Comparison of cerebral cranium volumes between cavalier King Charles spaniels with Chiari-like malformation, small breed dogs and Labradors

O bjectives : To ascertain whether cavalier King Charles spaniels (CKCSs) have a proportionately smaller caudal fossa compared with other small dogs and with Labradors. To evaluate if cerebellar herniation in CKCS correlates with caudal fossa volume.
M ethods : In this retrospective study, three-dimensional images were created from magnetic resonance imaging brain series of 117 dogs (split into three groups: CKCS, Labradors and small breeds) from which the volumes of the fossae and brain parenchyma were calculated. These volumes were transformed into percentages of total cranial cavity and parenchyma volumes, respectively. The percentages were statistically compared among the groups. The percentage of herniated cerebellum in the CKCS was compared using linear regression with the caudal fossa and parenchyma percentages.
R esults : Cavalier King Charles spaniels had a proportionately smaller caudal fossa compared with Labradors (P=0·002) but not to small breeds (P=0·103). Their caudal fossa parenchyma was proportionately the same volume as Labradors (P=0·976) but greater than small breeds (P=0·005). No relationship was found for the per cent of cerebellum herniated.
C linical S ignificance : The results support mesoderm insufficiency or craniosynostosis as the pathogenesis of Chiari-like malformation (CM) in CKCS. It presents evidence for overcrowding of the caudal fossa due to a mismatch of brain parenchyma and fossa volumes as to why CKCS and not other small dogs are affected.     

Influence of head positioning on the assessment of Chiari-like malformation in Cavalier King Charles spaniels

Chiari-like malformation (CM) is almost omnipresent in the Cavalier King Charles spaniels (CKCS), often leading to syringomyelia (SM). Morphometric studies have produced variable results concerning relationship between the brain parenchyma within the caudal cranial fossa (CCF) and SM. The present study assesses the effect of head position, one potential confounder. Magnetic resonance images of CKCS with CM were reviewed in extended and flexed head positions. Volumes were calculated from transverse T2-weighted brain images. Mid-sagittal images were used for measurement of cerebellar herniation and CSF space between cerebellum and brainstem. Fourteen CKCS were included into the study, seven dogs with CM and seven with CM/SM. There was no difference between the relative brain parenchyma within the CCF in extended position and flexed position, or the brain parenchyma within the rostral and middle cranial fossae proportion. Cerebellar herniation and CSF space between cerebellum and brainstem were significantly increased in the flexed position. Cerebellar herniation and CSF space differed significantly between CM and CM/SM in a flexed head position. Volumetric measurements did not vary with head position. Cerebellar herniation and CSF space between the cerebellum and the brainstem were larger in a flexed head position.     

Distribution of syringomyelia along the entire spinal cord in clinically affected Cavalier King Charles Spaniels

Chiari-like malformation (CM) and syringomyelia (SM) is an important disease complex in the Cavalier King Charles Spaniel (CKCS) but data about the anatomical distribution of SM along the spinal cord are lacking in veterinary medicine. The objective of this study was to define the anatomic distribution of SM in CKCS clinically affected by CM/SM. Magnetic resonance imaging (MRI) of the brain and the entire spinal cord of 49 dogs was performed and different morphological parameters compared.Syrinx formation was present in the C1–C4 region and in other parts of the spinal cord. The maximal dorsoventral syrinx size can occur in any region of the spinal cord and the total syrinx size was positively correlated with age. Seventy-six per cent of CKCS with a cranial cervical syrinx also have a syrinx affecting more caudal spinal cord regions. MRI restricted to the cervical region may underestimate the extent of SM and the severity of the disease process in the majority of dogs.     

The association between Chiari-like malformation,ventriculomegaly and seizures in cavalier King Charles spaniels

Cavalier King Charles spaniels (CKCSs) with Chiari-like malformation (CM) and associated seizures are frequently diagnosed with idiopathic epilepsy. There could be an association between ventriculomegaly (V) or caudal fossa overcrowding (CCFP) and seizures. A retrospective case-control study was performed using MRI to investigate the possible association between these morphological abnormalities and seizures. Seizure semiology and, where possible, electroencephalographic (EEG) abnormalities were documented. Eighty-five CKCS with CM were included, 27 with seizures. There was no association between V or CCFP and seizures (P = 0.10 and 0.71, respectively). Seizures were classified as having partial onset in 61% of individuals in the study population (95% CI 42.41–76.43%). Another cause of recurrent seizures in CKCS (such as familial epilepsy) is suspected, as previously reported.     

