Giant serpentine middle cerebral artery aneurysm

Case contributed by Peter Mitchell
Diagnosis certain


Headache, facial dysaethesia for 3 days. Hypertension.

Patient Data

Age: 65 years
Gender: Male

A mass lesion of heterogeneous density lies in the left sylvian fissure, with a vividlyenhancing serpentine channel shown on the post contrast images.

A thrombosed mixed fusiform/saccular giant aneurysm, measuring up to 4 x 5.2 cm, is centered within the left Sylvian fissure, splaying the major left MCA branches.

The inferior irregular non-thrombosed portion of the aneurysm, measuring 10 mm diameter, arises from a posterior branch of the left MCA M2 segment.

This communicates directly with a 5 mm diameter serpiginous channel, which winds through the thrombosed body of the aneurysm to terminate at the dome's superomedial margin, apparently in direct communication with a tiny left parietal branch.

Despite the aneurysm's size, there is only mild to moderate mass effect and surrounding vasogenic edema, adjacent sulcal effacement and up to 4-5 mm midline shift to the right.

Multiple T2 hyperintense lesions are scattered elsewhere through the frontoparietal white matter of both cerebral hemispheres.

Appearances are in keeping with chronic small vessel ischemic change, relatively excessive for age.

There is a large, irregular fusiform aneurysm arising off an early branch of the left MCA.

There is a stenotic portion at the proximal portion of the aneurysm with post-stenotic dilatation measuring 8mm (this is the greatest diameter of the patent segment of the aneurysm).

The aneurysm extends posterior and lateral for at least 8cm and then terminates in a left parietal branch.

No other aneurysms are noted or vascular malformations are noted.


Case Discussion

Serpentine aneurysms are characteristically encountered at the MCA, with the "serpentine" referring to the meandering patent channel through the large and predominantly thrombosed MCA aneurysm. 

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