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|LETTER TO EDITOR
|Year : 2021 | Volume
| Issue : 4 | Page : 1058-1059
Hidden in Plain Sight! Importance of SWI in MR Imaging for Diagnosis of a Developmental Venous Anomaly
Ritwik Chakrabarti1, Vivek Gupta2, Manoj Goyal3, N Khandelwal4
1 Department of Radio-Diagnosis, Postgraduate Institute of Medical Education and Research, Sector 11, Chandigarh, India
2 Paras Hospitals, Sector 22, Panchkula, Haryana, India
3 Department of Neurology, Postgraduate Institute of Medical Education and Research, Sector 11, Chandigarh, India
4 Sanjivani Diagnostics, Sector 11, Chandigarh, India
|Date of Submission||15-Nov-2017|
|Date of Decision||14-Mar-2018|
|Date of Acceptance||22-Mar-2020|
|Date of Web Publication||2-Sep-2021|
Paras Hospitals, Sector 22, Panchkula, Haryana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chakrabarti R, Gupta V, Goyal M, Khandelwal N. Hidden in Plain Sight! Importance of SWI in MR Imaging for Diagnosis of a Developmental Venous Anomaly. Neurol India 2021;69:1058-9
|How to cite this URL:|
Chakrabarti R, Gupta V, Goyal M, Khandelwal N. Hidden in Plain Sight! Importance of SWI in MR Imaging for Diagnosis of a Developmental Venous Anomaly. Neurol India [serial online] 2021 [cited 2021 Oct 22];69:1058-9. Available from: https://www.neurologyindia.com/text.asp?2021/69/4/1058/325303
Developmental venous anomalies (DVAs) represent the most common type of cerebral vascular malformations, which are considered variants of normal venous development. These are usually incidental findings. However, they can also present with focal neurological deficit, hemorrhage, epileptic seizure, and infarction. Here, we discuss a case of a developmental venous anomaly that would have gone undetected on conventional magnetic resonance (MR) sequences if susceptible weighted imaging (SWI) had not been done.
A 43-year-old female presented with one to two episodes of generalized tonic-clonic seizures (GTCS) each month for the last four months. Neurological examination was normal. Electroencephalogram (EEG) showed generalized epileptic activity. An magnetic resonance imaging (MRI) study of the brain was requisitioned to rule out any structural cause. The conventional MR sequences like T1, T2, and FLAIR showed no apparent abnormality in the brain [Figure 1]a, [Figure 1]b, [Figure 1]c. Post-contrast T1-weighted image showed small linear enhancement [arrow in [Figure 1]d], which was not enough to diagnose any specific pathology. However, on [SWI, [Figure 1]e and [Figure 1]f, a prominent venous channel was noted in the left frontal region, likely draining into the superficial middle cerebral vein, with multiple foci of blooming suggestive of a bunch of smaller draining veins, surrounding its course in deep frontal white matter. No edema or mass effect or diffusion restriction was noted. These imaging findings were classical of a developmental venous anomaly (venous angioma).
|Figure 1: Axial T1 (a), T2 (b) and FLAIR (c) images are apparently normal with no focal lesions appreciated. Post-contrast image shows a linear enhancement (d). SWI sequence (d, e) shows a prominent draining vein in the left frontal lobe surrounded by multiple foci of ‘blooming’ suggestive of DVA|
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SWI is the imaging techniqsue that uses magnetic susceptibility differences of the blood, iron, and calcium in various tissues for MRI. Paramagnetic substances like deoxyhemoglobin, hemosiderin, and ferritin, increase the magnetic field, resulting in a positive phase relative to the surrounding parenchyma appearing bright on phase images. Diamagnetic substances like calcium cause a negative phase shift appearing black on phase images.
SWI is a well established and useful sequence in the evaluation of multiple neurologic disorders like traumatic brain injury, hemorrhagic disorders involving central nervous system (CNS), various CNS vascular malformations, cerebral infarction, neoplasms, and neurodegenerative disorders with intracranial calcification or iron deposition. Recent research has also highlighted some more novel uses of SWI in routine clinical problem solving, i.e. Mishra et al. described the utility of SWI in differentiating cerebellopontine angle schwannomas from meningiomas with very high sensitivity, while Kumar et al. described a new sign ('torch fire' sign) visualized in the putamen on SWI, in hypoxic-ischemic injuries.
Developmental venous anomalies are formed by radially arranged medullary veins that converge on a transcortical or subependymal large collector vein, with a characteristic appearance often described as 'Medusa head'. Non-contrast computed tomography (NCCT) scans are usually normal. On contrast-enhanced CT (CECT) – multiple linear and/or punctate enhancing foci that converge on a well-delineated collector vein is seen. Conventional spin-echo sequences, while sensitive for detecting high flow vascular malformations, which are seen as flow voids, are less sensitive in the detection of low flow vascular malformations having slow multidirectional flow. Post-contrast T1 sequences show a stellate collection of linear enhancing structures converging on the transparenchymal or subependymal collector vein. Because of slow flow, blood deoxygenates, showing striking linear hypointensities on SWI. On digital subtraction angiography (DSA) - arterial phase is normal; venous phase shows the typical hair-like “Medusa head” appearance of dilated medullary veins with a prominent draining vein. These lesions can be missed on conventional MR sequences as the occurrence of white matter abnormalities is less common. Furthermore, these DVAs can be associated with focal neurological deficit, hemorrhage, infarction, and seizures.
In summary, vascular malformations with attenuated slow flow, like developmental venous anomalies (DVAs) can often be entirely missed with flow-dependent conventional neuroimaging techniques. Hence, although the role of SWI is well established in detecting slow-flow vascular malformations, we discussed a case where one such lesion is entirely occult in conventional sequences, being detected only with SWI and hence highlighting the importance of including the SWI sequence in routine brain imaging protocols to make this diagnosis, as SWI depends on the presence of deoxyhemoglobin and not flow for visualization of these lesions.,,
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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