Neurological signs and results of magnetic resonance imaging in 40 cavalier King Charles spaniels with Chiari type 1-like malformations

In human beings a Chiari type 1 malformation is a developmental condition characterised by cerebellar herniation and syringohydromyelia. Abnormalities compatible with such a malformation were identified by magnetic resonance imaging in 39 cavalier King Charles spaniels with neurological signs and in one neurologically normal cavalier King Charles spaniel that was examined postmortem. The dogs with these abnormalities had a wide variety of neurological signs, but there was no apparent correlation between the neurological signs and the severity of cerebellar herniation, syringohydromyelia or hydrocephalus.     

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.     

Association between cervical and intracranial dimensions and syringomyelia in the cavalier King Charles spaniel

O bjectives : To investigate the possible association between caudal fossa area and cervical vertebral dimensions and the presence of syringomyelia in cavalier King Charles spaniels.
M ethods : From magnetic resonance imaging scans of 78 cavalier King Charles spaniels, measurements were made of the widest vertical spinal width at C1/C2, C2, C2/C3 and C3; angulation of the C2/C3 spine; and estimated caudal fossa area. A correlation between these measurements and syringomyelia was sought.
R esults : A total of 59 dogs with and 19 without syringomyelia were compared. Older dogs had a significantly higher incidence of syringo-myelia. No difference in incidence was noted between genders. There was no significant difference in vertebral canal width at C1/C2 and C2, or angulation of C2/C3 between syringomyelia and non-syringomyelia groups. The width of the canal at C2/C3 and C3 was significantly increased in syringomyelia dogs. There was no significant difference in the caudal fossa area between groups.
C linical S ignificance : Although syringomyelia was shown to be more prevalent in older dogs, the age beyond which dogs were considered at greater risk was not deducible from the dataset. The association identified between wider spinal canal at C3, and C2/C3 and syringomyelia presence is of questionable clinical significance, as the difference between syringomyelia and non-syringomyelia groups is too small to be measured in a clinical setting.     

MORPHOLOGY OF THE CAUDAL FOSSA IN CAVALIER KING CHARLES SPANIELS

Chiari malformations and syringohydromyelia are an important disease complex in Cavalier King Charles Spaniels. Although abnormalities in caudal fossa morphology are considered major contributors to the development of this disease, limited information exists on the range of morphologies in Cavalier King Charles Spaniels and on the relationship of these to clinically evident disease. Sixty-four Cavalier King Charles Spaniels were studied. Each underwent a neurologic examination and magnetic resonance imaging of the cervical spine and brain. T2-weighted sagittal images were used to determine both the morphologic characteristics and volume of the caudal fossa in each dog. This volume was also analyzed as a percentage of total cranial cavity volume. Each attribute was correlated with neurological grade and presence of syringohydromyelia. Fifteen dogs had neurologic signs, and 59 had morphologic abnormalities of the craniocervical junction. While 27 dogs had syringohydromyelia, 13 of these were clinically normal. Cerebellar herniation and occipital dysplasia were common findings but were not associated with syringohydromyelia. Dorsal compressive lesions were noted at the first and second cervical vertebral junction. Factors associated with the presence of neurologic signs included syringohydromyelia and the ratio of caudal fossa/total cranial cavity volume; dogs with signs had significantly larger syringohydromyelia than asymptomatic dogs. Caudal fossa size was not associated with syringohydromyelia. A positive association was identified between foramen magnum size and length of cerebellar herniation. The prevalence of craniocervical junction abnormalities is high in Cavalier King Charles Spaniels. While several factors are associated with neurologic signs, occipital hypoplasia appears to be the most important factor.     

