Myelographic diagnosis and results of surgical treatment of caudal cervical spondylomyelopathy in dogs: a retrospective study (2000–2010) Robert Srnec1,

The outcomes of six different surgical techniques of caudal cervical spondylomyelopathy treatment in dogs with static and dynamic spinal cord compressions were assessed. Out of 425 dogs with cervical spine diseases, caudal cervical spondylomyelopathy was diagnosed in 69 dogs. Dynamic myelographic study was performed in 48 of them as a diagnostic method necessary for choosing the appropriate technique of surgical treatment. Twenty-five out of the 48 dogs underwent surgery. The best results of the surgical treatment of static compression were achieved with a ventral slot (89% of the nine surgical interventions) with partial improvement 48 h after surgery and marked improvement 8 weeks after surgery. For dynamic compressions, vertebral traction and stabilization with intervertebral washer plus vertebral body screws and polymethylmethacrylate bridge was found to be the most successful surgical treatment with significant improvement in 62% of the thirteen surgical interventions 8 weeks after surgery. In 5 dogs (20%), two intervertebral spaces with caudal cervical spondylomyelopathy were surgically treated. Recurrence was observed in 6 dogs (24%) after the mean period of 20 months (5 to 44 months) after surgery. Direct ventral slot decompression could be recommended for clinical cases of the caudal cervical spondylomyelopathy with static compression, and intervertebral washer plus vertebral body screws and polymethylmethacrylate bridge for dogs with dynamic compression, respectively. Our findings refer to the results of surgical treatment in a relatively large number of dogs with caudal cervical spondylomyelopathy and can help surgeons to choose an effective surgical method of treatment in dogs with wobbler syndrome based on dynamic myelographic study findings. Wobbler syndrome, canine, neck surgery, spinal cord compression Caudal cervical spondylomyelopathy (CCSM), the synonym for wobbler syndrome, is a relatively common disease in large and giant breed dogs (Sharp and Wheeler 2005). There are two different groups of dogs with wobbler syndrome. Firstly, it affects juvenile giant breed dogs (typically the Great Dane) with the congenital absolute osseous compression causing a narrowing of the spinal canal or with vertebral malarticulation. This osseousassociated wobbler syndrome commonly affects more intervertebral spaces and sites of the lesions often lead to multiple serious compressions (Da Costa et al. 2012). Secondly, it affects middle-aged large breed dogs (typically the Doberman pinscher) with congenital asymptomatic relative spinal canal stenosis (predisposition factor) causing subsequent degenerative changes of the intervertebral disc and surrounding soft tissues. The second type of CCSM is also called the disc associated wobbler syndrome (Da Costa 2010). The basic step in diagnosis is well performed clinical examination taking into consideration medical history and personal data (breed predisposition, age and sex, duration of problems, degree of neurological signs); however, treatment is the mostly dependent to results of diagnostic imaging examination (Sharp et al. 1992). Despite the available examination on computed tomography (CT) or magnetic resonance imaging (MRI), myelographic examination is still the one most widely used (Robertson and Thrall 2011). Dynamic myelographic study is a fast and accessible method which uses stress projections that help specify the dynamics of ACTA VET. BRNO 2012, 81: 415–420; doi:10.2754/avb201281040415 Address for correspondence: MVDr. Robert Srnec Department of Surgery and Orthopaedics Small Animal Clinic, Faculty of Veterinary Medicine University of Veterinary and Pharmaceutical Sciences Brno Palackeho tř. 1/3, 612 42 Brno, Czech Republic Phone: +420 541 562 342 , +420 775 385 533 Fax: +420 541 562 344 E-mail: [email protected] http://actavet.vfu.cz/ compression depending on the positioning of the cervical spine. Thus way we differentiate static or dynamic compression. In dynamic lesions it is important to evaluate the changing of compression in traction (traction responsive or non-responsive) for choosing the best technique of surgery (McKee and Sharp 2002). Prognosis of CCSM significantly differs not only depending on the type of lesion and duration of the neurological signs but also on correct evaluation of myelography and the subsequent choice of the method of treatment. It can be either conservative or surgical method. Surgical methods include methods of direct decompression (ventral, dorsal, sporadically lateral) or indirect decompression (traction and stabilisation). The aim of this retrospective clinical study is to characterize types of lesions based on the dynamic myelographic study and to assess the results of surgical treatment of dogs with CCSM depending on the selected surgical method. Materials and Methods Data from the records of the Department of Surgery and Orthopaedics of the Small Animal Clinic, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno (SAC UVPS Brno) in the period between January 2000 and December 2010 were used to analyze dogs with CCSM. In the group of dogs with neurological findings, the frequency of CCSM was determined. We collected data concerning the breed, sex, age and weight. Basic clinical and neurological examination of dogs was performed according to Garosi (2004). Dogs were divided into 6 groups based on the severity of neurological findings characterized using a modified scale (grade 0–5) of neurological dysfunctions (Table 1) (McKee et al. 1999). Plain radiographs and contrast myelography of the cervical spine in latero-lateral and ventro-dorsal projection were then performed in general anaesthesia. Dogs without complete dynamic myelographic examination were excluded from the reference group. Depending on the myelographic study, we evaluated compression of the spinal canal, the site of compression (intervertebral space), number of lesions (simple, dual, multiple), location of compression within the spinal canal (ventral, dorsal, lateral, combined “hour-glass” compression) and the type of compression (static or dynamic). Results were evaluated only in dogs surgically treated for CCSM. A total of six methods of surgery of CCSM were used in the reference group: 1 direct decompression with the ventral slot method (SLOT), 2 indirect decompression using intervertebral washer (IVW) plus vertebral body screws (BS) and polymethylmethacrylate (PMMA) bridge (IVW+BS-PMMA), 3 indirect decompression using intervertebral washer and cancellous autograft (CAG) (IVW and CAG), 4 indirect decompression using intervertebral washer plus buttress plate (BP) and cancellous autograft (IVW+BP and CAG), 5 indirect decompression using buttress plate and cancellous autograft (BP and CAG), 6 indirect decompression using smooth pins and PMMA bridge (P-PMMA). We noted the type of performed surgery, evaluation of clinical finding before the surgery, 48 h after the surgery and 8 weeks after the surgery, and the recovery time from surgery to final clinical status (in weeks). Long-term monitoring of dogs included life expectancy after the surgery and the monitoring of recurrences of CCSM after surgical treatment (in weeks). Twenty-five dogs (52.1% CCSM completely detected with myelography) were treated surgically; in 5 dogs the surgery was performed in two intervertebral spaces simultaneously. A total of 30 intervertebral spaces with CCSM (n = 30) were assessed. The frequencies of different surgical methods were: SLOT (n = 10), IVW+BS-PMMA (n = 13), IVW and CAG (n = 4), IVW+BP and CAG (n = 1), BP and CAG (n = 1) and P-PMMA (n = 1). In dogs that underwent surgery in two intervertebral spaces, evaluation of each intervertebral space was individual and the level of 416 Table 1. Modified scale of neurological dysfunction in dogs (McKee et al. 1999). Grade 0 Healthy patients with no clinically apparent neurological problems Grade 1 Neck pain without leg ataxia Grade 2 Mild ataxia of hind limbs with no neurological deficit in forelimbs Grade 3 Moderate ataxia of hind limbs with/without neurological deficit in forelimbs Grade 4 Severe ataxia of hind limbs with/without neurological deficit in forelimbs Grade 5 Very severe ataxia with inability of movement without help, tetraplegy