ivas typically occur secondary to moyamoya disease ( mmd ) , head trauma , intracranial arteriovenous malformations ( avm ) , and infection . a recent review by yuan et al . estimated the prevalence of these conditions to be : mmd ( 50.9% ) , hypertension ( 15.1% ) , avm ( 5.7% ) , and tuberculous infection ( 1.9% ) . idiopathic ivas accounted for 26.4% of all cases.13 ) most reports of idiopathic ivas describe true aneurysms , while only 1 report described the presence of a superior cerebellar artery pseudoaneurysm protruding into the fourth ventricle.7 ) to the best of our knowledge , this is the first reported case of an idiopathic lenticulostriate artery ( lsa ) pseudoaneurysm protruding into the right lateral ventricle and causing an ivh that was successfully treated with microsurgical resection . a 28-year - old man presented with sudden onset of severe headache without any definite history of trauma . he was previously diagnosed with bipolar disorder and had been taking lithium for 3 years . computed tomography ( ct ) an enhanced small round lesion ( 4.5 mm in diameter ) was found on the medial surface of the right caudate nucleus by contrast ct ( fig . the patient underwent external ventricular drainage ( evd ) for the ivh . the following day , digital subtraction angiography ( dsa ) was performed and revealed an aneurysm arising from the distal part of the medial lsa ( fig 2a ) . the patient recovered without any newly developed neurological deficits and a follow - up ct scan showed complete resolution of the ivh . following removal of the evd catheter , a short - term follow - up of the aneurysm was recommended , to which the patient agreed . however , dsa performed a month later revealed a slightly enlarged aneurysm ( 4.23.2 mm ) . endovascular obliteration of the aneurysm was deemed impossible due to the small caliber of the lsa . instead , the aneurysm was clipped via the interhemispheric transcallosal approach with assistance of a neuro - navigation system . the aneurysm was found in the right lateral ventricle , attached to the caudate nucleus ( fig . , we decided to clip the neck of the aneurysmal sac rather than undertake a complete resection . this was particularly important since the patient did not present any neurological deficits prior to surgery . a protruding pulsating sac partially enveloped by a hematoma was observed , and 2 aneurysm clips were successfully applied to the most proximal part of the sac ( fig . dsa performed 4 days later revealed a considerable residual aneurysm sac beside the clips ( fig . 2b ) . given the risk of rebleeding , a second operation was planned for complete resection of the aneurysm . after revised craniotomy and careful dissection of the caudate nucleus , the aneurysm sac and clips were completely removed ( fig . short- and long - term memory tests were performed , and memory impairment was not observed . examination of the vascular wall structure by elastin staining failed to show an elastin layer around the hematoma . since there was no evidence or history of recent head trauma , this case was regarded as idiopathic lsa pseudoaneurysm causing ivh . in our patient , enhanced ct angiography revealed an enhanced nodular lesion without evidence of vascular connections . additional magnetic resonance imaging ( mri ) showed peripheral t1-weighted hyperintensity , with a laminated pattern of mixed t1 signal and t2 hypointensity related to blood flow . these findings are similar to a previous neuroimaging study of a sphenoid sinus internal carotid artery pseudoaneurysm.8 ) however , in our case , the extent and origin of the aneurysm could not be identified with mri . instead , the most useful information for diagnosis and treatment was obtained by dsa . initial dsa revealed the aneurysm ( 7.54.5 mm ) arose from the distal part of the medial lsa . a literature review showed that 14 out of 15 patients presenting with idiopathic ivas underwent surgical or endovascular treatment , and their prognoses were relatively better than the patient who received conservative treatment : this patient died due to rebleeding.5 ) moreover , in cases of iva associated with mmd , 2 patients died during conservative management.4 ) these findings support active treatment of patients with ivh presenting with ivas , but in this case , the patient did not present any symptoms after evd care . short - term follow up was decided after careful consideration because surgical or endovascular treatment could lead adverse effect . however , treatment of iva became crucial because follow - up dsa performed a month later highlighted changes in the aneurysm 's shape and size . endovascular treatment can be considered because endovascular intervention seems to improve the prognosis for traumatic and mycotic intracranial pseudoaneurysms.1)2 ) among idiopathic iva cases , 4 cases who received endovascular treatment showed good outcome.3)9)12)13 ) endovascular embolization with embolic materials like glue and onyx are usually used.6 ) however , there are some disadvantages to this technique . since most ivas arise from small distal branches as in this case , it is usually difficult to navigate a microcatheter accurately . moreover , accidental reflux of the embolic source may result in embolization of an unintended vessel . we decided to apply clips at the neck of aneurysm to avoid tissue damage of caudate nucleus during exploration of parent artery , but iva remained . two previous reports of successful clipping relate to the parent arteries being visibly located at the tela choroidea.10)11 ) furthermore , pseudoaneurysms usually consist of a ruptured vessel wall and an extravascular hematoma covered in thin connective tissue . given the anatomic features of these aneurysms , placement of clips is challenging.6 ) except for these special cases , trapping of the aneurysm is essential for complete obliteration of the aneurysm from the parent circulation . we recommend that active treatment with endovascular or surgical trapping should be considered for patients presenting with ivh caused by iva , especially when the iva is a pseudoaneurysm . this study was approved by seoul national university bundang hospital institutional review board l-2013 - 553 .
we report a rare case of an idiopathic pseudoaneurysm causing intraventricular hemorrhage ( ivh ) . a 28-year - old man presented with sudden onset of severe headache . 
 he underwent external ventricular drainage for an isolated ivh in the right lateral ventricle . digital subtraction angiography ( dsa ) revealed that the aneurysm ( 7.54.5 mm ) arose from the distal part of the medial lenticulostriate artery . following removal of the external ventricular drainage catheter , 
 the aneurysm decreased in size ( 4.02.3 mm ) . 
 however , follow - up dsa revealed a slightly enlarged aneurysm ( 4.23.2 mm ) with morphologic change . 
 the aneurysm was clipped via the interhemispheric transcallosal approach , but postoperative dsa revealed a residual aneurysm sac beside the clips . 
 given the risk of rebleeding , a second operation was planned for complete resection of the aneurysm . 
 after revised craniotomy and careful dissection of the caudate nucleus , the aneurysm sac was completely resected . 
 histopathological examination revealed that the aneurysm was a pseudoaneurysm . 
 the patient recovered without any neurological sequel and was discharged.to the best of our knowledge , this is the first reported case of an idiopathic lenticulostriate artery pseudoaneurysm protruding into the right lateral ventricle and causing an ivh that was successfully treated with microsurgical resection .