Management strategies for posterior cerebral artery aneurysms: a proposed new surgical classification

Endovascular Treatment in Precommunicating Segment Aneurysms of Posterior Cerebral Artery

BACKGROUND

Precommunicating (P1) segment aneurysms of the posterior cerebral artery are rare, with few studies reported to date. Herein, we address the clinical and radiologic outcomes of their endovascular treatment.

METHODS

For this study, we retrieved prospectively collected data on 35 consecutive patients with 37 P1 aneurysms, analyzing the clinical ramifications and morphologic outcomes of treatment. All subjects received endovascular interventions between January 2001 and October 2021.

RESULTS

There were 16 aneurysms (43.2%) of P1 segment sidewalls and 21 (56.8%) at P1/posterior communicating artery junctions. Five (13.5%) were fusiform, and 14 (37.8%) were ruptured. In 14 patients (40%), 16 aneurysms (43%) were associated with intracranial arterial occlusive disease of the anterior circulation. Selective coiling was undertaken in 34 aneurysms (91.9%), using single (n = 24) or double (n = 4) microcatheters, microcatheter protection (n = 2), or stents (n = 4); and trapping was done in 3 (8.1%). No procedure-related morbidity or mortality resulted. Excluding the trapped lesions, angiographic follow-up of 29 aneurysms obtained >6 months after embolization (mean, 12.4 month) revealed stable occlusion in 21 (72.4%), with some recanalization in the other 8 (minor: 3/29, 10.4%; major: 5/29, 17.2%).

CONCLUSIONS

Aneurysms of P1 segment (vs. other locations) are strongly associated with intracranial arterial occlusive disease of the anterior circulation and thus are likely flow related. Endovascular treatment of such lesions seems safe and efficacious, despite the array of technical strategies that their distinctive anatomic configurations impose.

Trans-lateral ventricular approach for surgical treatment of high-located P2-P3 junction posterior cerebral artery aneurysms: from anatomical research to clinical application

BACKGROUND

Posterior cerebral artery (PCA) aneurysms, though rare, pose treatment challenges. Endovascular therapy is the preferred option, but microsurgery becomes necessary in certain cases. Various microsurgical approaches have been suggested for PCA aneurysms, particularly those at the P2-P3 junction. This study highlights the trans-lateral ventricular approach (TVA) for addressing these complex aneurysms. This study aims to assess the feasibility and safety of the trans-lateral ventricular approach (TVA) for treating high-located complex PCA aneurysms at the P2-P3 junction. The study evaluates both clinical outcomes and anatomical considerations.

METHODS

Two cases of PCA aneurysms at the P2-P3 junction were treated using TVA in 2019. Navigation-guided entry via the interparietal sulcus was planned. Ventriculostomy was performed from the cortex to the lateral ventricle's atrium. Medial atrial floor dissection exposed PCA's P2-P3 segments. Neuronavigation and ultrasound-aided guidance was used. Anatomical studies on fixed and contrast-perfused specimens refined the approach.

RESULTS

Both cases saw successful aneurysm clipping. The unruptured aneurysm patient was discharged in 6 days. The poor-grade SAH patient required extended ICU care, moving to rehabilitation with mRS = 4. The unruptured complex aneurysm case exhibited no deficits, returning to work in 3 months. Anatomical dissections validated TVA for high-located P2-P3 junction PCA aneurysms.

CONCLUSION

While endovascular therapy remains primary, this study demonstrates the viability of navigation-guided TVA for select high-located P2-P3 junction PCA aneurysms. Successes and challenges underscore the importance of patient selection and anatomical awareness.

Case report: isolated trochlear nerve palsy associated with posterior cerebral artery aneurysm

We describe a case of isolated trochlear nerve palsy caused by an unruptured posterior cerebral artery (PCA) aneurysm in an 82-year-old male who consulted an ophthalmologist after developing diplopia. Magnetic resonance angiography showed a left PCA aneurysm in the ambient cistern, and T2WI showed an aneurysm compressing the left trochlear nerve to the cerebellar tentorium. Digital subtraction angiography revealed that the lesion was located between the left P2a segment. We attributed this isolated trochlear palsy to left PCA unruptured aneurysm pressure. Thus, we performed stent-assisted coil embolization. The aneurysm was obliterated, and trochlear nerve palsy improved completely.

Endovascular treatment of P3 segment of posterior cerebral artery aneurysm with stent and coils

Posterior cerebral artery (PCA) aneurysms are rare and usually arise from proximal portion of the artery. The distal location is even less frequent, and aneurysms in this location tend to be larger and dissecting. Although they can be treated by direct surgery, recently endovascular procedures have been preferred in some centers. We report a case of large aneurysm of the posterior cerebral artery in a 45-year-old female presenting with headache. An uneventful endovascular treatment was performed with stent and platinum coils achieving total occlusion of the aneurysm, and the patient had good recovery. The findings are compared to earlier reports and literature regarding the issue is discussed.

Microsurgical and Tractographic Anatomical Study of Transtemporal-Transchoroidal Fissure Approaches to the Ambient Cistern

BACKGROUND

Approaching ambient cistern lesions is still a challenge because of deep location and related white matter tracts (WMTs) and neural structures.

OBJECTIVE

To investigate the white matter anatomy in the course of 3 types of transtemporal-transchoroidal fissure approaches (TTcFA) to ambient cistern by using fiber dissection technique with translumination and magnetic resonance imaging fiber tractography.

METHODS

Eight formalin-fixed cerebral hemispheres were dissected on surgical corridor from the temporal cortex to the ambient cistern by using Klingler's method. The trans-middle temporal gyrus, trans-inferior temporal sulcus (TITS), and trans-inferior temporal gyrus (TITG) approaches were evaluated. WMTs that were identified during dissection were then reconstructed on the Human Connectome Project 1021 individual template for validation.

RESULTS

The trans-middle gyrus approach interrupted the U fibers, arcuate fasciculus (AF), the ventral segment of inferior frontoocipital fasciculus (IFOF), the temporal extensions of the anterior commissure (AC) posterior crura, the tapetum (Tp) fibers, and the anterior loop of the optic radiation (OR). The TITS approach interrupted U fibers, inferior longitudinal fasciculus (ILF), IFOF, and OR. The TITG approach interrupted the U fibers, ILF, and OR. The middle longitudinal fasciculus, ILF, and uncinate fasciculus (UF) were not interrupted in the trans-middle gyrus approach and the AF, UF, AC, and Tp fibers were not interrupted in the TITS/gyrus approaches.

