Carotid diaphragm: an unusual and easily missed cause of internal carotid artery stenosis.

Abstract

A 79-year-old retired railway worker presented to the ophthalmology department with a history of two episodes of transient loss of vision in the left eye, each lasting approximately 10 minutes, highly suggestive of amaurosis fugax. He had an extensive past medical history including a myocardial infarction, hypertension and peripheral vascular disease. In addition, he was an ex-smoker on lipid-lowering drugs and was taking regular aspirin. On physical examination, he had bilateral carotid bruits but no other cardiovascular or neurological abnormality was demonstrated. He was referred to the department of vascular surgery following duplex scanning of his carotid arteries. Initial duplex scanning carried out by an experienced sonographer revealed increased peak systolic and end diastolic velocities in the right internal carotid artery, indicating a greater than 70% stenosis. Velocities in the left internal carotid artery were normal, excluding stenosis, although slight turbulence of flow was noted. As these results did not correlate with the clinical scenario, a repeat duplex scan was performed. It was only on the second occasion by careful scanning of the left internal carotid artery that a thin diaphragm across the carotid bulb with a small central lumen was identified (Figures 1a and b). The high velocity blood flow through this lumen associated with turbulent flow downstream correlated with a greater than 70% stenosis of the left internal carotid artery. An echolucent, eccentric plaque causing a tight stenosis of the left external carotid artery was also noted. A left carotid endarterectomy was performed and the intraoperative findings correlated with the ultrasound findings. The excised specimen is shown in Figures 2a and b. The patient made an uneventful postoperative recovery and is now asymptomatic. Histology confirmed that the 2.2 cm x 1.5 cm tubular, internal carotid artery atheromatous plaque contained a thin diaphragm 6 mm across with a 1 mm central hole. The diaphragm was composed of dense fibrous tissue while the central lumen was lined by endothelium (Figures 3a and b).