Aproximación Diagnóstica en Microcefalia (Developmental Medicine and Child Neurology)

1. DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY ORIGINAL ARTICLE
Diagnostic approach to microcephaly in childhood: a two-center
study and review of the literature
MAJA VON DER HAGEN1
| MARK PIVARCSI2,3
| JULIANE LIEBE1
| HORST VON BERNUTH4,5
|
NATALIYA DIDONATO6
| JULIA B HENNERMANN7,8
| CHRISTOPH B€
UHRER9
| DAGMAR WIECZOREK10
|
ANGELA M KAINDL2,3
1 Abteilung Neuropaediatrie, Medizinische Fakult€
at Carl Gustav Carus, Technische Universit€
at Dresden, Dresden; 2 Department of Pediatric Neurology;
Charit
e – Universit€
atsmedizin Berlin, Berlin; 3 Institute of Neuroanatomy and Cell Biology; Charit
e – Universit€
atsmedizin Berlin, Berlin; 4 Department of Pediatric
Immunology; Charit
e – Universit€
atsmedizin Berlin, Berlin; 5 Labor Immunologie Berlin; Charit
e Vivantes GmbH, Berlin; 6 Institut f€
ur Klinische Genetik; Medizinische
Fakult€
at Carl Gustav Carus, Technische Universit€
at Dresden, Dresden; 7 Department of Pediatric Endocrinology; Gastroenterology and Metabolic Disease, Charit
e –
Universit€
atsmedizin Berlin, Berlin; 8 Villa Metabolica; Department of Pediatrics, University Medical Center of the Johannes Gutenberg University Mainz, Mainz;
9 Department of Neonatology; Charit
e – Universit€
atsmedizin Berlin, Berlin; 10 Institute of Human Genetics; University Duisburg-Essen, Essen, Germany.
Correspondence to Angela M Kaindl, Department of Pediatric Neurology, Charit
e – Universit€
atsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
E-mail: angela.kaindl@charite.de
This article is commented on by Holden on page 705 of this issue.
PUBLICATION DATA
Accepted for publication 15th January
2014.
Published online 12th March 2014.
ABBREVIATIONS
cMRI Cranial magnetic resonance
imaging
CGH Comparative genomic hybridiza-
tion
OFC Occipitofrontal head circumfer-
ence
AIM The aim of this study was to assess the diagnostic approach to microcephaly in
childhood and to identify the prevalence of the various underlying causes/disease entities.
METHOD We conducted a retrospective study on a cohort of 680 children with microcephaly
(399 males, 281 females; mean age at presentation 7–8mo, range 1mo–5y) from patients
presenting to Charit
e – University Medicine Berlin (n=474) and University Hospital Dresden
(n=206). Patient discharge letters were searched electronically to identify cases of
microcephaly, and then the medical records of these patients were used to analyze
parameters for distribution.
RESULTS The putative aetiology for microcephaly was ascertained in 59% of all patients,
leaving 41% without a definite diagnosis. In the cohort of pathogenetically defined
microcephaly, genetic causes were identified in about half of the patients, perinatal brain
damage accounted for 45%, and postnatal brain damage for 3% of the cases. Microcephaly
was associated with intellectual impairment in 65% of participants, epilepsy was diagnosed
in 43%, and ophthalmological disorders were found in 30%. Brain magnetic resonance
imaging revealed abnormalities in 76% of participants.
INTERPRETATION Microcephaly remains a poorly defined condition, and a uniform diagnostic
approach is urgently needed. A definite aetiological diagnosis is important in order to predict
the prognosis and offer genetic counselling. Identifying gene mutations as causes of
microcephaly increases our knowledge of brain development and the clinical spectrum of
microcephaly. We therefore propose a standardized initial diagnostic approach to microcephaly.
Microcephaly is defined as an occipitofrontal head circum-
ference (OFC) below the third centile or more than 2 stan-
dard deviations (SD) below the mean for sex, age, and
ethnicity.1,2
The term ‘severe’ microcephaly is applied to an
OFC more than 3SD below the mean. Microcephaly is asso-
ciated with a reduction in brain volume and often intellec-
tual and/or motor disabilities. The pathogenesis of
microcephaly is heterogeneous, ranging from genetic causes
to environmental factors that can have an impact on devel-
opmental processes that influence brain size.3–5
Any condi-
tion that affects important processes of brain growth, such
as progenitor cell proliferation, cell differentiation, and cell
death, can thus induce microcephaly. Anomalies leading to
microcephaly may exclusively affect cerebral development
(non-syndromal microcephaly) or may be associated with
extracranial malformations and/or facial dysmorphism (syn-
dromal microcephaly).
Microcephaly may be evident at birth (primary micro-
cephaly) or postnatally (secondary microcephaly). The
child with secondary microcephaly has a normal OFC at
birth and then subsequently the relative OFC drops to a
value more than 2SD below the mean. These terms do not
imply distinct aetiologies. Both primary and secondary
microcephaly can be acquired or genetic. The distinction
of primary and secondary microcephaly enables clinicians
to rank the likelihood of a putative diagnosis according to
disease prevalence.
The phenotype of microcephaly is variable and the spec-
trum of associated disorders is large, with more than 900
entries in the Online Mendelian Inheritance in Man com-
732 DOI: 10.1111/dmcn.12425 © 2014 Mac Keith Press

2. pendium for the clinical sign ‘microcephaly’ as of January
2014. The aim of the present study was to analyse in a large
cohort of patients with microcephaly (1) the frequency of
(putative) causes of microcephaly; (2) the frequency of
structural brain abnormalities, intellectual disability, and
associated disorders; (3) the diagnostic steps taken to define
the underlying disease; and (4) the number of cases in
which the diagnostic approach was successful. We also pro-
pose uniform data documentation and a standardized initial
diagnostic approach to children with microcephaly.
METHOD
Patients with microcephaly were recruited from all chil-
dren who presented to the Departments of Paediatric Neu-
rology at the Charit
e – University Medicine Berlin and the
Dresden University of Technology between 2000 and 2010
and between 2006 and 2011, respectively. Patients were
identified by carrying out a computer-based search through
patient discharge letters using the terms ‘microcephaly’,
‘developmental delay’, and ‘intellectual disability’, and their
corresponding ICD-10 Classification of Mental Disorders
numbers.6
Thus, 680 patients (399 [59%] males, 281
[41%] females) with microcephaly were eligible for our
study (Charit
e – University Medicine Berlin, n=474; Dres-
den University of Technology, n=206). Eighty-eight fami-
lies (12%) reported consanguinity.
We reviewed the medical records of all the patients
included in our study: medical history, clinical, laboratory,
genetic, and radiological data were collected using an
anonymous form in a database. All parameters were analy-
zed for distribution within the entire patient group. Owing
to the retrospective nature of our study, not all data were
available across the entire cohort. Microcephaly was
defined as an OFC below the third centile for sex and age.
