A couple months ago, our Havanese puppy, Zoe (5 months old at the time) ran into her crate to get a toy and on her way out, she fell on her side and started yelping in pain. We could not figure out what was wrong..we thought she may have injured her leg, because she wasn't walking right and didn't want to walk due to the pain. We took her to her vet, and our vet right away realized that whatever was wrong, it was neurological and recommended we go to the speciality emergency clinic nearby.
At the emergency clinic, the internist thought it might be meningitis, which is often fatal in dogs. We started treating with IV antibiotics and pain medicine and she stayed overnight. The next day, a neurologist saw her, and based on her x-ray, he diagnosed Zoe with Atlantoaxial Subluxation, as he could not see a dens or odontoid process on her imaging. She received an MRI and spinal tap to be confirm the diagnosis.
Atlantoaxial subluxation/instability (AAI) is a rare diagnosis that is either congenital or due to trauma. When congenital, it is often in toy breed dogs such as yorkies and toy poodles, but it can affect any toy dog usually less than 1 year old and from mild trauma, such as jumping off furniture. I have not found it be reported in a Havanese anywhere online. Dogs with congenital AAI have an absence or hypoplasia (smaller size) of the dens, which is a protruding thin piece of bone on the 2nd cervical vertebrae (axis of C2) that fits into the first cervical vertebrae (atlas or C1) and keeps C1 and C2 aligned. Without the dens, whenever Zoe would flex her neck or bend it forward, space would form between the two vertebrae at the back and C2 would slide behind C1 in the front, causing compression of her spinal cord.
Zoe was very fortunate that she was diagnosed quickly and has an outstanding neurologist. She wore a neck brace to remind her not to flex her neck for 3 months. After her initial episode, she started to walk again, but 2.5 months after, she had another scary episode where her back legs were paralyzed again. We immediately started her on a steroid taper and by the end of the week, she was walking, although still a bit ataxic (wobbly). We spoke with her neurologist, and he said since she could stand, we didn't need emergent surgery and could wait until the scheduled day, which was in two weeks.
At 8 months old, her bones were mature enough for her to undergo surgery, the only permanent treatment. On tuesday this week, she had her C1 and C2 vertebrae stabalized with screws and a bone cement. She is walking, and we expect a full recovery.
This was an extremely scary and emotional ride for my husband and I. Growing up with dogs, I never expected anything like this to happen. As Havanese are becoming more popular, I wanted to share our story, in case AAI would ever affect another Havanese. We did let our breeder know. It is a "congenital" condition, however it is rare and may have just been a random genetic mutation that only affected Zoe. So far, her litter mates have not had any health issues. We love Zoe so much, and we are so happy with how well she is doing.
For more information, I found this link helpful: