Anterior communicating artery aneurysm and left canal wall down mastoidectomy

Case contributed by Kenny Sim


Acute confusion.

Patient Data

Age: 77
Gender: Male


Within the cistern of the lamina terminalis, there is a 6mm mass in the region of the anterior communicating artery.

No acute intracranial hemorrhage. Cortical volume is age-appropriate. There is no hydrocephalus. There is minor bilateral periventricular white matter hypodensity, most in keeping with chronic small vessel ischemia. Within the anterior aspect of the right middle cranial fossa, there is a CSF density extra-axial collection immediately anterior to the right temporal lobe. This may represent an arachnoid cyst.

Previous canal wall down mastoidectomy on the left. Right maxillary sinus mucosal thickening and prior surgery. No suspicious osseous lesion.


No acute intracranial abnormality.

6 mm mass within the cistern of the lamina terminalis is highly suspicious for an anterior communicating artery aneurysm. Correlation with any known history, otherwise further investigation with CTA is recommended.

Case Discussion

The patient proceeded to CTA circle of Willis which confirmed a 6mm anterior communicating artery aneurysm.


Canal wall down mastoidectomy involves resection of the lateral wall of the mastoid, Koerner's septum and the posterosuperior wall of the external auditory canal.

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