Low‐Field MRI and Multislice CT for the Detection of Cerebellar (Foramen Magnum) Herniation in Cavalier King Charles Spaniels

Background

Cavalier King Charles Spaniels (CKCS) have a high prevalence of Chiari‐like malformation (CM). Herniation of the cerebellum into the foramen magnum is a key diagnostic feature for CM. Midsagittal MR images are the preferred technique for visualizing cerebellar herniation (CH).

Objective

To investigate whether CT can be used to diagnose CH.

Animals

Fifteen client‐owned CKCS dogs referred for investigation of the brain and cranial cervical spine on MRI and CT.

Methods

Two reviewers retrospectively analyzed midsagittal T1WSE and T2WSE MR images and midsagittal pre‐ and postcontrast 2D multiplanar reformatted CT images from each dog for the presence of CH. And, if present, the length (mm, CHL) of the herniation was measured. The results were analyzed statistically.

Results

There was no significant difference between the different observers and techniques for the detection of CH and measurement of CHL. Overall, the CHL was longer on the CT images.

Conclusion and Clinical Importance

Both techniques are useful for detecting CH and measuring CHL. Because CHL does not have a known direct impact on the clinical presentation of CM, CT can be used as a diagnostic tool in a routine clinical practice for CM in CKCS when MRI is not available. We emphasize that MRI is the standard screening technique in CKCS for breeding purposes to detect the presence of CM and SM and, at the current time, CT cannot replace MRI.     

Syringomyelia: current concepts in pathogenesis, diagnosis, and treatment

Syringomyelia is a condition that results in fluid-containing cavities within the parenchyma of the spinal cord as a consequence of altered cerebrospinal fluid dynamics. This review discusses the history and the classification of the disorder, the current theories of pathogenesis, and the advanced imaging modalities used in the diagnosis. The intramedullary pulse pressure theory (a new pathophysiologic concept of syringomyelia) also is presented. In addition, the current understanding of the painful nature of this condition is discussed and the current trends in medical and surgical management are reviewed.     

Serotonin Concentrations in Platelets,Plasma, Mitral Valve Leaflet,and Left Ventricular Myocardial Tissue in Dogs with Myxomatous Mitral Valve Disease

Hypothesis/Objectives

Altered serotonin (5‐hydroxytryptamine, 5HT) signaling is postulated in development and progression of canine myxomatous mitral valve disease (MMVD). Little is known regarding platelet, plasma, valvular, or myocardial 5HT concentration ([5HT]) in affected dogs. We quantified [5HT] in platelet‐rich plasma (PRP), platelet‐poor plasma (PPP), mitral valve leaflets (MV), and left ventricular myocardium (LV).

Animals

Forty‐five dogs comprised 4 plasma groups of Cavalier King Charles Spaniels (CKCS) or non‐CKCS, either healthy (CON) or MMVD affected: CKCS CON (n = 12); non‐CKCS CON (n = 8); CKCS MMVD (n = 14); non‐CKCS MMVD (n = 11). Twenty‐four dogs comprised 3 tissue groups: MMVD (n = 8); other‐HD (heart disease) (n = 7); non‐HD, extracardiac disease (n = 9).

Methods

High‐performance liquid chromatography measured PRP, PPP, MV, and LV [5HT].

Results

Platelet‐rich plasma platelet [5HT] was greater in CKCS CON (1.83 femtograms/platelet [fg/plt]; range, 0.20–4.76; P = .002), CKCS MMVD (1.58 fg/plt; range, 0.70–4.03; P = .005), and non‐CKCS MMVD (1.72 fg/plt; range, 0.85–4.44; P = .003) versus non‐CKCS CON (0.92 fg/plt; range, 0.63–1.30). There was no group difference in PPP [5HT]. MV [5HT] was significantly higher in MMVD (32.4 ng/mg; range, 8.4–106.7) versus non‐HD (3.6 ng/mg; range, 0–28.3; P = .01) and LV [5HT] was significantly higher in MMVD (11.9 ng/mg; range, 4.0–104.8) versus other‐HD (0.9 ng/mg; range, 0–10.1; P = .011) and non‐HD (2.5 ng/mg; range, 0–6.9; P = .001).

Conclusions and Clinical Importance

Platelet [5HT] was highest in healthy CKCS and both MMVD groups, but plasma [5HT] showed no group differences. Tissue [5HT] was highest in MV and LV of MMVD‐affected dogs, suggesting altered 5HT signaling as a potential feature of MMVD. Interactions of platelet, valvular, and myocardial 5HT signaling warrant further investigation.     