CONCLUSION

Surgical planning of the ambient cistern lesions requires detailed knowledge about WMTs. Fiber dissection and tractography techniques improve the orientation during surgery and may help decrease surgical complications.

Serpentine aneurysm of the posterior cerebral artery treated by internal maxillary artery bypass followed by parent artery occlusion: a case report and literature review

Serpentine aneurysms of the posterior cerebral artery (PCA) treated by the internal maxillary artery (IMA) bypass are rare. Here, the authors report the case of a 34-year-old male patient who presented with a half-year history of gradual severe headache and right-sided limb monoparesis and paresthesia lasting for 1 week. Preoperative angiograms showed a serpentine aneurysm in the left distal PCA, which was treated with internal maxillary artery-radial artery-posterior cerebral artery (IMA-RA-PCA) bypass followed by parent artery occlusion (PAO). The postoperative course was uneventful; radiological images revealed that the aneurysm disappeared, and there was good graft patency and excellent perfusion of the distal PCA territories. To the authors' knowledge, this is the first and only case of distal PCA serpentine aneurysm to be treated by IMA-RA-PCA bypass followed by proximal PAO. These findings suggest that IMA bypass surgery is a good and feasible treatment option for serpentine aneurysms of the PCA that can preserve the parent artery. Moreover, the anatomic segments of the PCA and different treatment options available for PCA serpentine aneurysms are also discussed in this study.

The oculomotor-tentorial triangle. Part 1: microsurgical anatomy and techniques to enhance exposure

OBJECTIVE

Access to the ventrolateral pontomesencephalic area may be required for resecting cavernous malformations, performing revascularization of the upper posterior circulation, and treating vascular lesions such as aneurysms. However, such access is challenging because of nearby eloquent structures. Commonly used corridors to this surgical area include the optico-carotid, supracarotid, and carotid-oculomotor triangles. However, the window lateral to the oculomotor nerve can also be used and has not been studied. The authors describe the anatomical window formed between the oculomotor nerve and the medial tentorial edge (the oculomotor-tentorial triangle [OTT]) to the ventrolateral pontomesencephalic area, and assess techniques to expand it.

METHODS

Four cadaveric heads (8 sides) underwent orbitozygomatic craniotomy. The OTT was exposed via a pretemporal approach. The contents of the OTT were determined and their anatomical features were recorded. Also, dimensions of the brainstem surface exposed lateral and inferior to the oculomotor nerve were measured. Measurements were repeated after completing a transcavernous approach (TcA), and after resection of temporal lobe uncus (UnR).

RESULTS

The s1 segment and proximal s2 segment of the superior cerebellar artery (SCA) and P2A segment of the posterior cerebral artery (PCA) were the main contents of the OTT, with average exposed lengths of 6.4 ± 1.3 mm and 5.5 ± 1.6 mm for the SCA and PCA, respectively. The exposed length of the SCA increased to 9.6 ± 2.7 mm after TcA (p = 0.002), and reached 11.6 ± 2.4 mm following UnR (p = 0.004). The exposed PCA length increased to 6.2 ± 1.6 mm after TcA (p = 0.04), and reached 10.4 ± 1.8 mm following UnR (p < 0.001). The brainstem surface was exposed 7.1 ± 0.5 mm inferior and 5.6 ± 0.9 mm lateral to the oculomotor nerve initially. The exposure inferior to the oculomotor nerve increased to 9.3 ± 1.7 mm after TcA (p = 0.003), and to 9.9 ± 2.5 mm after UnR (p = 0.21). The exposure lateral to the oculomotor nerve increased to 8.0 ± 1.7 mm after TcA (p = 0.001), and to 10.4 ± 2.4 mm after UnR (p = 0.002).

CONCLUSIONS

The OTT is an anatomical window that provides generous access to the upper ventrolateral pontomesencephalic area, s1- and s2-SCA, and P2A-PCA. This window may be efficiently used to address various pathologies in the region and is considerably expandable by TcA and/or UnR.

Fenestration in the P1 Segment of the Posterior Cerebral Artery

The posterior cerebral artery (PCA) has been noted in literature to have anatomical variations, specifically fenestration. Cerebral arteries with fenestrations are uncommon, especially when associated with other vascular pathologies. We report a case here of fenestrations within the P1 segment of the right PCA associated with a right middle cerebral artery (MCA) aneurysm in an elder adult male who presented with a new onset of headaches. The patient was treated with vascular clipping of the MCA and has recovered well. Identifying anatomical variations with appropriate imaging is of particular importance in neuro-interventional procedures as it may have an impact on the procedure itself and consequently post-interventional outcomes.

Fetal-type posterior cerebral artery: the pitfall of parent artery occlusion for ruptured P2 segment and distal aneurysms

OBJECT

P2 segment and distal aneurysms are rare lesions of the cerebrovascular system. The efficacy and safety of endovascular occlusion for these types of aneurysms remain controversial. The aim of this study was to reveal risk factors for endovascular parent artery occlusion of ruptured P2 segment and distal aneurysms.

METHODS

Between March 2010 and November 2012, 812 patients with a ruptured intracranial aneurysm were admitted to the authors' hospital. Among them, 11 patients presented with P2 segment and distal posterior cerebral artery (PCA) aneurysms. These patients were subjected to endovascular treatment. Periprocedural data and clinical and angiographic records were studied retrospectively.

RESULTS

Of the patients with a ruptured PCA aneurysm, 2 of them underwent selective aneurismal coiling, and the remaining patients were treated with simultaneous occlusion of the parent artery. Patients with an adult-type PCA (n = 6), treated with either selective coiling or simultaneous parent artery occlusion, had no serious neurological deficits on follow-up. Four patients with a fetal-type PCA that was also occluded intraoperatively exhibited newly developed permanent paralysis and hemianopsia. However, 1 patient with a fetal-type PCA aneurysm that was selectively coiled recovered without complications. No recanalization was observed in any of the treated aneurysms.

