Omsk; How and When Should You Fix a Chiari?

By the time we had our follow-up appointment with Dr. Moores, our first neurosurgeon, Christopher was doing remarkably better.  The obvious migraines were gone, and the headache had gone from a daily 8 to a baseline of 3/4, even though it never went away.  This was enough improvement for him to begin doing math and grammar studies again.  We told Dr. Moores what all we’d done at the behest of Johns Hopkins and the information we’d learned since we’d last seen him.  

We also told Dr. Moores we'd sought out a second opinion because we'd been advised by a dear friend who's a pediatric ER doc that Chiari I Malformations are over-diagnosed.  He said he agrees.  In his opinion, there are a whole lot of people in the world with headaches, represented by the red circle.  There are slightly less than 1 in 1000 people with a Chiari I Malformation.  But most of those people are asymptomatic, and only discover they have a Chiari I because a scan of the brain/neck is done for a completely unrelated reason.  So the percentage of people whose Chiari defects actually cause headaches is represented by the overlap of those two circles.

Figure 1--My interpretation of Dr. Moores' Venn Diagram describing the relationship between Chiari and Headache.

The obvious question, which of course we asked, was what category does Christopher fall into?  He feels that the back of Christopher's skull cuts in to the base of his brain so as to inhibit his posterior cerebrospinal fluid flow such that he has zero functional flow as soon as he stands up.  But wait.  Christopher's a kid.  And kids grow.  Can't this all just be a problem where his current brain size is out of sync with his skull size and, if we're patient, he'll grow until they're back in phase again?  After all, when I look at my 12 year old's photos, it was at about age 9 that his face really started changing shape.  Unfortunately, all that skull change is confined to the front of the head.  The back of the head, and particularly the posterior fossa, don't change much after age 4.  The brain itself also reaches 99% of its final size by age 4, even though the connections it forms continue developing in some parts well into the 20s.  Dr. Groves had answered this question in exactly the same way.

Image 1--In this study, it's fairly obvious that there's a nice bright white line of CSF flowing around the top of Christopher's brain, and along the front of his brainstem.  Down the back of his brainstem?  Not so much.  Behind his cerebellum?  Eek.


So.  In Dr. Moores' estimation, Christopher will never be headache free without surgery to decompress the base of his brain.  He wasn't as worried as Dr. Groves about operating without eliminating the other causes of headache.  But he also feels it’s non-emergent right now because there's no syrinx or obvious optic nerve compression.  Scott, who hadn’t yet met Dr. Moores, agreed that his bedside manner is impeccable and his explanations, rooted in physics, just.make.sense.

Both neurosurgeons were in complete agreement as to what they would do to fix it:  A Chiari decompression via craniectomy of the foramen magnum, laminectomy of C1, and a duraplasty.

Figure 2--The opening of the foramen magnum is enlarged by removing small sections of bone, as well as widening the interior diameter of C1 if necessary.  They can't make the posterior fossa larger, but they can remove the pressure it exerts on the back of the brain.  Image courtesy of the Mayfield Clinic.

Figure 3--Posterior diagram showing the new skull configuration after surgery.  Duraplasty is done to enlarge the dural space and reintroduce proper CSF flow.  Image courtesy of the Mayfield Clinic.