Association of carotid artery atheromatous plaque types with cerebral perfusion.

Background: In an attempt to define the association of internal carotid artery atheromatous plaque morphology with potential cerebral ischaemia, we have investigated the relationship of different carotid plaque types with defects in cerebral perfusion.

Methods: In 130 patients requiring surgical correction of internal carotid artery stenoses greater than 70%, defects in cerebral perfusion due to both haemodynamic insufficiency and intracerebral vessel occlusion were identified using single photon emission computed tomography scans (SPECT). Carotid artery plaques in these patients were classified as homogeneous or heterogeneous based on preoperative Doppler Duplex Scanning and on the macroscopic characteristics of the plaques recorded by the surgeon during carotid endarterectomy, with sub-classification into potentially embolus-generating and non- embolus-generating plaques. In individual patients, plaque types were then correlated with the perfusion defects found in the SPECT scans.

Results: Of 130 patients, 112 (86%) had cerebral perfusion defects. In 56 asymptomatic patients in the study, 48 (85.7%) had perfusion defects as did 64 (86.5%) of 74 symptomatic patients. Cerebral infarcts were seen in 41 (31.5%). Occlusive infarcts (66%) were twice as frequent as haemodynamic insufficiency infarcts (34%). Eighteen patients with small cerebral infarcts on SPECT scanning gave no medical history of cerebral symptoms. Statistical analysis of the results revealed that there was no statistically identifiable association between carotid plaque type and the generation of cerebral symptoms or infarction.

Conclusion: This study found that internal carotid plaque morphology has no statistically significant association with perfusion defects, symptoms or cerebral infarction in patients with significant internal carotid artery stenosis. Also, it is suggested that haemodynamic cerebral infarction may be more common that previously believed (34% of infarcts identified in the study). Further, it is suggested that plaque morphology alone is not an indication for carotid endarterectomy.