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Medial temporal lobe changes with endovascular procedures

      Background

      Vascular disease contributes powerfully to the trajectory of decline in AD and also to vascular dementia. Whereas the medial temporal lobes (MTL) are vulnerable to AD, this region is not typically a focus of study in vascular dementia. For patients with severely occluded carotid arteries, carotid endovascular procedures (carotid endartorectomy or stenting) are important interventions which rapidly restore flow to the brain and prevent stroke. Our lab has found that several patients undergoing these procedures experience memory declines. Because the MTL is crucial for memory we investigated whether there were volumetric changes in this region following endovascular procedures.

      Methods

      Structural MRI (T1) images were collected in 42 patients before and after endovascular procedures. Postoperative MRI was collected within 48 hours after intervention. Automated volumetric measurement was performed using Freesurfer. The volumes were normalized (divided by the total intracranial volume) and difference scores comparing pre to post surgery were computed for each patient. These change scores were compared to zero using t-tests for each MTL.

      Results

      T-tests comparing volumetric surgical change scores for left and right MTL indicated that there was an increase in volume from pre to post procedures bilaterally (p<.01). The effect was observed in most patients (31 in left MTL and 30 in the right MTL) irrespective of the side of the procedure.

      Conclusions

      This is the first study to report an increase in MTL size associated with carotid endovascular procedures. The functional significance on cognition is unclear but the fact that procedures to treat occluded flow alter MTL volume suggests that vascular occlusive disease has direct effects on the MTL.