Haeron K, Berg J, Bonczynski, J, Suarez C, and Bergman P. Upper Thoracic Disc Disease (T1-T9) in Large-Breed Dogs. Journal of the American Animal Hospital Association 2014 (50):105-111
Summarised By Dr Liesel van der Merwe BVSc MMedVet(Med)
Why they did it.
IVDD is one of the the most common neurological disease in dogs. The cervical , caudal thoracic and lumbar discs are most commonly affected. Little data exists on IVDD in large breed dogs. According to the data available thoracolumbar involvement is most common in large breed dogs with multiple sites affected. German shepherd dogs were most commonly affected (33%)n=99. The authors practice diagnosed several large breed dogs, predominantly GSD, with upper thoracic IVDD, thus prompting a proper retrospective review.
What they did
The authors reviewed the medical records of all dogs with a neuroanatomic diagnosis clinically and an IVDD confirmed on MRI between 2008 and 2011. Cases were excluded if any other concomitant spinal disease was thought to be the primary problem: such as caudal cervical spondylomyelopathy, discospondylitis. Dog breeds were separated into small and large breed categories, with 22.7kg as the cut-off point.
What they found
723 dogs from 97 different breeds were diagnosed with IVDD and met inclusion criteria in the review period. There were 196 (27.1%) large breed dogs of which Labrador retrievers (n=41) and German Shepherd dogs (n=37) and mixed breed dogs (n=29)were most common. Also included were American pitbull terriers (n=15) and doberman pinschers (n=9). The mean age of small breed dogs was 7 yrs (1 yr – 19yr) , which was significantly lower than that of the large breed dogs; 8.6yrs(6m-14 yrs). The least common lesion location was T1-T9. No small breed dogs had a lesion in T1-T9, but 21 large breed dogs (10.7%) had a lesion in this region : and it was even more prevalent in the German Shepherd dog (29.7%) and the Labrador Retriever (28.6%). Large breed dogs were also significantly more likely to have multiple sites affected than small breed dogs. Multiple sites were also more common in the T1-T9 affected group – the majority outside the thoracic region.
Take Home Message
Historically it was thought that the T1-T10 region was resistant to IVDD due to the extra stability provided by the intercapital ligament. In this study 10.7% of all large breed dogs diagnosed with IVDD had upper thoracic (T1-T9) lesions. Most of these were Labrador Retrievers and German Shepherds.
Because Upper thoracic (T1-T9), thoracolumbar (T9-L4) and degenerative myelopathy all have chronic and progressive signs with similar neuroanatomic localisations, diagnostic imaging of the entire region should be recommended in all cases.