Canine intracranial gliomas: Relationship between magnetic resonance imaging criteria and tumor type and grade

Abstract

Limited information is available to assist in the ante-mortem prediction of tumor type and grade for dogs with primary brain tumors. The objective of the current study was to identify magnetic resonance imaging (MRI) criteria related to the histopathological type and grade of gliomas in dogs. A convenience sample utilizing client-owned dogs (n=31) with gliomas was used. Medical records of dogs with intracranial lesions admitted to two veterinary referral hospitals were reviewed and cases with a complete brain MRI and definitive histopathological diagnosis were retrieved for analysis. Each MRI was independently interpreted by five investigators who were provided with standardized grading instructions and remained blinded to the histopathological diagnosis. Mild to no contrast enhancement, an absence of cystic structures (single or multiple), and a tumor location other than the thalamo-capsular region were independently associated with grade II tumors compared to higher grade tumors. In comparison to oligodendrogliomas, astrocytomas were independently associated with the presence of moderate to extensive peri-tumoral edema, a lack of ventricular distortion, and an isointense or hyperintense T1W-signal. When clinical and MRI features indicate that a glioma is most likely, certain MRI criteria can be used to inform the level of suspicion for low tumor grade, particularly poor contrast enhancement. Information obtained from the MRI of such dogs can also assist in predicting an astrocytoma or an oligodendroglioma, but no single imaging characteristic allows for a particular tumor type to be ruled out.

A comparison of clinical, magnetic resonance imaging and pathological findings in dogs with gliomatosis cerebri, focusing on cases with minimal magnetic resonance imaging changes‡

“…Surface contact was characterized as absent or present and any apparent contact of T2‐hyperintensity with the meninges was considered surface contact. If any portion of a lesion involved the internal capsule, thalamus or brainstem, that lesion was considered deep. Absence or presence of cystic structures was recorded.…”

“…If any portion of a lesion involved the internal capsule, thalamus or brainstem, that lesion was considered deep. Absence or presence of cystic structures was recorded.…”

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 variety of tumor “specific” findings relating to MRI have been reported variably in several studies, some of which are listed below. Peritumoral hyperintensity (edema) on T2‐weighted images is a relatively common finding and has been suggested to be more common in astrocytomas as compared to oligodendrogliomas and in rostrotentorial as compared to infratentorial meningiomas 15, 52. Edema also has been reported to be particularly severe in relatively rare intracranial granular cell tumors 57.…”

Thermal Therapy Approaches for Treatment of Brain Tumors in Animals and Humans

“…20 Presumptive diagnosis and treatment may rather be based on the appearance of the tumor on computed tomography (CT) or MRI images. 17,18,30 …”