Dissecting aneurysms of the vertebral artery: a management strategy

OBJECT: The authors present a retrospective analysis of their experience in the treatment of vertebral artery (VA) dissecting aneurysms and propose a management strategy for such aneurysms, with special emphasis on the most formidable VA dissecting aneurysms, which involve the origin of the posterior inferior cerebellar artery (PICA). METHODS: Since 1998, 18 patients with VA dissecting aneurysms, 11 of whom presented with subarachnoid hemorrhage (SAH), have been treated by endovascular surgery at the authors' institution. Obliteration of the entire segment of the dissected site with coils (internal trapping) was performed for aneurysms without involvement of the origin of the PICA (12 cases; among these the treatment-related morbidity rate was 16.7%). The treatment strategy applied to PICA-involved VA dissecting aneurysms presenting with SAH (three cases) included proximal occlusion of the parent artery followed by internal trapping of the aneurysm (one case), proximal occlusion of the parent artery followed by occipital artery (OA)-PICA bypass (one case), and two-staged internal trapping of the aneurysm involving double PICAs (one case). For PICA-involved VA dissecting aneurysms that were not associated with SAH at presentation (three cases), OA-PICA bypass was performed and followed by internal trapping of the aneurysm (two cases). In the remaining case in which a fetal-type posterior communicating artery was present, internal trapping was performed following successful balloon test occlusion (BTO). Overall, there was no sign of infarction in the PICA territory, despite complete occlusion of aneurysms involving the PICA. There was no recurrent bleeding or ischemic symptoms during the follow-up periods. The overall treatment-related morbidity rate for the VA dissecting aneurysms involving the PICA was 16.7%. CONCLUSIONS: Dissecting VA aneurysms that do not involve the PICA can be safely treated by internal trapping. For those lesions that do involve the PICA, a decision-making algorithm is advocated to maximize the efficacy of the treatment as well as to minimize the risks of treatment-related morbidity based on BTO.     

Treatment of vertebral artery aneurysms with posterior inferior cerebellar artery-posterior inferior cerebellar artery anastomosis combined with parent artery occlusion

BACKGROUND: In patients with aneurysms that involve the origin of the posterior inferior cerebellar artery (PICA) and require occlusion of the vertebral artery (VA), revascularization of the PICA is commonly performed. We present six patients with dissecting VA aneurysms who underwent PICA-PICA anastomosis combined with parent artery occlusion. METHODS: After a lower lateral suboccipital craniectomy and partial resection of the jugular tubercle, anastomoses were performed in a side-to-side fashion at the posterior medullary segment of the PICA. The VA was subsequently occluded by clipping proximal and distal to the aneurysm, and the PICA was occluded by clipping distal to the aneurysm. RESULTS: Postoperative cerebral angiography demonstrated patency of the anastomosis and regression of the aneurysm in five of six patients. The remaining patient experienced hemorrhage from contralateral VA dissection and subsequently died. One patient experienced myopathy of the lower extremities secondary to intraoperative fixed board compression and developed permanent lower extremity muscular weakness. The remaining four cases experienced no new neurologic deficits. CONCLUSION: PICA-PICA anastomosis is a useful procedure for reconstruction of the PICA when parent vessel occlusion or trapping is necessary to exclude a VA aneurysm involving the origin of the PICA.     

Distal aneurysm of the posterior inferior cerebellar artery--report of 3 cases

The incidence of posterior fossa aneurysm is reported to be 4-15% of all intracranial aneurysms in large series. Most aneurysms of the posterior inferior cerebellar artery (PICA) arise at the origin of the PICA. However, aneurysms of the distal part of the PICA have only rarely been described. This report presents three cases of distal PICA aneurysm with subarachnoid hemorrhage. Two aneurysms were located in the superior retrotonsillar segment of the PICA in two cases, and another was located in the tonsillohemispheric branch in one case. Obliteration of these aneurysms was comparatively easily done by bilateral suboccipital craniectomy. Computerized tomography (CT) was done in two cases. CT scan of the second case revealed a hematoma in the cerebellar vermis, and that of the third case revealed hemorrhage in the fourth and third ventricles. These findings seem to be common in subarachnoid hemorrhage of this lesion and may suggest the rupture of distal PICA aneurysm.     

