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Clinical Case 114: Skull and Crackedbones

This case is inspired by a recent Twitter discussion with fellow Pads ED enthusiasts – Tessa Davis [ @TessaRDavis ] , Andrew Tagg [ @andrewjtagg ] , Rachael Rowlands [ @rachrwlnds ] and whoever else was reading.

As a background – you probably should read my previous ramblings about Paediatric head injury assessments here: Kids Coconuts and CTs

I think that the PECARN decision tool [MdCalc clickable version HERE ] is probably the most useful and robust data out there for making the call on children with minor head injuries in the ED.  In the past we have often taught or been taught to observe kids for hours and hours, or CT them.  The PECARN data set certainly has changed my practice in the last 5 years.

I now use it to identify children whom are at extremely low risk and feel confident to discharge them with follow-up instructions of course , one needs to be assured that the parents / carers are comfortable with this and able to access appropriate follow-up if required.  The PECARN study also gives us a basis for discussing the risks of observation, imaging and non-investigation in kids who are not in the low-risk group.

Now take a look at this part of the PECARN Algorithm – this is the section for kids aged under 2 years of age.

Screen Shot 2015-03-21 at 10.16.20 pm

The majority of kids that I see in this group are little ones who have walked / run / fallen head first into something solid.  They usually have a frontal “egg” or laceration over the forehead.

So lets walk through the algorithm.  If this kid has a large frontal haematoma then it is going to be tough to say that they do not have a skull fracture, or at least you may think you can feel something.  Let’s face it – pushing on a fresh, boggy swelling over a kids head is just plain cruel!

If you think that you can palpate a fracture – then they immediatley jump into the ‘high risk’ group i.e. the group that is recommended to CT early.  This was about 1 in 8 of the kids in this age group.

However, if there is no fracture palpable then you are very likely heading down the pathway to simple observation, or possibly into the super low-risk group.

Hence the question of the presence or absence of a skull fracture seems to be a big hinge-point when it comes to making this decision.  And here is what I suspect:  we are terrible at picking these!  OK, I understand that the PECARN trial is a pragmatic set-up.  It was a simple clinical call – was the clinician able to palpate a fracture.  However, in reality this does seem very subjective and prone to bias.

Enter our friend – the Ultrasound.  Is there nothing we cannot do with the probe?

Ultrasound is useful in picking fractures elsewhere in the body – particularly in superficial bones.  So can we detect skull fractures with any accuracy?

Well there are a few smallish trials looking gat this question in the literature:

One form New York, Jim Tsung and co. in Paediatrics, June 2013 – “Accuracy of Point-of-Care Ultrasound for Diagnosis of Skull Fractures in Children”

Another from Riera et al in Paediatric Emergency Care, May 2012 – “Ultrasound Evaluation of Skull Fractures in Children: A Feasibility Study”  This one had more small kids in it – i.e.. mean age 2 years

These are small trials – 115 patients combined.  19 had a fracture on CT – so the incidence was ~ 16%.  Like many POCUS papers they show the usual characteristics of bedside ultrasound techniques – very specific and reasonably sensitive – so if you see a fracture – there almost certainly is a fracture, but you will miss 15 – 20 % potentially based on the numbers here.  In the Tsung paper – only one fracture was missed – that was a fracture that was adjacent to the hematoma – rather than directly beneath it.  So you could improve this with a more thorough scan field.  In terms of likelihood ratios: bedside US give a +LR of 27 (excellent!) and a -LR of 0.13 (pretty good!).  As always – we need more data to validate this and make it more generally applicable.

So how would a bedside skull US fit into the PECARN pie?

Hard to say what our “Sensitivity and specificity” is for clinical palpation of skull fractures – I would guess we are 50% sensitive and 75% specific.

So using that as a comparison – we should be able rule in a few more kids who should probably get an early CT.

So will this mean we do more CTs?  I think not – as there are a lot of kids who have a nasty looking egg on the head – and we are often biased by the external picture into believing that we can feel a ‘step’ as we are worried and want to rule out badness.  So if we scan the kids with the ugly looking hematoma and find no fracture on US – then this would probably be a group where it is safe to push them into the “observe, wait ‘n see” strategy.  Although US is not super sensitive – it surely must be better than a subjective prod over a boggy lump.

[Note: if you use a stand-off pad or lots of gel – you can do this US without inflicting much pain at all.  No pressure needs to be applied.  So I think this is a more humane approach to the kids with a large, boggy swelling of the noggin.]

So overall I think that US would allow us to separate the goats from the sheep – allow us to create a bit of diagnostic daylight between these 2 groups:

(1) Those who definitely have a fracture and may need early imaging of the brain

(2) Those at lower risk of fracture who can be safely observed.

Bedside US probably doesn’t add too much to the kids whom can be classified as very low risk by the PECARN algorithm.

My practice is to promptly discharge kids who meet the “extremely low risk” criteria.  I give the parents reassurance and information for what to look out for.  But… this is my new pet peeve…  forcing a kid / family to sit in the ED for 4 – 6 hours to have “Neuro obs” completed seems like a really antisocial and low-yielding exercise in this group.  So if I am satisfied that the parents understand the risk and what to do if… happens, and there is no NAI question – I will send them home from triage.

Love to hear how you manage this common problem in your ED.

 

Casey

Comments

  1. Kylie Baker says:

    Love it Casey. Experience based medicine at its finest.

  2. Richard Pincus says:

    I like USS a lot -- BUT

    KIDS UNDER 2 ONLY

    with your frontal haematoma or in fact with any haematoma you do not have to “rule out a skull fracture” at all. For PECARN you only have to NOT FEEL ONE. The rule and common sense requires that you attempt to feel one and if you DO FEEL ONE you must do a CT no matter where the haematoma (if any ) is.

    If you do not feel one and the GCS is 14 or 15 and the parent thinks the child is acting normally and the mechanism of injury is not severe, and no Hx of LOC, you are done so no CT is required by the rule. But you or the parents may feel one is necessary for all kinds of other good reasons.

    If there is a frontal heamatoma, the rule does not change. If the is a non-frontal haematoma, it does. It requires a CT REGARDLESS of having no hx of LOC no severe mechanism etc UNLESS the physician decides to observe instead based on the various factors starting with her experience (stuff to the right of your second box.)

    Doing an informal USS is a great idea as it will make you get a CT in the very few who are USS positive. A formal USS should be even better. Because we know many fractures are missed now in my view we should be doing USS in every case if it is available, but it makes no difference to the PECARN rule.

    One further comment. We none of us (I hope) would rely on intelligent parents where any rule or your gestalt or anything says you need neuro obs. Only nurses can do that, and those of us that have actually seen a blown pupil found unexpectedly at neuro ons after HI know that.

    Nothing to stop you using the parents as a further safeguard where formal neuro ons are NOT required, though. That does no qualify as observation tho’.

  3. Dr Janelle Trees says:

    Very helpful article and discussion. US info is particularly helpful for those of us remote from CT who may have an US machine.

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