So I touched on one of the ‘issues’ that young children with achondroplasia may encounter; hydrocephalus. Declan shows signs, but the extra fluid is not negatively affecting him at this time…which is, of course, awesome. Almost all achon children have large heads, and most are secondary to benign ventriculomegaly and excess extraaxial fluid accumulation. Thankfully, only about 5% of children with achondroplasia will develop symptomatic hydrocephalus that would require shunting.
There are a few serious concerns that can occur in babies and young children with achondroplasia. Hydrocephalus is one of them. They stem (ha!) from an area located at the base of one’s skull, actually the hole in the bottom of your occipital bone (of the cranium), where your brainstem (medulla oblongata, anyone?) meets your spinal cord. This hole, called the foramen magnum, is often too small in people with achondroplasia, creating a fit that’s too tight for the brainstem and spinal cord. Because of this tight fit, it can restrict the flow of cerebrospinal fluid, causing excess fluid to build up in the ventricles of the brain (hydrocephalus).
Another very serious problem that can happen is compression of the spinal cord (in this same area, because of the small foramen magnum). The medulla oblongata (bottom part of the brainstem) that meets the spinal cord at the foramen magnum, controls some serious stuff. It contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic, involuntary functions, such as breathing, heart rate and blood pressure. Compression in this area is very serious and can even cause death if not carefully monitored and assessed. Risk of death from this complication is about 2-5%, with death being caused by damage to lower medullary respiratory control centers and consequent central apnea (this is almost exclusively a risk during their first year of life). This is why it’s so, so important for all achon babies to have a brain and cervical spine MRI done within their first few months (Declan’s wasn’t done until 6 months, but he had a CT scan at 6 weeks). First to identify if there is a problem, and then to use as a baseline to compare with future MRI images. Declan indeed has a ‘tight’/small foramen magnum, but there is no indication of compression at the moment.
It’s a bit hard, being armed with all of this information. Declan was sick a few months ago (remember that tummy bug?), and the first sign of anything being wrong was him violently vomiting all over himself in the car (and then all over my brother’s house/birthday party). Because he was the only one sick, everyone else was healthy and feeling fine (for the first 24 hours anyhow!), I have to admit…my mind went there. The neurosurgeons have all told me to be aware of the signs of compression. Vomiting being one of them. And now as a POLP, it’s my job to know these things.
The precarious nature of an achon baby’s neck and spine is the reason I was never ‘allowed’ to put Declan in a sling or wrap or carrier. Also no vibrating/bouncy chairs or swings. No umbrella strollers. No jolly-jumpers or jumparoos. No trampolines when he’s older. No high impact collision sports. And for those first few months, if you were lucky enough to hold my sweet little bundle, you also got a brief ‘how-to’ in holding an achon baby.
And so…we monitor the growth of Declan’s head circumference closely. And as his mom, I’ve learnt to watch for signs of intracranial pressure. Watching and feeling his large, throbbing soft spot on the top of his head, monitoring the prominent veins on the sides of his forehead, looking for ‘sun-setting eyes’. And in a few weeks we’re off to see a pediatric ophthalmologist who will peek in and behind his eyes, which will also tell us if there’s any pressure in there to be concerned about.
So yes, my baby has a big head…I already know that. In fact I know more about that beautiful, blonde big head and the intricate goings-on inside than any mother ever wants to know. But thanks for the keen observation and for pointing it out to me.