Friday, 13 May 2016

The Dysfunctional Dictionary of Developmental Delay

Children who have not reached a developmental milestone frequently present to primary care.  Sometimes the concern is raised by a parent but often it is another family member, a teacher or a health care professional who spots the ‘delay’.   Often, there is no significant problem.  Some children just do their developing differently.  This is not developmental delay.  However, true developmental delay is quite prevalent and the terminology used is frankly misleading both to clinicians and parents.  Understanding what is wrong with the words used is the key to coming to grips with this difficult subject.

The Dysfunctional Dictionary of Child Development

Milestones – this word is used to describe the age at which a child should do a thing.  In the same way that children behave unpredictably, they may not meet these targets.  These ‘norms’ are based on population studies.  Because children vary they may not fall within a specific milestone norm.  Some children skip a milestone entirely (e.g. crawling) but hit their next milestone (e.g. cruising) normally.

Developmental delay – This term suggests that a child is simply late getting to a developmental level.  If there is a pathological developmental delay, this is unlikely to be the case.  If a child has true delay, they will almost certainly be permanently behind their chronological age. In other words they will not 'catch up'.  (see diagram above)

Developmental delay – Another problem is that the term implies there is always a neurodevelopmental cause.  This fails to give weight to the fact that delay can be due to something which obstructs development.

Global Developmental Delay – A child has GDD if they are delayed in at least two of the developmental domains.  They can be developing normally in the other two and is therefore a misnomer.

Developmental impairment – This is a more accurate term than developmental delay.  It’s just that I think that it doesn’t sound very nice.

Intellectual impairment – this is the correct term if we are talking about the over 5 year old.  Developmental delay or impairment should only be used for the under five year old.  Who knew?

Of course we need terminology and this vocabulary is what we have to work with.  We just need to know the limitations of the words we use so that they cause minimal confusion.

What is a primary care clinician to do when a child has a possible developmental delay?  Because there is so much variability in children it is reasonable to watch and wait (in the absence of red flags) when there is a ‘late’ milestone in an isolated domain.  If the delay persists or involves more than one domain then the chances of a significant problem is higher.

It is worth considering the causes of delay that can be relatively easily identified.  Delay in one domain is more likely to have such a cause.  For example, a child under the age of 2 who is not meeting their gross motor milestones may have dislocated hips.*  A child with speech delay may have ‘glue ear’.  These problems will obstruct development so early identification of such things can be life-changing.

Another cause that could be identified in Primary care is Muscular Dystrophy.  Although rare, this is an important cause of delayed mobility in boys.  A normal Creatinine Kinase (CK) is an easy way to rule this out if a boy is not achieving gross motor milestones.

What should I do in primary care?
  • Take the history
  • Examine the child including
    • Primitive reflexes
    • Tone and posture
    • Head circumference
  • If delay is limited to one domain, look for an identifiable/ treatable cause
    • Speech – hearing test/ speech and language assessment
    • Gross motor – check lower limbs including hip dislocation. Test CK in boys.
    • Fine motor – test visual acuity
    • Social – encourage environmental stimulation if appropriate.  Consider possible autistic spectrum disorder.
  • Observe initially if appropriate or refer if red flags
While most cases of true developmental delay are idiopathic, advances in genetic testing mean that a cause can often be found. Although this rarely leads to specific treatment that does not mean that we should not investigate for a cause.  It is very important to most parents to find out why their child has developmental delay both for understanding and to help get appropriate support.  In addition a diagnosis may have a recurrence risk in future pregnancies.

Edward Snelson
Dysfunctional Lexicographer

*Congenitally dislocated hips is now more correctly named 'Developemental Dysplasia of the Hip')

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