Inclusion Criteria

All must be answered “YES”.

·        Vascular imaging demonstrating occlusion an internal carotid artery

NOTE:  The above inclusion criteria may be demonstrated by any vascular imaging modality (e.g. Doppler ultrasound, magnetic resonance angiography, CT angiography or intra-arterial catheter arteriography). Validation of sensitivity and specificity of non-arteriographic modalities versus arteriography is not required since all participants must have catheter arteriography to determine final eligibility.

·        Transient ischemic attack (TIA) or ischemic stroke in the hemispheric carotid territory of the occluded carotid artery

·        This is a clinical diagnosis based on all available data that does not require confirmation by neuroimaging. Participants with TIA or infarction restricted to the retina only are not eligible, but those with combined retinal and hemispheric carotid territory syndromes will be eligible. In participants with hemisensory or hemimotor signs or symptoms, including single limb, specific hemispheric signs or symptoms (e.g. aphasia) will not be required for inclusion but absence of cerebellar and brainstem signs or symptoms will be required.

·        Participants who have previously undergone endarterectomy for stenosis of the ipsilateral external carotid or contralateral internal carotid artery are eligible whether or not they have had recurrent symptoms.

·        Participants who have undergone carotid endarderectomy (CEA) for symptomatic carotid stenosis who develop a post-operative carotid occlusion but experience no further symptoms after the time of surgery are not eligible unless further symptoms occur.

·        Most recent qualifying TIA or stroke occurring within 120 days prior to performance date of PET

·        Modified Barthel Index ³12/20

·        Language comprehension intact, motor aphasia mild or absent such that effective communication with the participant is possible

·        Age 18-85 years inclusive

·        Competent to give informed consent

·        Legally an adult

·        Geographically accessible and reliable for follow-up

Exclusion Criteria

All must be answered “NO”.

·        Non-atherosclerotic carotid vascular disease

      The intent is to include only atherosclerotic carotid occlusion. All other non-atherosclerotic conditions (for example, moya-moya disease, fibromuscular dysplasia, carotid dissection, arteritis, radiation-induced vasculopathy such as that following irradiation for neck cancer) are excluded.  These entities are given as examples, not as an all-inclusive list.

·        Blood dyscrasias

       This includes the following conditions ONLY:

              Polycythemia vera

              Essential thrombocytosis

              Sickle cell disease (SS or SC)

      This is an all-inclusive list. The following conditions are NOT EXCLUSIONS: anticardiolipin antibodies, lupus anticoagulant, protein S, C, or antithrombin III deficiency, Factor V Leiden or other causes of activated protein C resistance, prothrombin gene mutations.

·        Known heart disease likely to cause cerebral ischemia (Echocardiography is not required.)

      This includes the following conditions ONLY:

             Prosthetic Valves

             Infective endocarditis

             Left atrial or ventricular thrombus

             Sick sinus syndrome

             Myxoma

             Cardiomyopathy with ejection fraction < 25%

      This is an all-inclusive list. The following conditions are NOT EXCLUSIONS: atrial fibrillation, patent foramen ovale, atrial septal aneurysm.

·        Other non-atherosclerotic condition likely to cause focal cerebral ischemia

·        Any condition likely to lead to death within 2 years

·        Other neurological disease that would confound follow-up assessment

·        Pregnancy

·        Subsequent cerebrovascular surgery planned which might alter cerebral hemodynamics or stroke risk

      This includes contralateral internal or common carotid endarterectomy or angiopalsty, ipsilateral external carotid artery endarterectomy or angioplasty, carotid stump closure, vertebral or basilar artery angioplasty, any arterial grafting procedures to the carotid or vertebral arteries.

·        Any condition which in the participating surgeon’s judgment makes the participant an unsuitable surgical candidate

·        Concurrent participation in any other experimental treatment trial

·        Participation within the previous 12 months in any experimental study that included exposure to ionizing radiation

·        Acute, progressing or unstable neurological deficit (Neurological deficit must stable for 72 hours prior to the performance of PET).

If supplemental arteriography is required, allergy to iodine or X-ray contrast media, serum creatinine > 3.0 mg/dl or other contraindication to arteriography

·        Allergy or contraindication to aspirin

·        Medical indication for treatment with anticoagulant drugs, ticlopidine, clopidogrel or other antithrombotic medications such that these medications cannot be replaced with aspirin in the perioperative period as deemed necessary by the COSS neurosurgeon if the participant is randomized to surgical treatment

NOTE: Participants with any of the medical conditions specified in exclusion criteria 17 through 20 can become eligible if the exclusion criterion no longer applies within 120 days of onset of the most recent qualifying event.

·        Uncontrolled diabetes mellitus (FBS > 300 mg%/16.7 mmol/L)

·        Uncontrolled hypertension (systolic BP>180, diastolic BP >110)

·        Uncontrolled hypotension (diastolic BP <65)

·        Unstable angina

PET Criteria

·        Ipsilateral:contralateral OEF ratio in the middle cerebral artery territory > 1.130 determined from the ratio image of  O¹⁵O / H₂¹⁵O counts.

 Arteriographic Criteria

Intra-arterial catheter contrast arteriography documenting the following:

·        Occlusion of the symptomatic internal carotid artery.

·        Intracranial and extracranial arteries suitable for anastomosis in the opinion of the participating surgeon.