Intraparenchymal extravasation of gadolinium mimicking an enhancing brain tumor

Abstract

Gadolinium (Gd)-enhanced magnetic resonance imaging plays an essential role in the detection, characterization, and staging of intracranial neoplasms and vascular abnormalities. Although Gd is helpful in a majority of situations, it can lead to diagnostic misinterpretation in the setting of active vascular extravasation. Scarce reports of intracranial extravasation of Gd are present in the literature. Here, we report the first case of surgically proven spontaneous intraparenchymal extravasation of Gd mimicking an enhancing intra-axial neoplasm in a pediatric patient. Early and accurate recognition of Gd extravasation is critical in obtaining the accurate diagnosis and triaging patients expeditiously into proper avenues of care.

Introduction

Gadolinium (Gd) enhanced magnetic resonance imaging (MRI) plays an essential role in the detection, characterization, and staging of intracranial neoplasms and vascular abnormalities. Although Gd is helpful in the majority of situations, it can lead to diagnostic misinterpretation in the setting of active vascular extravasation. Scarce reports of intracranial extravasation of Gd are present in the literature.^1–4 However, these publications focus on adults, with contrast extravasation in known or suspected hemorrhages, typically in the postsurgical/post-procedural setting. Here, we report the first case of surgically proven intraparenchymal extravasation of Gd mimicking an enhancing intra-axial neoplasm in a pediatric patient.

Case report

A previously healthy nine-month-old male presented to the emergency department with one day of lethargy and decreased movement of his right arm. Given these clinical symptoms, a non-contrast head computed tomography (CT) scan was performed for further evaluation. The head CT showed a large space-occupying lesion centered in the left insula, with internal heterogeneously attenuating blood products and surrounding vasogenic edema (Figure 1). CT angiography (CTA) of the head was subsequently performed, which demonstrated a small focus of arterial-phase contrast enhancement along the lateral aspect of the lesion, which appeared to be discontinuous from surrounding normal-appearing vessels (Figure 2).

Figure 1.

Axial non-contrast head computed tomography (CT) through the level of the basal ganglia shows a large mass-occupying lesion with associated vasogenic edema centered on the left insula containing heterogeneously attenuating blood products. The mass results in local mass effect with effacement of the left lateral ventricle.

Figure 2.

Coronal CT angiography maximum intensity projection of the head demonstrates a small focus of arterial-phase contrast enhancement, the so-called angiographic spot-sign (straight arrow), along the lateral aspect of the lesion (asterisk), which appears to be discontinuous from surrounding normal-appearing vessels (curved arrow).

MRI with and without Gd contrast, which was obtained for further characterization of this mass-like lesion, showed a T1-hypointense and T2-isointense lesion centered on the left insular lobe, with internal locules of blood at various stages of evolution (Figure 3). On the contrast-enhanced T1-weighted images, the lesion demonstrated heterogeneous and avid enhancement, which appeared to be centered in its lateral aspect, near the focus of contrast enhancement on the CTA (Figure 3). There was extensive signal loss involving nearly the entire lesion on the susceptibility-weighted images (Figure 4). Additional smaller foci of susceptibility artifact were seen in the bilateral posterior parietal lobes, as well as adjacent to the lesion in the left insular cortex (Figure 4). A small linear structure with deep susceptibility artifact was also seen adjacent to the dominant mass. Given the presence of blood products and avid enhancement associated with this lesion, there was concern for an aggressive underlying neoplasm.

Figure 3.

Axial T2 FLAIR (a), T2 (b), T1 (c), and post-contrast fat-saturated T1 weighted (d) images show a predominantly T1-hypointense and T2-isointense lesion centered on the left insular lobe, with internal locules of blood at various stages of evolution (arrows). On the contrast-enhanced T1-weighted image, the lesion demonstrates heterogeneous and avid enhancement, which is most prominent in its lateral aspect (curved arrow), in the region where the focus of arterial-phase contrast enhancement was seen on the CTA (Figure 2).

Figure 4.

Axial SWAN images (a–c) demonstrate extensive susceptibility artifact involving nearly the entire lesion. Additional smaller foci of susceptibility artifact are seen in the bilateral posterior parietal lobes (arrows) in (b) likely representing smaller cavernous hemangiomas. In (c), a small linear structure (curved arrow) with deep susceptibility artifact is seen adjacent to the dominant mass and likely represented a thrombosed developmental venous anomaly.