Association between the findings on magnetic resonance imaging screening for syringomyelia in asymptomatic Cavalier King Charles spaniels and observation of clinical signs consistent with syringomyelia in later life

A questionnaire-based study was used to investigate the association between the findings on magnetic resonance imaging (MRI) screening for syringomyelia (SM) in 79 asymptomatic Cavalier King Charles spaniels (CKCS) and the subsequent development of clinical signs consistent with SM in later life. Owners reported clinical signs consistent with SM in 13/79 (16%) dogs at the time of the questionnaire. A significantly greater proportion of CKCS with a syrinx visible on MRI screening showed clinical signs in later life (9/25, 36%) than dogs without a visible syrinx (4/54, 7%; odds ratio 6.9). Whether the findings of MRI screening can be used to indicate the likelihood of an asymptomatic CKCS developing clinical signs consistent with SM in later life warrants further prospective study in a larger cohort of dogs.     

Comparison of high‐field MRI and multidetector CT for grading Chiari‐like malformation and syringomyelia in Cavalier King Charles Spaniels

Chiari‐like malformation (CM) and syringomyelia (SM) are common illnesses that can cause debilitating neuropathic pain in Cavalier King Charles spaniels (CKCS). The current imaging modality to screen CKCS for CM/SM is MRI of the brain and cervical spine. Magnetic resonance imaging provides good soft tissue detail and contrast of the cerebellum and cervical spinal cord. Computed tomography (CT) is another cross‐sectional imaging technique that facilitates brain and neck evaluation; however, soft tissue resolution does not match that of MRI. Computed tomography benefits include identification of concurrent craniocervical junction anomalies (atlantooccipital overlap) and shorter imaging/anesthesia times with the ability to use only sedation. The aim of this retrospective, method comparison study is to assess the utility of multidetector CT for screening CM and SM in CKCS as compared to high‐field MRI. Three groups of observers with different levels of experience graded CM and SM based on the British Veterinary Association/Kennel Club CM/SM classification criteria. Thirty CKCS underwent multidetector CT and 3 Tesla MRI studies. Computed tomography and MRI studies were reviewed at different timepoints to minimize bias. Computed tomography has lower Cohen's Kappa agreement for each observer group compared to MRI. The intraclass correlation coefficient averaging CM and SM for all groups was excellent using MRI, while CT was poor for SM and moderate for cerebellar herniation. Greater observer experience resulted in a higher agreement for CT and MRI. Magnetic resonance imaging should remain the standard for screening of CM and SM as CT can result in misclassification and greater disagreement.     

Morphometric analysis of the cranial cavity and caudal cranial fossa in the dog: a computerized tomographic study.

This investigation was initiated to develop a reliable and simple computerized tomography (CT) method for evaluating the morphometry of the cranial cavity (CC) and caudal cranial fossa in the dog. We obtained linear, area, and volume measurements of the entire CC and the caudal fossa compartment in 24 dogs, using transverse and reformatted sagittal and dorsal CT images. The ratios between the CC and the caudal fossa volumes were calculated, as were the ratios between the CC and caudal fossa midsagittal (MS) areas. There were statistically significant correlations between absolute volume data and certain linear measurements, a positive correlation between volume ratio and weight, and significant differences in absolute volume values and volume ratio between males and females. The volume ratio, MS area, and certain linear measurements included in this study can be considered as accurate parameters to evaluate the relative size of the CC to caudal fossa in the dog. Such quantitative measures may be useful in systematically characterizing Chiari-type malformations and other developmental anomalies in the dog.     

The Intercondylar Fossa of the Normal Canine Stifle: An Anatomic and Radiographic Study

The intercondylar fossa (ICF) in dogs consists of a cranial outlet, intercondylar shelf, caudal arch, caudal outlet, a medial wall, and a lateral wall. The normal cranial outlet is bell-shape and, in mixed-breed dogs (mean body weight 19.2 kg, N = 21), measured 5.8 mm cranially, 8.1 mm centrally, and 10.3 mm caudally. The ICF is oriented 12° from the dorsal plane of the femoral diaphysis and obliqued 7°, proximolateral to distomedial, in the sagittal plane. To adjust for dog size, a fossa width index (FWI) was calculated by dividing the cranial outlet width by the distance between epicondyles. The normal FWI as determined in this study was 0.18 cranially, 0.25 centrally, and 0.32 caudally. The fossa height index was 0.31. Contact between the ICF and the cranial cruciate ligament began at about 115° of extension. The contact area moved cranially in the intercondylar fossa as the stifle was extended. Evaluation of the ICF can be performed radiographically but positioning is critical.     

