Intracranial Ring Enhancing Lesions in Dogs: A Correlative Ct Scanning and Neuropathologic Study

Abstract

This retrospective analysis of 15 dogs with postcontrast ring enhancing brain lesions, each detected by a single Computed Tomography [CT] examination, searched for any association between their CT appearance and the pathologic diagnosis. In a subgroup of these dogs [n = 7] necropsied within 2 days of the last CT scan, we evaluated whether there was any anatomic correlation between the ring zone and the histopathologic features of the lesions. Our study consisted of eight dogs with primary brain tumors [3 meningiomas, 3 astrocytomas, 1 mixed glioma, 1 oligodendroglioma], 4 with metastatic brain tumors [2 fibrosarcomas, 1 mammary carcinoma, 1 melanoma] and 3 with non‐neoplastic brain lesions [2 intraparenchymal hemorrhages, 1 pyogranulomatous meningoencephalitis]. The overall size and shape of the contrast enhancing CT lesions, as well as the thickness, surface texture and degree of enhancement of the ring were subjectively evaluated. No association was found between the CT lesion characteristics and the pathologic diagnosis. In the sub‐group of dogs euthanatized within 2 days of the CT examination, distinct histologic features which anatomically correlated with the zone of ring enhancement were found in 3 of 7 lesions. The findings of this study are consistent with those of ring‐enhancing lesions in people, and indicates that CT ring enhancement is a non‐specific phenomenon which can occur in a variety of neoplastic and non‐neoplastic lesions in the dog.

Contrast Media Enhancement of Intracranial Lesions in Magnetic Resonance Imaging Does Not Reflect Histopathologic Findings Consistently

“…Here the central area was nonenhancing, although both peripheral and central areas were consisted solely of neoplastic cells and neither necrosis/cavitation nor hemorrhage was observed in the center. These findings challenge the view that the nonenhancing center of a ring‐enhancing lesion is necrotic, cystic, or hemorrhagic . Perhaps, the addition of perfusion and diffusion sequences in the analysis would explain some of the paradoxical findings, at least in lesions with viable tissue but without contrast enhancement.…”

“…The presence and patterns of enhancement may improve lesion detection and obtaining a final diagnosis . In some instances, the enhancement pattern might also deliver information about the type of underlying disease, such as in ring enhancement, where the nonenhancing center often consists of a necrotic, cystic, or hemorrhagic area . Consequently, certain enhancement patterns are often considered to be associated with a specific diagnosis but this is not always consistent .…”

“…[8][9][10][11] In some instances, the enhancement pattern might also deliver information about the type of underlying disease, such as in ring enhancement, where the nonenhancing center often consists of a necrotic, cystic, or hemorrhagic area. 3,6,[12][13][14][15] Consequently, certain enhancement patterns are often considered to be associated with a specific diagnosis but this is not always consistent. 12 It is unclear why a different enhancement pattern occurs within a given pathologic entity and whether contrast enhancement in intracranial lesions is determined mostly by the presence of specific tissue changes.…”

Use of Contrast-Enhanced CT in the Diagnosis of Abscesses in Cattle

“…A ring is created by a zone of blood vessels, reactive astrocytes, and fibroblasts that surround a central core of necrosis due to various causes. The ring enhancement effect thus suggests that necrosis results from either a defective blood-brain barrier in this zone and/or retention of contrast material in the abnormal vascular tissue due to loss of autoregulation [8]. In this study, the ring patterns were detected at pharyngeal and pulmonary abscesses in Case 2 and cerebellar abscess in Case 1.…”

“…The degree and pattern of enhancement are variable according to diseases [4]. A ring pattern of enhancement is detected in cases of abscess [3,5], although ring enhancement has been reported with neoplastic and non-neoplastic brain lesions in dogs as well [8]. A ring is created by a zone of blood vessels, reactive astrocytes, and fibroblasts that surround a central core of necrosis due to various causes.…”