CONCLUSIONS

Endovascular occlusion of an aneurysm and its parent artery is a safe and effective method for managing adult-type P2 segment and distal aneurysms. However, the authors' clinical data suggest that this method is of high risk for patients with fetal-type PCA aneurysms.

Endoscopic Endonasal Clipping of Intracranial Aneurysms: Surgical Technique and Results

OBJECTIVE

Microsurgical clipping of intracranial aneurysms requires meticulous technique and is usually performed through open approaches. Endoscopic endonasal clipping of intracranial aneurysms may use the same techniques through an alternative corridor. The aim of this article is to report a series of patients who underwent an endoscopic endonasal approach (EEA) for microsurgical clipping of intracranial aneurysms.

METHODS

We conducted a retrospective chart review. Surgical outcome and complications were noted. The conceptual application and the technical nuances of these procedures are discussed.

RESULTS

Ten patients underwent EEA for clipping of 11 intracranial aneurysms arising from the paraclinoidal internal carotid artery (n = 9) and vertebrobasilar system (n = 2). The internal carotid artery aneurysms projected medially, whereas the vertebrobasilar artery aneurysms were directly ventral to the brainstem with low-lying basilar apices. One patient required craniotomy for distal control given the size and thrombosed nature of the aneurysm. Proximal and distal vascular control with direct visualization of the aneurysm was obtained in all patients. In all cases, aneurysms were completely occluded. Among complications, 3 patients had postoperative cerebrospinal fluid leakage and 2 other patients had meningitis. Two patients suffered lacunar strokes. One recovered completely and the other remains with mild disabling symptoms.

CONCLUSIONS

EEAs can provide direct access for microsurgical clipping of rare and carefully selected intracranial aneurysms. The basic principles of cerebrovascular surgery have to be followed throughout the procedure. These surgeries require a skull base team with a neurosurgeon well versed in both endoscopic endonasal and cerebrovascular surgery, working in concert with an otolaryngologist experienced in skull base endoscopy and reconstruction.

Characteristics of Posterior Cerebral Artery Aneurysms

BACKGROUND:

Posterior cerebral artery (PCA) aneurysms are rare lesions. Because of their low incidence, the individual or institutional experience is usually limited.

OBJECTIVE:

To identify specific anatomic features related to PCA aneurysms based on the analyses of pretreatment angiograms.

METHODS:

We performed a detailed angiographic study of 81 patients with a diagnosis of 93 PCA aneurysms. Fifty-three patients underwent computed tomography angiography, 49 underwent digital subtraction angiography, and 6 underwent magnetic resonance angiography. Between 1980 and 2012, a total of 120 patients with 136 PCA aneurysms and 11 352 patients with 16 444 intracranial aneurysms were treated at our institutions.

RESULTS:

There were 29 ruptured and 64 unruptured PCA aneurysms. The distribution of the aneurysms along the PCA segments was P1 (n = 39; 9 ruptured), P1/P2 junction (n = 25; 9 ruptured), P2 (n = 21; 5 ruptured), and P3 (n = 8; 6 ruptured). The median aneurysm size was 7 mm for the ruptured and 4 mm for the unruptured aneurysms. Saccular aneurysms (n = 69, 74%) had a typical projection for each location: P1 segment, upward (67%); P1/P2 junction, anterior/upward (80%); P2 segment, lateral (67%); and P3 segment, posterior (50%). Multiple aneurysms were seen in 43 patients. PCA aneurysms related to arteriovenous malformations were observed in 10 patients.

CONCLUSION:

PCA aneurysms are infrequent lesions, often associated with multiple aneurysms and arteriovenous malformations and are fusiform in shape. Most ruptured PCA aneurysms are smaller than 10 mm and usually distally located. At each PCA segment, saccular PCA aneurysms have a typical dome orientation.

Endovascular treatment of a giant dissecting aneurysm of the posterior cerebral artery. A case report and literature review

We describe the case of a 60-year-old man who presented with a giant dissecting aneurysm of the left P2 segment. Intracranial dissecting aneurysms often occur in the vertebrobasilar system, but rarely involve the posterior cerebral artery (PCA). PCA aneurysms tend to have some peculiar features and therefore may be considered a separate entity, even from the vertebrobasilar aneurysms. The patient was treated by endovascular occlusion of both parent vessel and the aneurysm, and he tolerated the procedure well with a complete resolution of clinical deficit, following volume reduction of the aneurysm. This paper presents additional evidence to literature reports suggesting that endovascular parent artery occlusion with coils is an effective and well-tolerated treatment for distal PCA aneurysms. Our review contributes to collect data regarding the incidence of recurrence as a measure of long-term efficacy of this therapeutic approach.

Suggested connections between risk factors of intracranial aneurysms: a review

The purpose of this article is to review studies of aneurysm risk factors and the suggested hypotheses that connect the different risk factors and the underlying mechanisms governing the aneurysm natural history. The result of this work suggests that at the center of aneurysm evolution there is a cycle of wall degeneration and weakening in response to changing hemodynamic loading and biomechanic stress. This progressive wall degradation drives the geometrical evolution of the aneurysm until it stabilizes or ruptures. Risk factors such as location, genetics, smoking, co-morbidities, and hypertension seem to affect different components of this cycle. However, details of these interactions or their relative importance are still not clearly understood.

Microsurgical and tractographic anatomical study of insular and transsylvian transinsular approach

This study is to define the operative anatomy of the insula with emphasis on the transsylvian transinsular approach. The anatomy was studied in 15 brain specimens, among five were dissected by use of fiber dissection technique; diffusion tensor imaging of 10 healthy volunteers was obtained with a 1.5-T MR system. The temporal stem consists mainly of the uncinate fasciculus, inferior occipitofrontal fasciculus, Meyer’s loop of the optic radiation and anterior commissure. The transinsular approach requires an incision of the inferior limiting sulcus. In this procedure, the fibers of the temporal stem can be interrupted to various degrees. The fiber dissection technique is a very relevant and reliable method for neurosurgeons to study the details of brain anatomic features. The DTI fiber tracking technique can identify the fiber tracts of the temporal stem. Moreover, it will also help further functional study of human insula.