It was further categorized as primary if it was first apparent
at birth or secondary if it occurred postnatally. Proportion-
ate microcephaly was defined as OFC, length, and weight
below the third centile for sex and age, whereas dispropor-
tionate microcephaly was defined as isolated microcephaly,
implying length and/or weight to be above the third cen-
tile for sex and age. Cognitive development was assessed
using the Bayley Scales of Infant Development, the Wechs-
ler Preschool and Primary Scale of Intelligence, the
Wechsler Scale of Intelligence for Children or for Adults,
a Snijders–Oomen Non-verbal Intelligence Test, and the
Kaufman Assessment Battery for Children or for Adoles-
cents, depending on the age of the child. If results of a
specific test were not available, cognitive development was
estimated based on the clinical status and the history of
the patient (e.g. schooling for children with intellectual
disability). Methods of testing regarding the severity of
cognitive or motor deficit varied within one institution.
RESULTS
Our cohort comprised 680 patients with microcephaly.
There was a predominance of male patients (59% [n=399]
male, compared with 41% [n=281] female). The children
first presented at a mean age of 7 to 8 months (range 1mo
to 5y). Microcephaly was proportional in 42% (n=288) and
disproportional in 40% (n=269) of the patients, and classi-
fication was not possible in 18% (n=123) of cases. Primary
and secondary microcephaly could be differentiated in
42% of patients (n=287), with primary microcephaly occur-
ring in 38% (n=109) and secondary microcephaly in 62%
(n=178) of all patients in whom OFC at birth was docu-
mented. Among patients with primary microcephaly, there
was a slight predominance of individuals with proportional
microcephaly (proportional, n=86; disproportional, n=48).
We were able to obtain data regarding the gestational age
of 433 patients: 64% (n=277) were born at term and 36%
(n=156) were born preterm. Severe perinatal complications
were reported in 27% (n=183) of the cohort.
Intellectual disability or neurodevelopmental delay was
diagnosed in 65% of patients (n=442). We were able to
obtain data with regards to schooling for 24% (n=164) of
the total cohort. Of these, 28% of the children (n=46) were
integrated in mainstream schools and kindergarten and
72% of the children (n=118) received special education.
Epilepsy was diagnosed in 43% (n=291) of the patients.
Regarding the association between cognitive impairment
and the microcephaly classification, the following distribu-
tion was noted: (1) 74% (n=214) of 288 patients with pro-
portional and 61% (n=165) of 269 patients with
disproportional microcephaly displayed intellectual disabil-
ity; and (2) cognitive impairment was detected in 34%
(n=98) of patients with primary and 57% (n=163) of
patients with secondary microcephaly (primary and second-
ary microcephaly could be specified in 287 patients). Our
data analysis revealed that in 18% of the cases proportional
microcephaly was not differentiated from disproportional
microcephaly, and in 58% of the cases microcephaly was
not classified into primary or secondary microcephaly dur-
ing the diagnostic work-up. This made it impossible to ret-
rospectively define the microcephaly phenotype of a
patient.
Cranial magnetic resonance imaging (cMRI) or cerebral
ultrasound was performed in 72% (n=491) of our cohort at
a mean age of 23 months. The results were abnormal in
63% (n=310) of cases. Of the 299 children who were
assessed by cMRI, abnormal findings were found in 76%
(n=227). The most frequent structural brain lesions, apart
from microencephaly, were anomalies of the white matter,
found in 40% (n=90), and gyration defects, found in in
14% (n=31) of all radiologically assessed patients. White
matter abnormalities included periventricular leukomalacia
and delayed or disturbed myelination. Further frequent
structural brain lesions included corpus callosum anomalies
What this paper adds
• The distribution of various aetiologies of microcephaly in the largest cohort
of children to be studied to date.
• The rate of success in diagnosing microcephaly is illustrated.
• A uniform data documentation and standardized initial diagnostic approach
to children with microcephaly is proposed.
Diagnostic Approach to Microcephaly in Childhood Maja von der Hagen et al. 733

3. in 31% (n=70) and anomalies of the cerebellum in 15%
(n=33) of the radiologically examined children.
Non-central nervous system abnormalities and malforma-
tions associated with microcephaly were revealed through
medical history, physical examinations, and further tests.
Disorders of the eyes were diagnosed in 30% (n=207) of the
patients, of the ears in 8% (n=51), of the heart in 14%
(n=93), of the kidneys and the urinary tract in 13% (n=89),
and of the gastrointestinal tract in 9% (n=58). Other disor-
ders included facial dysmorphism in 19% (n=127) of
patients, and anomalies of the oropharynx such as cleft pal-
ate in 13% (n=87), of the skeletal system in 13% (n=91), of
the skin in 2% (n=12), and of the hair in 1% (n=9) of the
patients.
The putative aetiology of microcephaly was documented
in 59% of the patients (n=403). Among the total cohort of
680 patients, pathogenesis was genetic or presumably
genetic in 29% (n=194). Other causes of microcephaly
included craniosynostosis in 2% (n=14), perinatal brain
injury in 27% (n=182), and postnatal brain injury in 2%
(n=13). In 41% the aetiology remained unclear. Genetic
abnormalities were numerical chromosome aberrations or
microdeletions/duplications in 24% (n=46) and monogenic
disorders in 30% (n=58); the remaining diagnoses were puta-
tive genetic syndromes based on the patient phenotype and/
or the family constellation (consanguinity and/or several
family members exhibiting a similar phenotype; Table I).
DISCUSSION
Evaluation of a child with microcephaly
In the current retrospective study, we assessed the diagnos-
tic approach to patients with microcephaly and identified
the prevalence of various underlying causes of the disorder.
Our cohort is, to our knowledge, the largest cohort studied
so far, with most previously published cohorts staying well
below 100 cases.7–14
Males predominated among patients
with microcephaly presenting to our clinical centres (59%
males [n=39] compared with 41% females [n=281]); the
distribution of proportional and disproportional micro-
cephaly was almost equal, but there was a predominance of
secondary (postnatal) microcephaly relative to primary
(congenital) microcephaly (62% vs 38% of the 287 patients
in whom type of microcephaly was specified). The differ-
ence between affected males and females might be
explained by mutations in X-chromosomal recessive genes,
which primarily affect males.
Phenotype evaluation and microcephaly classification
The majority of children with microcephaly presented with
neurological symptoms in infancy at a mean age of 7 to
8 months. Neurodevelopmental delay or intellectual dis-
ability was the most frequent reason for referral to our
departments (65% of all cases), and epilepsy was another
common reason (43% of all cases). This is in line with the
data of Abdel-Salam et al.,15
who reported an overall prev-
alence of epilepsy in children with microcephaly of 40.9%.
Epilepsy seems to be more common in children with
Table I: Causes of microcephaly in our cohort (n=680)
Microcephaly cause n %
1. Genetic cause 194 28.5
Microcephaly syndromes with numerical
chromosomal aberrations or microdeletion
and/or duplication syndromes
46 6.8
Microdeletion and/or duplication syndromes 28
Trisomy 11/22 1
Patau syndrome, trisomy 13 1
Down syndrome, trisomy 21 4
Pallister–Killian syndrome, tetrasomy 12p 1
Unbalanced deletion of chromosome
12/duplication of chromosome 17
1
Pitt–Hopkins syndrome, deletion 18q21.2 1
Microdeletion 22q11 2
Klinefelter syndrome 3
Triple X syndrome 2
Mosaics 2
Monogenetic microcephaly syndromes/diseases 58 8
with autosomal dominant inheritance 13
Cornelia de Lange syndrome 2
Werner syndrome 1
Currarino syndrome 1
Charcot–Marie–Tooth disease 1A 1
Kabuki syndrome 2
Mowat–Wilson syndrome 1
Generalized epilepsy with febrile seizures (SCN1A) 1
Glucose transporter type 1 deficiency (GLUT1) 1
Tuberous sclerosis 1
Congenital Rett syndrome (FOXG1) 2
with autosomal recessive inheritance 17
Primary autosomal recessive microcephaly 1 2
Nijmegen breakage syndrome 1
Nijmegen breakage
syndrome-like disorder (RAD50)
1
Marinesco–Sj€
ogren syndrome 1
Warburg micro syndrome 1
Congenital muscular dystrophy
with a-dystroglycan deficiency (POMT1)
2
a-Thalassaemia 1
Metachromatic leukodystrophy 1
Niemann–Pick disease type C 1
Dyggve–Melchior–Clausen disease 1
Cohen syndrome 1
Batten disease 1
Carnitine palmitoyltransferase
IA deficiency (CPTIA)
1
Methylenetetrahydrofolate reductase
deficiency (MTHFR)
1
3-Methylcrotonyl-CoA Carboxylase 1 deficiency
(MCCC1)
1
with X-chromosomal inheritance 21
Rett syndrome (MECP2) 13
Duchenne muscular dystrophy 2
Becker muscular dystrophy 1
L
eri–Weill syndrome 1
Pelizaeus–Merzbacher disease 1
Menkes syndrome 1
Allan–Herndon–Dudley syndrome (MCT8) 1
Incontinentia pigmenti 1
With complex inheritance/not classified 7
Angelman syndrome 6
Prader–Willi syndrome 1
2. Putative genetic cause due to phenotype or family
constellationa
90 13
3. Perinatal brain injury 182 26.7
Birth complications 118
Maternal disease during pregnancy 25
Exposure to teratogen substances 30
Other pregnancy disorders 9
4. Postnatal brain injury 13 1.9
Infarct 4
734 Developmental Medicine Child Neurology 2014, 56: 732–741

4. secondary microcephaly than in those with primary micro-
cephaly.15,16
In addition, microcephaly has been identified
as a risk factor for intellectual disability and therapy-refrac-
tory epilepsy.13,17,18
Among children with neurodevelop-
mental delay, secondary microcephaly is more common
than primary microcephaly (57% vs 34% of patients with
classified microcephaly; n=287). In this retrospective data
analysis of children with intellectual disability, proportional
microcephaly was more common than disproportional
microcephaly (74% vs 61% of patients with classified
microcephaly; n=557). Whether proportional microcephaly
is more predictive of developmental delay than dispropor-
tional microcephaly is an open question as the available
data are conflicting.18
In our cohort, of the 164 children for whom data could
be obtained with regards to schooling, 72% did not attend
mainstream schools or kindergarten but rather needed spe-
cial education. It needs to be noted here that children
examined at the paediatric neurology departments repre-
sent a selective cohort of mainly symptomatic patients with
microcephaly, and thus it is difficult to estimate the preva-
lence of children with microcephaly and normal psycho-
motor development.
Further clinical findings frequently identified in patients
with microcephaly were ophthalmological disorders (30%),
facial dysmorphism (19%), anomalies of the oropharynx
including cleft palate (13%), and anomalies of the heart
(14%), kidneys and of the urinary tract, as well as of the
skeletal system (13% each) and of the gastrointestinal tract
(9%). This emphasizes the need for a multidisciplinary
approach to patients with microcephaly. Ophthalmological
and audiological disorders and complex ear anomalies have
been associated in variable prevalence with microcephaly,13
and, therefore, the patients with microcephaly of unknown
aetiology require screening and follow-up monitoring.
In nearly a third of the patients, the underlying disease
could be diagnosed without further extensive diagnostic
work-up or with focused genetic testing based on patient
history revealing intrauterine brain damage (e.g. drug
abuse), or severe perinatal complications (e.g. severe
asphyxia), or on presentation with a typical phenotype of a
known syndrome (e.g. Down syndrome). We detected a
large degree of variability in the data available for individ-
ual patients and therefore conclude that a standardized
assessment of medical history, clinical examination, and
performed studies is urgently required. We suggest using
the term ‘primary microcephaly’ instead of ‘congenital
microcephaly’ and ‘secondary microcephaly’ rather than
‘postnatal microcephaly’ and clearly defining whether a
microcephaly is proportional or disproportional. The exact
classification can direct future diagnostic investigations and
potentially allow a prognosis. Even in a university-based
paediatric neurology setting the diagnostic approach and
documentation is not standardized or uniform, and in our
cohort microcephaly was of unknown origin or unclassified
in a high percentage of cases.
Neuroimaging
cMRI or cerebral ultrasound was performed in 72% of all
children with microcephaly, and the majority of these patients
underwent imaging by the second year of life (the mean age at
which cMRI was performed was 23mo, and cranial ultrasound
was performed in the first months of life). Children in whom
cMRI was performed before 24 months of age often under-
went repeated MRI studies to assess myelination after
24 months, by which age most myelination is complete. The
results were abnormal in 63% of the patients. Of the 299 chil-
dren who were assessed by cMRI, abnormal findings in addi-
tion to microcephaly were found in 76%. The higher
prevalence of abnormal findings in cMRI analyses points to
cMRI as the more sensitive imaging method for the identifi-
cation of brain lesions and anomalies associated with micro-
cephaly. Abnormal findings in addition to microcephaly
comprise white matter anomalies (40%), corpus callosum
anomalies (31%), infratentorial lesions (15%), and gyration
defects (14%). Recent neonatal and prenatal imaging studies
suggest that agenesis of the corpus callosum occurs at least
1:4000 live births, and other imaging studies have demon-
strated that 3% to 5% of individuals assessed for neurodevel-
opmental disorders have agenesis or hypoplasia of the corpus
callosum.19–21
Agenesis of the corpus callosum can have
genetic causes or result from various exogenous factors such
as infectious, vascular, or toxic effects. White matter anoma-
lies were, as expected, particularly frequent in preterm infants.
MRI has been reported to be valuable in the evaluation of
children with developmental delay and at least one further
neurological sign, including atypical head circumference.22
Jaworski et al.23
found that the percentage of imaging abnor-
malities was highest in patients with microcephaly and a
known history of perinatal or postnatal brain injury (91%).
