A rare neurovascular surgery at ivy hospital (large p-com aneurysm with fetal pca operated at ivy hospital by dr vineet saggar)

a rare neuro-vascular surgery at ivy hospital (large p-com aneurysm with fetal pca operated at ivy hospital by dr vineet saggar)

what is fetal pca ?

Posterior cerebral arteries are terminal branches of basilar arteries . Normally in adults it comunicates with anterior circulation or ICA via small posterior communicating arteies as shown in figure below

DIAGRAM OF CIRCLE OF WILLS

The term fetal-type PCA is also used when there is still a communication with the basilar artery through a hypoplastic P1 segment of the PCA. Others refer to it only when the P1 segment is not visible or when the PCA does not fill after contrast injection of a vertebral artery. In a full FTP(fetal type posterior circulation), uni- or bilateral, the P1 segment is not visualized on CT or MRI or does not fill after injection of contrast in a vertebral artery. A partial FTP, uni- or bilateral, is when the P1 segment is smaller than the PCoA. In an intermediate posterior circle configuration, the P1 segment is as large as the PCoA. The adult configuration, finally, is the situation in which the P1 segment is larger than the PCoA, the PCoA sometimes even being absent as shown in figure below

Kameyama and Okinaka described four types of what they called the ‘embryonic PCA’, combining the morphology of the posterior part and the anterior part of the circle of Willis . In type A, the A1 segment of the ACA is larger on the side of the FTP than on the contralateral side. In type B, the A1 is smaller on the side of an FTP. In type C, the ACAs are normal. The bilateral FTPs were called the ‘primitive-type embryonic derivation’. Although their definitions are not used in the literature, it could be important to assess the combination of anterior and posterior part of the circle of Willis, since it makes a difference if e.g. an ICA has to feed an MCA, both ACAs and a PCA, compared with an MCA and a PCA only.

Variations of FTPs a The A1 segment of the ACA is larger on the side of the FTP than on the contralateral side. b The A1 segments smaller on the side of an FTP. c ACAs are normal. d ‘Primitive type embryonic derivation’. e Normal adult type circle of Willis.

CLINICAL AND SURGICAL SIGNIFICANCE

Collateral circulation in the brain is important for maintaining a sufficient level of cerebral blood flow in case of obstructive disease in the main afferent arteries. This arterial network consists of extracranial and intra- cranial routes. The intracranial collateral vessels comprise the so-called primary collaterals, consisting of the arterial segments of the circle of Willis, which are used in case of acute need, and the secondary collaterals such as the ophthalmic artery and the leptomeningeal vessels, which develop after an ischemic stimulus when the primary collaterals are insufficient [1] . The leptomeningeal vessels arepresent or develop between the anterior (ACA), middle (MCA) and posterior cerebral arteries (PCA). They can represent an important connection between the internal carotid artery (ICA) and the vertebrobasilar system. Leptomeningeal collaterals can develop in the majority of circle of Willis configurations. However, one variant of the circle of Willis, the fetal variant (FTP), makes leptomeningeal collaterals between the ICA and the vertebrobasilar system impossible to develop since both the MCA and the PCA are connected to the internal carotid system and not to the vertebrobasilar system. An important consequence of the fetal variant of the circle of Willis could be an increased stroke risk in patients with obstructive arterial disease and following surgical interventions if accidently PCom is sacrificed or occluded during surgery for aneurysms. The most rapidly recruited collaterals are the communicating arteries of the circle of Willis. In FTPs, the ICA covers a larger area to provide with blood than in the ‘normal’, non-FTP configuration of the circle of Willis. It is probable that patients with ICA obstruction and a fullFTP more often encounter ischemic problems than patientswith a ‘normal’ circle, in which the PCoA is preserved and leptomeningeal vessels can develop between the carotid and the vertebrobasilar system. Patients who also have a missing contralateral A1 segment, thus having to feed the area of the ACAs, an MCA and a PCA with 1 ICA could be even more at risk.

CASE REPORT

A 56 year old female presented in our OPD with history of headache for past one month . She has had an episode of severe headache followed by loss of consciousness . CT head plain revealed Sub arachnoid haemorrage in sylvian fissure and basal cisterns more on left side. CT angiogram revealed multiple aneurysms: Pcom on left side which was large approx1.5 x 2 cms and small DACA( Distal anterior Cerebral artery)2 x 3 mm and small Right MCA aneurysm measuring 4 x 5 mm in size . Also patient had full Fetal type posterior circulation on left side . Due to location of SAH and large size of Pcom aneurysm it was identified as site of rupture. Large size of aneurysm and Fetal posterior circulation made surgery risky and there was increased risk of ischaemic deficits in posterior circulation if Fetal Pcom was accidently clipped during surgery. However Large Pcom aneurysm was successfully operated by us and patient was discharged without any deficit.

ANGIGRAPHY IMAGES SHOWING MULTIPLE ANEURYSMS WITH LARGE PCOM ANEURYSM