RENAL SONOGRAPHIC MEASUREMENTS IN THE DOG PRECEDING AND FOLLOWING UNILATERAL NEPHRECTOMY

The purpose of this study was to establish sonographic baseline values for normal kidneys initu and to document sonographic changes following unilateral nephrectomy. Normal canine renal measurements were determined sonographically prior to and following unilateral nephrectomy. These included: cortical thickness (cranial, caudal, dorsal, ventral, lateral and medial), medullary measurements (cranial and caudal) and measurements of the renal silhouette (length, height and width). The latter group of measurements was obtained to determine renal volume. Normal parameters were obtained from sixteen healthy dogs prior to nephrectomy; the unilateral nephrectomy group was comprised of eight of these animals, the remaining eight dogs were part of an allo-transplant study.¹ The mean sonographic value for the length of the kidney was 60.3 mm ± 6.4 (n = 26) while the widths and heights were 34.7 ± 3.8 (n = 27) and 27.8 mm ± 3.3 (n = 26) respectively. Renal cortical measurements were found to be smallest dorsally and ventrally on sagittal and transverse sonograms. The largest volumes were the cranial pole on sagittal scans and the lateral pole on the transverse scans. Pearson correlation coefficient for volume resulted in r values of 0.88, 0.78 and 0.72 for length, height and width (n = 25, dif = 24) respectively.     

RADIOGRAPHIC IMAGING OF THE CANINE INTERCONDYLAR FOSSA

The intercondylar fossa is believed to play an important role in the pathology of cranial cruciate ligament rupture and therefore has received considerable attention in the last decade. Accurate radiographic imaging of the intercondylar fossa requires that the central x-ray beam pass through the center of the intercondylar "tunnel". The anatomy of the canine intercondylar fossa is similar to humans, however, the orientations of the intercondylar fossa's differ. Consequently, the positioning techniques described for humans are not appropriate for the dog. To pass through the center of the dog, intercondylar fossa, the central x-ray beam should be 12° (S.D. 1.7°) caudal from the femoral diaphysis in the sagittal plane and obliqued caudolateral to craniomedial 7° (S.D. 0.60°) (caudo78°proximo7° lateralcraniodistomedial oblique). Cross table positioning was used with the hip flexed and the radiograph cassette placed on the cranial surface of the stifle. However, superimposition of the tuber ischii and soft tissues caudal to the femur made 15° to 20° the best angle obtainable. There was not a significant difference (p = 0.17) in the notch width index between a 12° versus 20° angle of the central x-ray beam caudal to the femoral diaphysis, both with 7° of external rotation of the stifle. The notch width index of 0.252 obtained from radiographic measurements was not significantly different from measurements obtained grossly of 0.254 (n = 26; p = 0.69). Failure to oblique the central x-ray beam caused a significant (p = 0.0008) decrease in the apparent fossa width radiographically.     

Chiari-like malformation and syringomyelia in normal cavalier King Charles spaniels: a multiple diagnostic imaging approach

Objectives : The objectives of the study were (1) to report the incidence of Chiari‐like malformation and syringomyelia in a normal French cavalier King Charles spaniel breeding population; (2) to precise the standard computed tomography dimensions of the caudal fossa and (3) to investigate the use of ultrasonography in diagnosis of this syndrome. Methods : Clinically normal adult cavalier King Charles spaniel underwent ultrasonographic examination of the spinal cord and caudal fossa. Computed tomography was used to measure the caudal fossa and magnetic resonance imaging allowed syringomyelia and cerebellar herniation identification. Results : Of the 16 dogs in the study, seven had syringomyelia (43·7 per cent). All dogs had cerebellar herniation, suggesting Chiari‐like malformation and also a tendency to occipital dysplasia. Computed tomography measurements of the caudal fossa are reported. In one dog, a syrinx was identified by ultrasonography. The only difference between dogs with or without syringomyelia was that dogs with Chiari‐like malformation/syringomyelia were statistically older. Clinical Significance : The incidence of Chiari‐like malformation and syringomyelia may be high in an asymptomatic population of cavalier King Charles spaniel . Computed tomography measurements reported in this study should now be compared with those of a symptomatic population to evaluate the hypothesis that dogs with Chiari‐like malformation/syringomyelia syndrome have a smaller caudal fossa. This study did not identify a smaller caudal fossa in an asymptomatic cavalier King Charles spaniel population with syringomyelia. Ultrasonography probably has a low sensitivity for diagnosis of Chiari‐like malformation/syringomyelia.     