Aneurysm on the cortical branch (P4 segment) of the posterior cerebral artery. Case report

A 75-year-old woman presented with a rare aneurysm on the distal portion (P(4)) of the posterior cerebral artery (PCA) causing subarachnoid hemorrhage (SAH) and manifesting as sudden onset of headache, nuchal rigidity, and nausea. Computed tomography on admission revealed thin SAH in the left parietooccipital sulcus. Cerebral angiography demonstrated a small saccular aneurysm on the cortical branch of the left PCA. The aneurysm was successfully clipped via the occipital interhemispheric approach. Distal PCA aneurysms frequently affect middle-aged persons and tend to be small, with good clinical course but may cause visual field defects. Direct aneurysm clipping is recommended for patients without visual defect from the onset. Parent artery occlusion by the endovascular technique should be considered for patients with visual loss caused by the initial hemorrhage.

Through the choroidal fissure: a quantitative anatomic comparison of 2 incisions and trajectories (transsylvian transchoroidal and lateral transtemporal)

BACKGROUND

We compared the transsylvian transchoroidal (TSTC) approach with the lateral transtemporal (LTT) approach. Both approaches proceed through the choroidal fissure but through different incisions and along different trajectories.

METHODS

Four fixed, silicon-injected heads (8 sides) were used. Nine strategic anatomic points within the dissections were compared between the TSTC and LTT approaches in 7 other silicon-injected heads (14 sides). Neuronavigation was used to gather coordinates from selected points of both approaches to calculate surgical angles and distances to common targets.

RESULTS

The surgical angle of the TSTC approach for the inferior choroidal point was wider compared with the LTT approach (P < .05). The surgical angles for the P2a-P2p point were similar for both approaches. In the TSTC approach, the P2-P3 point angle was smaller than in the LTT approach (P < .05). The TSTC approach provided (except for the P2-P3 point) significantly shorter distances to all defined anatomic targets compared with the LTT approach. When the posterior cerebral artery was the target in the TSTC approach, the hippocampus was retracted 3 to 8 mm compared with 8 to 13 mm in the LTT approach.

CONCLUSION

We quantitatively described anatomic features of the TSTC approach and compared them with the LTT approach. For approaching the mesial temporal region, the TSTC approach offers an adequate surgical angle and shorter or similar distances proximal to P2-P3 and requires less temporal lobe and hippocampal retraction than the LTT approach. Such information can help surgeons select the optimal approach to the mesial temporal lobe and its surrounding structures. The TSTC approach should be considered for lesions located in the medial temporal region.

Microvascular anatomy of the medial temporal region: part 1: its application to arteriovenous malformation surgery

BACKGROUND

The medial temporal region (also called the temporomesial or mediobasal temporal region) is the site of the most complex cortical anatomy.

OBJECTIVE

To investigate the anatomic variability of the arterial supply and venous drainage of each segment of the medial temporal region (MTR), and to discuss and illustrate the implications of the findings for surgery of arteriovenous malformations (AVM) of the MTR.

METHODS

Forty-seven cerebral hemispheres and 10 silicon-injected cadaveric heads were examined using x3 to x40 magnification. Illustrative surgical cases of MTR AVMs were selected.

RESULTS

The anterior choroidal artery (AChA) gave rise to an anterior uncal artery in 83% of hemispheres and a posterior uncal or unco-hippocampal artery in 98%. The plexal segment of the AChA gave off neural branches in 38%. The MCA was the site of origin of anterior uncal, unco-parahippocampal, or anterior parahippocampal arteries in 94% of hemispheres. An anterior uncal artery arose from the internal carotid artery (ICA) in 45% of hemispheres. The posterior cerebral artery (PCA) irrigated the entorhinal area through its anterior parahippocampal or hippocampo-parahippocampal branches in every case. A PCA bifurcation was identified in 89% of hemispheres, typically at the middle segment of the MTR. The most common pattern of bifurcation was by division into posteroinferior temporal and parieto-occipital arterial trunks. The anterior segment of the basal vein had a predominant anterior drainage in 35% of hemispheres, and the middle segment had a predominant inferior drainage in 16%.

CONCLUSION

An understanding of the vascular variability of the MTR is essential for accurate microsurgical resection of MTR AVMs.

Treatment of Distal Posterior Cerebral Artery Aneurysms

OBJECTIVE

This is the largest contemporary series of distal posterior cerebral artery (PCA) aneurysms treated by use of endovascular coiling and stenting as well as surgical clipping, clip wrapping, and bypass techniques. We propose a new treatment paradigm.

METHODS

The location, size, type of aneurysm, clinical presentation, treatment, complications, and outcomes associated with 34 distal PCA aneurysms in 33 patients (15 females, 18 males; mean age, 44 years) were reviewed retrospectively.

RESULTS

The most common presenting symptom was headache in 19 (58%) followed by contralateral weakness or numbness in 6 (18%) and visual changes in 4 (12%). Eight aneurysms were giant. Of the remaining 26 aneurysms, 17 were fusiform/dissecting, 5 were saccular, and 4 were mycotic. Treatment was primarily endovascular in 22 patients, 12 of whom also had a concomitant surgical bypass procedure. Nine patients underwent microsurgical clipping, and 3 underwent combined treatment of clipping and coiling and/or stenting. There were no significant differences in outcomes between the groups (P = .078). The recurrence rate in patients undergoing coiling was 22% and 0% in patients undergoing clipping. Fourteen aneurysms (41%) involved treatment with an occipital artery-to-PCA bypass or an onlay graft. Compared with their preoperative status, these patients had significantly worse outcomes than those without a bypass (P = .013).

CONCLUSION

Bypass techniques for the treatment of distal PCA aneurysms are associated with a higher rate of complications than once thought. In our new treatment paradigm, bypass is a last resort and reserved for patients in whom balloon-test occlusion fails, who refuse parent-vessel sacrifice, and who cannot undergo primary stenting with coiling or clip wrapping.

Results of surgical management for posterior cerebral artery aneurysms: 7-year experience in the endovascular era

PURPOSE

Unlike most posterior circulation aneurysms, posterior cerebral artery (PCA) aneurysms can be surgically approached, we believe, without significant technical difficulty or procedural morbidity. We report our recent experience to assess procedural complications and clinical outcomes for PCA aneurysms.

