Abstract
BackgroundAtlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs. So far, most studies have focused on bones and ligaments related to AAI, and there are no studies on the suboccipital muscles (SOMs) that occupy a large area from the occipital bone to C2 in dogs. This study evaluated the cross-sectional area (CSA) and fat infiltration of the SOMs using magnetic resonance imaging (MRI), specifically, T1-weighted images, in normal dogs (≤ 5 kg) and AAI dogs. The relationship between the severity of the neurological symptoms of AAI (group A and group B) and the values from MRI was also assessed.ResultsAAI dogs had significantly smaller CSA (P = 0.029) and greater fat infiltration (P = 0.044) of the SOMs compared to normal dogs. AAI dogs with mild neurological symptoms for a long period (group A) had greater fat infiltration than AAI dogs with severe neurological symptoms (group B) (P = 0.035).ConclusionsThe muscle changes are most likely due to spinal cord compression resulting from instability; however, the possibility that chronic changes of the muscle may play an additional role in maintaining stability in this region cannot be excluded. This study provides fundamental quantitative information of the SOMs in normal and AAI dogs.
Highlights
Atlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs
The AAI dogs were split into two groups based on severity of the neurological symptoms, where group A of AAI dogs were older than group B (P = 0.001)
This study found that AAI dogs had significantly smaller crosssectional area (CSA) of the suboccipital muscles (SOMs) and greater fat infiltration in the muscles compared to normal dogs
Summary
Atlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs. Most studies have focused on bones and ligaments related to AAI, and there are no studies on the suboccipital muscles (SOMs) that occupy a large area from the occipital bone to C2 in dogs. This study evaluated the crosssectional area (CSA) and fat infiltration of the SOMs using magnetic resonance imaging (MRI), T1-weighted images, in normal dogs (≤ 5 kg) and AAI dogs. Atlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs, including Maltese, Chihuahua, Toy Poodle, Pomeranian, and Yorkshire Terrier [1]. Similar studies have been conducted on the thoracolumbar (TL) epaxial muscles in veterinary medicine [13, 14], no studies have evaluated the SOMs occupying a large area of this region from the occipital bone to C2 in dogs using MRI
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