Abstract
Head size naturally differs between female and male infants, and it is age-dependent. The skull is filled with the brain, cerebrospinal fluid and vascular structures. The shape and size of the head is determined by the above components, as well as skull thickness, rate of the fusion of the cranial sutures, and the development of the frontal sinuses. This article aims to outline a best practice assessment of head circumference and discuss abnormalities that could be seen in general practice.
The GP Curriculum and abnormal head growth in children
Mange and appropriately treat common and rare but important paediatric conditions encountered in primary care Demonstrate an understanding of the importance of multiagency working (working across professional and agency boundaries) Co-ordinate care with other primary care professionals, paediatricians and other appropriate specialists, leading to effective and appropriate care provision Manage conditions and problems which may present early and in an undifferentiated way Have a thorough understanding of normal development, and be able to recognise delayed development through childhood
Head circumference (HC) at birth can be influenced by gestational age, breech presentation and excessive skull moulding. It is an important measurement that is routinely included in child health surveillance examinations. Technique is important in order to accurately monitor HC over time. Centile shifts (decrease or increase in centile) within the normal range occur commonly, and seem mainly to reflect measurement error or regression to the mean (Wright & Emond, 2015). A study of children with a HC crossing below the percentile found that 60% had no identifiable pathology (Wright, Inskip, Godfrey, Williams, & Ong, 2011). Abnormal subsequent measurements of HC may indicate pathology.
When to measure HC
In the UK, measurement of HC is generally recommended after birth and at 8 weeks, with a lack of evidence for its usefulness thereafter (Hall & Elliman, 2003). Midwives, health visitors, paediatricians and GPs routinely measure HC. Measurement of HC in the first 48 hours of life can be misleading, as the resolution of moulding during birth requires time. Therefore, HC should be measured in the first 2–5 days of life. Generally, routine measurement of HC should not be part of a complete physical examination of a healthy normal child. Measurements of HC should be carried out in specific circumstances, such as patients with facial dysmorphology, epilepsy, neurodevelopmental delay, and those at high risk of abnormal head growth (e.g. maternal use of drugs, alcohol during pregnancy).
How to measure HC
Head measurement technique.
How to assess a patient with an abnormal HC
The majority of children and infants with abnormal heads are normal. There are some specific symptoms and signs that can indicate pathology. Evaluation of patients with suspected abnormal head growth should involve obtaining previous measurements and plotting all to identify the trend of head growth.
To put an abnormal HC growth trend into context, it is important to gather a detailed medical history. In particular, the maternal use of cocaine and alcohol, medications during pregnancy, prematurity, birth asphyxia, history of head injury or central nervous system infection are relevant.
Special considerations and clinical assessments of a patient with an abnormal head.
When to refer a child with an abnormal HC
Many infants and children will be monitored in the community by health visitors or GPs and their measurements and development will be normal. Those children with persistent abnormal measurements or growth trend require further investigation. Differentiation of primary and secondary abnormal HC will help clinicians to formulate a differential diagnosis. The infant with secondary abnormal head growth has a normal HC at birth that then subsequently drops or rises to two standard deviations (2SDs) below or above the mean.
Red flags among patients with an abnormal HC.
In secondary care, the child’s history and examination will be revisited. Further tests may include blood tests looking for endocrine and metabolic problems. Karyotyping and comparative genomic hybridisation-array can identify underlying genetic causes. Some children will need brain imaging to look for congenital problems intracranially.
If children have other neurodevelopmental problems, they will be assessed by a number of health professionals in secondary care. Those with complex needs are often managed by a multidisciplinary team, including other allied health care professionals, paediatricians, neurologists and radiologists.
Abnormal head growth
Two to three percent of the ‘normal’ population might have a large or small head (more than 2SDs above or below the mean). Parents should be reassured that the majority of healthy and well-appearing children with small or large heads will have no underlying medical condition. Some will have a genetically determined head size. Abnormal HC can be broadly caused by genetic disorders, perinatal and / or postnatal brain injury.
Macrocephaly
Causes of macrocephaly.