The proportion of patients with microcephaly and one or
more extracranial congenital anomalies in whom imaging
abnormalities were detected was somewhat lower (67%).23
Although most of the radiological findings were rather
unspecific and did not enable a specific diagnosis, in some
cases they directed the diagnostics towards further meta-
bolic screening or genetic testing. In some patients, the
identification of a specific pattern of brain injury enabled
the attending physician(s) to refrain from further diagnostic
work-up. The small percentage of children in whom the
cMRI finding led to specific genetic testing and enabled a
diagnosis included those with autosomal recessive primary
Table I: Continued
Microcephaly cause n %
Encephalitis 5
Non-accidental injury (‘battered child’) 3
Concussion 1
5. Craniosynostosis 14 2.1
6. Unknown cause 277 40.7
Total 680 100
a
Phenotype such as mitochondriopathies, family constellation such
as consanguinity, and several affected children.
Diagnostic Approach to Microcephaly in Childhood Maja von der Hagen et al. 735

5. microcephaly, lissencephaly and further gyration defects,
Pelizaeus–Merzbacher disease, mitochondriopathies, and
tuberous sclerosis.
Genetic assessment
Genetic diagnostics were performed in 51% (n=308) of all
patients; diagnostic tests included karyotyping, array com-
parative genome hybridization (array-CGH) analysis, chro-
mosomal breakage analysis, and sequencing of selected
genes. Of all patients in whom the cause of the microceph-
aly was suspected to be genetic, the genetic abnormality
was determined through karyotyping in 2% to 3% of cases
and, in recent years, also through array-CGH analysis in
about 4% of all patients (this rate is likely to rise further
in the years to come in Germany as a result of the increas-
ing application of array-CGH analyses in the routine diag-
nostic work-up and of exome sequencing in the research
setting for intellectual disability). In many patients the ini-
tial tests produced normal results and thus were subse-
quently often followed by more specific/directed genetic
analysis. Through this approach, a specific genetic cause
was identified in 15.3% of all patients (n=104): numerical
chromosome aberrations and microdeletions/duplications
in 6.8% (n=46) and monogenic disorders (e.g. Rett syn-
drome, Angelman syndrome) in 8.5% (n=58; Table I). Our
approach thereby follows current recommendations for the
diagnostic work-up for intellectual disability.24
According
to the proposed diagnostic algorithm, in the investigations
of neurodevelopmental delay, array-CGH analyses present
the next diagnostic step.24
In a subgroup of patients with microcephaly, a genetic
aetiology is strongly suspected owing to phenotype and/or
family history (further family members affected, consan-
guineous parents), even if karyotyping, array-CGH, and
sequencing of selected genes are not conclusive. In this
group, whole-exome or whole-genome sequencing may
allow for the identification of the underlying genetic
abnormality. The possibilities for genetic analyses have
changed dramatically within the last decade, and micro-
array analyses have become a criterion standard. Next-gen-
eration sequencing methods are likely to clarify the
underlying cause in patients in whom the aetiology of
microcephaly is unknown. However, dysmorphological
evaluation is important for the diagnosis of children with
syndromes.
Aetiology of microcephaly and the success rate of the
approach to its diagnosis
The aetiology of microcephaly is highly variable and heter-
ogeneous. In our study, genetic causes accounted for 29%
(n=194) of all patients with microcephaly, followed by peri-
natal brain injury in 27% (n=182), postnatal brain injury in
2% (n=13), and craniosynostosis in 2% (n=14). In 41% of
patients the aetiology remained unclear. Inborn errors of
metabolism, e.g. mitochondriopathy, Menkes disease, and
methylenetetrahydrofolate reductase deficiency, were
counted as genetic causes. They occurred in about 3% of
the total cohort and rarely resulted in non-syndromal (iso-
lated) congenital microcephaly. The exact prevalence of
inborn errors of metabolism among children with micro-
cephaly is unknown. However, based on previous studies
of children with global developmental delay, it is likely to
be from 1% to 5%, similar to our finding.13,25–28
The underlying cause of microcephaly in our cohort was
identified in 59% of cases (n=403), meaning that the fami-
lies of 41% (n=277) of patients may carry the burden of
not knowing the reason for their child’s microcephaly. In
these cases, the utility of genetic and clinical counselling is
limited. In our cohort, perinatal brain injury accounted for
a large proportion (27%) of the patients with microcephaly
(n=181), many of whom were born preterm. Both depart-
ments of paediatric neurology are associated with large
neonatal intensive care units that offer the highest level of
care and are involved in the neurodevelopmental follow-up
of children. This may also account for the high rate of
perinatal brain damage in our cohort. Furthermore, it
needs to be noted here that an underlying genetic cause
may have caused preterm birth and rendered a patient
more susceptible to, or mimicked, perinatal damage. A
comprehensive history, growth records for the child and
the close family, and a detailed physical examination may
suggest a diagnosis or direct further testing.
In summary, our data show that microcephaly is still
poorly defined and that the diagnostic approach in children
with microcephaly is not uniform. In a large subgroup, it
was not possible to make a definite diagnosis using the cur-
rent approach. We, therefore, propose uniform data docu-
mentation and a standardized initial diagnostic approach to
a child with microcephaly.
Diagnostic algorithm for the initial evaluation of
paediatric microcephaly
A standardized, evidence-based, algorithmic approach is
needed for the rapid identification of frequent causes of
microcephaly as well as rare diseases, which can later be
studied in research projects in order to decipher the phe-
notype and pathomechanism of genetically defined dis-
eases. We have developed a standard questionnaire that
can be used to document the patient’s own history and
family history, the clinical status (Fig. S1, online support-
ing information), and further diagnostic work-up results in
the case that history and clinical evaluation do not identify
the underlying cause (Fig. S2, online supporting informa-
tion). Based on our data and previously published data, we
further propose a common initial approach to children
with microcephaly (Fig. 1).
Standardized assessment of medical history and physical
examination
The first diagnostic step towards identifying a child with
microcephaly is gathering a comprehensive medical and
family history and collecting detailed clinical examina-
tion data. For the purpose of standardization, we propose
a questionnaire in which the relevant data can be
736 Developmental Medicine Child Neurology 2014, 56: 732–741

6. recorded, including the age at onset, severity, family
history (pedigree), and putative causes such as perinatal
brain damage, metabolic diseases, and genetic causes
(Fig. S1).
In the questionnaire we have adopted the microcephaly
terminology as stated in the introduction: primary micro-
cephaly evident at birth and secondary postnatal, propor-
tionate and disproportionate microcephaly depending on
OFC, weight, and height of a patient. We are, of course,
aware of the numerous additional microcephaly terminolo-
gies used in the literature, but these are, in our view,
unnecessary and hamper a standardized diagnostic
approach. The distinction of primary and secondary micro-
cephaly enables clinicians to rank the likelihood of a puta-
tive diagnosis according to timing of microcephaly
occurrence in individual disease entities, although for many
diseases the exact classification of microcephaly has not
been reported. The classification of microcephaly into pro-
portionate or disproportionate microcephaly is important,
as identification of proportionate microcephaly should,
e.g., prompt diagnostic steps with respect to dystrophy in
an infant or toddler.
