Computed tomography and magnetic resonance findings in two dogs and a cat with intracranial lesions

Magnetic resonance imaging diagnosis of brain tumors in dogs

A great deal of information is now available regarding the range of magnetic resonance imaging (MRI) features of many primary and secondary brain tumors from dogs. In this review, these canine neoplasms are grouped into meningeal masses, ventricular masses, intra-axial enhancing lesions, intra-axial mildly to non-enhancing lesions, and multifocal lesions. For each of these patterns, the major and sporadic neoplastic differential diagnoses are provided, and guidance on how to rank differential diagnoses for each individual patient is presented. The implication of MRI features such as contrast-enhancement, signal intensities and location is discussed. However, the information garnered from MRI must be correlated with all available clinical information and with epidemiological data before creating a differential diagnosis.

Linfoma primário de células T no líquido cefalorraquidiano de cão: relato de caso

Relata-se o diagnóstico de linfoma primário no sistema nervoso central em um cão Labrador Retrievier, de 10 anos de idade, que apresentava episódios convulsivos, incoordenação nos membros posteriores, head tilt, ataxia e sensibilidade diminuída no lado esquerdo. Constataram-se alterações laterais esquerdas, como ausências de propriocepção e de posicionamento tátil, alterações posteriores nas provas de carrinho de mão e de reação ao pulo e diminuição da extensão da postura e hemilocomoção. No líquido cefalorraquidiano (LCR), houve predomínio de linfócitos atípicos, caracterizados pela presença de anisocitose e anisocariose, nucléolos evidentes e anisonucleose, basofilia e microvacuolização citoplasmáticas, mitoses atípicas e corpúsculos linfoglandulares, compatíveis com linfoma, confirmado pelo exame histológico e imunocitoquímico, o qual revelou origem T, com expressão CD3+ e CD79-. A tomografia computadorizada não foi conclusiva e evidenciou diversas áreas hipodensas e intensificação de contraste na região de sulcos e giros do parênquima encefálico. A coleta do LCR foi essencial na rapidez do diagnóstico definitivo, indicando a natureza rara desta lesão primária.

Clinical signs, magnetic resonance imaging findings and outcome in 77 cats with vestibular disease: a retrospective study

Medical records of 77 cats that had clinical signs of vestibular disease and magnetic resonance imaging (MRI) of the head were reviewed retrospectively. The aetiological, clinical and MRI characteristics were described and evaluated for a relationship with patient outcome. Forty cats (52%) had signs of central vestibular dysfunction (CVD), which was part of a multifocal disease in 17 cats (43%). The most frequent causes of CVD were inflammatory conditions (18 cats; 45%), including bacterial inflammation as an intracranial extension of otitis interna (five cats; 13%), feline infectious peritonitis (three cats; 8%) and toxoplasmosis (two cats; 5%). Neoplasia (12 cats; 30%) and vascular disease (four cats; 10%) were respectively the second and the third most frequent causes of CVD. Thiamine deficiency was diagnosed in one cat based on MRI findings and improvement following vitamin B(1) supplementation. Of 37 cats (48%) with peripheral vestibular dysfunction (PVD), idiopathic vestibular syndrome (IVS) was suspected in 16 (43%) and otitis media/interna was suspected in 16 (43%). Within the group of cats with evident MRI lesions, the location of the imaged lesions agreed with the clinical classification of vestibular dysfunction in 52/55 (95%) cats. Most of the cats (nine cases; 56%) with presumed IVS had rapid and complete recovery of their clinical signs. As most of these cats presented with progressive clinical signs over 3 weeks they were classified as having 'atypical' IVS to differentiate them from cats with the typical non-progressive IVS. No underlying systemic diseases were documented in any of these cases. Statistically significant predictors of survival included neurolocalisation (central or peripheral vestibular system), age and gender. No difference in survival was observed between cats with presumed idiopathic peripheral syndrome and cats with otitis media/interna.

Computed tomography and cross-sectional anatomy of the brain in clinically normal dogs

OBJECTIVE

To provide a detailed anatomic description of brain structures in clinically normal dogs by means of computed tomography (CT).

ANIMALS

4 clinically normal adult German Shepherd Dogs weighing 30 to 35 kg.

PROCEDURE

Each dog was anesthetized and positioned in ventral recumbency for CT examination of the brain; transverse scans were completed at 2-mm intervals from the cribriform plate of the ethmoid bone to the cranial part of the atlas by use of a third-generation CT scanner. Contrast material was injected IV, and a second series of scans was completed. Images (with or without contrast) from all dogs were reviewed by use of a soft tissue setting (window width, 150 Hounsfield units; window level, 50 Hounsfield units). One of the dogs was euthanatized, and a 3.5% formaldehyde solution was perfused via the common carotid arteries. After fixation, the brain was embedded in gelatin and sectioned into 5-mm-thick transverse sections by use of a stainless-steel knife. Anatomic sections were photographed and compared with the corresponding CT views.

