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LETTER TO EDITOR
Year : 2013  |  Volume : 61  |  Issue : 6  |  Page : 697-698

Magnetic resonance angiography diagnosis of infundibula occurring at an unusual location: Source image should not be overlooked


Institute of Diagnostic and Interventional Radiology, The Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai 200233, China

Date of Submission06-Nov-2013
Date of Decision08-Nov-2013
Date of Acceptance08-Dec-2013
Date of Web Publication20-Jan-2014

Correspondence Address:
Ming-Hua Li
Institute of Diagnostic and Interventional Radiology, The Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai 200233
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.125402

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How to cite this article:
Chen H, Li MH. Magnetic resonance angiography diagnosis of infundibula occurring at an unusual location: Source image should not be overlooked. Neurol India 2013;61:697-8

How to cite this URL:
Chen H, Li MH. Magnetic resonance angiography diagnosis of infundibula occurring at an unusual location: Source image should not be overlooked. Neurol India [serial online] 2013 [cited 2019 Sep 15];61:697-8. Available from: http://www.neurologyindia.com/text.asp?2013/61/6/697/125402


Sir,

Infundibulum (IF) is funnel-shaped vascular enlargement in the origin of intracranial arteries and usually occurs at branching sites of the posterior communicating (PComA) and anterior choroidal arteries (AChA) from the internal carotid artery (ICA). We report a case of an infundibulm at ICAC4 segment which is a common site for aneurysms.

A 31-year-old woman, a diagnosed case of cerebral aneurysm at right ICAC4 segment at other facility, attended our hospital for an appropriate management. Her present symptom was transient dizziness. The lesion and the cerebral vasculature were well depicted clearly by magnetic resonance angiography (MRA) with volume rendering (VR) and maximum intensity projection reconstruction [Figure 1]. A dilated vessel was observed at the lateral side of C4 segment of right ICA and a diagnosis of cerebral aneurysm was made at first impression. However, the apex of the lesion was not as smooth as it should be but looked more like a near-rupturing or ruptured aneurysm which was not supported by the clinical status. Further review of the MRA source images [Figure 2], a small vessel arising from the aneurysm-like dilation was clearly delineated, infundibular dilation proved to the correct diagnosis.
Figure 1: Three - dimensional time - of - flight magnetic resonance angiography volume rendering (a) and maximum intensity projection (b) image showed an infundibulium at C4 segment of right internal carotid artery (arrow). The infundibulium was an out pouch of vessel origin and was hardly distinguished from an small aneurysm at this site

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Figure 2(a - d): Four continuous slices of three - dimensional time - of - flight magnetic resonance angiography source images confirmed the infundibulium as a small branching vessel originating from the out pouch was clearly delineated

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The high spatial resolution of MRA source images allows an accurate diagnosis and well depicts the relationship between parent vessel and small branching vessel with the infundibular dilation at its origin. The recognition of this variant is crucial for the follow-up and management plan. This is a rare case of IF at ICA-C4 segment where aneurysms are prone to develop and infundibulae are seldom seen.

The reported rate of IF dilation detected by angiography or at autopsy ranges from 7% to 25% respectively. [1] The ICA-C4 segment location is rare, in a prospective study all infundibulae were located at the origin of PComA or AChA. [2] While aneurysms at C4 segment of ICA are not uncommon and accounted for 16.9% of all unruptured aneurysms in patients with no prior history of subarachnoid hemorrhage. [3] Thus, it is quite possible to mistake infundibulae for aneurysms at this site. The key to the differential diagnosis is to determine the spatial relation between the IF/aneurysm: whether a branching vessel exists on the terminal side of the vessel enlargement. Digital subtraction angiography (DSA) has been the accepted "gold standard" for diagnosing intracranial vascular disease, although 2D-DSA sometimes mistakes an IF for a small aneurysm and vice versa because of its confined viewing angle or confusion with neighboring structures. However, intra-arterial DSA carries a 1% complication risk with a 0.5% rate of persistent neurologic deficit. [4],[5] Alternatively, VR three-dimensional time-of-flight MRA with 3.0 T is an ideal, non-invasive imaging examination for the identification of infundibulae and can be used as an effective approach in their diagnosis and surveillance. [2] However, one should be alert from the mistaken diagnoses of ICA infundibulae as aneurysms as has happened in this case. Difficulty in distinguishing between an aneurysm and an IF on VR-MRA alone is due to the lack of spatial resolution compared with 2D-DSA.We used a combination of source 2D-MRA images and VR-MRA for the diagnosis of IF. It provides unambiguous information for the recognition of the variant thus avoiding further invasive procedure, DSA. This patient teaches a lesion that infundibulae may even arise at unusual location and should be distinguished from aneurysms. Source image may be of great help to diagnosis.

 
  References Top

1.Ebina K, Ohkuma H, Iwabuchi T. An angiographic study of incidence and morphology of infundibular dilation of the posterior communicating artery. Neuroradiology 1986;28:23-9.  Back to cited text no. 1
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2.Sun ZK, Li YD, Li MH, Chen SW, Tan HQ. Detection of infundibula using three-dimensional time-of-flight magnetic resonance angiography with volume rendering at 3.0 Tesla compared to digital subtraction angiography. J Clin Neurosci 2011;18:504-8.  Back to cited text no. 2
[PUBMED]    
3.Unruptured intracranial aneurysms - Risk of rupture and risks of surgical intervention. International Study of Unruptured Intracranial Aneurysms Investigators. N Engl J Med 1998;339:1725-33.  Back to cited text no. 3
    
4.Cloft HJ, Joseph GJ, Dion JE. Risk of cerebral angiography in patients with subarachnoid hemorrhage, cerebral aneurysm and arteriovenous malformation: A meta-analysis. Stroke 1999;30:317-20.  Back to cited text no. 4
[PUBMED]    
5.Heiserman JE, Dean BL, Hodak JA, Flom RA, Bird CR, Drayer BP, et al. Neurologic complications of cerebral angiography. AJNR Am J Neuroradiol 1994;15:1401-7.  Back to cited text no. 5
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