The OFC should be measured several times with a
non-elastic measuring tape, and values should be plotted
in a centile or SD curve parallel to the other anthropo-
metric data. In utero head circumference can provide a
rough estimate of the time of the first deviation from the
norm in primary microcephaly. Frequent OFC measure-
ments early in life are justified by the high rate of brain
growth in the first 3 years.29
Measuring parental OFCs is
essential for the diagnosis of familial microcephaly. OFCs
are, unfortunately, often plotted in curves based on older
values taken from studies by Nellhaus30
or Prader et al.31
For children in industrial countries, the mean OFC is
larger than that indicated in the WHO standard values,
which are based on measurements taken from about 8500
children in Brazil, Ghana, India, Oman, and the USA
(www.who.int/childgrowth/en). We thus recommend
using the growth charts published by the Centers for
Disease Control and Prevention (CDC; www.cdc.gov/
growthcharts/). In several Anglo-Saxon countries, the
OFC is evaluated in SDs, and this can be calculated
based on the values for the mean and SD given on the
CDC site.
MICROCEPHALY
Specific
diagnostic test
Yes Yes Specific
diagnostic test
Clinical
follow-up
CGH-array
Syndromic
No
No
Normal
Abnormal
Malformation?
trauma?
disorder?
Lesions typical for metabolic
as infection, hypoxia, stroke,
postnatal brain damage such
Lesions typical for peri/
Cranial MRI
Yes
Secondary
Primary
indication for a specific disease?
Detailed medical/family history, clinical exam (see Fig. S1, online):
Yes
Initiate
specific
testing
(see Fig.
S2, online)
Nonconclusive
If diagnostic are still nonconclusive and genetic cause is suspected, consider panel diagnostic
Further testing depending on the phenotype
Ophthalmological exam, abdominal and heart ultrasound
Abnormal
Syndromic
(next generation sequencing) or, if family constellation allows, exome/genome sequencing
Laboratory and metabolic testing in blood, urine and CSF (see Fig. S2, online)
CGH-array
disorder?
disorder e.g. mitochondrial
infection or stroke?
brain damage such as
Malformation?
Lesions typical for prenatal
Lesions typical for metabolic
CMV in urine
Cranial ultrasound/MRI
Normal
No
Clinical
follow-up
CGH-array,
chromosomal
breakage, MCPH
genes
(see Table II)
No
Intellectual disability, developmental delay?
Figure 1: Diagnostic approach to a child with microcephaly. Based on our data and previously published data, we further propose a common initial
approach to a child with microcephaly. CGH-array, comparative genomic hybridization array; MRI, magnetic resonance imaging; CMV, cytomegalovirus.
Diagnostic Approach to Microcephaly in Childhood Maja von der Hagen et al. 737

7. In a child with primary or early infantile secondary
microcephaly, exogene factors that can damage the devel-
oping brain during pregnancy and perinatally should be
assessed in detail. Such factors include prenatal infections,
prenatal exposure to hypoxia, radiation, toxins, medica-
tions or drugs of abuse, preterm birth, and maternal
disease.
The last part of the questionnaire provides a compre-
hensive overview of important aspects of the clinical
assessment of a child with microcephaly, including a
neuropsychological evaluation. The latter is of particular
interest as children with microcephaly carry a higher risk
of developmental delay than their peers with normocephal-
y.13,14,18
The aim of the detailed clinical examination is to
pinpoint the neurological phenotype and identify signs of
major or minor abnormalities potentially leading to the
diagnosis of a syndromal microcephaly. This basic infor-
mation can be collected without high costs or further test-
ing and may help to resolve many of the potential
aetiologies of microcephaly in a child. Moreover, further
diagnostic work-up may not be indicated in a child with
microcephaly, but normal neurocognitive and motor devel-
opment, and no further signs of an underlying disease.
The combination of knowledge on disease prevalences
and the accumulated information obtained from the history
and detailed physical examination may already suggest a
specific diagnosis and direct diagnostic testing. This was
the case in one-third of the patients in our cohort. For
example, in a female patient, typical development in the
first months of life followed by development of secondary
microcephaly, loss of acquired skills, occurrence of intellec-
tual disability, and stereotypic movements will prompt
molecular genetic analysis of the MECP2 gene associated
with Rett syndrome. Similarly, a history of maternal alco-
hol abuse during pregnancy, typical facial dysmorphism,
and extracranial symptoms may lead to the diagnosis of a
fetal alcohol spectrum disorder, and a history of immuno-
deficiency, cancer, and microcephaly may hint towards the
work-up of chromosomal breakage syndromes. An over-
view of causes for primary and secondary microcephaly is
given in Tables II and III.
Approach to a child with microcephaly
In those individuals in whom the diagnosis remains unclear
following a comprehensive medical history and clinical
examination, we suggest MRI of the brain as the next step.
Although the majority of radiological findings were unspe-
cific in our cohort and did not enable a specific diagnosis,
they did direct further diagnostic measures. For example,
white matter disease indicative of leukodystrophy on cMRI
will tend to provoke metabolic investigations, whereas cer-
tain brain malformations, such as lissencephaly, lead first
to genetic testing.
Inborn errors of metabolism more often lead to secondary
microcephaly than to primary microcephaly. In secondary
microcephaly, metabolic investigations should be per-
formed, as indicated in Fig. 1. Routine metabolic screening
of all patients with microcephaly is not required, but tar-
geted metabolic studies should be performed based on find-
ings in the patient’s medical and family history, clinical
examination, and neuroimaging. In the case of leukodystro-
phy in particular, extensive metabolic and enzymatic diag-
nostic work-up should be initiated. Some inborn errors of
metabolism that are associated with an accumulation of toxic
metabolites or an intrauterine lack of metabolites may lead
to intrauterine brain damage and subsequently to primary
microcephaly (Table IV). These diseases include serine bio-
synthesis disorders (e.g. 3-phosphoglycerate dehydrogenase
deficiency, phosphoserine phosphatase deficiency), which
are associated with further neurological symptoms such as
muscular hypotonia and epilepsy and are diagnosed by
analyses of amino acids in blood and cerebrospinal fluid.32
Table II: Causes of primary microcephaly: overview
1. Genetic causes
Numerical chromosomal aberrations or microdeletion and/or
duplication syndromes
Trisomy 13, 18, 21 etc.