Suboccipital craniectomy, dorsal laminectomy of C1, durotomy and dural graft placement as a treatment for syringohydromyelia with cerebellar tonsil herniation in Cavalier King Charles spaniels

OBJECTIVE: To evaluate retrospectively the efficacy of the suboccipital craniectomy and dorsal laminectomy of C1 with durotomy and placement of a dural graft for treatment of syringohydromyelia (SHM) because of cerebellar tonsil herniation in Cavalier King Charles spaniels (CKCS). This technique is used with great success in human medicine. STUDY DESIGN: Four CKCS diagnosed by Magnetic resonance imaging (MRI) of SHM because of cerebellar tonsil herniation and not responsive to medical therapy underwent a suboccipital craniectomy and dorsal laminectomy of C1 (2 dogs) and of C1 and partial C2 (2 dogs) with durotomy and placement of a dural graft. Three dogs were evaluated neurologically 24 hours, 1 month, and 3 months postoperatively and evaluations were compared with preoperative neurological examination. Repeat MRI took place 3 months postoperatively. RESULTS: Neurological examinations showed neither improvement nor progression of clinical signs 3 months postoperatively. MRI showed no regression of syrinx size 3 months postoperatively. CONCLUSION: Improvement was not seen. Given the progressive nature of the disorder, evaluation over a longer period of time is necessary to detect if progression has stopped. Some modification to the surgical technique is needed to accomplish the same results as in human medicine. A study of a larger population is needed to attain more reliable information. CLINICAL RELEVANCE: Suboccipital craniectomy and dorsal laminectomy of C1 with durotomy and placement of a dural graft is a feasible technique in CKCS, but needs some modification to accomplish the same results as in human medicine.     

Radiography,Computed Tomography and Magnetic Resonance Imaging of Craniofacial Structures in Pig

The pig has recently become popular as a large animal experimental model in many fields of biomedical research. The aim of this study is to evaluate the basic anatomical structures in the head region of the pig to lay the groundwork for its practical clinical usage or pre‐clinical research in the future. We used three different diagnostic imaging methods: radiography, computed tomography (CT) and magnetic resonance imaging (MRI). The analysis showed that radiographic imaging is suitable only for general evaluation of the facial area of the pig skull. CT images showed excellent spatial definition of bony structures of the whole craniofacial area, and MRI images revealed fine soft tissue details. Radiography is preferentially suited to general assessment of bone structures of the facial skeleton; however, the thick layer of adipose tissue in the craniofacial region of the pig makes the imaging of some parts difficult or even impossible. CT is useful for revealing morphological details of mineralized tissues, whereas MRI is more suitable for soft tissue analysis and the detection of subtle pathologic changes in both bone and soft tissues. Therefore, before using pigs as an experimental model in craniofacial research, it is necessary to evaluate the suitability and disadvantages of potential imaging methods and how appropriate they are for accurate visualization of desired structures.     

Auscultation in mild mitral regurgitation in dogs: observer variation, effects of physical maneuvers, and agreement with color Doppler echocardiography and phonocardiography

Observer variation in diagnosing mild mitral regurgitation in dogs by cardiac auscultation was assessed by having 6 veterinarians with different levels of experience examine 57 Cavalier King Charles Spaniels. Comparisons with color Doppler echocardiography and phonocardiography were made, and the effects of 2 physical maneuvers on the auscultatory findings were evaluated. Using mildly diseased dogs, interobserver agreement in diagnosing the presence or absence of left-sided murmurs ranged from 63% to 88%. The agreement with phonocardiography (range, 53-91%) increased with the amount of observer experience. The 2 most experienced observers could discern soft ejection murmurs from regurgitant murmurs and were able to diagnose 89% of the dogs with regurgitant jets larger than 30% of the left atrial area. In general, less experienced observers diagnosed most jets larger than 50%. In many dogs with small jets, no murmur was found by auscultation and phonocardiography. The audibility of mild regurgitation was significantly reduced in dogs that were difficult to auscultate. Early systolic murmurs were typical of mild regurgitation, whereas holosystolic murmurs typified severe regurgitation. In a few dogs, late systolic murmurs alternated with holosystolic murmurs. Systolic clicks were found phonocardiographically in 18 dogs with mild to moderate regurgitation, but the audibility apparently was low. In many mildly affected dogs, physical maneuvers increased murmur intensity. Thus, some form of dynamic auscultation might facilitate the diagnosis of mild regurgitation. Auscultatory findings in mild regurgitation appear to depend on observer experience, circulatory status, and how difficult the dog is to auscultate.     

