TRIPASS XR تري باس

 

or torn veins. Blood can also extend into the SASs from

parenchymal hemorrhage that ruptures through the cortex

and pia, spilling into the adjacent SAS.

Trauma, "burst" aneurysm, vascular malformations, and

amyloid angiopathy are potential causes of subarachnoid

hemorrhage (SAH). The most common cause of SAH is trauma.

Traumatic SAH (tSAH) occurs when hemorrhage from

contused brain or lacerated cortical vessels extends into sulci

adjacent to the injury.

Aneurysmal SAH (aSAH): Nontraumatic "spontaneous" SAH

represents about 5% of all acute "strokes." The most common

cause of nontraumatic SAH is a ruptured intracranial saccular

("berry") aneurysm (aSAH). Because most saccular aneurysms

(SAs) are located either on the circle of Willis or at the middle

cerebral artery bifurcation, the most common locations for

aSAH are the suprasellar cistern and sylvian fissures.

aSAH can be focal or diffuse. Attempts to determine the

precise anatomic location of a suspected intracranial

aneurysm based on the distribution of SAH are necessarily

imprecise. Anterior interhemispheric aSAH is typically

associated with rupture of a superiorly directed anterior

communicating artery aneurysm. aSAH seen primarily in the

posterior fossa cisterns &/or 4th ventricle suggests a posterior

inferior cerebellar artery aneurysm. Middle cerebral artery bior trifurcation aneurysm may cause focal hemorrhage in the

adjacent sylvian fissure.

Perimesencephalic nonaneurysmal SAH (pnSAH): An

uncommon but important cause of SAH, pnSAH, is a clinically

benign variant that is probably venous in origin. pnSAH is

confined to the cisterns around the midbrain and anterior to

the pons.

Convexal SAH (cSAH): An uncommon subset of nontraumatic

SAH occurs over the dorsolateral surface ("convexity") of the

cerebral hemispheres. The basal and perimesencephalic

cisterns are typically spared. cSAH typically affects just 1 sulcus

or a grouping of adjacent sulci. Common etiologies in older

adults are amyloid angiopathy or vasculitis, whereas vasculitis

and reversible cerebral vasoconstriction syndrome are

common causes in patients < 60 years old. Cortical vein

occlusion with cSAH occurs at all ages.

Superficial siderosis (SS): Chronic, recurrent SAH results in

hemosiderin deposition on the pia and cranial nerves. The

brain, brainstem, cerebellum, and spinal cord can all be

affected, although the posterior fossa is most commonly

involved.

The classic clinical presentation of SS is in an adult with a

history of trauma or surgery, who presents with ataxia and

bilateral sensorineural hearing loss. A history of aSAH is

uncommon. SS is best identified on T2* (GRE or SWI).

Aneurysms and Arterial Ectasias

Terminology and overview: The word "aneurysm" comes

from the combination of 2 Greek words meaning "across" and

"broad." Hence, brain arterial aneurysms are widenings or

dilatations of intracranial arteries.

Intracranial aneurysms are generally classified by their

phenotypic appearance. Saccular or "berry" aneurysms are the

most common type. Fusiform aneurysms are focal dilatations

that involve the entire circumference of a vessel and extend

for relatively short distances. Ectasias refer to generalized

arterial enlargement without focal dilatation and are not true

aneurysms.

Saccular aneurysm (SA): As the name implies, SAs are focal

sac- or berry-like arterial dilatations. The vast majority are

acquired lesions, the result of an underlying genetically based

susceptibility plus superimposed mechanical stresses on

vessel walls. SAs lack the 2 strongest layers of blood vessel

walls, the internal elastic lamina and the muscular layer. The

aneurysm sac itself consists of only intima and adventitia.

Most SAs arise at major blood vessel bifurcations, where

hemodynamic stresses are highest. The vast majority of

intracranial aneurysms are located on the circle of Willis plus

the middle cerebral artery bi- or trifurcation. 90% are "anterior

circulation" aneurysms, i.e., on the internal carotid artery and

its branches. The posterior communicating artery is

considered part of the anterior circulation; the vertebrobasilar

artery and branches constitute the "posterior circulation."

Pseudoaneurysm (PA): PAs are focal arterial dilatations not