RADIOGRAPHIC AND COMPUTED TOMOGRAPHIC EVALUATION OF THE CANINE INTERCONDYLAR FOSSA IN NORMAL STIFLES AND AFTER NOTCHPLASTY IN STABLE AND UNSTABLE STIFLES

The role of the intercondylar fossa in cranial cruciate ligament injury has gained notable attention in humans and it's role is now being questioned in animals. Controversy exists regarding the accuracy of radiographs and computed tomography (CT) in evaluating the intercondylar fossa. This study compared radiographic and CT evaluation with gross evaluation of the intercondylar fossa. Six greyhounds were evaluated before notchplasty, immediately after notchplasty and 6 months after notchplasty in stable and unstable stifles. A fossa width index was used for comparison because it negates the effects of patient size and radiographic magnification. The fossa width index is calculated by dividing the width of the intercondylar fossa by the total condylar width.
The fossa width indices of dogs determined from radiographs and CT were not significantly different before notchplasty except for the cranial fossa width indices which were more inconsistent and tended to underestimate the size when compared to gross measurements. At six months, both stable and unstable stifles had refilling of the notchplasty, but the unstable stifles had significantly greater refilling resulting in no significant enlargement in intercondylar fossa size as compared to the prenotchplasty size. Osteophytes that occurred within the intercondylar fossa were less radiopaque and more easily visualized by computed tomography. Computed tomography provided several advantages, including clearer visualization of the intercondylar fossa, avoiding superimposition of the intercondylar fossa by caudal thigh muscles or tuber ischii and the ability to analyze the cranial and caudal components of the intercondylar fossa separately.     

Effect of signalment on the presentation of canine patients suffering from cranial cruciate ligament disease

Objective : To determine the effect of signalment on the incidence and presentation of patients suffering from cranial cruciate ligament disease. Methods : Data relating to 426 dogs (44 breeds) that met specific selection criteria were obtained from the hospital archive (2002 to 2008). Cases were followed up for 2 years. Results : The breeds most commonly presented with cranial cruciate ligament disease were Labrador retriever (16%), Rottweiler (15%), golden retriever (12%) and boxer (9%). Rottweilers were significantly more likely (69%; P=0·05) to develop and present with (50%; P=0·03) bilateral cranial cruciate ligament disease. Rottweilers presenting with cranial cruciate ligament disease were significantly younger (median 977 days; P<0·0001) than other breeds; golden retrievers being significantly older at presentation (median 1994 days; P=0·004). Neither sex nor neutered status significantly affected the incidence of developing (P=0·77 and P=0·30, respectively) or presenting with (P=0·62 and P=0·35, respectively) bilateral cranial cruciate ligament disease. Entire dogs were significantly younger than neutered dogs at presentation (P=0·0004). Entire female dogs presented significantly younger than neutered females (P=0·0002), entire males (P=0·01) and neutered males (P=0·0001). Clinical Significance : Breed affects the incidence of developing and presenting with bilateral cranial cruciate ligament disease. Breed and sex both affect the age that patients present with cranial cruciate ligament disease.     

Chiari-like malformation with syringomyelia in the Cavalier King Charles spaniel: long-term outcome after surgical management

