Good collaterals

Middle cerebral artery embolectomy remains controversial in the acute treatment of stroke. Patients who may benefit from this procedure are those who have good collateral circulation and can be operated on within the first few hours after the onset of symptoms. 

The following two examples show different configurations of the circle of Willis in two patients with occlusive ICA disease. While the 54-year-old patient in Fig. 15.12 suffering from left ICA occlusion shows good collateralization via the posterior communi-... 

During or following a cerebrovascular event, some brain areas may show relative or absolute hyperemia owing to good collateral flow, reperfusion after an occluded artery has been reopened and/or inflammation and vasodilatation in response to hypercapnia. In hyperemic areas, oxygen extraction fraction is low and there is luxury perfusion, indicating that flow is in excess of metabolic requirements, perhaps because the tissue has been irreversibly damaged. 

Good collateral vessels Early reperfusion Embohc stroke... 

The pial collateral circulation to the MCA territory, primarily from the anterior cerebral artery and to a lesser degree from the posterior cerebral artery, is the main determinant of the degree of CBF impairment, and thus the rate of neuronal loss [40], The strength of the collateral circulation is variable between patients and has been shown to be a significant predictor of clinical outcome and tissue fate [35, 105-107], The presence of a substantial ischemic penumbra (hypoperfused but viable tissue) is a marker of good collaterals, represents a therapeutic target that is tailored to each patient s individual physiology, and supersedes time as the more important parameter for the decision to proceed with lAT. 

If good collateral perfusion is unlikely, one then must consider whether one can afford to let the tissue become ischemic. As an example, it would be very reasonable to embolize a peripheral renal artery branch that was injured during a biopsy and sacrifice a small section of renal parenchyma, since it would have negligible effect on renal function. However if the main renal artery was ruptured during PTA, you would not want to embolize this artery except in dire situations since it would sacrifice the entire kidney. 

It is vital to understand the arterial anatomy and know the vascular supply distal to the planned embolization. In some VAAs, tissue ischemia can occur if the parent vessel is completely occluded. However, if good collateral flow exists, such as in... 

The liver receives a dual blood supply fromboth the hepatic arteries and the portal vein. Although good collateral flow exists, necrosis can occur if enough arterial supply is occluded at the time of embolization. Therefore, it is wise to assess the direction of blood flow in the portal vein because hepatofugal flow may increase the risk of infarction. One should be cautious and superselective when embolizing in the presence of portal vein thrombosis. 

Due to good collateral flow, complete occlusion of splenic, peripheral hepatic, and gastroduodenal... 

Internal Carotid Artery Occlusion Acute stroke due to a distal ICA T (T = terminus) occlusion carry a much worse prognosis than MCA occlusions. In a recent analysis of 24 consecutive patients (median NIHSS 19) presenting with T occlusions of the ICA who were treated by lAT using urokinase at an average of 237 minutes from symptom onset, only four patients (16.6%) had a favorable outcome at 3 months. Partial recanalization of the intracranial ICA was achieved in 15 (63%), of the MCA in 4 (17%), and of the ACA in 8 patients (33%). Complete recanalization did not occur. The presence of good leptomeningeal collaterals and age <60 years were the only predictors of a favorable clinical outcome. New treatment strategies, such as the combination of IV rt-PA and lAT, or the use of new mechanical devices may improve the outcome in these patients. 

Family and friends can be incredibly helpful resources in treatment if the client has a good relationship with them. As mentioned in Chapter 1, if the client has strained relationships with a certain family member or friend, it may not be wise to include that person if his or her participation threatens the client. In other instances, the client simply may not want the person to be involved. Therapists and clients should make certain that the client does want family members and friends involved prior to a therapists or counselors contacting them. Ethically speaking, it is important to respect the wishes of your client with regard to collateral involvement in therapy or treatment. Legally speaking, it is important for consent to be provided by the client for a therapist or counselor to speak with collaterals or to involve them in the therapy process. 

Thrombosis of the cavernous sinus is characterized by proptosis, chemosis, impaired vision and ophthalmoplegia. If it is not septic, prognosis is good because of collateral drainage and spontaneous recanalization. The same symptoms, with the exception of a possible bruit, may result from arteriovenous shunting in carotid-cavernous fistulae. The treatment of choice in this case is endovascular occlusion (thrombosis ) of the cavernous sinus. 

Stroke localization using clinical data is not infallible in about one-quarter of cases where a recent lesion is visible on brain imaging, it is not in the expected place (Mead et al. 1999). For example, although most pure motor strokes are caused by a lacunar infarct as a result of small vessel disease, in a few cases the CT or MR scan shows striatocapsular infarction caused by middle cerebral artery occlusion with good cortical collaterals... 

Kenakin, T. P. (2007). Collateral efficacy in drug discovery Taking advantage of the good (allosteric) nature of 7TM receptors. Trends Pharmacol. Sci. 28 407 115. 

Mortgage loan- A contract in which the borrower s property is pledged as collateral. It is repaid in installments. The mortgagor (buyer) promises to repay principal and interest, keep the home insured, pay all taxes and keep the property in good condition. 

In snmmary, a CDO is a very powerfnl tool that facilitates the needs of many market constituents. Like all tools, however, they have to be used properly. A CDO structured where the unique particulars of the collateral, the asset manager, and investor are considered, and most importantly balanced, begins to define the minimum standard of excellence that all good structnred financiers shonld respect. 

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