BRAIN MAGNETIC RESONANCE IMAGING CHARACTERISTICS IN DOGS AND CATS WITH CONGENITAL PORTOSYSTEMIC SHUNTS

Animals with a portosystemic shunt (PSS) often have neurologic abnormalities. Diagnostic imaging, including brain magnetic resonance (MR) imaging, is not performed routinely in these animals. In this study, brain MR images were obtained in 13 dogs and three cats with a PSS, and in 15 dogs and five cats that were neurologically normal and used as controls. All animals with a PSS had widened sulci. In addition, 10 out of 13 dogs with a PSS and one out of three cats with a PSS had hyperintense focal areas in the lentiform nuclei on T1-weighted (T1W) images, which did not enhance after intravenous gadolinium. Following surgical correction of the PSS, MR imaging examinations were repeated in one dog and one cat. The hyperintensity of the lentiform nuclei had decreased. This study indicates that MR imaging findings of widened sulci and hyperintensity of the lentiform nuclei on T1W images may be found in dogs and cats with a PSS.     

CLINICAL MAGNETIC RESONANCE VOLUMETRY OF THE HIPPOCAMPUS IN 58 EPILEPTIC DOGS*

Hippocampal atrophy, which is a component of hippocampal sclerosis and recognized commonly in human intractable epilepsy, is controversial in canine epilepsy. We examined the hippocampal volume in 58 epileptic dogs and 35 control dogs using magnetic resonance (MR) images, and calculated the relative hippocampal volume asymmetry of the right and left hippocampus. Subjectively, there were visible MR imaging abnormalities in seven of the 58 epileptic dogs (12%). The hippocampel volume asymmetric ratio of epileptic dogs (5.84±4.47%) was significantly greater than that of control dogs (1.62±0.88%). Using a cutoff threshold asymmetric ratio of 6% that is indicated in human epilepsy, 28 epileptic dogs (48%) were characterized as having unilateral hippocampus atrophy. The hippocampal volume asymmetry ratio cannot be used to detect bilateral atrophy. In conclusion, although less frequent than that observed in human epilepsy patients, hippocampal atrophy may occur in canine epilepsy.     

MEASUREMENT OF INTERTHALAMIC ADHESION THICKNESS AS A CRITERIA FOR BRAIN ATROPHY IN DOGS WITH AND WITHOUT COGNITIVE DYSFUNCTION (DEMENTIA)

The criteria for brain atrophy in dogs have not yet been established, because of wide variation in the morphology of the ventricles and sulci of the brain depending on the breed and size. In this study, we examined the thickness of the interthalamic adhesion in a transverse magnetic resonance image to investigate normal, to examine the correlation with age, body weight, and breed, and to assess whether measurement would be a useful indicator of brain atrophy. The animals used in this study were of various breeds and weight, and had no identifiable intracranial lesion. They were divided into two groups: a normal group (0.6-15-year-old, n = 66) and a demented aging group (12-18-year-old, n = 12). The interthalamic adhesion thickness in both T1- and T2-weighted transverse images were measured in all dogs. The interthalamic adhesion thickness in the normal and demented groups was 6.79 +/- 0.70 and 3.82 +/- 0.79 mm, respectively. The interthalamic adhesion thickness in the demented group was significantly smaller. In an analysis of the correlation of interthalamic adhesion thickness with age and weight in normal dogs, significant negative and positive correlation was recognized, respectively. However, the strength of these correlations was low. These results suggest that interthalamic adhesion thickness may be a good parameter for evaluating brain atrophy in dogs with cognitive dysfunction.