giant intracranial aneurysms have a lower propensity to bleed than small and medium - sized lesions and they may present with symptoms secondary to mass effect . while the diagnosis of a giant aneurysm can be readily made on radiology
if there is any circulating component within the aneurysmal sac , establishing a pre - operative diagnosis becomes difficult if the aneurysm is completely thrombosed .
the absence of a circulating component and the visualization of a large thrombus would lead to consideration of various other differentials depending on the location of the lesion .
a 45-year - old male presented with complaints of progressivelyworsening vision in his left eye and headache since 6 months .
he also complained of gait ataxia and occasional social incontinence of urine . on examination , visual acuity in
mri brain revealed a large left basifrontallesion extending superiorly and distorting the corpus callosum [ figure 1 ] .
the lesion was hyperintense on t1-weighted images ( wi ) [ figure 1a ] and hypointenseon t2wi[figure 1b ] .
the lesion did not enhance on gd - contrast sequences and no blood flow was demonstrated within the lesion on contrast mr angiography ( mra ) .
ct angiography ( cta ) demonstrated displacement of left anterior and middle cerebral arteries ; there was no enhancement within the lesion [ figure 1d ] .
( a ) t1-weighted coronal image showing a t1 hyperintense lesion . ( b ) t2wi demonstrating the hyppointense capsule as well as contents .
( d ) ct angiogram demonstrating the distortion of the left mca and acas based on the location and presence of a large thrombus , adifferential of giant cavernous hemangioma was considered .
however , the mri appearance of a well - delineated sac with a thrombus within it was not entirely concordant with this diagnosis .
however , digital subtraction angiogram ( dsa ) did not reveal any filling of contrast within the sac of the lesion .
the dsa also revealed that the left middle cerebral artery was displaced inferiorly by the lesion [ figure 2a ] .
the left a1 was not well visualized ; both a2s were filling on right carotid injection and a round shift of the a2s was noted [ figure 2b ] . since dsa did not demonstrate any contrast within the lesion , a possibility of intracerebral intravascular papillary endothelial hyperplasia ( masson 's tumor ) was also considered , although this is a rare lesion within the brain .
the a2s are shifted to the right due to the mass effect of the lesion .
no contrast is seen within the lesion a left pterional craniotomy was made and the lesion approached via the trans - sylvianroute .
there was a good plane of cleavage and capsular resection was performed in a piecemeal manner .
, a portion of the capsule was found to be significantlyadherent to the left a1-a2 junction .
there were areas of calcification in this area that further rendered dissection from the a1-a2 complex difficult [ figure 3a ] .
multiple perforators were found arising from the a1a2 junction and traversing posteriorly ; these were adherent to the capsule .
postoperative contrast - enhanced ct and mri revealed no residual capsule[figure 3b ] and subsequent dsa revealed preserved flow in all vessels and no fresh abnormality [ figure 3c ] .
histopathology of the resected specimen was diagnostic of aneurysmal wall with thrombus [ figure 3d ] .
follow - up dsa is planned to ensure that no regrowth of the aneurysm has occurred .
( a ) intraoperative image showing the optic chiasm ( star ) ; the lesion ( horizontal arrow ) is closely adherent to the left a1 ( vertical arrow ) .
( c ) postop angiogram demonstrating the right internal carotid artery supplying both a2 arteries across a patent acoma .
( d ) photomicrograph of the aneurysm wall composed of fibrocollagenous wall , congested blood vessels , lymphocytic infiltrate and hemosiderin laden macrophages ( h and e 400 )
spontaneousand complete thrombosis of giant intracranial aneurysm is reported to occur in 3 - 20% of cases .
the majority of giant aneurysms that have been reported to have undergone spontaneous thrombosis arose from the cavernous segment of the internal carotid artery .
there are singlecase reports of giant posterior cerebral artery , superior cerebellar artery and pericallosal artery aneurysmsthat underwent spontaneous thrombosis .
there exist no previous reports of giant anterior communicating artery aneurysms undergoing spontaneous thrombosis . in the present instance , aneurysm was not considered as the top preop differential since the lesion did not enhance on contract administration .
intra - operatively , the only clues to the nature of the lesion werethe presence of a multi - lamellatedthrombuswithin the cavity and the attachment to the anterior communicating artery .
totally thrombosed giant aneurysms can be confused with other tumors like cavernous hemangiomas , masson 's tumor , oligodendrogliomas and occasionally meningiomas .
there are several hypotheses to explain the phenomenon of spontaneous thrombosis in giant intracranial aneurysms .
the fundus of a giant aneurysm may itself compress the parent artery , resulting in stenosis and a low - flow state .
this may lead to intra - aneurysmal clot formation ultimately resulting in thrombosis of the aneurysm .
a large aspect ratio ( indicative of a small neck ) could also result in a low - flow state .
extension of the thrombus to the neckwould result in a further reduction of blood flow within the sac resulting in total thrombosis .
it is possible that in the present case similar mechanisms could have been responsible for complete isolation of the aneurysmal sac from the circulation .
the formation of a neo - intimal layer in the narrow neckcould explain the absence of bleedingdespite close dissection of the sac from the a1a2 junction .
pre - operative dsa is an absolute imperative to establish the diagnosis of large thrombosed intracranial mass lesions .
this lesion was not recognized as an aneurysm at surgery owing to the complete absence of bleeding and the calcification at the neck ; thus , the neck was not clipped .
however , it is generally recommended that a clip be placed across the neck since there have been several reports of regrowth of giant aneurysms that have not been clipped and completely excluded from circulation .
spontaneous thrombosis of giant intracranial aneurysms is a rare phenomenon . but aneurysms need to be considered in the differential diagnosis of mass lesions located in close proximityto cerebral vasculature .
the aim of surgery would be to decompress the surrounding neural structures . a clip application across the neck
may not be necessary if there is no filling of the sac while dissecting close to the neck .
 giant anterior communicating artery aneurysms are rare . 
 apatient presented with visual dysfunction , gait ataxia and urinary incontinence . 
 mri showed a giant suprasellar mass . at surgery , the lesion was identified as being an aneurysm arising from the anterior communicating artery . 
 the difficulty in preoperative diagnosis and relevant literature are reviewed . 
Introduction
Case Report
Discussion
Conclusions