Rare Genes: Cerebellar Hypoplasia

The last day of February is Rare Genes or Diseases Day, usually that's the 28th but 29th on Leap Year, so today we are supporting the cause Wear That You Care by wearing jeans to spread awareness about rare genes. Around our part of the world no one notices if you are wearing jeans, we're pretty casual here on the West Coast.  If I were better organized I'd have bought a pin that says "Cerebellar Hypoplasia" for each of us to wear, but the truth is Cerebellar Hypoplasia is so rare that I don't think they have pins for it.

I had a normal pregnancy but toward the end I was carrying rather large. Concerned I was having a large baby after 2 big(ish) babies and difficult deliveries my OB sent me in for an ultrasound. I was 8 months pregnant when I received the shock of my life. The imaging showed that our baby had something wrong with the shape of it's head (we didn't yet know if she was a boy or girl). Welcome to the world of rare diseases, a world I previously had the luxury of knowing nothing about.  All my life I'd believed that birth defects are the rare exception and "healthy babies" are the norm.  We tend not to talk about it and when it happens we are shocked. When we start talking about it you realize it's a lot more common than we realize.

When it does happen we understandably look for answers. Sometimes there are answers but sometimes questions just lead to more questions, as I would find out. Ainsley, at that ultrasound, appeared to have what is called craniosynostosis a condition we would discover is both rare but not terribly uncommon depending on your perspective (we started hearing stories of kids with craniosynostosis from all kinds of people after Ainsley was diagnosed with it) There are a number of syndromes that include craniosynostosis but it can also be "isolated" (appear alone as the only condition). And so we proceeded with an amniocentesis hoping for more information. The results showed a Balanced Chromosome Translocation. People think that it is rare but it's really not except that Ainsley's particular translocation hasn't been seen (that doesn't really mean anything either). Steve and I had our blood drawn to see if either of us had it, since Balanced Chromosome Translocations can exist without our knowledge with no symptoms what so ever. Neither of us had it, and so it was pronounced that Ainsley's translocation was "denovo" (new). The karyotype is 46,XXp(1;7) (p22;q31.2).

Reciprocal translocations are usually an exchange of material between nonhomologous chromosomes. Estimates of incidence range from about 1 in 500 ^[1] to 1 in 625 human newborns.^[2] Such translocations are usually harmless and may be found through prenatal diagnosis. However, carriers of balanced reciprocal translocations have increased risks of creating gametes with unbalanced chromosome translocations, leading to miscarriages or children with abnormalities. Genetic counseling and genetic testing are often offered to families that may carry a translocation. Most balanced translocation carriers are healthy and do not have any symptoms. But about 6% of them have a range of symptoms that may include autism, intellectual disability, or congenital anomalies. A gene disrupted or disregulated at the breakpoint of the translocation carrier is likely the cause of these symptoms.

So 8 months pregnant we thought we had a 6% chance of a birth defect and we already knew she had craniosynostosis. We learned all about the syndromes craniosynostosis could be a part of.  It was devastating. Having two healthy typical developing children I admit I thought "it couldn't happen to me." I held discriminatory beliefs that these type of things happened to different types of people than me. Birth defects occur across all socio-economic levels, to parents of all education levels, and is not an indication of drug or alcohol use or advanced maternal age. These factors can increase risk but often are not the sole cause. The truth is that birth defects can happen to anyone, but we don't talk about it because it's scary. Honestly though, I don't think there is any way to prepare for this. It's like getting in a car crash. We know it happens but always think it won't happen to us even though it happens to people of all types every day. Perhaps it's how we protect ourselves from fear. When it does happen we analyze and re-analyze any possibility that could have caused or prevented it.

The doctors couldn't make a diagnosis in utero. We were nervous but looked forward to the day Ainsley was born for the normal reasons but also thinking we would finally know what we were dealing with. Due to the insane amount of amniotic fluid I was told I would go into labor any day. That didn't happen so I was induced at full term. When Ainsley was born we were shocked to find out that she had stridor (noisy breathing) and she was quickly sent up to the NICU for breathing support. That would begin the search for a diagnosis about her airway. We thought it would be temporary and were devastated when the doctors were unable to diagnose the specific cause or treat it. She was transferred to Children's Hospital.

I was recovering from a vaginal birth to c-section (I spent 1 1/2 hours standing and pushing with no epidural before surgery) and Steve and I shared a cot in the parent rooms at the NICU. It was truly horrible. We were in shock and having to absorb a lot of new information very quickly.  She was put on a feeding tube (I knew nothing about them) and there was talk about a trach. (She was trached at 5 weeks and we would spend years searching for answers and solutions, traveling across the country twice to see specialists.)  Each day she saw more and more specialists. I noticed that she hadn't opened her eyes and was very concerned. Enter the head of ophthalmology, later a diagnosis of eyelid ptosis (fancy name for droopy eyelids, several surgeries followed). They sent in an orthopedist to inspect her and found hip dysplasia and began treatment in a Pavlik harness (she would later require surgery twice). My poor girl couldn't catch a break. Ainsley's craniosynostosis was pretty severe, likely the sutures fused early in the pregnancy and her forehead became misshapen (not just her skull) as her brain grew. The cranio-facial surgeon wanted CT scans to prepare for the first surgery that she would need when she was 3 months old. She was 3 days old when we learned by accident due to the scans that she also had a condition called Cerebellar Hypoplasia, so they brought in more specialists, a geneticist who wanted to enroll Ainsley in a research study (where her genes were analyzed) as well as his research partner, a top neurologist specializing in the field of hind brain malformations.