Comparison of the relative occipital bone volume between Cavalier King Charles spaniels with and without syringohydromyelia and French bulldogs

Our aim was to determine the relative volume of the occipital bone of Cavalier King Charles spaniels with and without syringohydromyelia and normal French bulldogs to reappraise the role of a possible insufficiency of the paraxial mesoderm in the pathogenesis of the caudal occipital malformation syndrome. Analysis of the occipital bone volume of 43 dogs based on computed tomography datasets was performed. Volume was determined by means of three-dimensional models. Using manual segmentation of the occipital bone in sagittal, transverse, and dorsal images, the volume of the occipital bone and the rest of the skull was calculated. The absolute occipital bone volume was put in relation to the total skull volume, the occipital bone index. For the Cavalier King Charles spaniels without syringomyelia, the median occipital bone index was 0.0681; for Cavalier King Charles spaniels with syringomyelia, it was 0.0646 and for French bulldogs, it was 0.0676. There was no global difference of the occipital bone index between examined groups (P = 0.4331). A reduced volume of the occipital bone was not found in Cavalier King Charles spaniels in general in comparison to French bulldogs, or in Cavalier King Charles spaniels with syringomyelia compared to Cavalier King Charles spaniels without syringomyelia. These results do not support occipital hypoplasia as a cause for syringomyelia development, challenging the paraxial mesoderm insufficiency theory. This also suggests that the term Chiari-like malformation, a term derived from human studies, is not appropriate in the Cavalier King Charles spaniel.     

Hereditary aspects of occipital bone hypoplasia and syringomyelia (Chiari type I malformation) in cavalier King Charles spaniels

A database of over 1300 cavalier King Charles spaniels spanning 20 generations was established by obtaining pedigree information from 45 dogs with syringomyelia secondary to occipital bone hypoplasia. These data were supplemented with published information from the breed club. The incidence of syringomyelia was very high in certain families and lines which had been extensively inbred. The affected dogs could be traced back to one bitch born in 1956 and the two offspring from her single litter. Four key dogs representing four major breeding lines consistently occurred within the individual pedigrees. If a dog had more than five of its eight great-grandparents descended from these four lines there was a greater chance of it having syringomyelia. The data from this preliminary study suggest that occipital bone hypoplasia is hereditary in the cavalier King Charles spaniel and that its inheritance is more likely to be autosomal recessive because both dam and sire must be inbred descendants from certain lines. However, the inheritance is more likely to be of variable penetrance or oligogenic than simple.     

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.     

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.     

Syringohydromyelia in Cavalier King Charles spaniels

Syringohydromyelia secondary to foramen magnum overcrowding is described in seven Cavalier King Charles spaniels. Clinical signs were consistent with a central spinal cord lesion. The most common signs were persistent scratching at the shoulder region with apparent neck, thoracic limb, or ear pain and thoracic limb lower motor neuron deficits. The diagnosis was made by magnetic resonance imaging. The syringohydromyelia is postulated to be a consequence of an occipital bone malformation resulting in a small caudal fossa and cerebellar herniation. Clinical signs improved but did not completely resolve when the dogs received treatment with corticosteroids or nonsteroidal anti-inflammatory drugs.     

Ultrasonographic appearance of the craniocervical junction in normal brachycephalic dogs and dogs with caudal occipital (Chiari-like) malformation

Ultrasonographic evaluation of the spine, especially of the spinal cord, has been rarely reported in dogs. The atlanto-occipital junction provides a small acoustic window through which examination of the craniocervical transition can be performed. Normal sonographic findings of this region in 10 normal brachycephalic dogs are presented and compared with sonographic findings from 25 Cavalier King Charles Spaniels with the caudal occipital malformation syndrome. Sonographic findings were compared with magnetic resonance imaging findings to determine the extent of cerebellar herniation and syringohydromyelia. Cerebellar displacement into the foramen magnum was clearly identified sonographically; however, syringohydromyelia was not discernable due to bone overlay.     

Use of breed-specific ranges for the vertebral heart scale as an aid to the radiographic diagnosis of cardiac disease in dogs.