METHODS

In our retrospective review of 15 consecutive patients with PCA aneurysms, six patients underwent surgical treatment, six patients had endovascular coiling, (three patients from the endovascular group also underwent surgical revascularization), and three patients were treated conservatively (medical or observation) (2001-2007). Clinical records were reviewed for: patient demographics; clinical presentation; aneurysm location, size, and morphology; treatment; procedural complications; outcome (clinical and angiographic).

RESULTS

Complete aneurysm obliteration with parent vessel or bypass patency was demonstrated by intraoperative angiography in all patients. One patient died and two patients suffered procedure-related permanent neurologic injury. Considering both surgical end endovascular treatment modalities, mortality was 8.3% and permanent morbidity was 16.6%. At mean clinical follow-up of 2-96 months (15.8 +/- 10.5 months), nine of ten patients had a Glasgow Outcome Score of 4 or 5. In patients who underwent bypass procedures, computed tomographic (CT) angiography or cerebral angiography demonstrated a patent functional bypass before the PCA occlusion.

CONCLUSIONS

Our findings for these 15 patients suggest the value of a multimodality of treatments for PCA aneurysms. Revascularization of the PCA can be performed with favorable technical results and clinical outcomes when the patency of the PCA cannot be preserved.

Peripheral intracranial aneurysms: management challenges in 60 consecutive cases

Object

The authors report the management and outcomes of 55 patients with 60 intracranial aneurysms arising distal to the major branch points of the circle of Willis and vertebrobasilar system.

Methods

Between July 1997 and December 2006, the authors' neurovascular service treated 2021 intracranial aneurysms in 1850 patients. The database was reviewed retrospectively to identify peripherally located intracranial aneurysms. Aneurysms that were mycotic and aneurysms that were associated with either an arteriovenous malformation or an atrial myxoma were excluded from review.

Results

The authors encountered 60 peripheral intracranial aneurysms in 55 patients. There were 42 small, 7 large, and 11 giant lesions. Forty-one (68%) were unruptured, and 19 (32%) had bled. Fifty-three aneurysms were treated surgically by using direct clip reconstruction in 26, trapping or proximal occlusion with distal revascularization in 21, excision with end-to-end anastomosis in 3, and circumferential wrap/clip reconstruction in 3. Coils were used to treat 6 aneurysms, and 1 was treated by endovascular parent artery occlusion. Overall, 49 patients had good outcomes, 4 were left with new neurological deficits, and 2 died.

Conclusions

Peripherally situated intracranial aneurysms are rare lesions that present unique management challenges. Despite the fact that in the authors' experience these lesions were rarely treatable with simple clipping of the aneurysm neck or endovascular coil occlusion, preservation of the parent artery was possible in most cases, and the majority of patients had a good outcome.

Endovascular management of posterior cerebral artery aneurysms. Initial experience

SUMMARY

The purposes of this study were to evaluate the efficacy and safety of the endovascular management of posterior cerebral artery aneurysms and compare the efficacy and safety of selective aneurysmal coiling and parent artery occlusion. We reviewed all cases with cerebral aneurysms and attention was paid to the patients with posterior cerebral artery aneurysms. Among 550 aneurysms, eight aneurysms in eight patients were located on the posterior cerebral artery, three of which presented with SAH, whereas five presented with different degrees of headache. Seven were located at the P2 segment and one at the P3 segment. One was a giant serpentine aneurysm, two were giant sac aneurysms, two were large and three were small. All aneurysms were successfully treated, five with selective aneurysmal coiling and three with parent artery occlusion. Two patients presenting with headache with giant aneurysms had suffered an aggravated headache for two weeks which then resolved. Others had an uneventful recovery. All patients were followed from 12 months to 56 months. Four selective aneurysmal coiling aneurysms received digital subtraction angiography, two of which needed another treatment and one was treated with parent artery occlusion, one of which recanalized slightly and one of which had further thrombosis. No rebleeding or any other symptom occurred. Whether selective aneurysmal coiling or parent artery occlusion was performed, endovascular management of PCA aneurysms was a safe and effective method. Under some conditions, parent artery occlusion was better than selective aneurysmal coiling.

Paediatric dissecting posterior cerebral aneurysms: report of two cases and review of the literature

INTRODUCTION

Intracranial aneurysms in the paediatric population are uncommon, accounting for 2% to 6% of all aneurysms, and spontaneous arterial dissection is rarely reported as the cause of aneurysms in children, especially in the posterior cerebral artery.

METHODS

Two cases of paediatric spontaneous posterior cerebral artery dissecting aneurysms are reported, one in a 33-month-old male child presenting with aneurysmal rupture and subarachnoid haemorrhage and the other in a 9-year-old boy with an unruptured aneurysm.

RESULTS

The first child was successfully treated by endovascular parent vessel occlusion without neurological deficit and in the second a spontaneous thrombosis of the aneurysm and its parent artery occurred associated with hydrocephalus and a favourable outcome.

CONCLUSION

Dissecting aneurysms are dynamic lesions with variable and unpredictable evolution and close follow-up and/or early treatment is warranted. Spontaneous arterial dissection is a rare, probably still under-recognized, cause of intracranial aneurysms that may be responsible for a significant number of aneurysms and spontaneous aneurysmal thromboses in children.

Microsurgical anatomy and quantitative analysis of the transtemporal-transchoroidal fissure approach to the ambient cistern

OBJECTIVE

Surgical approaches to ambient cistern lesions are complex. We investigated the microanatomy of the transtemporal-transchoroidal fissure approach to the ambient cistern with emphasis on exposure of the posterior cerebral artery.

METHODS

Dissections were performed bilaterally in five silicone-injected cadaveric heads. Critical anatomic distances, specifically with reference to the P2 segment of posterior cerebral artery in relation to the inferior choroidal point and P2-P3 junction, were measured with digital calipers. Other landmarks (temporal lobe tip, points from the temporal base to the choroidal fissure) were included for quantitative analysis.

RESULTS

The transtemporal-transchoroidal fissure approach provided adequate exposure of the ambient cistern, minimized temporal lobe retraction, and allowed assessment of regional microanatomy. The mean distance from the temporal base to the choroidal fissure measured 18.09 mm (range, 16.9-21.9 mm). The distances from the choroidal fissure to P2 varied at the coronal plane of the inferior choroidal point (mean, 6.96 mm; range, 3.6-12.0 mm) and the P2-P3 junction (mean, 6.02 mm; range, 4.3-6.9 mm), respectively.

