2017 年 45 巻 4 号 p. 302-305
The development and subsequent rupture of an aneurysm due to infundibular dilatation (ID) has rarely been documented. An 84-year-old woman was admitted to our hospital with a massive headache since the previous night. Computed tomography showed a diffuse subarachnoid hemorrhage and magnetic resonance angiography (MRA) demonstrated a right internal carotid-posterior communicating artery (IC-PC) aneurysm (AN), which protruded inward. In addition, an ID was noted at the junction of the right IC-PC junction. Neck clipping of the right IC-PC AN was performed the same day. Unexpectedly, the AN bulged outward from the internal carotid (IC); the AN was clipped, and we carefully explored the inside of the IC. The bulging portion was identified, and appeared to be the infundibulum.
Immediate postoperative computed tomography angiography confirmed the remaining AN inside the IC-PC. Neck clipping was performed to remove the residual lesion. The patient was discharged with no neurological deficit.
We analyzed follow-up MRAs. She was diagnosed as having a right IC-PC AN protruding in the lateral-inferior direction at the first examination, and has been followed up every 6 months or yearly. Almost 3 years later, we have confirmed de novo AN formation at the IC-PC junction, and the AN has been growing gradually.
ID has been defined as a triangular, conical, or rounded dilatation, and it is primarily located in the IC-PC. It is unclear whether this dilatation may be a preaneurysmal condition. Cases of progression to a saccular AN with the risk of rupture of a previously demonstrated ID have rarely been reported. We have conducted follow-up MRA for 5 years in our patient, and have only observed a de novo AN developing from ID of the right IC-PC junction. This case is another example indicating that ID may be a precursor to ANs.