Peripheral aneurysms of the posterior inferior cerebellar artery; analysis of 15 cases]

Peripheral aneurysms of the posterior inferior cerebellar artery (PICA) are rare. The authors report 15 cases of peripheral PICA aneurysms. Twelve of the aneurysms were discovered after their rupture and two were discovered after rupture of concomitant AVM, and one was detected incidentally. As to the location of aneurysms, more than half of the aneurysms arose at the telovelotonsillar segment. One patient had 2 aneurysms on the same peripheral PICA, which were not obvious on preoperative angiography because the ruptured one was partially thrombosed. Another rare case with aneurysm located at the internal auditory meatus is also reported. The findings of CT were characteristic, namely hemorrhage in the fourth ventricle without obvious hemorrhage in the basal cisterns, or only within the cerebellar vermian cistern. This phenomenon strongly suggested the possibility of rupture of peripheral PICA aneurysms. As to the surgical results, 10 patients (71%) of the 14 patients had a good recovery, and 1 patient (7%) with nonrupture aneurysm had a fair result due to pre-existing pontine hemorrhage. Three patients (21%) died. Rebleeding occurred in 3 patients, but cerebral vasospasm occurred in only 1 patient. Consequently, as peripheral PICA aneurysms are likely to be missed, and rebleeding is an unfavorable factor, one should try to demonstrate aneurysms with angiography, by using various methods such as subtraction or magnification.     

Characteristics and surgery of aneurysms of the proximal (A1) segment of the anterior cerebral artery

AIM: Proximal anterior cerebral artery (A1) aneurysms are considered to be rare or even unique. Proper surgical planning around A1 segment is particularly essential in order to avoid injury of tiny perforating arteries. METHODS: In 17 patients with angiographically or intraoperatively diagnosed A1 aneurysms, representing 0.8% of 2 124 aneurysm patients treated surgically at our institution between 1991 and 2003, clinical presentation, neuroradiological findings, surgical treatment methods and outcome were retrospectively analyzed. RESULTS: Sixteen patients presented with subarachnoid hemorrhage; A1 aneurysms were ruptured in 13 cases. Five patients (29%) had multiple aneurysms. In all cases A1 aneurysms were saccular and their maximum diameter ranged from 4 to 25 mm, average, 7.2 mm; in 4 cases they projected from the origin of the perforating artery, in 6 at the bifurcation of the internal carotid artery, in 5 at the anterior communicating artery and in 2 from the convexity of the parent artery. In 15 patients aneurysms were clipped via ipsilateral pterional approach and in the remaining 2, including a case with a second middle cerebral artery aneurysm, through contralateral approach. Eleven patients had excellent outcome, three good, and three died. CONCLUSIONS: Angiograms must be thoroughly analyzed to correctly assess origin of the aneurysmal neck, and to plan the operative procedure as radiological presentations of distal or proximal A1 lesions resemble those of anterior communicating artery and internal carotid artery bifurcation aneurysms, respectively. Contralateral approach may facilitate surgical elimination of selected A1 aneurysms or enable one-stage clipping in patients with multiple bilateral aneurysms.     

Multiple aneurysms of the PICA communicating artery: a case report

A case with unusual type of aneurysms in the distal posterior inferior cerebellar artery (PICA) is reported here. Though only two cases with a single aneurysm of the PICA communicating artery have been reported previously, the present case is the first one with multiple aneurysms in the PICA communicating artery. A 61-year-old woman with a sudden onset of severe headache, vomiting and unconsciousness was transferred to our hospital. CT scan revealed a hematoma in the fourth, third, and lateral ventricles, and a mild subarachnoid hemorrhage at the posterior fossa. Cerebral angiogram showed the right PICA supplying the hypoplastic left PICA territory through an anastomotic vessel. Two small aneurysms were seen at the tips of hairpin curves of an anastomotic vessel, "the PICA communicating artery". Suboccipital craniotomy was performed, and the ruptured aneurysm was clipped and the unruptured one was wrapped with cotton-sheet. After the operation, her clinical recovery went well and she was discharged on foot.     

Infra-posterior inferior cerebellar artery aneurysm arising after occlusion of the ipsilateral vertebral artery--case report.