Objective– To evaluate long-term success of cranial cervical decompression for management of canine Chiari-like malformation with syringomyelia (CM/SM).
Study Design– Retrospective clinical study.
Animals– Cavalier King Charles spaniels (n=15).
Methods– After diagnosis by magnetic resonance imaging (MRI) dogs had cranial cervical decompression with durotomy. Seven dogs had the durotomy patched with biocompatible collagen matrix. Clinical outcome was monitored for >12 months.
Results– All dogs either improved (80%) or were unchanged (20%) postoperatively. Postoperative MRI in 6 dogs revealed persistence of syringomyelia. Seven dogs (47%) subsequently deteriorated, 0.2–2.3 years after surgery (mean, 1.3 years) and 2 dogs were eventually euthanatized as a consequence. Twelve dogs were still alive, 1–6.5 years after surgery (mean, 2.5 years).
Conclusion– Cranial cervical decompression surgery is associated with low mortality and morbidity, and results in clinical improvement in most dogs. The procedure seemingly does not result in syrinx collapse and resolution. Clinical improvement may not be sustained and some dogs can be expected to deteriorate.
Clinical Relevance– Cranial cervical decompression surgery may have a role in management of CM/SM. In dogs with severe pain, it can improve quality of life for several years; however, it does not appear to adequately address the primary cause of syringomyelia. Further prospective study is needed to better understand the pathogenesis and treatment of this disorder. Because this condition causes neuropathic pain but does not necessarily result in euthanasia more information is needed on appropriate pain management for these patients.     

Influence of signalment on developing cranial cruciate rupture in dogs in the UK

Objectives : To investigate risk factors associated with cranial cruciate ligament rupture in dogs. Methods : Retrospective case‐control study: medical records of a first‐opinion veterinary practice were searched for dogs diagnosed with cranial cruciate ligament rupture (1995 to 2007). For each case, six unaffected dogs were randomly selected from all dogs presenting that day for comparison. Multi‐variable binary logistic regression was performed to assess the association of variables on likelihood of cruciate rupture. Results : Frequency of cranial cruciate ligament rupture was 1·19% [95% confidence interval (CI) 1·02 to 1.36%]. West Highland white terriers (n=17), Yorkshire terriers (n=14) and Rottweilers (n=11) were at significantly increased risk of cranial cruciate ligament rupture (P≤0·002). Rottweilers were at five times greater risk compared with other pure breeds (OR 5·12, 95% CI 2·281 to 11·494, P<0·001), obesity quadrupled the risk of cranial cruciate ligament rupture (OR 3·756, 95% CI 1·659 to 8·502, P=0·001) and females were twice as likely to suffer cranial cruciate ligament failure compared to males (OR 2·054, 95% CI 1·467 to 2·877, P<0·001). Dogs less than two years old were statistically less likely to sustain cranial cruciate ligament rupture than dogs older than eight years (OR 0·246, 95% CI 0·127 to 0·477, P<0·001). There was no significant difference in median weights (in kilograms) of neutered dogs, compared to their entire counterparts in either the case group (P=0·994) or in the control group (P=0·630). There was also no significant difference in body condition (‐underweight/normal weight/overweight/obese) of neutered versus entire dogs among the cases (P=0·243), or the controls (P=0·211). Clinical Significance : Cranial cruciate ligament rupture is more likely in Rottweilers and in female dogs, older dogs and obese dogs. Following multi‐variable analysis, it was established that neutering was not associated with increased risk of cranial cruciate ligament rupture.     

INTRA‐ AND INTEROBSERVER VARIABILITY OF ULTRASONOGRAPHIC MEASUREMENTS OF THE ADRENAL GLANDS IN HEALTHY BEAGLES

The aim of the present study was to establish which adrenal gland measurement was characterized by the least variations. To do this, we quantified the variability of seven different size measurements of the canine adrenal gland (maximal length, maximal height at the cranial and caudal poles on longitudinal and transverse images, and maximal width of the cranial and caudal poles) within observer, between observer, and between dogs based on three different measurements made by each of the three observers in six healthy Beagle dogs. The height of the caudal pole of both adrenal glands measured on longitudinal images had the lowest intra‐ and interobserver variability, while measurements of the length had the highest intra‐ and interobserver variability. Other measurements that were characterized by low intra‐ and interobserver variability were: height and width of the caudal pole on transverse images and height of the cranial pole on longitudinal images only. These results provide a basis for further study of the changes in adrenal gland size in dogs with pituitary‐dependent hyperadrenocorticism.     