Monogenetic microcephaly
Autosomal recessive microcephaly (MCPH1-10, MCPHA)
Nijmegen breakage syndrome (MIM#251260)
Autosomal dominant microcephaly
X-chromosomal microcephaly
Aicardi–Gouti
eres syndrome (MIM#225750, 610329, 610181,
610333, 612952)
Cockayne syndrome (MIM#216400, 133540, 216411)
Cornelia de Lange syndrome (MIM#122470, 610759, 614701,
300590, 300822)
Rubinstein–Taybi syndrome (MIM#180849)
Feingold syndrome (MIM#164280, 614326)
Rett syndrome, congenital (MIM#164874)
Mowat–Wilson syndrome (MIM#235730)
Smith–Lemli–Opitz syndrome (MIM#270400)
Seckel syndrome (MIM#210600, 606744, 608664, 613676,
613823, 61472)
Ligase IV syndrome (MIM #606593)
Mutations in ATRX gene (MIM*300032)
Mutations in ARX gene (MIM*300382)
Mutations in PQBP1 gene (MIM*300463)
Mutations in ASNS gene (MIM*108370)
Borjeson–Forssman–Lehmann syndrome (MIM#301900)
Imprinting disorders
Angelman syndrome (MIM#105830)
2. Metabolic cause (genetic aetiology)
Serine biosynthesis disorder
Sterol biosynthesis disorder
Mitochondriopathy, e.g. pyruvate dehydrogenase deficiency
Congenital disorders of glycosylation syndrome
Rare congenital metabolic diseases (see text)
3. Exogenic factors
Intrauterine infection
Toxoplasmosis, rubella, cytomegalovirus, herpes simplex,
varicella zoster virus, syphillis, human immunodeficiency
virus
Teratogens
Alcohol, cocaine, antiepileptic drugs, lead/mercury intoxication,
radiation
Disruptive incident
Vascular incident (stroke), intrauterine death of twin
Maternal disease
Hyperphenylalaninaemia
Maternal anorexia nervosa
Extreme insufficiency of placenta
4. Craniosynostosis
738 Developmental Medicine Child Neurology 2014, 56: 732–741

8. Smith–Lemli–Opitz syndrome, a disorder of sterol biosyn-
thesis, should be suspected when patients show typical clini-
cal signs such as minor facial anomalies, syndactyly, and
organ malformations.33
Furthermore, mitochondrial disor-
ders (e.g. pyruvate dehydrogenase defect, respiratory chain
defect, mitochondrial transporter defect)34–36
and congeni-
tal disorders of glycosylation (i.e. CDG-Id, -Ig, -Ik, -Ilc,
-Ile)37–40
should be tested in patients with primary micro-
cephaly. In addition, there are a few inborn errors of metab-
olism which are only very infrequently associated with
microcephaly at birth (disorders of cobalamin metabolism
such as the CbIC or CbIF deficiency)41,42
and a few inborn
errors of metabolism that are very rare but frequently associ-
ated with primary microcephaly (e.g. multiple sulphatase
deficiency, congenital neuronal ceroid lipofuscinosis,
leukotriene C4 synthesis defect)43–45
that need to be consid-
ered in the differential diagnosis. Patients with molybdenum
cofactor deficiency or sulphite oxidase deficiency are mostly
normocephalic at birth but develop secondary microcephaly
rapidly within the first weeks of life.46
None of these
described inborn errors of metabolism can be identified by
the established newborn infant screening programmes.
If the result of cMRI is normal or changes are unspe-
cific, i.e. do not suggest metabolic disease, our algorithm
follows current recommendations for the diagnostic
work-up of intellectual disability.24
In this case, array-
CGH analysis presents the second diagnostic step.24
Recent studies point to an average diagnostic yield of
chromosomal microarray analyses of 15% to 20% in
patients with intellectual disability.47–49
In the case of
autosomal recessive primary microcephaly, i.e. non-syn-
dromal primary microcephaly (OFC 3SD) and intellec-
tual disability without further severe neurological
abnormalities, analysis of the most common autosomal
recessive primary microcephaly genes such as WDR62
and ASPM using Sanger sequencing or panel diagnostics
(next-generation sequencing) is indicated.50
In syndromal
microcephaly, syndromologists should be consulted in
making a diagnosis, as they may be able to guide genetic
analysis effectively.
In the remaining subgroup of microcephaly patients in
whom genetic aetiology is strongly assumed and in whom
karyotyping, array-CGH, and Sanger sequencing of the
selected genes or next-generation panel sequencing are
inconclusive, large screening tests of disease-associated
genes and exome or genome sequencing may identify the
underlying genetic defect.
CONCLUSION
Microcephaly is a frequent clinical sign common in many
rare diseases. An exact diagnosis is important for counsel-
ling of the patient and the affected family regarding clinical
course, possible complications, optimized medical support,
and recurrence risk. Moreover, an exact diagnosis is also
important for future gene therapy approaches and the
development of neuroprotective therapies of perinatal brain
injuries. If currently available diagnostic tools cannot
establish a specific (genetic) diagnosis, modern technolo-
gies that are still being optimized at a research level might
provide a future diagnostic approach and become part of
the standard approach to patients with microcephaly.
Table III: Causes of secondary microcephaly: overview
1. Genetic causes
Numerical chromosomal aberrations or microdeletion and/or
duplication syndromes
e.g. Williams syndrome
Monogenetic microcephaly
Aicardi–Gouti
eres syndrome (MIM#225750, 610329, 610181,
610333, 612952)
Ataxia telangiectasia (MIM*607585)
Cohen syndrome (MIM#216400)
Early infantile epileptic encephalopathies, e.g. EIEE14
(MIM#614959)
Marden syndrome (%248700)
Mowat–Wilson syndrome (MIM#235730)
Rett syndrome (MIM#312750)
Rubinstein–Taybi syndrome (MIM180849)
Imprinting disorders
Angelman syndrome (MIM#105830)
2. Metabolic causes (genetic aetiology)
Phenylketonuria (untreated)
Glycine encephalopathy
Disorders of serine biosynthesis
Urea cycle disorders
Disorders of cobalamin metabolism
Organic aciduria
Disorders of neurotransmitters and biogenic amines
Congenital disorders of glycosylation syndrome (CDG)
Galactosaemia
Glucose transporter defect (GLUT1)
Leukodystrophies, e.g. Pelizaeus–Merzbacher diseases
Mitochondriopathies
Menkes diseases
Neuronal ceroid-lipofuscinosis (NCL)
Peroxisomal disorders
Disorders of sterol biosynthesis
Disorders of purine and pyrimidine metabolism
Molybdenum cofactor deficiency and sulphite oxidase deficiency
Disorders of pyridoxine metabolism
Lysosomal storage disorders, e.g. mucolipidosis, multiple
sulphate deficiency, Gaucher disease type 11
3. Exogenic factors
Perinatal brain damage
Hypoxic–ischaemic encephalopathy
Perinatal infection, e.g. herpes simplex virus, rubella virus, and
syphilis (if acquired in third trimester)
Perinatal/postnatal haemorrhagic and ischaemic insult
Perinatal intracranial haemorrhage/thrombosis
Perinatal teratogens
Postnatal brain damage
Infections, e.g. meningitis, encephalitis
Intracranial haemorrhage/thrombosis
Traumatic brain injury, intracranial haemorrhage
Haemorrhagic and ischaemic insult
Psychosocial deprivation
Malnutrition
Toxic, e.g. lead toxicity, uraemic encephalopathy
(renal insufficiency)
X-irradiation
Endocrinology, e.g. hypothyroidism, hypopituitarism
Chronic or systemic disorders, e.g. congenital
heart disease, anaemia
Vitamin B12 deficiency in fully breastfed infant of vegan mothers
Structural brain anomalies
E.g. holoprosencephaly. May also be of genetic aetiology,
e.g. HPE1–9
4. Craniosynostosis
Diagnostic Approach to Microcephaly in Childhood Maja von der Hagen et al. 739

9. ACKNOWLEDGEMENTS
The authors thank Christoph H€
ubner, Theodor Michael, Denise
Horn, Birgit Spors, Gabriele Hahn, Rainer John, Sigrid Tinschert,
and Pierre Gressens for discussions. Our research was supported by
the Charit
e – Universit€
atsmedizin Berlin, the Technische
Universit€
at Dresden, the German Research Foundation (DFG,
SFB665), the BIH (Berlin Institute of Health, Helmholtz Stiftung),
the Sonnenfeld Stiftung, and the Deutsche Gesellschaft f€
ur Musk-
elkranke (DGM). The authors state that they had no interests that
might be perceived as posing conflict or bias.
