Aneurysms of the posterior cervicocranial circulation: clinical and angiographic considerations

Endovascular treatment of AICA flow dependent aneurysms. A report of three cases and review of the literature

Peripheral anterior inferior cerebellar artery (AICA) aneurysms are rare, accounting for less than 1% of all cerebral aneurysms. To our knowledge 34 flow-related cases including the present study have been reported in the literature. Three patients harbouring four flow dependent aneurysms were referred to our institution. Two patients presented with subarachnoid hemorrhage, one presented with cerebellar manifestations. They were all treated by endovascular embolization of the aneurysm as well as the parent artery using liquid embolic material. Two cases were embolized using NBCA, Onyx was used in the third case. No bleeding or rebleeding were encountered during the follow-up period which ranged from five to nine months. One patient developed facial palsy, cerebellar symptoms and sensorineural hearing loss. The remaining two cases did not develop any post treatment neurological complications. Endovascular management of flow-dependent AICA aneurysms by parent artery occlusion is feasible and efficient in terms of rebleeding prevention. Post embolization neurological complications are unpredictable. This depends upon the adequacy of collaterals from other cerebellar arteries.

Flow patterns and velocity distributions in the human vertebrobasilar arterial system. Laboratory investigation

OBJECT

The authors conducted a study to elucidate the relationship between the flow patterns and the formation of aneurysms at the bifurcation of the basilar artery (BA).

METHODS

Six isolated, transparent vertebrobasilar arterial systems were prepared from humans postmortem, and flow patterns and velocity distributions were studied in detail using flow visualization and cinemicrographic techniques.

RESULTS

The authors found that if the diameters of 2 vertebral arteries (VAs) were nearly equal and they formed a symmetrical inverted Y-shaped junction with the BA, the BA flow was also symmetrical. The fluid elements that flowed into the BA from 2 VAs traveled almost parallel to the vessel wall of the BA without mixing with each other, and then they flowed out through ipsilateral superior cerebellar and posterior cerebral arteries. In contrast to this, if the diameters of 2 VAs were very different or the BA was badly bent, the BA flow was disturbed as a result of the formation of swirling and secondary flows. The approaching velocity profile at the BA's terminal bifurcation was flattened if the inverted Y-junction was symmetrical, and it was sharpened if the junction was asymmetrical. Thus, in the latter case, fluid elements impinged on the vessel wall around the flow divider of the bifurcation with much larger velocities and, hence, larger kinetic energy, compared with the case of a symmetrical inverted Y-junction, exerting high fluid pressures, wall shear stresses, and wall tensions on the vessel wall there.

CONCLUSIONS

The symmetrical structure of the inverted Y-junction in a normal vertebrobasilar arterial system provides a flattened approaching velocity profile at the terminal bifurcation of the BA, lowering the hemodynamic stresses (pressure, tension, and shear stress) exerted on the wall of the bifurcation. This may account for the relatively low incidence of aneurysm formation at this site.

Ruptured intrameatal AICA aneurysms--a report of two cases and review of the literature

BACKGROUND

Aneurysms of the distal part of the anterior-inferior cerebellar artery (AICA) are rare. Most are located in the cerebellopontine angle close to the internal auditory meatus. To our knowledge, only 13 patients with the aneurysm located inside the internal auditory meatus have been reported in the literature.

METHOD AND FINDINGS

We present two cases of ruptured intrameatal AICA aneurysms that were treated in our center in the past year. The locations and clinical manifestations are discussed and all 13 previously published cases are reviewed.

CONCLUSION

Exposure and decompression of all structures in the internal auditory meatus, careful manipulation of the nerves and vessels, temporary trapping of the aneurysm, and careful dissection of the neck to avoid partial clipping are the essential steps when treating intrameatal AICA aneurysms to reduce the risk of postoperative neurological deficits.