The vertebral heart scale was measured on right lateral recumbent thoracic radiographs of 320 dogs of six popular breeds, including for each breed at least 20 dogs with no clinical signs of cardiovascular or respiratory disease and at least 19 dogs with cardiac or respiratory disease. There were significant differences between the mean values of the scale for the different breeds; the normal boxer dogs had a significantly higher mean value than the normal dogs of all the other breeds, and the labrador retrievers had a significantly higher mean value than all the other breeds except the boxer and the cavalier King Charles spaniel. For all the breeds except the boxer, there was a trend for dogs with cardiac disease (but not respiratory disease) to have higher mean values on the scale than normal dogs of the same breed; however, at the optimal value of the scale for distinguishing between dogs of each breed with and without cardiac disease, the sensitivity and specificity were relatively low, in the range 58 to 83 per cent. The scale was most accurate for the diagnosis of cardiac disease in the Yorkshire terrier and the cavalier King Charles spaniel, breeds affected by predominantly dilative forms of cardiac disease. In contrast, it was very inaccurate in the boxer, a breed that has a higher incidence of cardiac diseases associated with concentric hypertrophy.     

Chronic valvular disease in the cavalier King Charles spaniel in Sweden.

The prevalence of chronic valvular disease was studied in 494 cavalier King Charles spaniels with a mean (+/- sd) age of 3.0 +/- 2.7 years. Cardiac murmurs were detected in 65 (13.2 per cent) of the dogs. Among 61 cavalier King Charles spaniels with a mean age of 6.4 +/- 2.8 years, cardiac murmurs were detected in 32 (52 per cent). In both groups of dogs the prevalence of cardiac murmurs was low among dogs younger than three years (1.9 per cent) but increased with age (P < 0.001). The estimated ages at which 50 per cent of the dogs had developed murmurs were 7.5 and 6.2 years, respectively. When 39 of the 61 dogs were re-examined three years later, cardiac murmurs were detected in 28 (72 per cent), and the intensities of the murmurs had generally increased (P < 0.05). Nine (28 per cent) of the dogs which had previously had murmurs had been euthanased for signs of congestive heart failure whereas none of the dogs which had been free of murmurs had died from congestive heart failure. Animal insurance statistics from 1982 to 1990 (1983 excluded) for dogs less than 10 years old showed that claims for veterinary care or death or euthanasia were five times more common in the cavalier King Charles spaniel than in dachshunds (P < 0.001) and eight times more common than the mean for all other insured breeds (P < 0.001).     

Congenital pleuroperitoneal hernia presenting as gastrothorax in five cavalier King Charles spaniel dogs

Five cavalier King Charles spaniels were examined for acute onset of respiratory distress. Thoracic radiographs demonstrated diaphragmatic hernia and tension gastrothorax, visible as a distended stomach occupying the left caudal thoracic cavity. Exploratory midline coeliotomy confirmed congenital pleuroperitoneal diaphragmatic hernia with herniation and dilatation of the stomach. The hernia configuration was consistent in all cases, with a defect affecting the left diaphragmatic crus. Congenital pleuroperitoneal diaphragmatic hernia is a rare condition caused by a defect in the dorsolateral diaphragm. Defects of the left crus of the diaphragm could result in the herniation of the stomach into the thoracic cavity with possible subsequent tension gastrothorax. Cavalier King Charles spaniels may have a predisposition to this condition. Tension gastrothorax is an acute life‐threatening consequence of gastric herniation through a diaphragmatic defect that must be promptly recognised and surgically treated.     

Xanthinuria in a family of Cavalier king Charles Spaniels

Summary

Xanthine calculi were found in a 7‐month‐old male Cavalier King Charles spaniel with urethral obstruction and renal insufficiency. Because the only two other reported cases of naturally occurring xanthine urolithiasis concerned a Cavalier King Charles and a King Charles spaniel the urine of the littermates and parents of the patient were also examined for xanthinuria. Semi‐quantitative analysis revealed high urine concentrations of hypoxanthine and xanthine in the patient and his female littermate. Quantitative analysis by high‐pressure liquid chromatography (HPLC) of the urine samples from the family of this Cavalier King Charles spaniel and nine control dogs revealed that hypoxanthine and xanthine excretion was 30 and 60 times higher in the affected patient and the female littermate than in the others dogs. The pattern of xanthinuria, which is caused by a deficiency of the enzyme xanthine oxidase, in the relation diagram of this family of Cavalier King Charles Spaniels was consistent with an autosomal recessive mode of inheritance.     