CONCLUSION

The transtemporal-transchoroidal fissure approach provides a corridor to the ambient cistern and P2-P3 junction while minimizing temporal lobe retraction and avoiding interruption of temporal lobe venous drainage. Because of widely variable vascular anatomy, access to posterior cerebral artery lesions using this approach requires preoperative imaging to identify the specific location of the P2-P3 junction.

Clinical Features of Aneurysms of the Posterior Cerebral Artery: A 15-year Experience with 21 Cases

OBJECTIVE:

To investigate the characteristic clinical behavior and develop guidelines for the clinical management of posterior cerebral artery aneurysms, we reviewed 21 cases treated during a 15-year period.

METHODS:

Between 1988 and 2002, we treated 21 patients (10 male, 11 female; mean age, 49.8 yr) with posterior cerebral artery aneurysms at Kumamoto University Hospital and its affiliated hospitals. Data relating to the clinical, radiological, and surgical approaches were analyzed.

RESULTS:

There were 20 saccular aneurysms, 6 of which were giant or large aneurysms, and 1 dissecting aneurysm. Of the 21 patients, 15 presented with subarachnoid hemorrhage; in 3 patients, an unruptured saccular aneurysm was found incidentally during an evaluation for other cerebral pathological conditions. Two patients presented with progressive homonymous hemianopsia because of the mass effect of the aneurysm, and 1 patient experienced the sudden onset of homonymous hemianopsia because of thrombosis of the aneurysm and afferent artery. Open or endovascular surgery was performed in 19 patients: 14 made a good recovery, 2 had a moderate disability because of angiospasm or infarction after aneurysm trapping, 1 had a severe disability because of angiospasm and cerebral contusion, and 2 died because of severe angiospasm. Of 2 conservatively treated patients, 1 made a good recovery but the other died as a result of rebleeding.

CONCLUSION:

Posterior cerebral artery aneurysms have specific clinical characteristics compared with aneurysms located elsewhere. The aneurysmal site and size and the surgical technique did not significantly influence treatment outcomes.

Relevance of occlusion test in endovascular coiling of posterior cerebral artery (p2 segment) aneurysms

SUMMARY

P2 segment aneurysms are located on the posterior cerebral artery (PCA) between the junction of the posterior communicating artery with the PCA and the quadrigeminal cisternal part of the PCA. We reviewed our experience with endovascular coiling in such aneurysms. Clinical and pre-procedural data from four patients, referred for endovascular treatment of P2 segment aneurysms, were retrospectively studied for factors influencing post-interventional neurological deficits caused by ischemia of the PCA distal territory. Balloon occlusion was done in three patients and patient tolerance was assessed using clinical and anatomic criteria. Embryologic and anatomic features of the PCA were reviewed. Balloon occlusion test and endovascular coiling of aneurysms was possible in three patients. Control angiogram after embolization showed elimination of aneurysms from the circulation and the distal PCA filled through leptomeningeal anastomoses. One patient deteriorated due to aneurysmal rupture soon after the balloon occlusion test and coiling could not be done. In the other three patients post-intervention CT and MRI images showed PCA territory infarcts in spite of demonstration of good collateral circulation distal to the occluded PCA. In conclusion, P2 aneurysms can be effectively treated by endovascular coiling without a balloon occlusion test. While the balloon occlusion test does not contribute to clinical decision-making it may be associated with potential morbidity and mortality.

Treatment strategy for aneurysms of the posterior cerebral artery

SUMMARY

The authors carried out a retrospective review of the records of 12 patients with aneurysms of the posterior cerebral artery (PCA). Four were asymptomatic, 1 presented with a mass effect, and 7 with a subarachnoid haemorrhage (SAH). Of the 7 ruptured aneurysms, 3 were embolized and 2 were clipped. However, 2 patients died from rebleeding before any treatment. Of the 5 unruptured aneurysms, 1 was embolized with coils but the remaining 4 have been conservatively observed. No aneurysms have ruptured during the follow-up period, and 3 have thrombosed spontaneously. According to our results, the PCA aneurysms should be treated aggressively in the early phase. Although the preservation of the anatomical integrity of the PCA should naturally be one of the prime objectives, PCA occlusion may sometimes be inevitable when treating large or fusiform aneurysms. On the other hand, conservative therapy is one of the options for the treatment of incidentally encountered unruptured ones, because these have the possibility of spontaneous thrombosis.

MICROSURGICAL APPROACHES TO THE PERIMESENCEPHALIC CISTERNS AND RELATED SEGMENTS OF THE POSTERIOR CEREBRAL ARTERY: COMPARISON USING A NOVEL APPLICATION OF IMAGE GUIDANCE

OBJECTIVE

To describe the exposure obtained through six approaches to the perimesencephalic cisterns with an emphasis on exposure of the posterior cerebral artery and its branches.

METHODS

Dissections in 12 hemispheres exposed the crural, ambient, and quadrigeminal cisterns and related segments of the posterior cerebral artery. A Stealth Image Guidance workstation (Medtronic Surgical Navigation Technologies, Louisville, CO) was used to compare the approaches.

RESULTS

The transsylvian approach exposed the interpeduncular and crural cisterns. The subtemporal approach exposed the interpeduncular and crural cisterns as well as the lower half of the ambient cistern. Temporal lobe retraction and the position of the vein of Labbé limited exposure of the quadrigeminal cistern. Occipital transtentorial and infratentorial supracerebellar approaches exposed the quadrigeminal and lower two-thirds of the ambient cistern. Transchoroidal approaches exposed the posterior third of the crural cistern, the upper two-thirds of the ambient cistern, and the proximal quadrigeminal cistern. Transchoroidal approaches exposed the posterior portion of the P2 segment (P2p) in 9 of 10 hemispheres and were the only approaches that exposed the lateral posterior choroidal arteries and the plexal segment of the anterior choroidal artery. Occipital transtentorial and infratentorial supracerebellar approaches provided access to the P3 segment in all cases and exposed the P2p segment in 4 of 10 hemispheres. The subtemporal approach provided access to the cisternal and crural segments of the anterior choroidal and medial posterior choroidal arteries and exposed the P2p segment in 3 of 10 hemispheres.

