Relationship between decreased cerebral blood flow and amnesia after microsurgery for anterior communicating artery aneurysm.

Objective: Postoperative amnesia after surgery for anterior communicating artery aneurysm might be associated with the damage of the basal forebrain. Our purpose was to verify whether decreased regional cerebral blood flow (rCBF) in basal forebrain could be related to the degree of postoperative amnesia.

Methods: Regional voxel rCBF data analyzed using three-dimensional stereotactic surface projection on I-IMP-SPECT were compared between ten patients with postoperative amnesia and 13 normal subjects. The Severity (average Z score of the voxels with a Z score that exceeds a threshold value of 2) was calculated. The cerebral lobes with rCBF exhibiting Severity > 2 in all patients were identified. In these lobes, we then examined whether there was a gyrus exhibiting Severity that was negatively related to memory quotients (MQs).

Results: In the right subcallosal gyrus, there was a significant negative correlation between Severity and visual MQ (ρ= -  0.884, p = 0.0007) or general MQ (ρ =- 0.853, p = 0.0017). In the right anterior cingulate gyrus, there was a significant negative correlation between Severity and verbal MQ (ρ = - 0.769, p = 0.0092). In the right rectal gyrus, there was a significant negative correlation between Severity and general MQ (ρ =  -  0.811, p = 0.0044). No significant correlations were found between Severity in other brain regions and verbal, visual, or general MQ.

Conclusions: The decreased rCBF in the subcallosal gyrus included in the basal forebrain, anterior cingulate gyrus, and the rectal gyrus in the right hemisphere was related to postoperative amnesia.