CHARACTERISTICS OF CEREBROSPINAL FLUID FLOW IN CAVALIER KING CHARLES SPANIELS ANALYZED USING PHASE VELOCITY CINE MAGNETIC RESONANCE IMAGING

Syringomyelia is an important morbidity source in Cavalier King Charles Spaniels. Although abnormal cerebrospinal fluid (CSF) flow secondary to Chiari malformations is thought to cause syringomyelia in humans, this relationship is unknown in dogs. We used phase-contrast magnetic resonance (MR) imaging to evaluate CSF flow in dogs. Fifty-nine Cavalier King Charles Spaniels were assigned a neurologic grade reflecting their neurologic status. Five normal control dogs of other breeding were imaged for comparison. The presence of syringomyelia was noted from sagittal MR images. The pattern and velocity of CSF flow were assessed using phase-contrast cine MRI at the foramen magnum, C2–C3 disc space, and within syrinxes. Flow was measured most easily with the neck flexed to mimic standing. CSF flow velocity in the dorsal aspect of the subarachnoid space at the foramen magnum was significantly higher in control dogs than Cavalier King Charles Spaniels ( P =0.035). Flow was obstructed at the foramen magnum in 41 of 59 Cavalier King Charles Spaniels. Turbulent flow and jets were associated with syringomyelia presence and severity, and CSF flow velocity at C2/3 dorsally was inversely related to the presence of syringomyelia ( P =0.0197). Peak dorsal subarachnoid space CSF flow velocity at the foramen magnum and C2–C3 were together highly predictive of syringomyelia. CSF flow can be assessed in dogs using phase-contrast cine MRI. Obstruction to flow at the foramen magnum is common in Cavalier King Charles Spaniels and CSF flow pattern and velocity are related to the presence of syringomyelia.     

Imaging diagnosis and clinical presentation of a Chiari malformation in a Thoroughbred foal

A newborn Thoroughbred foal was presented to the clinic with ambiguous neurological deficits, spinal anomalies and a soft tissue swelling dorsal to the lumbar vertebral column. The foal was alert but unable to rise and stand. With radiography, ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) a lumbar dysraphic anomaly, cerebellar herniation and coincidental skeletal abnormalities were documented. Finally, a meningomyelocele was defined and, in context with the cerebellar herniation through the foramen magnum, the foal was diagnosed to have a Chiari malformation. The MRI examination corresponded best with the post mortem findings. Although 3‐dimensional imaging methods have been considered superior regarding full and detailed assessment of the congenital malformation, radiography and ultrasonography also provide essential information to diagnose dysraphic lesions at reduced costs and efforts. A Chiari malformation should be considered as a differential diagnosis in foals with neurological deficits.     

Chiari‐like malformation in two cats

Two male, neutered, domestic, shorthaired cats were evaluated for progressive paresis and ataxia. Neurological examinations suggested a spinal cord lesion in each case. Complete blood examination and cerebrospinal fluid analysis were unremarkable in both cats. MRI revealed malformation of the occipital bone with herniation of the cerebellar vermis through the foramen magnum but without syringomyelia. Chiari‐like malformation was suspected in both patients. MRI repeated one year later in both cats because of progression of clinical signs yielded the same findings as the initial scans. Foramen magnum decompression in one cat was associated with resolution of clinical signs.     