Aneurysmal Expansion Presenting as Facial Weakness: Case Report and Review of the Literature

OBJECTIVE AND IMPORTANCE:

Facial paralysis and hemifacial spasm are rare presentations of aneurysms in the posterior fossa. We report an unusual case of rapidly progressive facial palsy caused by the acute expansion of an arteriovenous malformation-associated anteroinferior cerebellar artery aneurysm. The case is notable for the rapid progression of symptoms and their precise correlation with radiographic changes, emphasizing the potential dynamic nature of aneurysms associated with arteriovenous malformations.

CLINICAL PRESENTATION:

A 56-year-old woman with severe headache and nausea was seen in a local emergency room, where she underwent a neurological examination with unremarkable results and a head computed tomographic scan demonstrating acute hemorrhage in the ambient cisterns. Conventional and computed tomographic angiograms demonstrated an arteriovenous malformation in the right cerebellopontine angle fed by the anteroinferior cerebellar and superior cerebellar arteries. A micro-aneurysm measuring 3 mm was noted within the internal carotid artery on the meatal loop of the anteroinferior cerebellar artery. Two weeks later, a rapidly progressive right facial weakness developed in the patient, progressing to complete facial plegia over 12 hours, and complete sensory neural hearing loss. Repeat angiography demonstrated expansion of the previously visualized aneurysm to 8 × 4 mm.

INTERVENTION:

The patient was taken to surgery for clipping of the aneurysm, which required petrous drilling to unroof the canal. She has experienced substantial recovery of facial nerve function.

CONCLUSION:

Although compression of the VIIth–VIIIth nerve complex is an unusual presentation for posterior fossa aneurysms, it represents an important potential complication of vascular pathological features. The rapid aneurysmal expansion, confirmed by imaging and correlating with the rapid onset of symptoms, gives an impressive demonstration of the anatomic changes that can occur in an aneurysm associated with an arteriovenous malformation.

Intracanalicular aneurysm at the meatal loop of the distal anterior inferior cerebellar artery: a case report and review of the literature

BACKGROUND

Distal aneurysms of the anterior inferior cerebellar artery (AICA) are rare. Most of the reported cases have been located near the internal auditory meatus. Among these cases, only six located in the internal auditory meatus have been reported in the literature.

METHODS

A 64-year-old female presented with sudden onset of severe headache. Computed tomography (CT) revealed moderate subarachnoid hemorrhage and Gd-DTPA enhanced magnetic resonance imaging (MRI) showed a small high-intensity mass at the right cerebellopontine angle. Although initial digital subtraction angiography (DSA) showed no vascular abnormalities, repeated DSA disclosed a saccular aneurysm at the top of the meatal loop of the right AICA. The patient underwent a suboccipital craniectomy on the 18th day after the hemorrhage

RESULTS

. In this case, the aneurysm was completely buried in the internal auditory meatus. After unroofing the meatus, the aneurysm was successfully clipped. After 3 months of hospitalization, the patient was discharged with right-sided deafness, partial facial palsy, and no other complications.

CONCLUSIONS

We discuss some of the clinical features and pitfalls in the surgical management of intracanalicular AICA aneurysms and review previous reports of similar cases.

Distal anterior inferior cerebellar artery aneurysms. Report of four cases

Aneurysms of the distal anterior inferior cerebellar artery (AICA) are rare; fewer than 100 cases have been reported. The authors detail their experience with four cases and present endovascular as well as microsurgical management options. The medical records and neuroimaging studies obtained in four patients who were treated at a single institution were reviewed. Clinical presentations, neuroimaging and intraoperative findings, and clinical outcomes were analyzed. There were three men and one woman; their mean age was 43 years. Two patients presented with acute subarachnoid hemorrhage (SAH), and two presented with ataxia and vertigo (one with tinnitus, the other with hearing loss). Angiographic studies demonstrated aneurysms of the distal segment of the AICA. In one patient with von Hippel-Lindau syndrome and multiple cerebellar hemangioblastomas, a feeding artery aneurysm was found on a distal branch of the AICA. Three of the patients underwent successful surgical obliteration of their aneurysms, one by clipping, one by trapping, and one by resection along with the tumor. The fourth patient underwent coil embolization of the distal AICA and the aneurysm. All patients made an excellent neurological recovery. Patients with aneurysms in this location may present with typical features of an acute SAH or with symptoms referable to the cerebellopontine angle. Evaluation with computerized tomography, magnetic resonance (MR) imaging, MR angiography, and digital subtraction angiography should be performed. For lesions distal to branches coursing to the brainstem, trapping and aneurysm resection are viable options that do not require bypass. Endovascular obliteration is also a reasonable option, although the possibility of retrograde thrombosis of the AICA is a concern.