RESULTS

Most features of the brain that were identified on anatomic sections could be identified on the corresponding CT scans despite the low contrast between structures, particularly if adjacent bony and soft tissue structures were used as landmarks. Additional anatomic structures surrounding the brain were also identifiable on the CT images.

CONCLUSIONS AND CLINICAL RELEVANCE

Images obtained in this study could be used as a guide for evaluation of CT images of the brain in dogs with brain diseases.

Thick-section reformatting of thinly collimated computed tomography for reduction of skull-base-related artifacts in dogs and horses

Computed tomography (CT) of the caudal fossa of 10 canine and nine equine cadaver heads was performed with conventional slice widths of 5 and 10 mm, respectively, and with thin collimations of 1 and 2 mm, respectively. Reformatting of thinly collimated slices was done by addition of thinly collimated slices to section thicknesses of 5 and 10 mm, respectively. Seventy-six pairs of conventional and reformatted images of identical anatomic locations were evaluated for magnitude of skull-base-related artifacts and image noise. A film-based subjective evaluation of artifact and noise was performed by four radiologists on a five-point score system. There was a statistically significant reduction of artifacts of canine and equine heads by 33% and 50%, respectively, on reformatted images compared with conventional ones but no difference in image noise. On objective artifact assessment based on the magnitude of standard deviation of attenuation values in the interpetrosal region, there was a statistically significant reduction of artifacts of canine and equine heads by 23% and 39%, respectively, on reformatted images. Thick-section reformatting significantly improves image quality of CT scans of the caudal fossa in dogs and horses.

Usefulness of MRI Compared with CT for Diagnosis of Mesenteric Lymphoma in a Dog

We evaluated the usefulness of MRI and compared it with CT for diagnosis of mesenteric lymphoma in a dog. The results in the plain CT, dynamic CT and plain MR (T1WI and T2WI) images suggested that the mass was a large single nodular lesion with abundant blood perfusion. On enhanced MRI(T1WI) , the mass was depicted as a tumor with adhesion to the gut wall. Exploratory laparotomy confirmed the mass was consistent with the findings on enhanced MRI. We think that MRI might be a useful imaging tool for diagnosis of canine mesenteric lymphoma.

Results of magnetic resonance imaging in dogs with vestibular disorders: 85 cases (1996-1999)

OBJECTIVE

To determine results of magnetic resonance (MR) imaging in dogs with vestibular disorders (VD) and correlate results of MR imaging with clinical findings.

DESIGN

Retrospective study.

ANIMALS

85 dogs.

PROCEDURE

Information on signalment, clinical signs, and presumptive lesion location was obtained from the medical records, and MR images were reviewed.

RESULTS

27 dogs had peripheral VD, 37 had central VD, and 21 had paradoxical VD. Of the 27 dogs with peripheral VD, 11 (41%) had MR imaging abnormalities involving the ipsilateral tympanic bulla compatible with otitis media (6 also had abnormalities involving the petrous portion of the ipsilateral temporal bone compatible with otitis interna), 7 (26%) had MR imaging abnormalities compatible with middle ear neoplasia, 2(7%) had an ipsilateral cerebellopontine angle lesion, and 7 (26%) did not have MR imaging abnormalities. All dogs with central and paradoxical VD had abnormalities evident on MR images. Of the 37 dogs with central VD, 13 (35%) had an extra-axial lesion, 6 (16%) had an intra-axial lesion, and 18 (49%) had multiple intra-axial lesions. In 23 (62%) dogs with central VD, lesions on MR images corresponded with location suspected on the basis of clinical signs. Of the 21 dogs with paradoxical VD, 12 (57%) had an extra-axial lesion, 5 (24%) had an intra-axial lesion, and 4 (19%) had multiple intra-axial lesions. Location of lesions on MR images agreed with location suspected on the basis of clinical signs in 19 (90%) dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that MR imaging may be helpful in the diagnosis and treatment of VD in dogs.

Contrast enhancement in magnetic resonance imaging using intravenous paramagnetic contrast media: a review

Interest in magnetic resonance (MR) imaging as a major diagnostic tool in veterinary clinical medicine is increasing. Most MR studies are performed with the use of contrast enhancement via intravenous injection of paramagnetic gadolinium-containing contrast media. A vast number of publications are available regarding the use of contrast media in humans. The purpose of this paper is to assist practicing veterinary radiologists in understanding mechanisms of MR contrast enhancement. This paper reviews certain aspects of MR contrast enhancement, including physical, chemical and biologic characteristics of most common MR contrast media targeted primarily at the central nervous system (CNS). Authors also describe processes that explain changes in signal intensity on the MR images.