CONCLUSION

Surgical approaches to lesions of the perimesencephalic cisterns must be tailored to the site of the pathological findings. The most challenging area to expose is the upper half of the ambient cistern, particularly the P2p segment of the posterior cerebral artery.

A Combined Subtemporal and Transventricular/Transchoroidal Fissure Approach to Medial Temporal Lesions

OBJECTIVE

To minimize therapeutic morbidity such as cognitive function disturbance and vascular injury to perforating arteries, preoperative functional mapping of the basal temporal lobe functions was performed and the medial temporal lesions were resected via a combined subtemporal and transventricular/transchoroidal fissure approach.

METHODS

Twenty-one patients with medial temporal lesions including tumors, arteriovenous malformations, and medial temporal lobe epilepsy underwent operation. The neurovascular structures in the ambient cistern were first dissected free from the medial temporal lobe with a conventional subtemporal approach. Then, the temporal horn was opened through the basal surface of the temporal lobe. Finally, the ambient cistern was accessed from the temporal horn through the choroidal fissure. In five patients whose lesions were revealed to be located on the dominant side by preoperative intracarotid amytal administration test (Wada test), functional mapping of the basal temporal lobe language cortex was monitored for 1 week by use of a subdural electrocorticogram grid before the extirpation surgery. The entrance point from the temporal base to the temporal horn was determined by the result of the functional mapping.

RESULTS

The lesions were resected safely and completely in all cases. Language and cognitive functions were preserved even in patients with the basal language area on the dominant side.

CONCLUSION

Surgeons can confirm the important neurovascular structures from the subtemporal route and from the transtemporal horn route by a combined subtemporal and transventricular/transchoroidal fissure approach. This approach is especially effective for avoiding ischemic complications by allowing direct confirmation of the anterior choroidal and thalamoperforating arteries.

“Tangential” Resection of Medial Temporal Lobe Arteriovenous Malformations with the Orbitozygomatic Approach

OBJECTIVE

Arteriovenous malformations (AVMs) of the medial temporal lobe are usually resected through subtemporal-transcortical approaches that provide a trajectory that is perpendicular to the plane of the AVM. The pterional approach is sometimes used for AVMs in the uncus and amygdala, but it is not recommended for AVMs in the hippocampal region because it provides a “tangential” approach with limited access to posterior feeding arteries and draining veins. The orbitozygomatic approach enhances exposure along this tangential trajectory and was used in a consecutive series of 10 patients to determine its advantages.

METHODS

During a 5.7-year period, 43 patients underwent resection of temporal lobe AVMs, 10 of which were located in the medial temporal lobe (amygdala and uncus [Region A] or hippocampus, parahippocampus, and fusiform gyrus [Region B]). AVMs were evenly distributed by region and by hemispheric dominance and included two Spetzler-Martin Grade IV lesions. An orbitozygomatic approach was used in all cases.

RESULTS

Complete resection was accomplished in nine patients, and one patient underwent multimodality management with postoperative stereotactic radiosurgery. Good outcomes (Rankin outcome score ≤2) were observed in all patients, and six patients were improved neurologically at late follow-up (mean, 1.3 yr). No permanent language deficits were produced by this approach.

CONCLUSION

The orbitozygomatic approach maximizes the exposure of the tangential approach to medial temporal lobe AVMs and has advantages over traditional lateral approaches. It provides early access to critical feeding arteries from the anterior choroidal artery, posterior cerebral artery, and posterior communicating artery; it minimizes temporal lobe retraction and risk to the vein of Labbé; and it avoids transcortical incisions or lobectomy that might impact language and memory function. For these reasons, it may be the optimal approach for small- and medium-sized compact AVMs in the dominant medial temporal lobe.

Aneurysms of the Posterior Cerebral Artery: Retrospective Review of Surgical Treatment

A series of 10 cases of posterior cerebral artery (PCA) aneurysms were retrospectively reviewed. There were five men and five women aged 38 to 68 years (mean 57.5 years). Seven patients presented with subarachnoid hemorrhage. Two aneurysms were found incidentally during clinical examination for stroke. One aneurysm was associated with moyamoya disease. All aneurysms were saccular. The aneurysms arose from the P1 segment in three patients, the P1/P2 junction in three patients, the P2 segment in three patients, and the P3 segment in one patient. Two patients died before operation and one patient refused surgery. Aneurysmal clipping was performed for seven patients. All aneurysms except the P2 and the P3 aneurysms were treated via the pterional approach. Four patients had excellent outcome, but one patient with a P3 aneurysm developed homonymous hemianopsia due to thrombosis of the parent vessel and another patient with a P2 aneurysm had moderate disability from the initial insult. Coil embolization has been indicated as the first choice of therapy, but PCA aneurysms are good candidates for direct clipping.

Treatment and outcome in 30 patients with posterior cerebral artery aneurysms

OBJECT

The records of 30 patients with posterior cerebral artery (PCA) aneurysms treated during a 12-year period were reviewed to determine outcome and the risk of visual field deficit associated with PCA sacrifice.

METHODS

Clinical data and treatment summaries for all patients were maintained in an electronic database. The Glasgow Outcome Scale (GOS) and modified Rankin Scale (mRS) scores were determined by an independent registrar. Visual field changes were determined by review of medical records. Twenty-eight patients were treated with open surgery, one of them after an attempt at detachable coil embolization failed. Two patients underwent successful endovascular PCA sacrifice. The mean GOS and mRS scores in 18 patients with unruptured aneurysms were 4 and 2, respectively, at discharge. Subarachnoid hemorrhage (SAH) from other aneurysms and neurological deficits caused by the PCA lesion or underlying disease contributed to poor outcomes in this group. The mean GOS and mRS scores in 12 patients with ruptured aneurysms were 4 and 4, respectively, at discharge. One patient died of severe vasospasm. Neurological deficits secondary to SAH and, in one patient, treatment of a concomitant arteriovenous malformation contributed to poor outcomes in the patients with ruptured aneurysms. Seven patients with normal visual function preoperatively underwent PCA occlusion. One patient (14%) developed a new visual field deficit.