Aneurysm of the distal anterior inferior cerebellar artery at the medial branch: a case report and review of the literature

BACKGROUND

Distal aneurysms of the anterior inferior cerebellar artery (AICA) are rare. Most have been located at the cerebellopontine angle. Only three cases, including ours, located in the medial branch of the AICA have been reported in the literature.

METHODS

A 55-year-old female presented with epilepsy that she experienced for the first time. Computed tomography and magnetic resonance imaging revealed no abnormality. Digital subtraction angiography (DSA) disclosed a rare aneurysm at the medial branch of the distal anterior inferior cerebellar artery. In the blood workup on her admission, a mild inflammatory sign was found, and bacterial aneurysm was suggested as the presumptive differential diagnosis. Repeated DSA was performed 3 months after admission, but the aneurysm did not disappear. She then underwent a suboccipital craniotomy in the prone position.

RESULTS

The aneurysm was clipped and partially resected for the pathological examination. Histologic examination revealed a true aneurysm. She was discharged without neurological deficit.

CONCLUSIONS

In this report, we summarize the previous cases and discuss the location and clinical manifestations of aneurysms of the AICA through a review of the literature.

Value of CT angiography in the evaluation of a peripheral anterior inferior cerebellar artery aneurysm: case report

We report a case of a peripheral anterior inferior cerebellar artery (AICA) aneurysm in a 66-year-old woman. Computed tomography angiography (CTA) demonstrated a saccular aneurysm in the left AICA. A subsequent vertebral digital subtraction angiography using our standard injection technique failed to demonstrate the aneurysm. However, the aneurysm was visualized on a follow-up injection performed with an increased contrast dose and injection rate. CTA proved to be critical in the detection of this aneurysm which could have been easily overlooked on a conventional angiogram.

Aneurysm of the internal auditory artery: our experience and review of the literature

The aneurysms of the internal auditory artery (IAA) situated distal from anterior inferior cerebellar artery (AICA)-IAA junction, are extremely rare lesions. A case of distal aneurysm if IAA is presented causing subarachnoid haemorrhage (SAH) and complete ipsilateral deafness. After the neurosurgical treatment the hearing of the patient definitely improved. The literature of distal aneurysms of AICA is reviewed focusing on the clinical features of these malformations, causing cerebello-pontine angel (CPA) symptoms with or without SAH.

Aneurysms of the posterior cerebral artery: do they present specific characteristics?

A series of 7 cases of PCA aneurysm treated between 1978 and 1992 were analytically reviewed together with 79 cases culled from the literature. In comparison to those localized elsewhere, PCA aneurysms are more frequently large, more frequently present with tumour-like symptoms and appear at an earlier age. Surgical outcome was evaluated in relation to clinical onset, site and size of the aneurysm, the surgical procedures adopted for excluding it and pre-operative clinical grading appeared to influence outcome. The fact that site, size and surgical technique do not significantly influence prognosis is probably due to the rich collateral flow present in the areas fed by the posterior cerebral artery. The authors conclude that, clinically speaking, PCA aneurysms should be considered as a separate group.

