Thursday, 26 July 2018

Paediatric Examination by the Book - (Easter egg- When to measure head circumference in a child and what it means)

You know that book that you had when you were learning how to do a clinical examination?  Even books have a teaching style.  Mine was like an old school maths professor.  It taught me that there is only one correct answer and often only one correct way to get to the answer.  And stop doodling Snelson!

If I had owned a paediatric examination text I imagine it would have been more like a literature teacher.  I'm imagining Robin Williams in Dead Poet's Society.  It would teach me that you're never going to approach the same problem the same way twice, and you will probably even find that the answer changes.  Who would like a chocolate?

Having moved from primary to secondary care environments has been an interesting experience.  I recall my first awakening to the differences between two approaches to examination when many years ago I saw a young person with earache.  I was a newly appointed paediatric trainee, but having recently left General Practice I was well accustomed to such presentations.  For reasons I cannot recall, I discussed the case with a consultant and found myself being asked about the systemic examination.  I then had a genuinely useful discussion about what constitutes a full examination.  I had done a detailed throat, ear and neck examination but had absolutely no idea what this young person's spleen was doing that day.  Discuss...

In paediatrics there is no such thing as a routine examination.  This is for several reasons.  Having a routine only works if the same approach works regardless of age or cooperation of the child.  It doesn't.  I am sometimes asked by medical students whether they should be palpating the trachea or percussing the chest of a child.  The obtuse answer is that you should do these things when they are useful and practical.  Often they are not.  If they are, do it.

In any case, examination is normally tailored to the situation.  If a child presents with a finger injury, I presume that the GMC will let me off if I don't check to see if the child has developed a cardiac complication.  Paediatrics is a speciality that quickly teaches you not to think in terms of routine.  Children may have their own opinions about what is about to happen and you often find yourself asking whether something is worth the battle.

General Practitioners have made an art form of the focused examination.  The way that this works is that by the time an examination takes place, the clinician has heard the history and thought about the possible causes of the symptoms in that patient, given their age and past medical history.  What is examined is made up of a selection of what that clinician needs to support or refute each differential diagnosis.

This way of working is very different to the way that hospital medics tend to approach the same problem.  The default in secondary care tends to be a full systemic examination (if that is a thing) in all cases, injury not withstanding.  Each approach has strengths and weaknesses.




























The best approach is probably a combination of the two.  Having a minimum general examination is of value as is the ability to tailor your examination to the patient and the presentation.  There are some elements of examination which are just not part of most peoples routines.  Whatever is left off the "do it every time" list, you need to know and remember when to do it as part of the focused element of an examination.

Let's look at head circumference as an example of something that is routine for some clinicians in secondary care paediatrics but not for most clinicians in primary care or emergency medicine.

How to measure head circumference
Picture credit: https://ftjmikesouth.wordpress.com/

As long as it is done properly, with the correct equipment, measuring head circumference is easy and a more reliable growth parameter than length in babies.  Like any growth parameter, the recorded value is of little use without context.


Head circumference is usually measured either as part of routine monitoring of growth or as part of the assessment of an infant or toddle who has presented with a problem.  In either case, the interpretation of the measurement needs to be in context of a clinical assessment.  The most important elements of this are feeding history, concerns about growth, developmental assessment and neurological examination.

What constitutes abnormal head circumference?

The Great Ormond Street Guide to head circumference (1) suggests the following criteria as abnormal:
  • The child’s head circumference measurement indicates excessive or limited growth. 
  • Their head is an abnormal shape or size (eg if the measurement falls outside 99.6th or 0.4th centile on the chart. 
  • The head circumference is >2 centile lines above or below their height or length measurement. 
What causes abnormal head circumference?

In many cases, HC outside of the 98th or 2nd centile (or where it is disproportionate) is constitutional.  That is to say that it is genetic but without underlying abnormality.  Just as some people are taller or shorter, some people have bigger or smaller heads.  In these cases, there is no other abnormality (including development) and the measurement usually closely follows a centile line.
























































When do I need to check a head circumference?

Well, if you work in secondary care paediatrics, you may well find that you are supposed to be checking it on all your patients under a certain age.  If that's not you then these are some of the common indications to check:
  • Noticeably large or small head
  • Growth problems
  • Feeding problems
  • Vomiting infants
  • Any history of symptoms or event with a possible neurological cause (including BRUE/ALTE)
  • Developmental concerns or impairment
  • Asymetrical head shape
  • Child with congenital abnormality of any kind
Why vomiting infants?  It's rare as anything can be but brain tumours can present in babies as vomiting.  Of course, because it is such rare pathology, it is rarely considered early.  Although it is not going to identify a problem very often, checking HC in these babies is harmless and could help to make a diagnosis earlier.

What about the asymmetrical heads?  Positional plagiocephaly is a benign moulding of the skull which is now very commonly seen in infants.
Picture credit: Gzzz https://commons.wikimedia.org/wiki/File:Plagiocephalie.JPG

There was a sharp rise in the incidence of plagiocephaly after the "Back to Sleep" campaign advised to only allow babies to sleep on their backs until old enough to roll over.  This change had a huge impact on the number of cot deaths but it meant that more babies had flattening of the back of their heads, or an asymmetry caused by a tendency to look to one side.

There has been much debate about plagiocephaly treatment but the majority of experts without conflict of interest agree that this is a benign condition (no neurological effects) which tends to improve, if not always completely resolve, as the infant becomes a toddler.

Benign though it is, positional plagiocephaly is common enough to create a risk that craniosynostosis (plagiocephaly's evil twin) might be missed.  Avoid that pitfall by measuring and monitoring the head circumference.  Also check for a ridged suture and a misshaped or small fontanelle.

After making sure that the shape is not due to craniosynostosis, parents can be advised to
  • Give the baby time on their tummy when awake
  • Change the position of interesting things around the cot.  Alternatively, place the baby's head at the opposite end of the cot on alternate days.
  • Alternate the side the baby is held when feeding and carrying
  • Consider using a sling to carry the baby instead of being flat in a pram.

But what about the spleen?  Somehow it just doesn't feature in the assessment of positional deformational plagiocephaly as long as craniosynostosis has been ruled out.  What does the book say?  Well, that is a question worth discussing with your literature teacher.

Edward Snelson
Literally not a teacher
@sailordoctor

Disclaimer: I've just realised- I was better at maths than literature.  Ignore everything I've said.  Clearly I'm in the wrong speciality.
References
  1. Head circumference: measuring a child, Great Ormond Street Hospital online, downloaded from https://www.gosh.nhs.uk/health-professionals/clinical-guidelines/head-circumference-measuring-child on 24/7/2018

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