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|Year : 2019 | Volume
| Issue : 5 | Page : 1331-1333
A Pericallosal Lipoma Case with Abnormal Vasculature Mimicking Arteriovenous Malformation
Mehmet Fatih Erbay1, Mehmet Tecellioglu2
1 Department of Radiology, Inonu University School of Medicine, Turgut Ozal Medicine Center, Malatya, Turkey
2 Department of Neurology, Inonu University School of Medicine, Turgut Ozal Medicine Center, Malatya, Turkey
|Date of Web Publication||19-Nov-2019|
Prof. Mehmet Fatih Erbay
Department of Radiology, Inonu University School of Medicine, Turgut Ozal Medicine Center, Malatya - 44280
Source of Support: None, Conflict of Interest: None
Pericallosal lipomas (PCLs) are rare tumors of the central nervous system. They may be associated with some parenchymal and vascular anomalies of brain. Magnetic resonance imaging is the modality of choice to assess the extent of the PCLs and possible concomitant malformations such as callosal agenesis/disgenesis. Computerized tomography angiography may be indicated to evaluate the vasculature of the lesion. We report here a case of PCL with rare features including asymptomatic callosal agenesis, bilateral choroid plexus lipomas and abnormal vasculature.
Keywords: Callosal agenesis, CTA, MRI, pericallosal lipomaKey Message: We present here a case of PCL associated with asymptomatic callosal agenesis, abnormal vasculature, and choroid plexus lipomas (CPLs) with its nonenhanced computerized tomography (CT), magnetic resonance imaging (MRI), and computerized tomography angiography (CTA) findings.
|How to cite this article:|
Erbay MF, Tecellioglu M. A Pericallosal Lipoma Case with Abnormal Vasculature Mimicking Arteriovenous Malformation. Neurol India 2019;67:1331-3
| » Case History|| |
A 29-year-old woman was referred to neurosurgery department of our institution with complaint of continuous headache for 15 days. Her neurological examination was normal. Nonenhanced cranial CT revealed a hypodense midline mass with central density of −90 to −100 HU. The mass was also covered with a shell-like periferal calcification (bracket sign). Cranial MRI revealed a hyperintense nonenhancing midline mass extending into lateral ventricles and choroid plexus on both T1 and T2 sequences. Inside the mass, moderately increased vascular flow voids were masquerading an arteriovenous malformation (AVM) and the corpus callosum was absent on sagittal T2 images. On susceptibility weighted images, the mass had a hypointense border representing fat–water interface. The high signal of the mass on T1 images was darkened on T2 fat-saturated sequence [Figure 1]. There were also enlarged veins draining into superior sagittal sinus and Galen vein on thin slice contrast-enhanced sagittal MR images. Based on the imaging findings, we made the diagnosis of tubulonodular PCL. Because the patient refused to undergo digital subtraction angiography (DSA), we performed CTA with bolus-tracking technique for further evaluation of the vasculature of the lesion. In the first steps of postprocessing, we could not see the A2 segment of the left anterior cerebral artery (ACA) and anterior communicating artery (ACom) clearly. So we thought it might be an azygos ACA variation, but right after window adjustments in three-dimensional (3D) volume rendering reconstructed images, we managed to see a very thin proximal segment of A2 and Acom. On the other hand, there was an enlarged and mildly tortuous right A2 segment passing through the center of the mass [Figure 2]. We did not detect any aneurysmal structure or AVM nidus or any early draining vein. The patient was re-examined after the detection of callosal agenesis. No neurological and psychomotor retardation was evident.