Computed Tomography and Magnetic Resonance Imaging of an Epidermoid Cyst in a Foot of a Horse

An 18-year-old Quarter Horse mare was evaluated because of moderate left forelimb lameness of 4 weeks’ duration. The clinical evaluation and diagnostic perineural analgesia localized the lameness to the distal portion of the left forelimb. There was swelling on the dorsal and lateral aspect of the coronary band. Radiography, ultrasound, magnetic resonance imaging, and computed tomography of the foot revealed circumscribed well-capsulated soft tissue mass causing a focal deformation of the dorsolateral border of the middle phalanx. The treatment aimed to remove the mass surgically and stabilized the interphalangeal joint, but the owner elected human euthanasia before treatment attempt. Histopathology diagnosis was an epidermoid cyst, which was characterized by multilayers of keratin surrounded by stratified squamous epithelium. Although rare, an epidermoid cyst should be considered as a differential diagnosis for space-occupying mass in horses’ foot that develops chronic lameness after trauma. This report describes the multimodality appearance of the epidermoid cyst.     

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.     

Agreement and Repeatability of Linear Vertebral Body and Canal Measurements Using Computed Tomography (CT) and Low Field Magnetic Resonance Imaging (MRI)

Objective— To evaluate agreement and repeatability of vertebral column measurements using computed tomography (CT) and magnetic resonance imaging (MRI).
Study Design— Retrospective observational study.
Animals— Dogs (n=18) with disc associated wobbler syndrome; Dog cadavers (n=3).
Methods— Five measurements of the 5th cervical vertebra were performed: vertebral body length (VBL), vertebral canal height (VCH), vertebral body height (VBH), vertebral canal width (VCW), and vertebral body width (VBW). Measurements were performed independently twice by 2 observers. Bland-Altman plots were created to evaluate agreement. Cadaveric vertebrae with soft tissue removed had the same variables and actual dimensions measured.
Results— The largest discrepancy between CT and MRI measurement was for VBL (mean difference±SD=1.262 mm±1.245; P <.001), with the difference for all the other variables being acceptable. The 1st measurement was significantly higher than the 2nd only for VBL using CT (mean difference=0.476 mm±1.120; P =.009), with all other variables having acceptable differences. Mean difference for all measurements between 2 observers was small, except for VBL using CT (mean difference=0.762 mm±1.042; P <.001). Only the difference for VBL between CT and cadaver specimens was statistically significant.
Conclusions— Our results suggest high repeatability and good agreement for most vertebral measurements of interest. VBL measurement using CT was considered problematic.
Clinical Relevance— Provided limitations are understood, linear measurements of vertebral dimensions from CT and MRI images can be used clinically.     

Computed Tomography of the Prostate Gland in Healthy Intact Dogs and Dogs with Benign Prostatic Hyperplasia

To date, there is only scarce data on the evaluation of the prostate gland in dogs using computed tomography (CT). The aims of our study were to describe CT features of BPH in dogs and to determine the size of the prostate gland in healthy male dogs and dogs with benign prostatic hyperplasia (BPH) through CT. Additionally, we aimed to compare and establish the most useful parameters for CT measurements of the prostate in patients with BPH. The study population consisted of 20 healthy intact male dogs and 20 male intact dogs with confirmed BPH. Pre‐ and post‐contrast CT studies were evaluated. The most common CT features in dogs with recognized BPH were symmetrical prostatomegaly and heterogeneity of the prostatic parenchyma. The mean prostatic density (D) was 56HU (±4.39) in pre‐contrast CT images and 84HU (±8) in post‐contrast images in dogs with BPH. The mean prostatic length (L) was 43.87 mm (±11), the mean width (W) amounted to 48.95 mm (±8.76) and the mean height (H) reached 44.9 mm (±9.48) in clinically affected patients. The mean ratios were: rL ? 2,12 (±0.5); rW ? 2.39 (±0.53) and rH ? 2.16 (±0.39) in the BPH group. The prostate should be considered to be enlarged when rL exceeds 3.05; rW exceeds 3.38 and rH exceeds 2.94. Our findings indicated that CT is a useful tool in diagnosing prostate disorders, including BPH. The heterogeneity, density and ratios of prostatic length, width and height can be useful parameters in the diagnosis of BPH.     

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.