What was not reassuring during this period is that we saw the doctors Googling Ainsley's combination of conditions trying to determine if there was anything in any obscure medical journal about the combination of her various conditions occurring with other patients, in other words a syndrome. There wasn't. Cerebellar Hypoplasia can often occur with a rare syndrome called Dandy-Walker Syndrome. Sometimes CH will be characterized as Dandy-Walker Variant or Dandy-Walker Malformation. But none of these were quite like the appearance of Ainsley's brain. The CH is the most important of Ainsley's conditions. I searched out information about her condition on the Internet, finding more about Cerebellar Hypoplasia in cats (it occurs often in cats) than humans.

The doctors kept repeating something that drove me crazy, "Ainsley will teach us about herself." This is doctor speak for we have no freakin' clue.  We moved on with our lives dealing as best we could with rather extreme circumstances, all while having a 5 and 3 year old.  I combed the Internet searching for information, hoping that there might be another parent out there with a child with Ainsley's combination of "rare conditions" who might give me some insight of what to expect or even hope for treatment.

Would my child be able to walk? to talk? to eat? live an independent life? live a normal life expectancy? How long would she need the trach and feeding tube? No one could tell me for sure. We were connected with services and started receiving in home therapy when Ainsley was just 4 months old. I learned from these therapists and then spent countless hours teaching things that come naturally to other children: holding a toy, tummy time, rolling over, sitting, crawling, standing, pointing, turning pages of a book, pinching (fine motor strengthening to prepare for handwriting), eating, making sounds, sign language, PECS, AAC all on top of the medical needs (suctioning, tube-feeding etc), surgeries and normal needs of any child. Because she and the other two kids had those too. Those were dark times as I dealt with the feelings of grief over losing all semblance of a normal life.

During those early years I reached out to on-line support groups, for parents of children with tracheostomies and Cerebellar Hypoplasia. I felt comfort in knowing other parents were dealing with the same very difficult issues. I spent a lot of time looking up the conditions that were mentioned hoping that maybe it would help me figure out what was going on with Ainsley. Maybe find answers or a cure, or treatment. What I learned is that there are many many thousands of kids out there with thousands of different types of conditions. Some find the cause of the condition(s) and some don't.  Sometimes the conditions have been seen together before and so doctors have given it a convenient "syndrome" name that may help shed light on what we can expect by grouping these individuals together. I thought it would be easier if Ainsley had a syndrome so I might know what to expect. But then I also saw that kids with the same syndrome or diagnosis often vary in the ways they are affected and may not have some of the markers that are often seen with the syndrome or diagnosis.

In addition to Dr. Dan Doherty, the expert Ainsley had seen several times since birth we consulted with one of the top experts in hind brain malformations who relocated to Seattle a few years ago, Dr. William Dobyns. Ainsley's CH looks kind of like Ponto-Cerebellar Hypoplasia but for a variety of reasons isn't typical of PCH either. In light of Rare Diseases Day I thought I would share what his report says, below. Since then we befriended Dr. Andrea Poretti, a colleague of Dr. Doherty, another expert on CH who is active in our CH group.  He kindly reviewed her scan and agreed with the Dr. D's. These men have seen thousands of brain scans.  All agreed that Ainsley didn't neatly fit CH or PCH.

The gyral pattern was distorted by her skull shape, but otherwise appeared normal. I also thought her hippocampi, basal ganglia, thalamus and white matter appeared normal. Her third and lateral ventricles and corpus callosum also appeared normal. I saw mildly thin brainstem indicating hypoplasia of all 3 segments. The cerebellum was diffusely moderately small, with a striking up-rotated vermis and probably foliar dysplasia. The vermis was actually less severely affected than the cerebellar hemispheres. However, there was clearly no progression of the atrophy on serial MRI scans. This has previously been described as Dandy-Walker malformation; however, the preservation of the vermis in comparison to the hemispheres and a small posterior fossa size are both inconsistent with DWM. This has been compared to Pontocerebellar Hypoplasia or PCH, because of the relatively preserved vermis. However no progression was seen, so this also differs. Thus I believe it is best described as diffuse cerebellar hypoplasia with foliar dysplasia.

The label used for Ainsley's brain/cerebellum condition has changed several times over the years, above you see it described as Diffuse Cerebellar Hypoplasia with Foliar Dysplasia. I decided it is simplest to call it Cerebellar Hypoplasia. A lot of doctors aren't even familiar with Cerebellar Hypoplasia in it's simpler forms. Ainsley is rare among the rare. When you factor in her other conditions she is truly one of a kind.

I think there can be comfort in having a well understood condition. However, I've also come to the conclusion that it's not so bad to be rare, even if it sometimes feels isolating. Without a guidepost Ainsley can make her own path in life. We know it won't be easy but we keep inching onward, one inchstone at a time. We don't know how far she will get but we will try to enjoy the ride on the way to our destination. The doctors were right. Ainsley is teaching us about Ainsley. And really when you group all the people with rare diseases or rare genes together, it's really not so rare at all. Together we spread awareness, together we are not alone.