An 85-year-old woman had subarachnoid hemorrhage due to rupture of a very rare left infra-posterior inferior cerebellar artery (PICA) aneurysm, a saccular aneurysm located proximally at the junction of vertebral artery (VA) and PICA. Right vertebral angiography demonstrated the aneurysm since the left VA was occluded in the extracranial portion. The aneurysm projected in the opposite direction to common VA-PICA aneurysms. The angiographical and intraoperative findings imply this rare aneurysm resulted from the hemodynamic changes caused by the VA occlusion. Detailed exploration of angiography is emphasized to detect such rare aneurysms among the diversity of hemodynamic patterns in elderly patients with subarachnoid hemorrhage.     

Far lateral suboccipital approach for the treatment of proximal posteroinferior cerebellar artery aneurysms: surgical results and long-term outcome

OBJECTIVE: Proximal posteroinferior cerebellar artery (PICA) aneurysms are challenging to treat surgically, with high reported perioperative complication rates. We describe the perioperative course and long-term clinical outcomes obtained via a far lateral suboccipital approach in 20 consecutive proximal PICA aneurysms. METHODS: Data were collected prospectively on the first 20 proximal PICA aneurysms treated surgically by a single surgeon (ESC) between December 1997 and April 2003. All aneurysms were clipped via a far lateral approach. Patients with unruptured aneurysms were assessed at 3 and 12 months after surgery. For all subarachnoid hemorrhage patients, a battery of outcome tests was performed at 3- and 12-month intervals. Outcomes were then compared with those of a contemporaneously managed population of ruptured right-sided posterior communicating artery aneurysms. RESULTS: The far lateral suboccipital approach achieved adequate exposure in all cases. There were no intraoperative complications or intraoperative aneurysm ruptures. All patients with unruptured aneurysms were fully functional at long-term follow-up. At 3 months of follow-up, 93% of the subarachnoid hemorrhage patients achieved a Glasgow Outcome Scale score of 1 to 2. At 12 months of follow-up, 92% achieved a Glasgow Outcome Scale score of 1 to 2. Compared with the patients with a ruptured right-sided posterior communicating artery aneurysm, no difference could be found in quality of life or activities of daily living at either time point. CONCLUSION: The favorable outcomes and low postoperative morbidity in this subset of patients argues that clipping via this approach be considered a first-line therapeutic option. When performed in this manner, PICA aneurysm surgery seems to have no greater morbidity than right-sided posterior communicating artery aneurysm surgery.     

Management of inoperable cerebral aneurysms by the navigational balloon technique

Intravascular navigation with nondetachable balloons is a safe, effective method of treatment for inaccessible aneurysms of the internal carotid artery. The rate of ischemic complications is lower than that associated with carotid ligation, and the rate of subsequent hemorrhage is lower than that associated with either carotid ligation or direct clipping. Therefore, for many internal carotid artery aneurysms that originate at or proximal to the ophthalmic artery, the nondetachable balloon technique is an alternative treatment choice. During a 7-year period, 21 aneurysms of the internal carotid artery were treated by the nondetachable balloon technique. All 21 aneurysms were successfully excluded from the circulatory system by either proximal occlusion or trapping of the aneurysm neck. This series consisted of 8 carotid-ophthalmic artery aneurysms, 11 carotid-cavernous aneurysms (6 spontaneous, 5 traumatic), 1 petrous segment aneurysm, and 1 cervical segment aneurysm. At 3 years of follow-up, the following incidences were noted: transient ischemia, 4.7%; infarction, 9.6%; and hemorrhage, 0%. The complications were 1 case of transient hemiparesis and 2 late ischemic events. Fifty per cent of the patients underwent follow-up computed tomography, and thrombosis of the aneurysm was confirmed in all except one case, which was partially thrombosed.     

Are infundibular dilatations at risk of further transformation? Ten-year progression of a prior documented infundibulum into a saccular aneurysm and rupture: Case report and a review of the literature

Infundibular dilatations (IFDs) are conical, triangular, or funnel-shaped enlargements at the origin of cerebral arteries, and they are primarily located (7–25%) on the posterior communicating artery (PComA). Progression over time into a saccular aneurysm with a risk of rupture of a previously demonstrated IFD has rarely been reported. We report the case of a 60-year-old female who presented 10 years earlier with a subarachnoid hemorrhage caused by a left internal carotid artery aneurysm rupture. At that time, the carotid angiography showed the left internal carotid artery aneurysm and a right posterior communicating artery infundibular dilatation. Neck clipping for the left internal carotid artery aneurysm was performed and the patient was discharged with no neurological deficit. Ten years later, the patient suffered a second fatal subarachnoid hemorrhage; carotid angiography revealed a right posterior communicating artery aneurysm developed from the previously documented infundibular dilatation with a de novo right anterior choroidal artery aneurysm. This case is another proof of the small but growing number of examples of infundibular transformation over time, as well as their risk of progression into saccular aneurysms and subsequent rupture.     

Aneurysms of the ophthalmic segment. A clinical and anatomical analysis

The clinical, radiographic, and anatomical features in 80 patients with ophthalmic segment aneurysms were reviewed, and were categorized according to a presumed origin related to the ophthalmic (41 cases) or superior hypophyseal (39 cases) arteries. There was a marked female predominance (7:1) and high incidence of multiple aneurysms (45%) within this population. Clinical presentations included subarachnoid hemorrhage in 23 cases (29%) and visual deficits in 24 (30%); five patients exhibited both hemorrhage and visual loss. Twenty-eight aneurysms were incidentally identified. Ophthalmic artery aneurysms arose from the internal carotid artery (ICA) just distal to the ophthalmic artery, pointed superiorly or superomedially, and (when large) deflected the carotid artery posteriorly and inferiorly, closing the siphon. Abnormalities relating to vision were not identified until the aneurysm realized giant proportions. The optic nerve was typically displaced superomedially, which restricted contralateral extension until late in the clinical course; unilateral nasal field loss was seen in 12 patients. Nine patients had bilateral ophthalmic artery aneurysms which were often clipped via a unilateral craniotomy. Superior hypophyseal artery aneurysms arose just above the dural ring from the medial bend of the ICA, at the site of perforator origin to the superior aspect of the hypophysis, and had no direct association with the ophthalmic artery. The carotid artery was usually located lateral or superolateral relative to the aneurysm. These lesions could extend medially beneath the chiasm (suprasellar variant), producing a clinical and computerized tomography picture similar to a pituitary adenoma, or they could extend ventrally to burrow beneath the anterior clinoid process (paraclinoid variant). Preoperative categorization of these lesions according to their likely branch of origin provides excellent correlation with visual deficits and operative findings, and has allowed the author to clip 52 of 54 lesions, with very low operative or visual morbidity.     

De novo development of an aneurysm: case report

A case of the de novo formation of an aneurysm in a young woman is presented. At age 13 years, she had a spontaneous subarachnoid hemorrhage. Cerebral angiography showed an aneurysm of the bifurcation of the left internal carotid artery and a small aneurysm of the left anterior choroidal artery. At surgery, the aneurysm of the internal carotid artery was clipped, and the aneurysm of the left anterior choroidal artery was wrapped with muslin. Thirteen years later, the patient had another subarachnoid hemorrhage. Cerebral arteriography showed four aneurysms that had developed at previously angiographically normal sites. This case suggests that young patients with aneurysms might benefit from follow-up angiography in search of late aneurysm formation.     

Intracerebral hematoma due to ruptured nontraumatic middle meningeal artery aneurysm--case report.

A 77-year-old woman suddenly lost consciousness and presented with right hemiparesis. Computed tomography showed a large subcortical hematoma in her left frontal lobe associated with subarachnoid hemorrhage. The first impression was hemorrhage due to a ruptured aneurysm of the middle cerebral or the internal carotid artery on the left. Left internal carotid angiography showed no aneurysm or vascular anomaly, but back flow of contrast medium into the external carotid artery disclosed two saccular aneurysms arising from the anterior branch of the left middle meningeal artery (MMA). Emergent surgical intervention confirmed that the hematoma was due to ruptured MMA aneurysm. Nontraumatic MMA aneurysm should be recognized as a possible causative lesion of intracranial hemorrhage despite the extremely low incidence. External carotid angiography should be performed in patients with intracranial hemorrhage in whom no vascular cause can be detected in the internal carotid system.     

Ruptured aneurysm on a double origin of the posterior inferior cerebellar artery: a pathological entity in an anatomical variation. Report of two cases and review of the literature.

The posterior inferior cerebellar artery (PICA) is known to be very variable, and some of its anatomical variations can explain ischemic complications that occur during endovascular treatment of aneurysms. The authors report two cases of anatomical variation of the PICA that they have called its double origin, one of which gave rise to an aneurysm. The first patient was a 36-year-old man who presented with a subarachnoid hemorrhage related to the rupture of a PICA aneurysm. The aneurysm was treated by the endovascular route. Selective and superselective studies showed that the PICA origin was low on the fourth segment of the vertebral artery (VA). The aneurysm was located on an anastomosis between the PICA and a small upper arterial branch originating from the VA. Embolization was performed through the small branch with no problem, but a lateral medullary infarct followed, probably due to occlusion of the perforating vessels. The same anatomical variation was incidentally discovered in the second patient. To the authors' knowledge, neither this anatomical variation of the PICA nor the aneurysm's topography have been previously described angiographically. This highlights the role of angiography in pretreatment evaluation of aneurysms especially when perforating vessels or small accessory branches that are poorly visualized on angiographic studies are concerned, as in the territory of the PICA. Anatomy is sometimes unpredictable, and the surgeon must be very careful when confronted with these variations because they are potentially dangerous for endovascular treatment.     

Aneurysms of the distal posterior inferior cerebellar artery--analysis of 14 aneurysms in 13 cases

Thirteen cases of distal posterior inferior cerebellar artery (PICA) aneurysms are reported here. All the aneurysms were found after a subarachnoid hemorrhage. Dissecting aneurysm, incidentally found unruptured aneurysms, and aneurysms associated with arteriovenous malformation have been eliminated from this study. Characteristics for this type of lesion are a high rate of recurrent hemorrhage and rapid death due to direct compression of the brain stem, which clearly indicates the necessity of early surgery. Attention should be paid to the fact that angiography cannot always reveal aneurysms, especially when they are located in the peripheral PICA. One should also pay attention to multiple lesions and rapid growing acute subdural hematoma as initial findings for ruptured distal PICA aneurysm. Prognostic factors for these lesions are, vasospasm, especially when the aneurysm is located proximally in the PICA, and direct compression of the brain stem due to intraventricular hemorrhage when the aneurysm is located distally. It has been suggested that the pathogenesis of this lesion could be hemodynamic stress or embryogenesis. The shape and anomalous arterial structures of the 14 aneurysms presented here tend to agree with this suggestion. Our results suggest that the pathogenesis is hemodynamic stress that had developed due to embryological and/or arteriosclerotic factors.     

An autopsy case of persistent primitive hypoglossal artery with multiple cerebral aneurysms

An autopsy case of persistent primitive hypoglossal artery (PPHA) with multiple cerebral aneurysms is reported. A 54-year-old man with subarachnoid hemorrhage was admitted to Kuwana Hospital three days after the onset. The patient was stuporous and had stiffness of the neck. A computed tomogram showed hematoma in the interhemispheric fissure, subarachnoid hemorrhage in the basal cisterns and bilateral Sylvian fissures, and maxked dilatation of ventricles. Cerebral angiogram revealed the left PPHA and multiple aneurysms at the right anterior cerebral artery (A 2) (ruptured), anterior communicating artery, left anterior cerebral artery (A 1), left internal carotid-anterior choroidal artery junction, right internal carotid artery (C 1), and right middle cerebral artery. Neck clipping of the ruptured aneurysm and ventricular drainage were performed on the day of admission. Eight days after admission he died of rupture of the residual aneurysm. In pathological study, the PPHA was originated from the extracranial portion of the left internal carotid artery, 2 cm distal from the cervical carotid bifurcation, entered the intracranial space through the hypoglossal foramen, and turned into the basilar artery. There were six aneurysms which were shown on cerebral angiogram and another aneurysm on the left anterior inferior cerebellar artery. Microscopic examination revealed atherosclerotic change of the PPHA, true aneurysmal changes of the seven aneurysms and defect of tunica media (Forbus' medial gap) at all of the arterial bifurcations without early aneurysmal changes.     

Extracranial posterior inferior cerebellar artery aneurysm causing isolated intraventricular hemorrhage: a case report

The authors report the unusual case of an aneurysm arising on an extracranial loop of the left posterior inferior cerebellar artery (PICA). The computed tomographic scan showed an isolated hemorrhage in the lateral ventricles, and the lesion was recognized 1.5 cm below the foramen magnum at the level of the atlas. The literature concerning peripheral PICA aneurysms is reviewed and the clinical and radiological features of these lesions are discussed. A tendency for subarachnoid bleeding from distal PICA aneurysm ruptures to spread into the ventricular system is suggested. The diagnosis of distal PICA aneurysm should also be considered in cases of isolated intraventricular hemorrhage without obvious parenchymal or subarachnoid hemorrhage. The need for four-vessel angiography when studying patients suffering from a subarachnoid hemorrhage is stressed.     