Isolated trigeminal neuralgia secondary to distal anterior inferior cerebellar artery aneurysm

A 43-year-old woman complaining of severe pain of the right side of the face was admitted to the Department of Neurosurgery. It had been present for three months and diagnosed as trigeminal neuralgia. The CT scan without contrast material had been considered normal at that time. Three months later, after a favourable response to carbamazepine, she suddenly developed right occipital headache and drowsiness. On admission, she was alert, and neurological examination revealed only mild neck stiffness. Computed tomographic scan demonstrated an acute hematoma in the right cerebellopontine angle and in the fourth ventricle. Vertebral angiography revealed an aneurysm of the right anterior inferior cerebellar artery (AICA). A posterior fossa approach disclosed a large, nearly totally thrombosed, saccular AICA aneurysm, which showed minimal compression to the pons at the trigeminal root entry zone. The aneurysm was clipped and excised. She showed an excellent recovery and was free of pain in the early postoperative period and at the last examination 16 months later. Aneurysms in the distal AICA are very rare lesions. Only 31 cases have been published so far. Distal AICA aneurysm in an extremely unusual cause of trigeminal neuralgia secondary to aneurysmal compression. The literature concerning AICA aneurysms and their clinical manifestations is reviewed and discussed.

Peripheral anterior inferior cerebellar artery aneurysms

Two cases of peripheral anterior inferior cerebellar artery (AICA) aneurysms are reported. The first case was a 60-year-old man who showed frequent attacks of subarachnoid hemorrhage (SAH) and hearing disturbance. His aneurysm was obliterated by trapping the AICA and his neurologic status was unchanged compared with preoperatively. The second case had SAH without cranial nerve involvement; this aneurysm was obliterated by neck clipping. He was discharged without neurologic deficit. Peripheral AICA aneurysm has already been reported in 48 cases including arteriovenous malformation-associated cases. This aneurysm may show cranial nerve involvement (seventh and eighth) without SAH as in the case of internal carotid-posterior communicating artery aneurysms. We review the clinical signs of these cases and discuss them from the point of view of anatomic variations of the AICA and internal auditory artery.

Aneurysms of the peripheral portion of the anterior inferior cerebellar artery; report of two cases

Two cases of extremely rare aneurysms of peripheral portions of the AICA are reported with a review of the pertinent literature. According to reported surgical findings, nearly all of the aneurysms originated from arterial loops near the internal acoustic meatus. These aneurysms can therefore, cause the cerebellopontine angle syndrome, with or without subarachnoid hemorrhage.

Distal posterior cerebral artery aneurysm. Case report

A case of an unusual distal posterior cerebral artery (PCA) aneurysm is presented. The saccular aneurysm arose from a fetal PCA distal to the posterior temporal branch of the P3 segment. The aneurysm was treated by placing a clip on the PCA distal to the anterior temporal branch of the P2 segment. A ventriculoperitoneal shunt was also placed. The patient's postoperative recovery was unremarkable and without residual neurological deficit. The highly unusual location of this aneurysm is discussed and the neurosurgical literature is reviewed in detail.

Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus

An aneurysm of the anterior inferior cerebellar artery extending into the internal auditory meatus is reported. The patient developed headache and vomiting caused by a subarachnoid hemorrhage, and rapidly showed signs and symptoms of a lesion in the cerebellopontine angle soon after the onset. At operation, a clip was successfully applied to the neck of the aneurysm. The characteristic clinical findings are briefly reviewed.

Anterior inferior cerebellar artery aneurysm. Report of three cases

Three cases of aneurysms of the anterior inferior cerebellar artery are reported. Two of the aneurysms were located in the cerebellopontine angle and one in the ventral portion of the pons. Through a suboccipital craniectomy, beck clipping was performed on one aneurysm, neck ligation on another, and coating on the third. A discussion of the surgical procedures and complications includes a review of previous reports.

Posterior inferior cerebellar artery aneurysm in the fourth ventricle: acute surgical treatment

A case of an aneurysm of the posterior inferior cerebellar artery lying in the fourth ventricle is reported. The patient was surgically treated within a few hours after the onset of the subarachnoid hemorrhage by a microsurgical technique using direct exclusion of the aneurysm by a clip. The patient recovered completely following the operation.

