Browsing by Author "Heng, Hock Gan"

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    Cerebrospinal Fluid Drop Metastases of Canine Glioma: Magnetic Resonance Imaging Classification
    (Frontiers Media, 2021-05-03) Bentley, R. Timothy; Yanke, Amy B.; Miller, Margaret A.; Heng, Hock Gan; Cohen-Gadol, Aaron; Rossmeisl, John H.; Neurological Surgery, School of Medicine
    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.
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    Glioma Mimics: Magnetic Resonance Imaging Characteristics of Granulomas in Dogs
    (Frontiers, 2019-08-28) Diangelo, Lauren; Cohen-Gadol, Aaron; Heng, Hock Gan; Miller, Margaret A.; Hague, Devon W.; Rossmeisl, John H.; Bentley, R. Timothy; Neurological Surgery, School of Medicine
    Granulomas can "mimic" gliomas on magnetic resonance imaging (MRI) in human patients. The goal of this retrospective study was to report canine brain granulomas that were consistent with glioma based upon MRI, report their histologic diagnosis, and identify MRI criteria that might be useful to distinguish granuloma from glioma. Ten granulomas, initially suspected to be glioma based on MRI, were ultimately diagnosed as granulomatous meningoencephalomyelitis (n = 5), infectious granulomas (n = 3) or other meningoencephalitis (n = 2). Age was 1.6-15.0 years and two dogs were brachycephalic breeds. MRI characteristics overlapping with glioma included intra-axial, heterogeneous, T2-weighted hyperintense, T1-weighted hypointense to isointense mass lesions with contrast-enhancement. Signals on fluid attenuation inversion recovery, gradient echo and diffusion weighted imaging also matched glioma. Peri-lesional edema and mass effect were toward the high end of findings reported for glioma. MRI characteristics that would be considered unusual for glioma included dural contact (n = 4), T2-hypointensity (n = 2), concomitant meningeal-enhancement (n = 9), and minor changes in the contralateral brain (n = 2). Cerebrospinal fluid analysis revealed albuminocytological dissociation or mild pleocytosis. These cases show that granulomas can "mimic" glioma on canine brain MRI. In individual cases, certain MRI findings may help increase the index of suspicion for granuloma. Lack of pronounced cerebrospinal fluid pleocytosis does not exclude granuloma. Signalment is very useful in the suspicion of glioma, and many of these dogs with granuloma were of ages and breeds in which glioma is less commonly seen.