Questionnaire-based Analysis of Owner-reported Scratching and Pain Signs in Cavalier King Charles Spaniels Screened for Chiari-like Malformation and Syringomyelia.

BACKGROUND: Chiari-like malformation (CM) and syringomyelia (SM) cause a pain syndrome in Cavalier King Charles spaniels (CKCS). Clinical signs are not consistently apparent on neurologic examination, and owner reporting of signs provides vital clinical history. However, owner questionnaires for this disease are not well developed. OBJECTIVES: To develop a tool to capture owner-reported clinical signs for use in clinical trials and to compare owner-reported signs with the presence of pain on neurologic examination and SM on magnetic resonance imaging (MRI). ANIMALS: Fifty client-owned CKCS. METHODS: Owners completed a questionnaire and pain/scratch map. Each dog underwent a neurologic examination and craniocervical magnetic resonance imaging (MRI). Questionnaire responses were developed into scores, area of shading for pain/scratch maps was measured, and consistency of responses between these tools was assessed. Owner-reported findings were compared with neurologic examination findings and presence and severity of SM on MRI. RESULTS: Thirty-three dogs were symptomatic and 17 asymptomatic; 30 had SM. The most common sign of pain was crying out when lifted (n = 11). Extent of shaded areas on maps positively correlated with questionnaire scores for pain (r2  = 0.213, P = 0.006) and scratch (r2  = 0.104, P = 0.089). Owner-reported findings were not significantly associated with presence or severity of SM or neurologic examination findings. Owner-reported lateralization of signs was significantly associated with SM lateralization (P < 0.0001). CONCLUSIONS: The questionnaire and maps may be useful for clinical trials. Lack of association of owner-reported signs with SM highlights our lack of understanding of the pathophysiology of pain in this disease.

Longitudinal Study of the Relationship among Craniocervical Morphology, Clinical Progression, and Syringomyelia in a Cohort of Cavalier King Charles Spaniels.

BACKGROUND: Craniocervical junction (CCJ) anomalies and secondary syringomyelia are commonly diagnosed in Cavalier King Charles spaniel (CKCS). Familiarity with the natural history of these abnormalities is vital to understanding the disease syndrome. OBJECTIVE: To evaluate magnetic resonance imaging (MRI) predictors of worsening clinical signs, syringomyelia, and morphology in CKCS longitudinally. ANIMALS: Fifty-four client-owned CKCS, 5-13 years old; 50% currently symptomatic. METHODS: Longitudinal observational study. We enrolled CKCS with an MRI of the CCJ performed ≥3 years earlier. We used questionnaires and neurologic examinations to grade initial and current clinical status. Dogs that could be anesthetized were reimaged. Morphologic assessments included the presence and severity of: Chiari-like malformations, medullary position, atlantooccipital overlapping (AOO), dorsal atlantoaxial bands, and syringomyelia. Cranial cavity volumes and foramen magnum height were measured. RESULTS: Clinical status was evaluated in 54 dogs; 36/54 were reimaged. Mean follow-up was 71 months. Of initially asymptomatic dogs, 32% were symptomatic at re-evaluation. Of initially symptomatic dogs, 56% had worsened; 13% had improved with medical management. The morphology of the CCJ at initial imaging did not predict development of either new or worsened signs or syringomyelia by the time of re-evaluation. CONCLUSION: Craniocervical junction anomalies assessed in this study did not appear predictive of future clinical status or syringomyelia in our cohort. The impacts of syringomyelia, AOO, and atlantoaxial bands on future clinical status merit further study in larger groups of CKCS. Clinical progression in our cohort of medically managed CKCS did not differ substantially from published reports of those treated surgically.

Noninvasive Assessment of Neuromuscular Disease in Dogs: Use of the 6-minute Walk Test to Assess Submaximal Exercise Tolerance in Dogs with Centronuclear Myopathy.

BACKGROUND: Noninvasive methods of quantitating exercise tolerance in dogs with neuromuscular disease are needed both for clinical and research use. The 6-minute walk test (6MWT) has been validated as a reliable test of exercise tolerance in dogs with pulmonary and cardiac disease, but not in dogs with neuromuscular disease. HYPOTHESIS/OBJECTIVES: Distance walked and number of steps taken during 6MWT will differ between Labrador retriever dogs with centronuclear myopathy (CNM) and control (ie, healthy) littermates. ANIMALS: Eight purebred Labrador retrievers were drawn from a purpose-bred research colony (status: 3 clear, 2 carrier, and 3 homozygous mutants for the protein tyrosine phosphatase-like A (PTPLA) gene mutation associated with CNM). METHODS: Pilot, prospective, Case-controlled study. Researchers were blinded to disease status. Each dog was leash-trained and acclimatized to the testing area (length, 12.8 m). At the start of testing, each animal was fitted with a pedometer, a timer was started, and dogs were allowed to walk at their own pace for 6 minutes. Distance walked and pedometer readings were recorded. RESULTS: Degree of paresis varied among affected dogs, and was reflected by significant differences in distance walked between CNM-affected dogs and those with clear and carrier genotypes (P = .048). Pedometer readings did not vary according to genotype (P = .86). CONCLUSIONS: The 6MWT appears to differentiate between the ambulatory capacity of normal and CNM-affected dogs. Additional studies are needed to confirm this relationship in a larger number of dogs, and to evaluate the ability of the 6MWT to differentiate between dogs with variable severity of neuromuscular disease-associated exercise intolerance.

