SYRINGOMYELYA SECONDARY TO BRAIN MASSES IN 19 DOGS; CLINICAL AND MAGNETIC RESONANCE IMAGING FINDINGS

SYRINGOMYELYA SECONDARY TO BRAIN MASSES IN 19 DOGS; CLINICAL AND MAGNETIC RESONANCE IMAGING FINDINGS
S. Ródenas1,2,3, C. de la Fuente1, K. Marioni‐Henry3, S. Añor1, J Ezquerra4, J.R.E. del Castillo2

1Departament de Medicina i Cirurgia Animal. Facultat de Veterinària. Universitat Autònoma de Barcelona, Bellaterra, Spain2Faculté de Médicine Vétérinaire, Université de Montréal, Quebec, Canada.3Southern Counties Veterinary Specialists4Facultad de Veterinaria de Caceres, UEX.

Syringomyelia (SM) associated with posterior fossa tumours has a reported incidence of 5‐21% in people, with only sporadic reports of SM associated with supratentorial masses. In veterinary medicine, only 4 single case reports of SM secondary to intracranial masses in dogs have been published. In both, humans and dogs with SM secondary to brain masses, clinical signs associated solely with SM are uncommonly reported.

The purpose of this study was to describe the magnetic resonance imaging (MRI) and clinical findings in a population of dogs with SM associated with brain masses. Medical records from 4 institutions were retrospectively reviewed from 2006‐2012, and 19 affected dogs were identified. Medical records of 22 dogs with brain masses and no SM were used as controls. We hypothesized that: (1) cerebellar vermis herniation predisposes to the development of SM, (2) size and localization of the brain mass, severity of edema, presence of hydrocephalus and mass effect predispose to the development of foramen magnum (FM) herniation and SM, and (3) size of the syrinx predisposes to the development of symptomatic SM. The following MRI features were assessed: presence of FM and caudal transtentorial (CTT) herniation, location of the mass, skull and mass volume, edema, mass effect and hydrocephalus. Clinical signs were scored as: (0) clinical signs referable to brain alone, (1) predominance of brain signs versus spinal cord signs (2) predominance of spinal cord signs, and (3) spinal cord signs alone. An exploratory analysis was performed to identify potential risk factors and stepwise multivariate logistic regressions were performed to confirm the variables that contributed to the risk of the positives outcomes. Foramen magnum herniation was present in 78% of dogs in the SM group and in 22% of dogs in the control group. Dogs with FM herniation had significantly increased odds of SM (odds ratio (OR=16.093, 95% C.I. = [2.690, 96.262]) and dogs with dilated 3rd ventricle had increased odds of SM (OR = 20.872, 95% C.I. = [1.556, 279.90]). Presence of CTT herniation increased the odds of FM herniation (OR = 11.225, 95% C.I. = [2.066, 60.992]). There was no association between mass location and development of SM (cranial rostral fossa, 52.3%; CCF, 47.3% of dogs with SM). Presence of moderate to severe mass effect was associated with decreased odds of spinal cord signs (OR = 0.114, 95% C.I. = [0.010, 1.356]). This study showed that the main risk factor for developing SM secondary to a brain mass is the presence of FM herniation. Presence of a dilated 3rd ventricle was also associated with development of SM in dogs with brain masses. Finally, development of SM appeared to be independent of the mass location within cranial or caudal fossa.