SUPPORTING INFORMATION
The following additional material may be found online:
Figure S1: Microcephaly questionnaire. Comprehensive medi-
cal and family history and detailed clinical examination data can
be summarized in a standard questionnaire. CMV, cytomegalovi-
rus; IUGR, in utero growth retardation; OFC, occipitofrontal
head circumference; ENT, ears, nose, and throat.
Figure S2: Diagnostic work-up form for microcephaly. Diag-
nostic work-up results of patients with microcephaly can be sum-
marized in a standard form. MRI, magnetic resonance imaging;
CT, computed tomography; CGH-array, comparative genomic
hybridization array; FISH, fluorescence in situ hybridization;
MLPA, multiplex ligation-dependent probe amplification; qPCR,
quantitative real-time PCR; CSF, cerebrospinal fluid; DBS, dried
blood spots; electrophor, electrophoresis.
REFERENCES
1. Opitz JM, Holt MC. Microcephaly: general consider-
ations and aids to nosology. J Craniofac Genet Dev Biol
1990; 10: 175–204.
2. Woods CG. Human microcephaly. Curr Opin Neurobiol
2004; 14: 112–17.
3. Abuelo D. Microcephaly syndromes. Semin Pediatr Neu-
rol 2007; 14: 118–27.
4. Leroy JG, Frias JL. Nonsyndromic microcephaly: an
overview. Adv Pediatr 2005; 52: 261–93.
5. Holden KR, Lyons MJ. Microcephaly – acquired. In:
Maria BL, editor. Current Management in Child Neu-
rology. Shelton, CT: People’s Medical Publishing
House, 2009: 421–8.
6. World Health Organization. The ICD-10 Classification
of Mental and Behavioural Disorders: Clinical Descrip-
tions and Diagnostic Guidelines. Geneva: World Health
Organization, 1992.
7. Baxter PS, Rigby AS, Rotsaert MH, Wright I. Acquired
microcephaly: causes, patterns, motor and IQ effects, and
associated growth changes. Pediatrics 2009; 124: 590–5.
8. Stoler-Poria S, Lev D, Schweiger A, Lerman-Sagie T,
Malinger G. Developmental outcome of isolated fetal
microcephaly. Ultrasound Obstet Gynecol 2010; 36: 154–8.
9. Nelson KB, Deutschberger J. Head size at one year as a
predictor of four-year IQ. Dev Med Child Neurol 1970;
12: 487–95.
10. Ivanovic DM, Leiva BP, Perez HT, et al. Head size and
intelligence, learning, nutritional status and brain devel-
opment. Head, IQ, learning, nutrition and brain. Neuro-
psychologia 2004; 42: 1118–31.
11. Gale CR, O’Callaghan FJ, Bredow M, Martyn CN. The
influence of head growth in fetal life, infancy, and child-
hood on intelligence at the ages of 4 and 8 years. Pediat-
rics 2006; 118: 1486–92.
12. Hack M, Breslau N, Weissman B, Aram D, Klein N,
Borawski E. Effect of very low birth weight and subnor-
mal head size on cognitive abilities at school age. N Engl
J Med 1991; 325: 231–7.
13. Ashwal S, Michelson D, Plawner L, Dobyns WB.
Practice parameter: evaluation of the child with
microcephaly (an evidence-based review): report of the
Quality Standards Subcommittee of the American
Academy of Neurology and the Practice Committee of
the Child Neurology Society. Neurology 2009; 73: 887–
97.
14. Coronado R, Giraldo J, Macaya A, Roig M. Head cir-
cumference growth function as a marker of neurological
impairment in a cohort of microcephalic infants and
children. Neuropediatrics 2012; 43: 271–4.
15. Abdel-Salam GM, Halasz AA, Czeizel AE. Association
of epilepsy with different groups of microcephaly. Dev
Med Child Neurol 2000; 42: 760–7.
16. Qazi QH, Reed TE. A problem in diagnosis of primary
versus secondary microcephaly. Clin Genet 1973; 4: 46–52.
17. Chawla S, Aneja S, Kashyap R, Mallika V. Aetiology
and clinical predictors of intractable epilepsy. Pediatr
Neurol 2002; 27: 186–91.
18. Dolk H. The predictive value of microcephaly during
the first year of life for mental retardation at seven years.
Dev Med Child Neurol 1991; 33: 974–83.
19. Glass HC, Shaw GM, Ma C, Sherr EH. Agenesis of the
corpus callosum in California 1983–2003: a population-
based study. Am J Med Genet A 2008; 146: 2495–500.
20. Paul LK. Developmental malformation of the corpus
callosum: a review of typical callosal development and
examples of developmental disorders with callosal
involvement. J Neurodev Disord 2011; 3: 3–27.
21. Bodensteiner J, Schaefer GB, Breeding L, Cowan L.
Hypoplasia of the corpus callosum: a study of 445 con-
secutive MRI scans. J Child Neurol 1994; 9: 47–9.
22. Verbruggen KT, Meiners LC, Sijens PE, Lunsing RJ,
van Spronsen FJ, Brouwer OF. Magnetic resonance
imaging and proton magnetic resonance spectroscopy of
the brain in the diagnostic evaluation of developmental
delay. Eur J Paediatr Neurol 2009; 13: 181–90.
23. Jaworski M, Hersh JH, Donat J, Shearer LT, Weisskopf
B. Computed tomography of the head in the evaluation
of microcephaly. Pediatrics 1986; 78: 1064–9.
