Case Notes
History
72 year old male with transient left sided weakness; history of diffuse vascular disease; evaluate for arterial stenosis.Exam
CTA of the Head
This part of the stroke protocol CTA is performed after the 1st bolus of contrast and is referred to as the initial post contrast head CTA exam. Since there is no recirculation of contrast, it has the advantage of identifying stenoses and short segment occlusions without obscuration by pial collateral. On the other hand, it may underfilling patent, more distal, arteries, which, of course, also reduces the CT-density in the venocapillary pool within brain parenchyma. Thus, the initial post contrast head CTA tends to overestimate the depth of injury in the apparent stroke-zone.
Purpose
1. To define sites of afferent supratentorial arterial thrombosis or flow-limiting high-grade stenosis or lesser but tandem stenoses, or stenosis plus incomplete circle of Willis with isolated arterial circuit;
2. To define sites of afferent infratentorial arterial thrombosis or flow-limiting high-grade stenosis;
3. To determine features of vessel wall and intimal status;
4. To assess presence of tandem stenosis or stenosis plus incompetent circle of Willis;
5. In case of ICA stenosis/occlusion is there effective EC-IC collateral;
6. Is there a watershed stroke zone affecting the usual anastomotic arterial boundary zones;
7. in case of afferent arterial block, plus an incomplete circle of Willis, is there a potential end-of the-line type of watershed stroke;
8. To assess status of retrograde pial collateral and asses for any pial collateral gap between proximal thrombus & retrograde pial collateral;
9. To assess for delayed venous egress (need to prove on post contrast CT head whether it is just delayed or is actually persistently reduced or absent).
This part of the stroke protocol CTA is performed after the 1st bolus of contrast and is referred to as the initial post contrast head CTA exam. Since there is no recirculation of contrast, it has the advantage of identifying stenoses and short segment occlusions without obscuration by pial collateral. On the other hand, it may underfilling patent, more distal, arteries, which, of course, also reduces the CT-density in the venocapillary pool within brain parenchyma. Thus, the initial post contrast head CTA tends to overestimate the depth of injury in the apparent stroke-zone.
Purpose
1. To define sites of afferent supratentorial arterial thrombosis or flow-limiting high-grade stenosis or lesser but tandem stenoses, or stenosis plus incomplete circle of Willis with isolated arterial circuit;
2. To define sites of afferent infratentorial arterial thrombosis or flow-limiting high-grade stenosis;
3. To determine features of vessel wall and intimal status;
4. To assess presence of tandem stenosis or stenosis plus incompetent circle of Willis;
5. In case of ICA stenosis/occlusion is there effective EC-IC collateral;
6. Is there a watershed stroke zone affecting the usual anastomotic arterial boundary zones;
7. in case of afferent arterial block, plus an incomplete circle of Willis, is there a potential end-of the-line type of watershed stroke;
8. To assess status of retrograde pial collateral and asses for any pial collateral gap between proximal thrombus & retrograde pial collateral;
9. To assess for delayed venous egress (need to prove on post contrast CT head whether it is just delayed or is actually persistently reduced or absent).
Prior Study
Non-Contrast Head CTThere is a probable left high-cervical ICA acute intraluminal thrombus.
There are expected age related changes and a chronic post-ischemic lacunar infarct in the mesial Lt. thalamus.
No hyperacute post ischemic changes are evident.
CT Perfusion
There are changes consistent with Lt. ICA afferent obstruction (occlusion or high-grade stenosis) which slows the left hemispheric blood flow but has not significantly reduced in the CBV or CBF in either the left ACA or MCA or mesial P4 perfusion zones.
There is reduced perfusion in the left MCA-PCA watershed zone with reduced CBV/CBF/MTT.
There is delayed filling rate in the Lt. PICA perfusion zone, but the increased CBV indicates there is functional pial collateralization.
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CTA of the Neck
1. There are tandem Rt. carotid stenoses, the combination of which, are likely flow-limiting. However, the distal right ICA appears to fill normally.
2. There is diffuse atherosclerotic ulcerative plaque disease in left common carotid; there is no intimal dehiscence, no intraluminal soft clot, nor high grade stenosis.
3. Lt. ICA is occluded in its’ cervical segment just above the carotid sinus; there is limited functional EC-IC collateralization through the ophthalmic collateral with patent but reduced size of the intradural left ICA.
4. The Lt. vertebral artery has an origin stenosis and becomes completely occluded at the dural ring; The left intradural vertebral segment and the Lt. PICA origin are both occluded, but the distal PICA branches appear to fill in retrograde manner from the Lt. AICA. The Rt. vertebral is occluded in its’ proximal segment but is reconstitued by costocervical collaterals at the C3 level. The Rt. PICA origin is occluded but distal branches fill in retrograde from the Rt. AICA.