Cerebrospinal Fluid Drop Metastases of Canine Glioma: Magnetic Resonance Imaging Classification

Abstract

Dissemination of glioma in humans can occur as leptomeningeal nodules, diffuse leptomeningeal lesions, or ependymal lesions. Cerebrospinal fluid (CSF) drop metastasis of glioma is not well-recognized in dogs. Ten dogs with at least two anatomically distinct and histologically confirmed foci of glioma were included in this study. The 10 dogs underwent 28 magnetic resonance imaging (MRI) examinations, with distant CSF drop metastasis revealed in 13 MRIs. The CSF drop metastases appeared as leptomeningeal nodules in four dogs, diffuse leptomeningeal lesions in six dogs, and ependymal lesions in seven dogs; six dogs had a combination of lesion types. Primary tumors were generally T2-heterogeneous and contrast-enhancing. Many metastases were T2-homogeneous and non-enhancing. Diffuse leptomeningeal lesions were seen as widespread extra-axial contrast-enhancement, again very dissimilar to the intra-axial primary mass. Primary masses were rostrotentorial, whereas metastases generally occurred in the direction of CSF flow, in ventricles, CSF cisterns, and the central canal or leptomeninges of the cervical or thoracolumbar spinal cord. Seven of the dogs had received therapy limited to the primary mass, such as surgery or stereotactic radiation, then developed metastasis in the following months. CSF drop metastasis of glioma may take a very different appearance on MRI to the primary mass, including periventricular lesions that are more homogeneous and less contrast-enhancing, rostral horn signal changes, or leptomeningeal enhancement ventral to the brainstem or encircling the spinal cord.

Cranial Spinal Spreading of Canine Brain Gliomas after Hypofractionated Volumetric-Modulated Arc Radiotherapy and Concomitant Temozolomide Chemotherapy: A Four-Case Report

“…In addition, also in the work of Bentley et al [ 30 ], one dog received radiotherapy treatment with a nominal BED of 66.2 Gy (50 Gy in 20 fractions) similar to those prescribed in the present work while other dogs received stereotactic radiotherapy with doses in the range of 15–24 Gy with 1–3 fractions but none of them received combination radiotherapy and chemotherapy as a first approach.…”

“…In a recent article [ 30 ], ten dogs with histologically confirmed glioma foci were analyzed and divided into two groups: the first group (group “A”; seven dogs) presented initially with solitary lesions that subsequently metastasized. Cases in group “B” (three dogs) had multifocal lesions (primary and metastatic) at first presentation.…”

“…In all three dogs, complete necropsy revealed intracranial and spinal glioma. However, the goal of the reported retrospective multi-institutional study [ 30 ] was to describe the MRI findings of canine glioma CSF drop metastasis and categorize them according to the human classification system [ 31 ]. Based on the two canine case-reports [ 30 , 63 ], the authors of this study [ 30 ] hypothesized that the metastatic lesions would have different imaging characteristics compared to the primary tumor.…”

“…However, the goal of the reported retrospective multi-institutional study [ 30 ] was to describe the MRI findings of canine glioma CSF drop metastasis and categorize them according to the human classification system [ 31 ]. Based on the two canine case-reports [ 30 , 63 ], the authors of this study [ 30 ] hypothesized that the metastatic lesions would have different imaging characteristics compared to the primary tumor. To our knowledge, based on a regular review of the literature, there was only one clinical case by Nakamoto et al where a dog was treated with a combined radiotherapy and chemotherapy protocol [ 63 ].…”

“…In veterinary medicine, canine drop metastasis has been reported [ 28 ] but, to the best of our knowledge, only a single case-study reports systematic spinal-spread after exclusive radiation therapy of a primary intracranial mass classified histologically as a leptomeningeal oligodendroglioma [ 29 ]. Another recent paper [ 30 ] describes the MRI findings of cerebrospinal fluid (CSF) drop metastasis due to canine gliomas according to the human classification system [ 31 ].…”