“Basilar Perforator Aneurysm Communicating with Pseudoaneurysm Cavity: Case Report and Literature Review.”

(Presentation Number: EP-105)

Vistasp Jimmy Daruwalla, MD;1 Furqan Syed, MD;1 Amir R. Honarmand, MD;1 Ali Shaibani, MD.1 Michael C. Hurley, MD;1 Sameer A. Ansari, MD,PhD;1

1Department of Neuroradiology Northwestern University-Feinberg School of Medicine

The authors have no conflicts of interest or other disclosures to declare.

Background

• Basilar perforator aneurysms an exceeding rare but are detected on clinical imaging

for diffuse or perimesencephalic/pre-pontine SAH.

• Arterial hypertension and intracranial dissection pathology have been denoted as one

of inciting causes for perforator aneurysm development, but the exact etiology is

unknown.

• We describe a case of a 2-3 mm dissecting and ruptured basilar perforator aneurysm communicating with a separate, isolated 6 mm pseudoaneurysm cavity.

• This case illustrates an unusual communication of a small perforator aneurysm and pseudoaneurysm cavity that frankly ruptured into the peri-mesencephalic and pre-pontine cisterns resulting in subarachnoid hemorrhage.

• The case represents a difficult treatment paradigm with high morbidity and low potential for success either via endovascular coil embolization, flow diversion stenting, or microsurgical strategies.

Case Report• 76-year-old male with past medical history of hypertension, hyperlipidemia,

diabetes, atrial fibrillation, cecal arteriovenous malformation and acute myeloid leukemia presents with Hunt-Hess Grade 4/Fisher Grade 4 subarachnoid hemorrhage with prominent pre-pontomedullary hemorrhage extending along the foramen magnum.

• CT angiography (CTA) head/neck findings were initially suggestive of a 2-3 mm sidewall basilar artery aneurysm. 

• Conventional angiography was performed for potential endovascular treatment planning, but clearly identified the aneurysm arising superiorly from a lateral basilar artery perforator and separate from the basilar artery sidewall, on both 3-D rotational and subsequent magnified oblique DSA imaging.

• Subsequent outflow from the small perforator aneurysm was contained, superiorly into a channel communicating with a larger 6 mm saccular pseudoaneurysm cavity, also present on prior CTA head studies.

• These findings are consistent with a ruptured basilar perforator dissecting aneurysm and associated pseudoaneurysm cavity, exhibiting contrast stasis and slow washout in the capillary and venous phases.

• The patient remained a poor surgical candidate due to comorbid conditions including a poor clinical grade presentation, elderly age, and eloquent posterior circulation location for microsurgical access.

• The patient was placed on vasospasm prophylaxis and antihypertensive control as well as slightly normal to high ventriculostomy drainage parameters at 10-20 cm H2O.

• Our patient responded well to conservative therapy and will follow up within 3 weeks for a repeat MRI and MRA of brain.

Case Report

Imaging Findings

Figure 1: (A & B) Initial axial NCCT scans demonstrate Fisher grade 4 subarachnoid hemorrhage more pronounced at the prepontine cistern with intraventricular extension into both lateral ventricles and supratentorial hydrocephalus. (C & D) Axial and coronal MIP CTA reconstructions demonstrate a sidewall small aneurysm arising from the basilar artery (small arrow) with adjacent contrast cavity suspicious for pseudoaneurysm (big arrow).

Imaging Findings

• Figure 2: (E, F & G)) Left vertebral artery serial AP digital subtraction angiography (DSA) images and (H) right vertebral artery 3D DSA reconstruction demonstrate a small aneurysm (solid arrow) arising from a left basilar artery perforator (asterisk) connected by a short stalk (arrowhead) to a larger pseudoaneurysm cavity ( dotted arrow), opacified in the delayed capillary and venous phases.

Imaging Findings

• Figure 3: (I, J & K) Right vertebral AP and bilateral oblique DSA images performed after 4 days from the initial angiogram demonstrate normal appearance of the basilar artery with no evidence of the sidewall basilar artery aneurysm or the pseudoaneurysm cavity suggesting spontaneous thrombosis, but also poor visualization of the associated basilar perforator, probably also intervally occluded.

Discussion

• Basilar perforator aneurysms are rare lesions with very few reported cases.

• Basilar artery perforators have been stratified into caudal, middle and rostral perforators: caudal perforators range from 2-5 in number with a diameter of 80-600 um, middle perforators range from 5-9 in number with a diameter of 210-940 um, and rostral perforators range from 1-5 in number with a diameter of 190-800 um in diameter.

• Approximately 40-70% of these perforators anastomose with other perforators for redundancy. Aneurysms are commonly associated with the middle or rostral basilar perforators. Male predilection in basilar perforating aneurysms has also been noted [1].

• Basilar perforator aneurysms are slow opacifying aneurysms on conventional angiography due to the small caliber of the parent vessel and commonly harbor intra-aneurysm thrombus. These characteristics make diagnostic evaluation of basilar perforating aneurysm a challenging task.

• [1]Gross BA, Puri AS, Du. R. Basilar trunk perforator artery aneurysms. Case report and literature review. Neurosurg Rev. 2013 Jan; 36(1):163-8

Discussion • Although CTA has been the initial and non-invasive assessment for acute SAH, a

basilar perforating aneurysm can be easily missed due to its small size, variable location, and slow opacification and potential for obscuring intra-aneurysm thrombus [2].

• Hence it is important to maintain an index of suspicion for basilar perforating aneurysms in negative or equivocal imaging studies with careful assessment of follow-up conventional angiography in the delayed capillary and venous phases.

