maturational arrest has been found in
human adult PKU patients and also in animal models
of PKU.7,ll We have recently reported an animal
model of maternal PKU in which pregnant rats were
injected with phenylacetate. Brains of their offspring
were smaller than controls and had cortical dendritic
abnormalities. 16 Cortical pyramidal cells of layer 5
had few dendritic spines which were longer and
thinner than controls. Although the findings were
not precisely identical to those of our patient, the
similarities suggest that an animal model may be
useful in the experimental study of neuropathologic
correlates of the clinical features of maternal PKU

syndrome.

Levy HL: Maternal phenylketonuria and hyperphenylalaninemia. An international survey of the outcome of
untreated and treated pregnancies. N Engl J Med 1980;
303:1202-1208.

1983;309:1269-1274.
4. Lipson A, Buehler B,

Bartley J, Walsh D, et al: Maternal
hyperphenylalaninemia fetal effects.J Pediatr 1984;104:216-

1978;37:13-33.

References
1. Lenke RR,

Levy HL: Maternal phenylketonuria—Results of
dietary therapy. AmJ Obstet Gynecol
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3. Levy HL, Waisbren SE: Effects of untreated phenylketonuria
and hyperphenylalaninemia on the fetus. N Engl J Med

15. Purpura DP: Normal and aberrant neuronal development in
the cerebral cortex of human fetus and young infant, in
Buckwald NA, Brazier, MAB (eds): Brain Mechanisms in Mental
Retardation. New York, Academic Press, 1975, pp 141-169.
16. Lacey DJ: Cortical dendritic spine loss in rat pups whose
mothers were prenatally injected with phenylacetate ("Maternal PKU" model). Dev Brain Res 1986;27:283-285.

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