Table IV: Overview of most common congenital metabolic diseases associated with primary microcephaly
Disease Associated symptoms Diagnostic tests
Maternal phenylketonuria Intrauterine growth retardation, facial dysmorphism,
congenital heart defect, intellectual disability
Phenylalanine in maternal blood sample
Serine biosynthesis disorder Muscular hypotonia, epilepsy, intellectual disability Fasting amino acids in plasma and
cerebrospinal fluid
Sterol biosynthesis disorder Facial dysmorphism, syndactylia, organ malformation,
midline defects, genital malformations,
adrenal insufficiency, intellectual disability
Sterol analysis (7/8-dehydrocholesterol)
in plasma
Mitochondriopathy Lactic acidosis, further organ manifestation (e.g.
encephalopathy, myopathy, cardiomyopathy,
cerebral changes on magnetic resonance imaging)
Lactate and pyruvate in blood and
cerebrospinal fluid, organic acids in
urine, further tests including
enzymatic/genetic analyses depend
on clinical signs
Congenital disorders of glycosylation Broad clinical picture including intellectual disability,
dysmorphism, epilepsy, muscular hypotonia
Isoelectric focusing analysis of
transferrin in serum
740 Developmental Medicine Child Neurology 2014, 56: 732–741

10. 24. Romano C. The clinical evaluation of patients with
mental retardation/intellectual disability. In: Knight SJL,
editor. Genetics of Mental Retardation. Basle: Karger,
2010: 57–66.
25. Shevell M, Ashwal S, Donley D, et al. Practice parame-
ter: evaluation of the child with global developmental
delay: report of the Quality Standards Subcommittee of
the American Academy of Neurology and The Practice
Committee of the Child Neurology Society. Neurology
2003; 60: 367–80.
26. van Karnebeek CD, Houben RF, Lafek M, Giannasi W,
Stockler S. The treatable intellectual disability APP www
.treatable-id.org: a digital tool to enhance diagnosis
care for rare diseases. Orphanet J Rare Dis 2012; 7: 47.
27. van Karnebeek CD, Scheper FY, Abeling NG, et al. Eti-
ology of mental retardation in children referred to a ter-
tiary care center: a prospective study. Am J Ment Retard
2005; 110: 253–67.
28. Shevell MI, Majnemer A, Rosenbaum P, Abrahamowicz
M. Etiologic yield of subspecialists’ evaluation of young
children with global developmental delay. J Pediatr
2000; 136: 593–8.
29. Dekaban AS. Changes in brain weights during the span
of human life: relation of brain weights to body heights
and body weights. Ann Neurol 1978; 4: 345–56.
30. Nellhaus G. Head circumference from birth to eighteen
years. Practical composite international and interracial
graphs. Pediatrics 1968; 41: 106–14.
31. Prader A, Largo RH, Molinari L, Issler C. Physical
growth of Swiss children from birth to 20 years of age.
First Zurich longitudinal study of growth and develop-
ment. Helv Paediatr Acta Suppl 1989; 52: 1–125.
32. Tabatabaie L, Klomp LW, Berger R, de Koning TJ.
L-serine synthesis in the central nervous system: a
review on serine deficiency disorders. Mol Genet Metab
2010; 99: 256–62.
33. Goldenberg A, Chevy F, Bernard C, Wolf C, Cormier-
Daire V. [Clinical characteristics and diagnosis of
Smith–Lemli–Opitz syndrome and tentative phenotype-
genotype correlation: report of 45 cases. Arch Pediatr
2003; 10: 4–10.
34. Barnerias C, Saudubray JM, Touati G, et al. Pyruvate
dehydrogenase complex deficiency: four neurological
phenotypes with differing pathogenesis. Dev Med Child
Neurol 2010; 52: e1–9.
35. van Straaten HL, van Tintelen JP, Trijbels JM, et al.
Neonatal lactic acidosis, complex I/IV deficiency, and
fetal cerebral disruption. Neuropediatrics 2005; 36: 193–9.
36. Siu VM, Ratko S, Prasad AN, Prasad C, Rupar CA.
Amish microcephaly: long-term survival and biochemical
characterization. Am J Med Genet A 2010; 152: 1747–
51.
37. Kranz C, Sun L, Eklund EA, Krasnewich D, Casey JR,
Freeze HH. CDG-Id in two siblings with partially dif-
ferent phenotypes. Am J Med Genet A 2007; 143: 1414–
20.
38. Schollen E, Grunewald S, Keldermans L, Albrecht B,
Korner C, Matthijs G. CDG-Id caused by homozygosity
for an ALG3 mutation due to segmental maternal isodi-
somy UPD3(q21.3–qter). Eur J Med Genet 2005; 48:
153–8.
39. Morava E, Vodopiutz J, Lefeber DJ, et al. Defining the
phenotype in congenital disorder of glycosylation due to
ALG1 mutations. Pediatrics 2012; 130: e1034–9.
40. Morava E, Zeevaert R, Korsch E, et al. A common
mutation in the COG7 gene with a consistent pheno-
type including microcephaly, adducted thumbs, growth
retardation, VSD and episodes of hyperthermia. Eur J
Hum Genet 2007; 15: 638–45.
41. Chenel C, Wood C, Gourrier E, Zittoun J, Casadevall
I, Ogier H. [Neonatal haemolytic–uraemic syndrome,
methylmalonic aciduria and homocystinuria caused by
intracellular vitamin B 12 deficiency. Value of aetiologi-
cal diagnosis]. Arch Fr Pediatr 1993; 50: 749–54.
42. Gailus S, Suormala T, Malerczyk-Aktas AG, et al. A
novel mutation in LMBRD1 causes the cblF defect of
vitamin B12 metabolism in a Turkish patient. J Inherit
Metab Dis 2010; 33: 17–24.
43. Busche A, Hennermann JB, Burger F, et al. Neonatal
manifestation of multiple sulfatase deficiency. Eur J
Pediatr 2009; 168: 969–73.
44. Fritchie K, Siintola E, Armao D, et al. Novel mutation
and the first prenatal screening of cathepsin D deficiency
(CLN10). Acta Neuropathol 2009; 117: 201–8.
45. Mayatepek E, Flock B. Leukotriene C4-synthesis defi-
ciency: a new inborn error of metabolism linked to a
fatal developmental syndrome. Lancet 1998; 352: 1514–
17.
46. Carmi-Nawi N, Malinger G, Mandel H, Ichida K, Ler-
man-Sagie T, Lev D. Prenatal brain disruption in
molybdenum cofactor deficiency. J Child Neurol 2011;
26: 460–4.
47. Cooper GM, Coe BP, Girirajan S, et al. A copy number
variation morbidity map of developmental delay. Nat
Genet 2011; 43: 838–46.
48. Miller DT, Adam MP, Aradhya S, et al. Consensus
statement: chromosomal microarray is a first-tier clinical
diagnostic test for individuals with developmental dis-
abilities or congenital anomalies. Am J Hum Genet 2010;
86: 749–64.
49. Shoukier M, Klein N, Auber B, et al. Array CGH in
patients with developmental delay or intellectual disabil-
ity: are there phenotypic clues to pathogenic copy num-
ber variants? Clin Genet 2013; 83: 53–65.
50. Kaindl AM, Passemard S, Kumar P, et al. Many roads
lead to primary autosomal recessive microcephaly. Prog
Neurobiol 2010; 90: 363–83.
Diagnostic Approach to Microcephaly in Childhood Maja von der Hagen et al. 741