• Additional utilization of other cross-sectional modalities such as MR imaging may be more sensitive to thrombosed aneurysm components.

• On reviewing the paucity of literature, there has been debate on microsurgical and endovascular treatment versus conservative medical management of these lesions. Maeda et al reported 2 cases of cerebral aneurysms arising from basilar perforators manifesting as intracranial and subarachnoid hemorrhages.

• In both cases the aneurysm was resected and the parent artery was clipped, but postoperatively one patient was severely disabled and the other died of pneumonia leading to septic shock [3]

• [2] Mathieson CS, Barlow P, Jenkins S, Hanzely Z. An unusual case of spontaneous subarachnoid haemorrhage - a ruptured aneurysm of a basilar perforator artery. Br J Neurosurg. 2010 Jun;24(3):291-3

• [3] Maeda K1, Fujimaki T, Morimoto T, Toyoda T. Cerebral aneurysms in the perforating artery manifesting intracerebral and

subarachnoid haemorrhage--report of two cases. Acta Neurochir (Wien). 2001 Nov;143(11):1153-6.

Discussion • Another report by Hamel et al described surgical resection of the aneurysm after

failed attempt at endovascular coil embolization, resulting in a tension penumocephalus the patient suffering psychomotor slowing and gait ataxia [4].

• A literature review by Gross et al investigated twelve cases of basilar perforator aneurysm of which three were managed conservatively, only one patient developed transient third nerve palsy and hemiparesis due to cerebral vasospasm, but no permanent neurological sequelae. It was also noted that only two-thirds of patients treated surgically or by endovascular coiling remained neurologically intact, but 33% suffered from neurological sequelae [1]

• Due to the higher morbidity from complications of aggressive endovascular treatment and/or microsurgical clipping in this eloquent posterior fossa region and the inevitable sacrifice of a basilar perforator, conservative medical management may be considered.

• Basilar perforator aneurysms are supplied by low flow, small caliber arteries and may spontaneously thrombose [2], however the rehemorrhage rates of such lesions is unpredictable.

• [4] Hamel W, Grzyska U, Westphal M, Kehler U. Surgical treatment of a basilar perforator aneurysm not accessible to endovascular treatment. Acta Neurochir (Wien). 2005 Dec;147(12):1283-6.

Discussion • Alternative flow diverting stent reconstruction of the parent basilar artery has

been attempted to induce progressive thrombosis and chronic aneurysm regression while attempting to maintain perforator patency, but this methodology is unproven for this rare pathology.

• Peschillo et al presented 3 cases of basilar perforator aneurysms that were treated with flow diverting stents across the basilar artery, but complications occurred in all 3 patients.

• The first patient suffered from occlusion of the perforator leading to monoparesis of the upper extremity.

• The second procedure was complicated by immediate stent thrombosis, required emergent intravenous tirofiban therapy.

• The third patient suffered from intracranial hemorrhage along the external ventricular drain tract requiring surgical evacuation, secondary to the dual antiplatelet therapy as a prerequisite for placement of intracranial stents.

• Due to the risk of stent related thromboembolic complications to these vital basilar perforators and the contraindication of dual antiplatelets in the subarachnoid hemorrhage setting, flow diverting stents should be likely be avoided in cases of ruptured basilar perforator aneurysms [5].

•  • [5]Peschillo S, Caporlingua A, Cannizzaro D, Resta M, Burdi N, Valvassori L, Pero G, Lanzino G. Flow diverter stent

treatment for ruptured basilar trunk perforator aneurysms. J Neurointerv Surg. 2014 Dec 16. pii: neurintsurg-2014-011511. doi: 10.1136/neurintsurg-2014-011511.

Conclusion

• We describe a dissecting basilar perforator aneurysm communicating superiorly to a pseudoaneurysm cavity.

• We stress the importance of considering these lesions in the differential diagnosis of patients presenting with acute subarachnoid hemorrhage with normal or equivocal CT angiograms.

• Perforating aneurysms not only pose a diagnostic challenge, but are equally difficult to manage.

• Lack of definitive endovascular and microsurgical treatment options along with a wide variety of technical challenges and post-operative complications may compel conservative medical management for co-morbid patients.

References

• [1] Gross BA, Puri AS, Du R. Basilar trunk perforator artery aneurysms. Case report and literature review. Neurosurg Rev. 2013 Jan;36(1):163-8

• [2] Mathieson CS, Barlow P, Jenkins S, Hanzely Z. An unusual case of spontaneous subarachnoid haemorrhage - a ruptured aneurysm of a basilar perforator artery. Br J Neurosurg. 2010 Jun;24(3):291-3

• [3] Maeda K1, Fujimaki T, Morimoto T, Toyoda T. Cerebral aneurysms in the perforating artery manifesting intracerebral and subarachnoid haemorrhage--report of two cases. Acta Neurochir (Wien). 2001 Nov;143(11):1153-6.

• [4] Hamel W, Grzyska U, Westphal M, Kehler U. Surgical treatment of a basilar perforator aneurysm not accessible to endovascular treatment. Acta Neurochir (Wien). 2005 Dec;147(12):1283-6.

• [5] Peschillo S, Caporlingua A, Cannizzaro D, Resta M, Burdi N, Valvassori L, Pero G, Lanzino G. Flow diverter stent treatment for ruptured basilar trunk perforator aneurysms. J Neurointerv Surg. 2014 Dec 16. pii: neurintsurg-2014-011511. doi: 10.1136/neurintsurg-2014-011511.