Incidence of caudal occipital malformation syndrome and ultrasound, computed tomographic, magnetic resonance imaging findings in 16 clinically normal Cavalier King Charles Spaniel genitors
Jerome Couturier - Delphine Rault - Laurent Cauzinille

This prospective study was conducted at the Veterinary Imaging Center (Paris 15, France) in April 2006 on Cavalier King Charles dogs. These dogs belong to professional breeders and are clinically and neurologically normal. Ultrasound examination of the caudal fossa and the cranial cervical spinal cord was performed on awake animals. Under anaesthesia, a computed tomography study of the skull and a Magnetic Resonance Imaging study of the brain and cervical spinal cord were performed.

Materials and Methods

Sample Population, historical information and clinical examination


Sixteen CKCS genitors (from 2 different French breeders and from different lines) were included in the study. Criteria of inclusion were based on clinically, according to the owner, and neurologically, according to the neurologist, normal dogs without direct or indirect signs of Caudal Occipital Malformation Syndrome (COMS). Owners were asked for other neurological (seizures, facial paralysis, deafness), dermatological (dermatitis, otitis) and cardiac diseases. Chronic Mitral Valve Insufficiency was ruled out in each dog performing an echocardiographic exam within the 12 months prior to the study.

A complete clinical general and neurological examination was performed on each dog by Dr Couturier (without knowing historical information reported by the owner). The neurological exam included particular attention to cervicalgia, hyperesthesia, scratching, ataxia, paresia, abnormal head posture, scoliosis, strabismus, facial paralysis, cranial nerves deficit.

Ultrasound examination technique

The ultrasound examination was performed by a board-certified veterinary radiologist on awake dogs with a XX-MHz curvilinear-array transducer (Esaote). Diameter of the spinal cord was measured at C1-C2 and at the level of the foramen magnum with the head in physiological position and flexed at 90.

CT technique

Under general anaesthesia, the dogs were placed in sternal recumbency. The tuberculum sellae and the dens of axis were the cranial and caudal sagital limits included in the images of the skull. Sagital, transverse and dorsal images were acquired. Original CT data were transferred as DICOM images to an image analysis workstation (Osirix v 2.5.1). Linear measurements and area of the caudal fossa were obtained as described (Garcia-Real, Vet Rad 2004) in the sagital plane: from the dorsum to cranial aspect of the most dorsal part of the foramen magnum (CdF ds-crdfm), from the dorsum sellae to caudal aspect of the most dorsal part of the foramen magnum (CdF ds-cddfm), from the dorsum sellae to caudal aspect of the most ventral part of the foramen magnum (CdF ds-vfm) ; height of the foramen magnum (CdF hfm); area of the caudal fossa (CdF MS area). In the transverse plane at the level of the widest part of the caudal fossa, linear measurement of the maximum width of the fossa was obtained (CdF MW).

MRI technique

A 0.3T MR system was used to acquire the MR images. The dogs were placed in dorsal recumbency on the table. T1-weighted images of the brain and cervical spinal cord (up to first thoracic vertebra) were obtained in transverse and sagital planes. Measurements were made by using measurements tools of the MR system. Degree of hydrocephalus was estimated by calculating the ratio of cross-sectional area of the brain occupied by lateral ventricles in transverse images at the level of the pituitary gland (Median size of lateral ventricles) as described (Lu, Vet Rec 2003). Size of the cerebellum was estimated by calculating the ratio of cross-sectional area of the entire brain occupied by cerebellum in the mid-sagital image (Median size of Cerebellum). The degree of cerebellar herniation (Cerebellum herniation) was defined as the length of the cerebellum herniated within the foramen magnum; its length was measured from the line between ventral part of the foramen magnum and the primary fissure of the cerebellum (slightly different from the method used by Lu). Finally, the proportion of the foramen magnum occupied by the caudal brain stem was measured (Median size of foramen magnum occupied by brain stem) (as described by Lu, Vet Rec 2003).

Statistical analysis

The population was divided in 2 groups base on an imaging diagnosis of COMS (i.e. presence of a syrinx) : group 1: Normal; group 2: COMS. A third group was composed of the dogs presenting an imaging diagnosis of COMS and the dogs with a high degree of hydrocephalus: COMS+H. A variance homogeneity test of the data (F test) was performed first. Then, the comparison test (esperance equality test) was run according to the homogeneous or non homogeneous series.

Results

Statistical analysis of the results will be presented during the meeting.

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