Magnetic resonance imaging-based measures of atlas position: Relationship to canine atlantooccipital overlapping, syringomyelia and clinical signs.

Canine atlantooccipital overlapping (AOO) is characterized by a decreased distance between the dorsal arch of the atlas and the supraoccipital bone. Current diagnostic criteria for this condition are subjective and clinician-dependent; objective criteria are needed to allow a reliable and reproducible diagnosis in clinical and research settings and assess clinical significance. We propose four standardized MRI-based measurements to objectively assess the proximity of the atlas to the foramen magnum. Inclusion criteria for dogs in this study were bodyweight <15 kg, age >5 months, and availability of a complete MRI study performed with the craniocervical junction in extension. Exclusion criteria were space-occupying lesions and poor image quality (i.e. unclear bony margins). Measurements also included blinded determinations of skull type, presence of craniocervical junction anomalies and presence and severity of syringomyelia. Clinical status at the time of imaging was noted. Measurements were obtained in 271 dogs; these were reproducible and reliable. Findings varied by skull type: dolichocephalic dogs had smaller foramen magnum, whereas brachycephalic dogs had more cranially and dorsally positioned atlas bodies in comparison to the other skull types. Measurements also increased with increases in bodyweight. This study demonstrated a close association between AOO, syringomyelia and clinical signs. Toy and small breed dogs (including Cavalier King Charles spaniels) showed higher than previously reported prevalence of AOO; its occurrence was also associated with lower bodyweights within the study population of <15 kg toy/small breed dogs.

Dorsal compressive atlantoaxial bands and the craniocervical junction syndrome: association with clinical signs and syringomyelia in mature cavalier King Charles spaniels.

BACKGROUND: Dorsal compressive lesions at the atlantoaxial junction (ie, AA bands) occur in dogs with Chiari-like malformations (CMs), but their clinical relevance is unclear. OBJECTIVE: Investigate the influence of AA bands on clinical status and syringomyelia (SM) in mature cavalier King Charles spaniels (CKCS). ANIMALS: Thirty-six CKCS, 5-12 years of age, including 20 dogs with neuropathic pain. METHODS: Dogs were examined and assigned a neurologic grade. Magnetic resonance imaging (MRI) of the craniocervical junction was performed with the craniocervical junction extended and flexed (ie, normal standing position). Imaging studies were assessed for the presence of an AA band, CM, SM or some combination of these findings. Band and SM severity were quantified using an objective compression index and ordinal grading scale, respectively. RESULTS: Of 36 CKCS imaged, 34 had CM. Atlantoaxial bands were associated with the presence (P = .0031) but not the severity (P = .008) of clinical signs, whereas their presence was associated with both the presence and severity of SM (P = .0147, P = .0311, respectively ). Higher compression indices were associated with more severe SM (P = .0137). CONCLUSIONS: Prevalence of AA bands in older CKCS is high. Positioning of dogs in extension during MRI enhances the sensitivity of the study for detecting this important abnormality. There were significant associations among AA bands, clinical signs, and SM in dogs with CM; additional work is needed to understand whether or not this relationship is causal.

Medullary position at the craniocervical junction in mature cavalier King Charles spaniels: relationship with neurologic signs and syringomyelia.

BACKGROUND: Medullary elevation (ie, medullary kinking) at the craniocervical junction (CCJ) is reported in dogs with Chiari-like malformations (CM), but its diagnostic criteria and clinical relevance are unclear. OBJECTIVE: To describe the position of the medulla at the CCJ in mature cavalier King Charles spaniels (CKCS), and evaluate its relationship with clinical status and the presence of syringomyelia. ANIMALS: Thirty-six CKCS, 5-12 years of age, including 16 asymptomatic dogs. METHODS: Dogs were assigned a neurologic grade; magnetic resonance imaging (MRI) of the CCJ then was performed. The presence of a CM and syringomyelia was recorded and syringomyelia severity was quantified. Medullary position was quantified using the medullary kinking index, the elevation angle and obex position relative to the foramen magnum. The relationship between medullary position measures and presence and severity of neurologic signs and syringomyelia was investigated. RESULTS: Chiari-like malformation was found in 33 dogs; 26 of them had syringomyelia. Mean medullary kinking index was 46.4% (SD, 10.3), elevation angle was 132° (SD, 12) and obex position was 3.5 mm (SD, 0.8). A higher medullary kinking index was associated with the presence of neurologic signs (P = .0368). Obex position was associated with the presence (P = .0018) and severity of syringomyelia (P = .0164). CONCLUSIONS AND CLINICAL IMPORTANCE: There is a significant association between medullary elevation and clinical signs, whereas more caudal brainstem positions appear related to the presence of syringomyelia.