Multiple aneurysms of the distal posterior inferior cerebellar artery with recurrent hemorrhage undetectable on preoperative neuroradiological findings: case report

We report a rare case of multiple aneurysms of the distal posterior inferior cerebellar artery (PICA) associated with recurrent hemorrhage undetectable on preoperative neuroradiological findings. A 68-year-old woman was admitted to our hospital in April, 2003 because of a sudden onset of headache, back neck pain and nausea. CT scan at the time of admission showed a hematoma in the 4th & 3rd ventricles, and a mild subarachnoid hemorrhage (SAH) in the basal, right ambient & quadrigeminal cisterns. She had had a similar history of previous intraventricular hemorrhage and SAH in October, 2001. Three-dimensional CT angiograms and left vertebral angiograms performed at that time revealed an irregular vascular lesion at the tonsillomedullary segment (TMS) of the left PICA. However, the final diagnosis was unclear. Left vertebral angiograms at the time of the 2003 admission revealed an irregular vascular lesion in the same region more clearly and the size of aneurysmal dilatations had increased considerably. So, preoperative diagnosis of an irregular vascular lesion at the TMS of the left PICA (distal PICA aneurysm was not ruled out) was based on the above neuroradiological findings. The patient was surgically treated through the suboccipital approach. The TMS of the left PICA had made a difficulty loop formation was observed. Five distinct aneurysma were found on the TMS of the left PICA. To prevent bleeding, the ruptured aneurysm & three unruptured aneurysms were clipped and the residual unruptured one was wrapped with Bemsheets. Postoperative left vertebral angiograms demonstrated neither clipped aneurysms nor occlusive findings at the TMS of the PICA. The patency of the PICA was preserved. The postoperative course was uneventful and the patient was discharged without new neurological deficits. There has been no rebleeding during the one year since surgery. The 23 reported cases of multiple aneurysms of the distal PICA including our case were reviewed and their neuroradiological and clinical features are discussed.     

De novo cerebral aneurysms manifesting as repeated subarachnoid hemorrhage and cerebral ischemic stroke--case report

A 29-year-old man suffered repeated subarachnoid hemorrhage and cerebral ischemic stroke over a period of 6 years. Cerebral angiography at each episode disclosed development of multiple de novo aneurysms at the bilateral middle cerebral arteries (MCAs), internal carotid arteries, right anterior cerebral artery, and right vertebral artery. Two of the ruptured aneurysms were treated by surgical and endovascular treatment, but he died of the effects of rupture of a de novo right MCA aneurysm. Histological examination at autopsy disclosed marked degenerative changes in all layers of the cerebral vessels, which were probably congenital in origin.     

Characteristics of distal posteroinferior cerebellar artery aneurysms

OBJECTIVE: Distal posteroinferior cerebellar artery (PICA) aneurysms are rare and have not been well investigated previously. We report our series of 24 patients with 27 distal PICA aneurysms. METHODS: All patients with distal PICA aneurysms that were surgically treated at Shinshu University Hospital and its affiliated hospitals between 1983 and 2001 were reviewed retrospectively. Data relating to clinical, radiological, and intraoperative findings were analyzed. RESULTS: In our series, distal PICA aneurysms reached an incidence of 0.28 and 0.38% of all intracranial aneurysms and ruptured aneurysms, respectively. There were 23 ruptured and 4 unruptured distal PICA aneurysms. Of these, 74.1% were saccular, 7.4% fusiform, and 18.5% dissecting aneurysms. Primarily the telovelotonsillar segment of the PICA was affected. Usually, the surgical outcome was favorable and was influenced by the obstructive hydrocephalus and the preoperative grade. It was sometimes difficult to detect the ruptured distal PICA aneurysm on the initial angiogram, and an extracranial origin of the PICA was sometimes observed. CONCLUSION: This review summarizes the presentation and outcome of a large series of 24 patients with 27 distal PICA aneurysms, and we conclude that distal PICA aneurysms are benign entities compared with vertebral artery-PICA aneurysms. Characteristics that should be considered in the treatment of distal PICA aneurysms are discussed.