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Neuroradiology Case of the Week
Case 351
September 2008
Daniel Ginat, MD, MS and John P. Deveikis, MD
Clinical
Presentation: Patient is a 40-year-old female with headache and confusion.
Imaging Findings: CT angiography (Fig. 1) with volume rendering (Fig. 2) demonstrates fenestration in the proximal left M1 segment of the middle cerebral artery. Distally, the M1 and M2 segments show focal narrowing. The findings in the left M1 and the proximal M2 segment could be related to some spasm or dissection within the M1 segment. The supraclinoid internal carotid artery (ICA) contains segmental outpouchings, measuring up to 5 mm in diameter.
Cerebral arteriogram (Fig. 3) demonstrates severe spasm in the anterior and middle cerebral artery territories. As a result, the left M1 fenestration is not as clearly visualized. At least two foci of luminal widening of the left supraclinoid ICA suggest pseudoaneurysm.
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Figure 1: CT angiography, coronal reformation view. Left M1 fenestration (arrow); two foci of suspected supraclinoid internal carotid artery pseudoaneursyms (asterisk).
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| Figure 2: CT volume rendering clearly displays the fenestration (within circle). |
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| Figure 3: Left cerebral angiography also demonstrates the fenestration (arrow) and internal carotid artery pseudoaneurysms. There is severe spasm of the middle and anterior cerebral artery branches as well. |
Diagnosis: Middle Cerebral Artery Fenestration
Discussion: Fenestration of the middle cerebral artery (MCA) is uncommon, found to occur in 0.2 to 0.43% of patients who undergo cerebral angiography [1 & 2]. Fenestrations more commonly affect the posterior cerebral circulation, the basilar artery in particular, and are encountered in 0.6% of patients who undergo conventional angiography [2]. Fenestrations represent segmental arterial duplications in which each segment contains its own endothelial layer. They are considered anomalies and by themselves are usually of no clinical significance.
The main differential diagnosis for cerebral artery fenestration is aneurysm. Indeed, on axial CT angiograms, fenestrations have sometimes been mistaken for aneurysm, but this ambiguity can often be resolved using multiplanar reformats, 3D reconstructions, and conventional angiography [3]. However, fenestrations may actually predispose to cerebral aneurysm formation at an incidence rate of 3 to 7% [2 & 4]. Furthermore, fenestrations may predispose to thrombus formation and result in ischemic strokes in rare cases [4].
Other anomalies of the middle cerebral artery are rare and include accessory MCA, which arises from the ACA, MCA duplication, hypoplasia, and aplasia, anomalous MCA branch origin, single non-bifurcating MCA trunk. In contrast, normal variants, such as trifurcating MCA and early M1 division are much more common [5].
References:
- Gailloud P, Albayram S, Fasel JH, Beauchamp NJ, Murphy KJ. Angiographic and embryologic considerations in five cases of middle cerebral artery fenestration. AJNR Am J Neuroradiol. 2002 Apr;23(4):585-7. [PubMed]
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Loevner, L. Brain Imaging Case Review. Philadelphia: Mosby, 1999.
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Bharatha A, Fox AJ, Aviv RI, Symons SP. CT angiographic depiction of a supraclinoid ICA fenestration mimicking aneurysm, confirmed with catheter angiography. Surg Radiol Anat. 2007 Jun;29(4):317-21. [PubMed]
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Chen YY, Chang FC, Hu HH, Chao AC. Fenestration of the supraclinoid internal carotid artery associated with aneurysm and ischemic stroke. Surg Neurol. 2007;68 Suppl 1:S60-3; discussion S63. [PubMed]
- Osborn AG. Diagnostic Cerebral Angiography, 2nd ed., Lippincott Williams & Wilkins, New York, 1999.
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