Pharmacokinetics of single-dose rectal zonisamide administration in normal dogs.

BACKGROUND: Few medications are available for parental administration to animals with seizures. Rectal administration of medications is often used if the animal cannot be administered oral medications. HYPOTHESIS/OBJECTIVES: To determine the pharmacokinetic differences in zonisamide when administered rectally in either of 2 vehicles and p.o. to dogs. ANIMALS: Eight healthy research dogs. METHODS: Randomized cross-over design. Zonisamide, 10 mg/kg, was administered rectally in polyethylene glycol (PEG-R), rectally in water (H2O-R), and as an oral capsule. Plasma zonisamide concentrations were measured until 72 hours after administration. Zonisamide was quantitated by HPLC and plasma concentration versus time curve data was analyzed by using noncompartmental modeling. RESULTS: Mean maximum plasma zonisamide concentrations (µg/mL) were significantly higher after oral administration (11.56 ± 4.04) compared to H2O-R (5.00 ± 1.83) (P = .004). Disappearance half-life (hours) and mean time to maximum concentration (hours) were not significantly different between methods of administration. Mean relative bioavailability of PEG-R (85 ± 69%) was significantly higher than that of H2O-R (53 ± 37%) (P = .039). Dogs tolerated all dosing forms with no evidence of adverse effects. CONCLUSIONS AND CLINICAL IMPORTANCE: The vehicle in which zonisamide is dissolved influences rectal bioavailability, with PEG preferred to H2O-R. Because of the prolonged time to maximum concentration, rectal administration of zonisamide should not be used to treat status epilepticus in dogs. A dose higher than what was used in this study might be necessary, if currently recommended minimum therapeutic concentrations (10 µg/mL) are to be achieved with a single-dose administration.

Prevalence of urinary tract infection in dogs after surgery for thoracolumbar intervertebral disc extrusion.

BACKGROUND: Urinary tract infection (UTI) is a common complication in people with spinal cord injury (SCI). Dogs with acute intervertebral disc extrusion (IVDE) have similar risk factors for UTI when compared with human SCI patients and have a high perioperative prevalence of UTI. OBJECTIVES: Determine the prevalence of UTI in dogs for 3 months after surgery for thoracolumbar IVDE and identify risk factors for development of UTI. ANIMALS: Twenty-five dogs treated surgically for 26 acute disc extrusions. METHODS: Prospective study. Urinalysis and urine culture were performed perioperatively. At home, owners monitored urine with dipsticks every 48 hours for 1 month then once a week until 3 months. Dogs returned for assessment of motor function, urinalysis, and urine culture at 1 and 3 months after surgery. Presence of UTI over the 3-month period was correlated to potential risk factors. RESULTS: Ten dogs (38%) developed 12 UTIs over the 3-month period, with the majority occurring between weeks 1 and 6; 60% of the UTIs were occult. Hematuria in the absence of pyuria or UTI was a common finding in the perioperative period. Sex, breed, and ambulatory status influenced the risk of developing a UTI. CONCLUSIONS AND CLINICAL IMPORTANCE: There is a high prevalence of UTIs, many of which are occult, in the 3 months after surgery for thoracolumbar IVDE. These dogs should be routinely monitored for UTI with urine culture regardless of urinalysis results.

Diagnosis and surgical resection of a choroid plexus cyst in a dog.

A three-year-old neutered male toy fox terrier presented for a Chiari-like malformation. No neurological deficits were found on examination, although diffuse cervical, thoracolumbar and head pain were present. A mass within the fourth ventricle was apparent on magnetic resonance imaging (MRI) of the brain. The lesion was hyperintense to brain parenchyma on T2-weighted images, hypointense on T1-weighted images and there was strong, homogeneous contrast enhancement. The cystic mass was removed through a suboccipital craniectomy. Histopathology was consistent with a choroid plexus cyst. The dog recovered well from the procedure and was clinically normal three months after surgery. To the authors' knowledge this is the first description of the appearance of a choroid plexus cyst on MRI in a dog and of its surgical removal. Although they are an uncommon finding, choroid plexus cysts should be considered as a differential diagnosis for mass lesions within the fourth ventricle.