Retrospective Review of 50 Canine Intracranial Tumors Evaluated by Magnetic Resonance Imaging

Abstract

Magnetic resonance imaging (MRI) was performed on 50 dogs with intracranial neoplasia. The following tumor features were assessed: axial origin, location, shape, growth pattern, MRI signal intensity, evidence for edema, and paramagnetic contrast enhancement. Histologic diagnoses included 5 intracranially invading nasal tumors, 7 pituitary tumors, 22 meningiomas, 6 choroid plexus tumors, 7 astrocytomas, 1 ependymoma, and 2 oligodendrogliomas. Axial origin, site, shape, and growth pattern were important diagnostic characteristics for tumor type. Signal intensity Magnetic resonance imaging (MRI) is the preferred imaging method for human beings with central nervous system disease, and it has become increasingly available and affordable for use in veterinary medicine. The MRI features of canine neurologic disease have been described, but histologic diagnoses have not been available in all instance^.'.^ In this study, MRI scans of 50 histologically diagnosed canine intracranial tumors were evaluated retrospectively to identify distinguishing characteristics. Materials and Methods Selection CriteriaDogs with clinical signs of intracranial disease were referred to Washington State University Veterinary Teaching Hospital. The dogs were evaluated using a standard diagnostic protocol as part of a phase I clinical trial for boron neutron capture therapy, which was conducted with approval from the Animal Care and Use Committee.4.' Most dogs in the study had been treated with corticosteroids at the time of imaging. All patients had a complete MRI brain scan and histologic diagnosis of intracranial tumor. Patients with potential metastatic intracranial neoplasia were not included in the study. From the Magnetic Resonance Scan ProtocolDetails of the MRI protocol have been described previously.' Briefly, MRI was performed with a 1.5 T magnet (General Electric Signa, Milwaukee, WI). Under general anesthesia, dogs were placed in sternal recumbency, and a sagittal localizer series (time of relaxation or TR = 400 msec/time to echo or TE = 20 msec) was performed to delineate subsequent transverse images. Transverse proton density-weighted images (PDWI) and TZ-weighted images (TZWI) were obtained with a multiple spin echo series at TR = 2000 msec with TE = 20 to 30 and 80 to 90 msec. Transverse and sagittal precontrast and postcontrast T1-weighted images (T1 WI) were performed using TR = 800 msec and TE = 20 msec. Three to 5 mm slices with an interslice gap of 0 to 1.5 mm were obtained from the foramen magnum rostrally through the cribriform plate.

Exclusion of a Brain Lesion: Is Intravenous Contrast Administration Required after Normal Precontrast Magnetic Resonance Imaging?

“…In both human and veterinary medicine, the pattern of contrast enhancement has been used to evaluate tumor type,4, 5 predict seizure risk in cases of intracranial neoplasia,31 and differentiate neoplastic from non‐neoplastic lesions, such as postoperative scar tissue, irradiation injury, inflammation or cerebrovascular lesions 3, 32, 33. However, contrast enhancement patterns do not consistently reflect the histologic features of an intracranial lesion, with no association between MR images and histologic findings in approximately 25% of cases in 1 veterinary study 34…”

“…The findings observed on postcontrast sequences may assist in the further characterization of a brain lesion observed on precontrast sequences 3, 4, 5. However, the routine administration of gadolinium‐based contrast media has been questioned for human patients, especially if no lesion is observed on precontrast sequences 6.…”

Advances in Diagnostic and Treatment Modalities for Intracranial Tumors

“…Although many investigators have attempted to utilize a variety of imaging techniques to diagnose, and even grade, intracranial lesions in dogs, specificity, sensitivity, or both have been shown to be consistently suboptimal in numerous studies,12, 15, 16, 36, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56 particularly when applied to clinically relevant prospective random populations of patients. A majority of intracranial tumors in both dogs and cats are hypo‐ to isointense on T1‐weighted imaging, and hyperintense on T2‐weighted imaging.…”

“…A majority of intracranial tumors in both dogs and cats are hypo‐ to isointense on T1‐weighted imaging, and hyperintense on T2‐weighted imaging. The majority are also contrast enhancing after administration of gadolinium‐based contrast agents 12, 15, 16, 21, 54, 55. A variety of tumor “specific” findings relating to MRI have been reported variably in several studies, some of which are listed below.…”

Neoplasmas envolvendo o sistema nervoso central de cães: 26 casos (2003-2011)

“…Vários estudos retrospectivos internacionais vêm relatando os sinais clínicos, o diagnóstico, o tratamento e a prevalência dos neoplasmas no SNC de cães (Kraft et al 1997, Heidner et al 1991, Axlund et al 2002, Bley et al 2005, Dickinson et al 2006, Snyder et al 2006, Petersen et al 2008, Snyder et al 2008. No Brasil, entretanto, quase não há estudos acerca do tema.…”