|Figure 1: (a) Hyperintense midline mass extending into lateral ventricles on axial T1 image, (b) darkened signal of the lesion on fat-saturated T2 image, (c) vascular flow voids inside and around the lesion on T2 sagittal image, (d) hypointense border of the lesion representing the fat–water interface on susceptibility weighted image|
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|Figure 2: Hypodense midline mass with periferal calcifications (bracket sign) and bilateral CPLs are seen on axial noncontrast CT image (a). Oblique and coronal 3D volume rendering reconstructed (b and c, respectively) and coronal MIP (d). CTA images show enlarged right ACA A2 segment with abnormal branches (long arrow), rudimentary left ACA A2 (short arrow). Widened draining veins are best seen on sagittal T1 contrast images (not shown here)|
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| » Discussion|| |
Intracranial lipomas (ICLs) are rare fat-containing congenital masses which account for less than 0.1% of all diagnosed brain tumors., The most common location for ICLs is pericallosal cistern and so they are termed as pericallosal lipoma (PCL) when located here. PCL may be associated with callosal anomalies such as dysgenesis or agenesis and also with several vascular abnormalities and they may rarely extend into lateral ventricles. ICLs are rare tumors which are assumed to result from persistence and abnormal differentiation of the primitive meninx during the embryological development of subarachnoid cisterns. In the literature, they are classified into two groups based on their morphologic appearance and their location relative to corpus callosum. The anteriorly located bulky masses are termed as tubulonodular PCLs, whereas the posteriorly located ones are ribbon-like masses termed as curvilinear PCLs. Due to their possible earlier embryological presentation, the tubulonodular PCLs are believed to have a higher incidence of accompanying callosal anomalies than curvilinear PCLs. The majority of the PCLs are stable masses that are encountered incidentally and often require no surgical treatment.
The corpus callosum is the largest white matter tract in the brain and is thought to play a primary role in cognitive functions and functional connectivity. Therefore, it is hypothesized that developmental anomalies of corpus callosum are strongly related to behavioral and cognitive deficits. Agenesis of the corpus callosum may be an isolated finding, but it is often seen in other central nervous system (CNS) abnormalities with clinical signs that are mostly recognized at school age. Interestingly, in our case, no additional CNS malformations were detected on cross-sectional imaging studies. Furthermore, neuropsychiatric evaluation of the patient did not reveal any neurodevelopmental and psychiatric disorder or any intellectual deficit. She was entirely asymptomatic which is a rare situation in callosal agenesis.
In nearly 20%–50% of the cases, CPLs may accompany PCLs. Our case had bilateral concomitant CPLs. During the embryonic stage, the developing choroid plexuses are attached to the primitive meninx and enter into the lateral ventricles. The abnormal persistence of the primitive meninx may rarely result in occuring CPLs together with PCLs as in our case. Owing to the fact that PCL and arterial vessel development occur during the same embryological period (8th–10th gestational weeks), a relationship has been established between these two conditions and ICLs are mostly associated with several vascular abnormalities such as aneurysm, AVM, abnormal branches, dilatation and tortuosity of feeding arteries, and abnormal draining veins. In the literature, different explanations were proposed for the frequent coexistence of ICLs and abnormal vasculature. One of them is that aneurysm may also develop due to congenital structural deficiency because they have the same malformative origin with lipomas. Another explanation is that some factors secreted by the lipoma itself may weaken the arterial wall., In our case, particularly on sagittal T2 images, multiple enlarged signal void areas mimicking an AVM were present inside and around the lipoma. DSA is the reference standard for the evaluation and characterization of brain AVMs with its unique spatial and temporal resolution. It is able to delineate the arterial supply, nidus, and venous drainage of an AVM and to evaluate hemodynamic state, such as the degree of arteriovenous shunting, which are mostly difficult to see on noninvasive imaging. Besides this, a properly timed CTA performed by bolus-tracking method can readily depict an AVM nidus and may show feeding arteries and, if sufficiently opacified, early draining veins in the arterial phase. There are also studies in the literature revealing that particularly time-resolved whole-head CTA which is also called as dynamic 3D CTA may be an alternative noninvasive method for diagnosing and further evaluation of AVMs with its superior temporal resolution compared with conventional CTA or MR angiography. Because our patient refused any invasive intervention, we performed CTA with bolus-tracking method on a 256-slice multidetector CT device and showed the enlarged right ACA A2 segment with rudimentary left A2 segment and its abnormal branches inside the mass. With the absence of any nidus, aneurysm, and early draining veins, we excluded the existence of AVM.
In conclusion, PCLs are rare incidental tumors of brain which may be associated with several vascular abnormalities. When detected, MRI is the modality of choice to assess extension of these masses and the possible concommitant developmental brain anomalies. We suggest that a properly timed CTA may be a good alternative to DSA. Furthermore, CTA is superior to MR angiography in assessing the vasculature of the mass which are covered with peripheral calcification because coarse calcification itself may deteriorate the depiction of the vasculature due to distortion of local magnetic field.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]