Effectiveness of breeding guidelines for reducing the prevalence of syringomyelia

Several toy breed dogs are predisposed to syringomyelia (SM), a spinal cord disorder, characterised by fluid-filled cavitation. SM is a complex trait with a moderately high heritability. Selective breeding against SM is confounded by its complex inheritance, its late onset nature and high prevalence in some breeds. This study investigated the early outcome of existing SM breeding guidelines. Six hundred and forty-three dogs, 550 Cavalier King Charles spaniels (CKCS) and 93 Griffon Bruxellois (GB), were identified as having either one (454 dogs) or both parents (189 dogs) with MRI-determined SM status. Offspring without SM were more common when the parents were both clear of SM (SM-free; CKCS 70 per cent, GB 73 per cent). Conversely, offspring with SM were more likely when both parents had SM (SM-affected; CKCS 92 per cent, GB 100 per cent). A mating of one SM-free parent with an SM-affected parent was risky for SM affectedness with 77 per cent of CKCS and 46 per cent of GB offspring being SM-affected. It is recommended that all breeding dogs from breeds susceptible to SM be MRI screened; that the SM status at five years old is established; and all results submitted to a central database that can be used by dog breeders to better enable mate selection based on estimated breeding values.     

THE EFFECT OF ANGLE SLICE ACQUISITION ON COMPUTED TOMOGRAPHIC CERVICAL VERTEBRAL COLUMN MORPHOMETRY IN GREAT DANES

Computed tomography (CT) scans can be acquired with the transverse images aligned either parallel to the endplates or perpendicular to the vertebral canal. The purpose of this prospective cross‐sectional study was to determine the effect of angle acquisition on CT morphometric evaluation of the cervical vertebral column of Great Danes with and without cervical spondylomyelopathy. Twenty‐eight Great Danes (13 normal, 15 affected) were sampled. For each dog, a set of CT images was acquired with the transverse slices aligned parallel to the endplates and another one with the transverse images aligned perpendicular to the vertebral canal. For each different set, transverse slices from the cranial, middle, and caudal aspects of the individual vertebral bodies C2‐C7 were measured. Height, width, transverse area, right dorsal to left ventral height (RDLV), and left dorsal to right ventral height (LDRV) were recorded by a single observer at each location. For both affected and control dogs, significant differences between the measurements obtained from the two sets of transverse images were found only at the cranial aspect of the vertebrae (P = 0.005, P < 0.001, P < 0.001, P = 0.005, and P = 0.010 for height, width, area, RDLV, and LDRV, respectively). Measurements for the middle and caudal aspects did not differ. The funnel‐shape morphology of the cervical vertebral foramina in Great Danes with stenosis of their cranial aspect may be responsible for the significant differences found. Considering that the morphometric parameters were significantly affected by CT slice angle in the current study, authors recommend that a standardized scanning protocol be followed when morphometric evaluations using CT are planned.     

The Foramina of the Cervical Vertebrae of the Ox

All the macroscopically visible foramina of the atlas and axis in 20 oxen are examined and their size, incidence and connections described. The atlas possesses a canal connecting the atlantal fossa with the vertebral foramen. It is suggested that it be named “Canalis vertebroalaris”. The axis contains a prominent transverse canal rather than a foramen, with “cranial” and “caudal transverse foramina”. The canal occurs in an atypical location in 25 % of cases.     

A morphometric investigation on breed-specific features affecting sagittal rotational and lateral bending mobility in the canine cervical spine (c3-c7)

Vertebral and inter-vertebral parameters obtained in large breeds (n = 74), small breeds (n = 35), and Dachshunds (n = 30) were compared to reveal potential differences in the range of motion of the cervical spine between these three groups of breeds. Body size normalized dimensions of vertebral and inter-vertebral parameters and correlations between these indicate large canine breeds to have a tendency towards higher range of motion in sagittal rotation and lateral bending compared with Dachshunds and small breeds. Higher mobility in large breeds is based on significantly (P < 0.05) lower vertebral endplate heights and widths, shorter vertebral bodies and longer inter-vertebral discs, wider but shorter cranial and caudal articular surfaces, larger differences in width between caudal and cranial joining facets (compared with Dachshunds from C3/4 to C6/7, compared with small breeds from C4/5 to C5/6), and larger differences in length between caudal and cranial joining facets. Large differences in width between caudal and cranial joining facets were associated with small distances between the most medial (C3/4 to C6/7) and lateral (C3/4 to C5/6) aspects of the articular surfaces as well as with small differences in length between caudal and cranial joining facets (C3/4 to C5/6). This suggests that from C3/4 to C5/6 a higher range of motion in lateral bending is coupled to a lower range of motion in sagittal rotation. The present findings contribute also to explain the higher incidence of degenerative lesions of the cervical spine in large dogs.