Here's the e-mail I sent to multiple researchers and some of the responses I've gotten. I'll add the research to the links page.
My name is Amy Replogle and my daughter, Makenna, has Horizontal Gaze Palsy with Progressive Scoliosis. HGPPS is a relatively rare genetic disorder. Makenna diagnosis has been made by genetic confirmation testing through a research study at Children's Hospital of Boston with Dr. Elizabeth Engle. Dr. Joanna Jen at UCLA has also been instrumental in diagnosing Makenna.
I am writing to you today with a particular interest in determining if you know of any current research studies looking at the possible connection between the vestibular system and scoliosis. I know there have been numerous research studies on the topic related to AIS, but I wondered if anyone had looked at Infantile Scoliosis or, more importantly, kids with HGPPS. Because it is so rare, I am not sure what you may know about it, so forgive me if I offer too much information. In summary, HGPPS patients are ipsilaterally wired. The somatosensory and corticospinal tracts do not cross in the hindbrain. Amazingly enough, the only complications are a lack of lateral gaze and progressive scoliosis. The more I understand about the makeup of my daughter, the more amazed I am. And the more convinced I am that she (and other children like her) can offer a great deal of insight into the cause of idiopathic scoliosis.
I was hoping you might be able to offer suggestions of individuals or institutions I should contact. You can read Makenna's story at www.sosmakenna.com and see my personal (layman's) theory about the impact of a possible vestibular and proprioceptive dysfunction on the progression of scoliosis...
Thank you for taking the time to answer this e-mail!
Hi Ms. Replogle
Thank you for your email, which is very timely. We are very interested in the genetic relationship between HGPPS/the vestibular system/other forms of scoliosis. I am attaching our latest study that seems to point to genes involved in this system in idiopathic forms of scoliosis. This in turn has caused us to ask whether all scoliosis patients should have some form of neurophys testing and/or high resolution MRI to image the corticospinal tracts. However we have not reached the stage of formulating an actual protocol. As for other vestibular studies, I have attached a couple of papers that I hope are interesting. I'm very interested to hear more of your ideas!
I hope your daughter is well and I will definitely check out her website.
Very best regards
Our results have revealed that adolescent idiopathic scoliosis patients with severe curvature have sensorimotor integration impairment. However, we have not tested HGPPS patients therefore I cannot confirm that your daughter has sensorimotor integration impairment or vestibulomotor dysfunction. We are carrying a research project that aims to determine if there is a link between scoliosis, vestibulomotor alteration and genetic in patients with mild, severe or family history (the mother or sister has a scoliosis).
We could try to recruit HGPPS patients to help you better understand the mechanisms related to the development of a scoliosis. I will try to find the time to write down a grant proposal to be able to test some patients. If we ever succeed, I will contact you. The results, however, will not be available soon as research is a long process but I will give it a try for sure!
Dear Mrs Replogle,
Sorry for the delay in responding. There is a lot of information in your
email. I don't know if I will be able to answer even part of it.
First, I am not a medical doctor but a research scientist who uses an
animal model to study vestibular signal processing. And that is how we
got into this story since we saw that larval frogs do not compensate the
loss of one labyrinth but after metamorphosis develop a scoliotic
deformation. We know now that under these experimental circumstances
part of the vestibular nuclei are lost and descending spinal projections
degenerate. In our case we could convincingly show that the vestibular
deficit is not the consequence but the cause of the scoliosis.
So, the major effect is an asymmetry of signals that are mediated to the
spinal cord, which cause an asymmetric activity of the motoneurons and
hence an asymmetric pull of the muscles an thus on the skeletal elements
that is permanent.
The initial asymmetry in our case is caused by the vestibular deficit,
however it is conceivable that all asymmetries from different brain
areas that are mediated to spinal motoneurons can have the same effect.
This means that bilateral small differences in activity can be
manifested at the end.
The delayed onset of the scoliosis might be related to the increased
body growth and since girls are much more affected than boys might point
to the involvement of different hormones.
Links to some of the research that was suggested can be found on the links page~ in case you're up for a little light reading :)