Collateral pathway

It is well-established that the induction mechanism of LTP at the CA3-CA1 synapse of the Schaffer collateral pathway requires postsynaptic activation of the NMDA receptors (Ch. 15). The NMDA receptor seems to be a perfect cellular device to detect the synaptic coincidence between pre-synaptic and post-synaptic neurons, and to associate two events at the cellular level [8]. 

VA obstruction causes hemodynamic problems in approximately one third of patients with posterior circulation ischemia (Caplan et al. 2004). Asymmetrical caliber of the two VAs is normal. In the neck multiple nuchal and muscular branches provide a network for potential collateral pathways, that can be activated in VA obstruction. 

In patients with obstruction of the internal carotid artery, numerous collateral pathways that redistribute blood to the deprived site can maintain adequate cerebral blood flow. The CW is considered an important primary collateral pathway with its potential believed to be dependent on the presence and size of the component vessels, which vary among normal individuals (Alpers and Berry 1963 Baumgartner et al. 1997 Krabbe-Hartkamp et al. 1998 Macchi et al. 1996 Patrux et al. 1994 Schomer et al. 1994). Using special 2D... 

Hippocampal intrinsic afferents to the subiculum originate from other hippocampal regions. The CAl neurons send a dense projection to the subiculum and the CAS pyramidal cells project to all parts of the subicular complex through the Schaffer collateral pathway (Swanson et al., 1978). The extrahippocampal projections to the subiculum mainly originate from the raphe nuclei (Conrad et al., 1974), locus coeruleus... 

De Olmos J, Heimer L. 1980. Double and triple labeling of neurons with fluorescent substances the study of collateral pathways in the ascending raphe system. Neurosci Lett 19 7-12. 

Donoghue JP, Kitai ST (1981) A collateral pathway to the neostriatum from corticofugal neurons of the rat sensory-motor cortex an intracellular HRP study. J. Comp. Neurol, 210, 1-13. 

Collateral Pathways in the Event of Carotid Stenosis or Occlusion... 

Lesions with elevated diffusion c/w vasogenic edema resolve Lesions with decreased diffusion c/w cytotoxic edema that resolve - resolution may be related to early drainage of blood through collateral pathways or to seizure activity Lesions with decreased diffusion c/w cytotoxic edema that persist... 

As Tmax and TTP are only indirectly related to cerebral hemodynamics, it is more difficult to describe how these parameters are altered in ischemic conditions. In general, blood usually reaches underperfused tissue via stenotic vessels that reduce flow and delay bolus arrival, and/or via indirect collateral vessels that increase the time needed to reach the tissue, hi either case, the arrival of the injected contrast bolus is delayed, and Tmax is usually increased in underperfused tissue. However, Tmax is also increased in the tissue that is perfused by collateral pathways that are successful in maintaining normal blood flow to the tissue whose... 

Fig. 8.7 Nondeconvolution-based perfusion measurements in various hemodynamic conditions. Typical concentration-vs.-time curves are shown illustrating (U) underperfused brain tissue, (C) perfusion via collateral pathways resulting in preserved blood flow but delayed bolus arrival, and (H) postischemic hyperemia. A normal curve is presented for comparison (N). Bolus arrival time (Tmax) is late for collaterally perfused tissue, and is typically late for underperfused tissue, but is often early for hyperperfused tissue. TTP is late for underperfused and collaterally perfused tissue, and is often early for hyperperfused tissue...

Patients with portal hypertension will develop collateral pathways over time. Esophageal varices are very common, but gastric varices may also be observed (Schlesinger and Parker 2003 Itha and Yachha 2006). 

Extrahepatic collateral pathways to the liver may be established in various conditions such as follow-... 

After completion of the primary embolization procedure, it is important to check other potential collateral pathways. For example, profunda femoris and contralateral internal iliac arteries are injected following embolization of an internal iliac bleeding source. 

When contemplating LGI embolization there are some unique aspects of the history that need to be investigated. Knowing the past surgical history is important since prior intestinal surgery may have disrupted potential arterial collateral pathways and will increase the risk of an ischemic complication. If the patient has had radiation therapy to the... 

Fig.9.3a,b. Right iliac angiogram showed collateral pathways from the artery supplying the round ligament after embolization of both right internal iliac and uterine arteries... 

For this reason, when an embolotherapy is planned we recommend immediate cessation of prostaglandin Ej agonist infusion. In case of arterial spasm at the ostium of the uterine artery, the use of a coaxial system with a microcatheter is then required. It is possible to successfully catheterize the distal part of the uterine artery in most cases. In these circumstances, the preferred embolic agent is the one that can be easily delivered through a microcatheter, such as PVA (Polyvinyl alcohol) or Embospheres. We prefer to use particles with larger diameters, such as Embospheres 700-900 mg. Even if these particles are used for the above-mentioned reasons, additional Gelfoam embolization of internal iliac arteries is performed because of the extensive collateral pathways of the female pelvis. 

We should emphasize, however, that the IMA exclusion or embolization in patients with SMA stenosis or prior partial colectomy where the collateral pathways between the IMA and SMA have been interrupted, is not advised [31]. 

Overall attribution of this sample attempted to integrate the various forensic results into a self-consistent picture. The HEU was definitely not of US origin, as an initial emichment of 90% U is distinctly different from the 93.5% composition of US Oralloy. This conclusion was further supported by the extremely fine grain-size distribution. Moreover, while the collateral pathway indicators (paraffin wax, paper composition, and Pb-shield isotope ratios) both excluded and implicated multiple regions of the world. Eastern Europe was linked as a potential source of materials by all of these diverse analyses. 

Intrahepatic collateral pathways can develop in cirrhotic patients with portal hypertension. Park et al. (1990) classified them in 4 types type 1 when there is a vessel of large diameter that connects the right portal branch with the inferior vena cava type 2 when there are one or more communications between the portal vein and hepatic veins in one hepatic segment type 3 when there is an aneurysmatic shunt between peripheral branches of the portal vein and hepatic veins type 4 when there are multiple communications between portal peripheral branches and hepatic vein branches in both hepatic lobes. 

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