Hydrocephalus, a condition characterised by an accumulation of cerebrospinal fluid in the ventricular system, is probably the most important cause of macrocephaly. If this condition occurs before the sutures have closed, the head may reach an enormous size. If it occurs after the sutures have closed, there is a gradual dilatation of the ventricles with compression of the brain tissue. Therefore, in the early stages, hydrocephalus may be asymptomatic. Infants with hydrocephalus usually present with a full anterior fontanelle, splaying of cranial sutures, and later, distended scalp veins, ‘sunsetting’ of the eyes, vomiting, irritability and poor feeding. Malformation of the ventricular system in any place is a common mechanism of hydrocephalus. For example, Dandy–Walker syndrome should be suspected in any infant with macrocephaly and a prominent occiput.
Case study 1.
The following case study shows the importance of detailed clinical assessment when assessing macrocephaly.
An 8-month-old boy was seen because his parents were concerned that his head looked large. The history revealed no vomiting or feeding difficulties. His birth history was unremarkable. He was the only child born to unrelated parents and the parents had no other concerns. His neurodevelopment was appropriate for his age. His head circumference was 47 cm (98th centile) and he had a normal head shape and anterior fontanelle. Body weight was 9.5 kg (50th centile) and length 76 cm (75th centile). Systemic examination, including skin, spine and eyes was unremarkable. Neurological examination showed no abnormality or asymmetry. The head circumferences of his mother and father were 52 cm and 58.5 cm, respectively.
His parents were reassured and a follow-up appointment was arranged. At the age of 12 months, he remained fit and well, and his head circumference was 48.6 cm (98th centile). The parents were informed that their baby had benign familial macrocephaly.
In this scenario, one may consider two main differential diagnoses. Benign enlargement of the subarachnoid space is a cause of macrocephaly among healthy infants. In this condition, the infant usually has a large head at birth, large soft anterior fontanelle, but normal neurological examination and development. Another cause of macrocephaly in an infant with normal development and neurological examination is benign familial macrocephaly. In this condition, one or both parents might have a large HC. Brain imaging usually distinguishes this condition from benign enlargement of the subarachnoid space, but is rarely needed if the child is growing and developing normally in all other ways.
Microcephaly
Causes of microcephaly.
Infants with microcephaly due to perinatal events (e.g. hypoxic ischaemic encephalopathy) usually have developmental delay, seizures and cerebral palsy. The brain is also vulnerable to prenatal exposure to chemical agents, such as alcohol and phenytoin. Infants with fetal alcohol syndrome or phenytoin teratogenicity have a specific clinical phenotype. Metabolic disorders should be considered in infants with failure to thrive and a small head. In craniosynstosis, the skull is always misshapen with prominent bone ridging. Brain atrophy causes microcephaly in an infant with a normal head shape and overlapping of the skull bones. Congenital cytomegalovirus infection may manifest with microcephaly, although generalised petechial rash, hepatosplenomegaly and jaundice are common presentations to look out for among symptomatic infected infants.
Microcephaly is also a recognised finding of a variety of chromosomal disorders (e.g. Angelman syndrome and Rett syndrome). Clues to chromosomal disorders include the presence of dysmorphic features with or without hypotonia.
Conclusions
GPs may be faced with infants and young children with an abnormal HC. It is important that the measurements are recorded and checked at regular intervals if the child is at risk. However, it is also essential to inform the parents that if no risk factors are evident, it is possible that no pathology will be identified. This can help to reduce parental anxiety. Further investigations and onward referrals may be required if history and clinical examination reveal other abnormalities or the head is not growing along the child’s centile line.
Key points
HC should be measured in the first 2–5 days of life, and then in those with abnormal neurology or at high risk of abnormal head growth (e.g. perinatal insult), at appropriate intervals thereafter Head measurements should be plotted over time using appropriate charts for the age and sex of the patient Assessment of a child with an abnormal HC should include a thorough medical history comprising of previous head measurements, maternal use of cocaine or alcohol, medications during pregnancy, prematurity, birth history (e.g. prematurity, birth asphyxia), history of head injury or central nervous system infection Examination should include height, weight, inspection of the skin and eyes, inspection of the spine, neurodevelopmental assessment, neurological examination and parental HCs Early appropriate referral to a paediatrician and / or community team for further evaluation allows for prompt multidisciplinary input and optimal patient care