Subarachnoid hemorrhage secondary to an aneurysm of the ascending pharyngeal artery: case report

The authors report a patient presenting with subarachnoid hemorrhage (SAH) secondary to one of two saccular aneurysms arising from the dural branches of the ascending pharyngeal artery. The aneurysms were obliterated by surgery without complications. Satisfactory visualization of the aneurysms required selective external carotid angiography with magnification and subtraction. This case emphasized the need to include the external carotid system in conventional four-vessel angiography for evaluation of patients with SAH.

Microsurgical anatomy of the posterior cerebral artery

✓ In order to define the microsurgical anatomy, 50 posterior cerebral arteries (PCA's) were examined using × 3 to × 40 magnification. The PC A was divided into four segments: Pt was the segment proximal to the posterior communicating artery (PCoA); P2 extended from the PCoA to the posterior margin of the midbrain and was subdivided into an equal anterior (P2A) and posterior (P2P) half; P3 began at the posterior midbrain, ran within the quadrigeminal cistern, and ended at the anterior limit of the calcarine fissure. The PCA had three types of branches: 1) cortical branches to the cerebrum; 2) central branches to the brain stem; and 3) ventricular branches to the choroid plexus. The largest branches reaching the lateral surface of the cerebrum were located immediately anterior to the preoccipital notch, and in most cases were branches of the posterior temporal artery. This area offers a greater than 75% chance of finding a vessel large enough to perform a microvascular anastomosis. The central branches were of two types: 1) direct perforating, and 2) circumferential. The direct perforating branches arising on P1 were the posterior thalamoperforating arteries. The “thalamogeniculate artery,” the vessel said to be occluded in the “thalamic syndrome,” was also of the direct perforating type, but it was a series of small arteries arising from P2A and P2P rather than being a single vessel. The circumferential arteries usually arose from P1 and encircled the midbrain providing branches as far posteriorly as the colliculi. The branches to the choroid plexus were the medial and lateral posterior choroidal arteries; the former usually arose from P2A and entered the roof of the third ventricle, and the latter arose as a series of arteries from P2P and passed over the pulvinar to enter the lateral ventricle.

Anterior inferior cerebellar artery aneurysms. Case report

A 54-year-old man experienced a right occipital headache accompanied by a roaring sound, nausea, vomiting, right facial weakness, and stiff neck. Vertebral angiography revealed an aneurysm of the right anterior inferior cerebellar artery (AICA) at the internal acoustic meatus which was later excised with favorable results. The literature is reviewed; operations have been reported in eight other cases. Inconstant waxing and waning cerebellopontine angle symptoms and signs can be found when a history of subarachnoid hemorrhage is lacking.

Aneurysms of the posterior cerebral artery. Locations and clinical pictures

A classification of aneurysms of the posterior cerebral artery from a series of 8 personal cases and 34 cases collected from the literature is attempted. The classification is based on the topography and sites of origin of the cortical and central branches of the artery. The artery was divided into six sections which permitted the description of the origin and projection of typical aneurysms. Single cases of atypical aneurysms can be explained by the known vascular anomalies. The predilective site is section B (origins of the posteromedial choroidal artery and quadrigeminal artery), then section D with the main division of the posterior cerebral artery and origins of the anterior temporal artery, the anterior posterolateral choroidal artery, the hippocampal artery and the thalamogeniculate artery, and finally section C--the junction with the posterior communicating artery. Clinical syndromes corresponding to these locations are described. The classification, when considered together with improved angiographic technique and microsurgery, allows exact preoperative and peroperative definition of topography which in turn enables the avoidance of injury to functionally important typical and atypical central branches of the posterior cerebral artery.

Giant aneurysms of the posterior fossa presenting as space occupying lesions

In relation to the case history of a patient, who was observed at the Ursula Clinic, Wassenaar, Holland, a survey from the literature is given of 47 cases of giant aneurysms of the posterior fossa, which primarily presented as space occupying lesions.