The patient was taken urgently to the operating room by the neurosurgery team for decompression and evaluation for underlying neoplasm. Intraoperatively, the lesion was found entirely to be a hematoma, without evidence of an underlying mass (Figure 5). Given the absence of an underlying neoplasm, the constellation of imaging findings suggested that the enhancement seen on the MRI was due to active vascular extravasation of gadolinium into a parenchymal hematoma rather than from enhancement of an underlying mass. Pathology specimens confirmed hemorrhage and no evidence of neoplastic cells. A four-month follow-up MRI further confirmed the absence of an underlying neoplasm (images not shown). In retrospect, the constellation of pathologic and imaging findings was most consistent with multiple cavernous malformations, with an associated thrombosed developmental venous anomaly adjacent to the large bleeding and obliterated malformation.

Figure 5.

Intraoperative photograph shows a congealed hematoma (arrow) being suctioned out through a corticectomy in the inferior frontal lobe immediately superior to the Sylvian fissure. During surgery, the lesion was found entirely to be a hematoma, without evidence of an underlying mass.

Discussion

Abnormal intracranial enhancement is a result of the breakdown and altered permeability of the blood–brain barrier. This can occur from a wide variety of disease processes, including intracranial neoplasms, vascular abnormalities, infections, demyelinating lesions, and ischemia. Many of these pathologic entities can be readily diagnosed using a variety of imaging modalities, including CT, MRI, and various angiographic techniques. However, when vascular extravasation of contrast material is present, as in the case presented, it can potentially obscure the underlying diagnosis if not appropriately identified. In the present case, spontaneous extravasation of Gd into a large cavernous malformation was observed, mimicking an intra-axial neoplasm. This is the first reported case of intracranial Gd extravasation mimicking an enhancing brain tumor in the pediatric literature to our knowledge.

Intracranial extravasation of Gd is a rare event, with only limited case reports present in the literature. However, these cases have been entirely described in the adult population. For example, two previous case reports discuss extravasation of Gd into subdural or subarachnoid spaces in adults in the post-procedural/postsurgical setting.^1,2 Other reports have discussed active extravasation into intraparenchymal hematomas, mostly adult hypertensive hemorrhages.^3,4 These cases, whether they are in the post-procedural/postsurgical setting or in adults with intracranial hemorrhages, typically pose less of a diagnostic dilemma for radiologists. However, in comparison to adults where primary brain tumors are less common, contrast enhancement in a pediatric patient is particularly suspicious for an underlying primary neoplasm.

In the pediatric population, intracranial hemorrhage is commonly associated with underlying vascular lesions such as arteriovenous malformations, arteriovenous fistulas, and cavernous malformations. However, because brain and other central nervous system tumors are the most common cancer site in pediatrics, when a child presents with intracranial hemorrhage, there is typically high clinical suspicion for an underlying neoplasm, particularly when there is associated contrast enhancement. Furthermore, a large parenchymal hematoma may obscure the underlying lesion itself, making the diagnosis challenging on initial presentation. In these cases, maintaining a high index of suspicion is necessary for an appropriate diagnostic workup.

In our patient, the imaging findings were most consistent with multiple cavernous malformations in the setting of a large bleeding malformation, which mimicked a brain tumor due to internal enhancement on MRI. Cavernous malformations are angiographically occult slow-flowing vascular malformations that are made up of a collection of dilated sinusoidal vessels without intervening neural parenchyma. They are classically described on MRI as having a “popcorn ball” appearance of mixed hyper- and hypointense blood-containing locules, with a peripheral hemosiderin rim and extensive blooming artifact on susceptibility-weighted images. Notably, these lesions do not typically enhance, as there is minimal intervening tissue and extremely slow blood flow into the lesion. If enhancement is seen within a suspected cavernous malformation, alternative diagnoses should be entertained.

The imaging features in this case were atypical for a cavernous malformation, given the lack of classic imaging findings, such as the “popcorn” appearance and hemosiderin rim, as well as the unexpected presence of avid internal enhancement.⁵ However, a subtle finding on the CTA may have foreshadowed the enhancement pattern that followed on the MRI: the so-called CT angiographic spot sign. The spot sign has been shown to be highly predictive of hematoma expansion and is suggestive of active vascular extravasation.⁶ Therefore, when encountered, suspicion for possible intraparenchymal Gd extravasation should be heightened on follow-up MRIs.

Although findings may be subtle, early and accurate recognition of active Gd extravasation is critical in avoiding delays in treatment and decreasing morbidity and mortality. Whereas intracranial hemorrhages without signs of contrast extravasation or increased intracranial pressure may be managed conservatively, lesions with active extravasation typically require conventional microsurgical interventions for definitive management and stabilization. Because an underlying lesion may be obscured by hemorrhage and mass effect, obtaining an MRI after the acute phase is necessary to detect an underlying neoplasm or vascular malformation better. In the setting of hemorrhagic cavernous malformations not amenable to surgery, it is recommended that patients be followed with an annual MRI to assess for stability.⁵ However, routine follow-up for cavernous malformations, particularly incidentally discovered cavernous malformations, is not well established and is dependent on local practice standards.⁷

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.