Relationship of brain parenchyma within the caudal cranial fossa and ventricle size to syringomyelia in cavalier King Charles spaniels

Objectives : To assess if the volumes of the caudal cranial fossa (CCF), parenchyma within the caudal cranial fossa (CCFP) or ventricles (V) are associated with syringomyelia (SM) in cavalier King Charles spaniels (CKCS) with Chiari-like malformation (CM). To evaluate if volumes are associated with transverse syrinx width. Methods : Magnetic resonance images of 59 CKCS with CM were retrospectively reviewed and grouped with or without SM. Three-dimensional images were created and volumes of the fossae, brain parenchyma and ventricular system were calculated from which percentages of CCF, CCFP and V were created. If present, syrinx size was measured from its maximal transverse width. The percentages were statistically compared between groups, and correlation between percentages and syrinx dimensions was made. Results : CKCS with SM had significantly higher CCFP (P=0·0001) and V (P=0·0002) to those without but no significant difference in CCF (P=0·925). There was a positive correlation between CCFP and syrinx width (Pearson r=0·437) and ventricle size to syrinx width (Spearman r=0·627). Clinical Significance : A more marked overcrowding of the CCF is associated with SM, which may explain the high incidence of SM in CKCS with CM. The association between ventricle and syrinx dimensions supports the theory that SM development is the result of altered cerebrospinal fluid dynamics.     

Syringosubarachnoid shunt as a management for syringohydromyelia in dogs

Objective : To evaluate retrospectively the efficacy of syringosubarachnoid shunt for the management of syringohydromyelia/syringomyelia. Methods : Eleven dogs diagnosed with syringohydromyelia/syringomyelia by magnetic resonance imaging associated with Chiari‐like malformation underwent placement of a syringosubarachnoid shunt at the cervical (nine dogs) or lumbar (two dogs) spinal cord. In one dog, a suboccipital decompression (foramen magnum decompression) was performed 4 months before inserting a syringosubarachnoid shunt. All dogs were evaluated neurologically a few hours after surgery, 2 weeks and 6 months postoperatively. Retrospectively, cases were assigned a preoperative and postoperative pain score. Results : There were no intra‐ or peri‐operative complications. One dog (9%) was euthanased 5 weeks after surgery. Progressive neurological improvement was observed in nine dogs (81·8%) 2 weeks and 6 months postoperatively. No clinical improvement was seen in another dog (9%). One dog (9%) had replacement of the syringosubarachnoid shunt. Seven dogs (63·6%) were still alive 1 to 4 years (mean, 2·6 years) after surgery. Clinical Significance : Placement of a syringosubarachnoid shunt in the presence of a sufficiently large syrinx appears to be beneficial in dogs with Chiari‐like malformation and associated syringohydromyelia/syringomyelia.     

COMPARISON OF CLOSURE TIMES FOR CRANIAL BASE SYNCHONDROSES IN MESATICEPHALIC,BRACHYCEPHALIC, AND CAVALIER KING CHARLES SPANIEL DOGS

Premature closure of cranial base synchondroses has been proposed as the mechanism for brachycephaly in dogs and caudal occipital malformation syndrome (COMS) in Cavalier King Charles Spaniels. The purpose of this retrospective study was to compare times of closure for cranial base synchondroses in mesaticephalic, brachycephalic, and Cavalier King Charles Spaniel dogs. Cranial magnetic resonance imaging studies were retrieved for client‐owned dogs less than 18 months of age. Breed, age, skull conformation, and the open or closed state of cranial base synchondroses were independently recorded by two observers. For dogs with a unanimous observer agreement, regression analysis was used to test effects of age and gender on the open or closed status of synchondroses and differences between groups. A total of 174 dogs were included in MRI interpretations and 165 dogs were included in the regression analysis. Statistically significant differences in closure time of the spheno‐occipital synchondrosis were identified between brachycephalic and mesaticephalic dogs (P = 0.016), Cavalier King Charles Spaniels and mesaticephalic dogs (P < 0.0001), and Cavalier King Charles Spaniels and brachycephalic dogs (P = 0.014). Findings from the current study supported the theory that morphological changes leading to the skull phenotype of the Cavalier King Charles Spaniels could be due to an earlier closure of the spheno‐occipital synchondrosis.