CONCLUSIONS

Optimal treatment of PCA aneurysms is performed via one of several surgical approaches or by endovascular therapy. The approach is determined, in part, by the anatomical location and size of the aneurysm and the presence of underlying disease and neurological deficits.

Transcortical transchoroidal fissure approach for ruptured distal posterior cerebral artery (P2-P3 junction) aneurysm associated with packed intraventricular hemorrhage--two case reports

A 56-year-old man with ruptured right P2-P3 junction aneurysm and a 66-year-old man with ruptured left P2-P3 junction aneurysm of the posterior cerebral artery associated with acute-stage packed intraventricular hemorrhage. The aneurysms were successfully clipped through the transcortical transchoroidal fissure approach. This approach requires less retraction of the temporal lobe, provides a wider surgical field, and the P2 segment can be easily reached. The present approach is very useful for the treatment of ruptured aneurysms at the P2-P3 junction, in particular for acute stage surgery associated with packed intraventricular hemorrhage.

Totally thrombosed giant P2 aneurysm: a case report and review of literature

The diagnosis and treatment of intracranial saccular giant aneurysms is still difficult despite developments in neuroradiology, neuroanesthesiology and micro-neurosurgery. These aneurysms are usually located on major intracranial arteries and are rarely on distal branches of these arteries. An extra-axial 4 x 5 cm mass lesion in the left mediobasal temporal region was detected on the CT and MRI examinations of a 37 year old male patient who was admitted to our institution with headache and slight right-sided hemiparesis lasting for 2 months. The lesion was avascular on angiography. Surgery proved that the lesion was a totally thrombosed giant aneurysm of the P2 segment of posterior cerebral artery (PCA). The P2 segment was clipped proximal to the aneurysm with pterional-transsylvian approach and the aneurysm was totally excised. Giant aneurysms of the P2 segment are rare and 15 cases have been reported in the literature. This report presents a rarely seen totally thrombosed giant P2 aneurysms and discusses the difficulties in diagnosis and treatment.

Surgical indications and microsurgical anatomy of the transchoroidal fissure approach for lesions in and around the ambient cistern

OBJECTIVE

Opening the temporal part of the choroidal fissure (CF) makes it possible to expose the crural cistern, the ambient cistern, and the medial temporal lobe. We examined the microsurgical anatomy and the surgical indications for use of the trans-CF approach.

METHODS

The microsurgical anatomy encountered in the trans-CF approach for lesions in and around the ambient cistern was studied in three cadavers. On the basis of these cadaveric studies, the trans-CF approach was used during surgery in three live patients with such lesions.

RESULTS

The angiographic "plexal point," which indicates the entrance of the anterior choroidal artery as it enters the temporal horn of the lateral ventricle, was thought to be a key anatomic landmark of the trans-CF approach. A cortical incision for entry into the temporal horn should be made in the inferior temporal gyrus to minimize the potential damage to the optic radiations and to the speech centers. After the CF is opened posteriorly to the plexal point between the tenia fimbria and the choroid plexus, the posterior cerebral artery (PCA) in the ambient cistern can be observed with minimal caudal retraction of the hippocampus. In this study, surgical procedures using the trans-CF approach were successfully performed on patients with high-positioned P2 aneurysms whose PCA ran close to the plexal point or higher, whose medial temporal arteriovenous malformations were fed mainly by the PCA, and whose tentorial hiatus meningiomas protruded into the temporal horn through the CF, with no resulting postoperative visual or memory disturbances.

CONCLUSION

The trans-CF approach is especially useful in surgery for lesions in and around the ambient cistern.

Specific characteristics and management strategies of cerebral artery aneurysms: report of eleven cases

Owing to the deep location of the posterior cerebral artery (PCA) and its close relationship with the brainstem and surrounding vital structures, surgical treatment of aneurysms in this region is complex. This study was undertaken in an attempt to better delineate the surgical risks of PCA aneurysms. A retrospective analysis was undertaken in 11 patients with PCA aneurysm surgically treated between 1988 and 1996 at Shinshu University and its affiliated hospitals. Data regarding surgical strategy, surgical complications and outcomes were analysed. Seven aneurysms were saccular (including one mycotic) and the other four were fusiform, dissecting, thrombosed and an infundibular dilatation. The locations of the aneurysms were at the P1 segment in two patients, P1-P2 junction in two, P2 segment in six and P3 segment in one. Six saccular non-mycotic aneurysms were treated with neck clipping and the other five aneurysms were treated each with proximal occlusion of the parent artery, excision of the aneurysm or wrapping. All aneurysms were satisfactorily exposed except one large saccular aneurysm. Surgical outcomes were either good recovery or moderate disability in 10 patients, and severe disability in one patient with a large aneurysm due to temporal lobe contusion. In conclusion it is the responsibility of the surgeon dealing with rare PCA aneurysms to be aware of these specific characteristics and to appreciate which surgical technique is appropriate for each patient.

Surgical approaches for the treatment of aneurysms on the P2 segment of the posterior cerebral artery

OBJECTIVE

The P2 segment of the posterior cerebral artery has remained a challenging region to expose surgically. We establish a surgical strategy for P2-segment aneurysms.

METHODS

Each segment of the posterior cerebral artery was classified according to Zeal and Rhoton's classification. Fourteen of 18 P2-segment aneurysms were surgically treated. The patient's outcome, the aneurysm location, and the surgical procedures were evaluated. A cadaveric study was performed to clarify the surgical view obtained via three different surgical approaches.

RESULTS

Nine aneurysms were clipped, two were trapped, one was coated, and one was excised with parent artery reconstruction. Cerebral revascularization techniques were used for three patients. The pterional approach exposed the anterior half of the P2a segment. The subtemporal approach revealed the P2a segment, but its exposure was restricted by its localization in the ambient cistern. Via the occipital interhemispheric transtentorial approach, the P2p segment was visible and could be manipulated. When the posterior half of P2a segment was high on a coronal view of magnetic resonance imaging, it was extremely hard to access via any approach.

CONCLUSION

A surgical strategy for the P2 aneurysm can be planned with accurate prediction of the aneurysm location. When the localization of an aneurysm on the posterior half of P2a segment is high, a resection of brain tissue may be required.