Ica örserum
C1cervical segment. C2petrous segment: this is the horizontal segment located within the temporal bone. C3the lacerum segment, which is a small segment that starts from the petrous apex, passing above "ica örserum" foramen lacerum, and is covered by the trigeminal ganglion. C4the cavernous segment, also known as the carotid syphon, is subdivided into three segments, the posterior vertical, horizontal and anterior vertical.
Its branches are the meningohypophyseal trunk and the inferolateral trunk. C5the clinoid segment, terminates where the ICA passes into the subarachnoid space.
ica örserum3
C6 is the ophthalmic segment, which extends to the origin of the PcoA: its branches are the ophthalmic artery and the superior hypophyseal artery. Its branches are the AChoA and PCoA Common anatomical variants of the Ica örserum are: Aberrant ICA which presents clinically as a retrotympanic pulsatile mass in which the ICA runs posterolaterally in the hypotympanum; Persistent stapedial artery, vestigial branch, which passes between the cochlear promontory and the stapes and is associated with the absence of the foramen spinosum; Persistent trigeminal artery Fig.
Common anatomical variants are: Early bifurcation or trifurcation; MCA duplication. Posterior Circulation The posterior circulation is supplied by the terminal segment of the VA, the basilar artery and its branches Fig. V1, V2 and V3 are extracranial segments. V4 is the intradural segment which starts where the vertebral artery pierces the dura and runs superomedially, behind the clivus.
The VA joins the contralateral VA to form the basilar artery. V4 branches off from the posterior inferior cerebellar artery PICA. There is a supernumerary artery yellow arrowlinking the ICA and the basilar artery carotid basilar anastomosis Fig. It bifurcates or trifurcates before the sylvian fissure. It branches off from the perforating vessels and the anterior temporal artery.
The terminal segments of the vertebral artery v3 and v4the basilar artery ba and the proximal segments of the posterior cerebral arteries are shown p1 and p2 The BA runs in the prepontine cistern anterior to the brainstem and originates from the confluence of the two vertebral arteries. It bifurcates into two posterior cerebral arteries PCA at the level of the ica örserum cistern.
Common anatomical variants are fenestrations and duplications.
P1 ica örserum the precommunicating segment ica örserum runs from the basilar artery to the PCoA. P2 runs in the ambient cistern and branches off from the posterior medial choroidal artery and posterolateral choroidal artery. P3 is the quadrigeminal segment which runs in the quadrigeminal cistern posterior to the midbrain. P4 is the calcarine segment which terminates in ica örserum leading to the occipital and parietal lobes.
The branches of the COW are the perforating lenticulostriate arteries, the thalamoperforating arteries, and the thalamogeniculate arteries. Venous System Anatomy The intracranial venous system has two components: the dural venous sinuses and the cerebral veins Fig. The dural venous sinuses are large veins covered by dura mater invaginations which form their walls.
The superior sagittal sinus is a median structure localized in the outer margin of the falx cerebri; it originates from the foramen cecum anteriorly and terminates at the level of the torcular posteriorly. The inferior sagittal sinus is located in the inferior margin of the falx cerebri and communicates posteriorly with the vein of Galen, from which the straight sinus originates, directed to the torcular.
The transverse sinuses originate from the torcular, run laterally, become sigmoid sinuses at first and then internal jugular veins at the level of the jugular foramina. The cavernous sinuses are located laterally to the sella turcica and contain the ICA and the 6th cranial nerve. The cerebral veins are thin-walled venous structures located in the subarachnoid space directed toward the dural sinuses.
Venous drainage is typically centrifugal, except for the deep brain structures. Most of the brain is drained by the cortical veins. Since the evaluation of the intracranial circulation is frequently performed together with the vessels of the neck, refer to the neck protocol for a discussion of the technique. Some technical tips are useful for the evaluation of the intracranial circulation.
For CTA, a fast imaging scanner similar to the one used for the carotid arteries should be used.
Internal Carotid Artery and Its Aneurysms
The region of interest ROI used for the bolus tracking can be placed in the distal extracranial ICA segment, easily identifiable in the precontrast scans. Unlike body imaging, ToF is usually the most commonly used technique. CE- MRA is preferentially used in high-flow arterial disease, in the evaluation of a stenotic arterial segment, in the evaluation of AVM, and in the post-treatment follow-up of brain aneurysms.
The berry aneurysms are focal dilations, caused by a genetic susceptibility ica örserum mechanical stress on the vessel walls.
Intracranial Circulation
They originate in the arterial bifurcations where hemodynamical stress is higher. Fusiform aneurysms are caused by atherosclerosis and are characterized by arterial wall ectasia caused by damage to the tunica media. Blister aneurysms are small focal dilations, typically located in the supraclinoid ICA.