Hi and welcome to the Chiari forum,
For many children they will not know to express concern for some symptoms as they may consider them normal feelings/sensations since they have always had them and complain more about an activity that may trigger them or avoid certain activities as a result of not liking how they feel.
So do look to things like that more so then them telling u what hurts...like swinging on a swing, or a merry go round, blowing bubbles or blowing up balloons....certain things will trigger the symptom and a child will look to what caused it as the problem.
With children this young is it even more important to do testing for all related conditions and one big one is sleep apnea as it is related to Chiari in that many with Chiari do have this as well....or some sleep disturbance be it insomnia...or gasping for breath and waking every few hours.
The more u know b4 u consider surgery the better and if there is no time to do so, find a way to get it done as soon as u can post op,.
It would appear that the chromosome 16 microduplication may be inpart the reason ur child has Chiari as many with this condition have a smaller head and that in part is y so many of us have Chiari is the malformation of our skull....
The developmental issues could be from either or both.JMHO
I have a 15mo. old that had Chiari surgery on Halloween of 2012. She also can't tell me her symptoms, but here's our story:
We took her to the peditirician for her 9 mo. checkup and she noticed a slight tremor in her hands and said it just wasn't something a 9 mo. old should have. She referred us to Mayo Hospital in Rochester, MN. There, we saw a Pediatric Neorologist who, on top of the tremor, noticed some facial drooping, right side favoritism/left side weakness, etc. At home, she wasn't progressing either - she wasn't trying to crawl, talk, her eating was challenging - she gags all the time. He ordered an MRI & a swallow study. The swallow study showed nothing - she swallows just fine. The MRI showed a 9mm Chiari Malformation. He referred us to a Pediatric Neruosurgeon. 2 weeks later we had Decompression surgery and since then, things have been wonderful. She's progressing faster than ever. She crawled literally 3 weeks after she healed, she's picking up on things so fast - animal sounds, finding her eyes/nose/belly, etc. She wants to play with her sister when before, she didn't. Her balance seems better - she's pulling up to a standing position, when before when we put her in the position, she would just cry. And who knows how much of this is natural progression vs. post-surgery progression - but it's wonderful to see. Makes us happy we made the decision to have the surgery. We go back in April 2013 to have a follow up MRI to see where she's at.