- Department of Neurosurgery, Kurashiki Central Hospital, Kurashiki, Okayama, Japan
- Department of Neurosurgery, Himeji Medical Center, Himeji, Hyogo, Japan
- Department of Neurosurgery, Shiroyama Hospital, Habikino, Osaka, Japan
- Division of Neurosurgery, St. Michael's Hospital, Toronto, Ontario, Canada
Division of Neurosurgery, St. Michael's Hospital, Toronto, Ontario, Canada
DOI:10.4103/2152-7806.136701Copyright: © 2014 Fukuda H This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Fukuda H, Iwasaki K, Murao K, Yamagata S, Lo BW, Macdonald RL. Risk factors and consequences of unexpected trapping for ruptured anterior communicating artery aneurysms. Surg Neurol Int 11-Jul-2014;5:106
How to cite this URL: Fukuda H, Iwasaki K, Murao K, Yamagata S, Lo BW, Macdonald RL. Risk factors and consequences of unexpected trapping for ruptured anterior communicating artery aneurysms. Surg Neurol Int 11-Jul-2014;5:106. Available from: http://sni.wpengine.com/surgicalint_articles/risk-factors-and-consequences-of-unexpected-trapping-for-ruptured-anterior-communicating-artery-aneurysms/
Background:While clipping cerebral aneurysms at the neck is optimal, in some cases this is not possible and other strategies are necessary. The purpose of this study was to describe the incidence, risk factors, and outcomes for inability to clip reconstruct ruptured anterior communicating artery (ACoA) aneurysms.
Methods:Of the 70 cases of ruptured ACoA aneurysms between January 2006 and December 2013, our institutional experience revealed four cases of small ACoA aneurysms that had been considered clippable prior to operation but required trapping. When a unilateral A2 segment of anterior cerebral artery (ACA) was compromised by trapping, revascularization was performed by bypass surgery. Clinical presentation, angiographic characteristics, operative approach, intraoperative findings, and treatment outcomes were assessed.
Results:Very small aneurysm under 3 mm was a risk factor for unexpected trapping. The reason for unexpected trapping was laceration of the aneurysmal neck in two cases, and lack of clippaple component due to disintegration of entire aneurysmal wall at the time of rupture in the others. Aneurysms with bilateral A1 were treated with sole trapping through pterional approach in two cases. The other two cases had hypoplastic unilateral A1 segment of ACA and were treated with combination of aneurysm trapping and revascularization of A2 segment of ACA through interhemispheric approach. No patients had new cerebral infarctions of cortical ACA territory from surgery. Cognitive dysfunction was observed in three cases, but all patients became independent at 12-month follow up.
Conclusions:Unexpected trapping was performed when ruptured ACoA aneurysms were unclippable. Trapping with or without bypass can result in reasonable outcomes, with acceptable risk of cognitive dysfunction.
Keywords: Anterior communicating artery aneurysm, cerebral revascularization, cognitive function, subarachnoid hemorrhage, unexpected trapping
Rupture of anterior communicating artery (ACoA) aneurysm is one of the most common causes of aneurysmal subarachnoid hemorrhage (SAH).[
When ruptured ACoA aneurysms are treated with unexpected trapping, perforators from ACoA must be spared to prevent postoperative cognitive dysfunction.[
Here, we describe four cases of ruptured ACoA aneurysms, which were unexpectedly trapped. Through reviewing these cases, risk factors of unexpected trapping and operative strategy to preserve surrounding vessels are discussed.
Patients’ characteristics and preoperative workup
Between January 2006 and December 2013, the authors consecutively treated 70 patients with SAH from ruptured ACoA aneurysms. The choice of treatment, clipping or coiling, was determined according to discussions between surgical and endovascular teams. As a result, 32 cases were assigned to undergo surgical clipping. The morphology of the aneurysm such as broad neck or difficult access route was a factor influencing treatment decision away from coiling in a number of these cases. Formal approval of the institutional ethics review board was not required because of the retrospective nature of our analysis and information obtained from routine clinical care of these patients did not contain any unique identifiers linking these patients.
Computed tomography (CT) angiography was routinely obtained on admission. In surgically treated cases, catheter angiography was performed only when CT angiography provided insufficient information for clipping, or when responsible aneurysm was not detected. The size of the aneurysm was measured on CT angiography. Catheter angiography was only used to measure the size when CT angiography failed to detect the aneurysm.
Both pterional and interhemispheric approaches were used, but surgeons’ preference shifted to the interhemispheric approach over time, where it was selected for 3 cases in the first 16 cases, whereas for 10 in the latter 16 cases. The aneurysm was unexpectedly trapped in four patients where neck clipping was impossible. When unilateral A2 segment of ACA was compromised by trapping, revascularization with bypass surgery was added.
Postoperative patient management
If symptomatic hydrocephalus was present soon after SAH, an external ventricular drain was used to decompress the ventricular system. When hydrocephalus persisted, or if it developed late in the clinical course, ventriculoperitoneal shunt was inserted. Normal blood pressure and normal hydration were maintained to prevent symptomatic vasospasm, and oral calcium channel blocker or intravenous fasudil chloride was given if applicable. Rehabilitation of impaired cognitive function commenced by speech therapists as early as 2 days after operation and continued at least for 3 months. Outcome was assessed with the modified Rankin Scale (mRS) score at 12 months.
Fisher's exact probability test was used to statistically assess whether very small aneurysms are associated with incidence of unexpected trapping. Commercially available software (SPSS version 20, IBM Corp. Armonk, NY, USA) was used to create 2 × 2 contingency table and for analysis. Results were considered significant when P< 0.05.
Among 32 surgically treated ruptured ACoA aneurysms, unexpected trapping was performed in 4 cases and are summarized in
The reason for unexpected trapping was laceration of the aneurysmal neck in two cases, and lack of clippable component due to disintegration of entire aneurysmal wall at the time of rupture in the others. Bypass surgery for revascularization was performed in two cases, where unilateral A2 segment of ACA was compromised by trapping due to aplasia of ipsilateral A1 segment of ACA. Sole trapping without bypass was performed in the other two cases with bilateral equivalent A1 segment of ACA. Under this maximum revascularization strategy, none of the patients experienced ischemic complications of cortical ACA regions, or resultant leg weakness.
Cognitive dysfunction was observed in three patients out of four who underwent unexpected trapping. The cognitive dysfunction was relatively severe soon after operation, but gradually improved in 12 months, representing mRS 1-2. Detailed clinical course of each patient is described below.
Two cases with bilateral A1
Our initial two cases represent similar anatomical feature, operative findings, and clinical course. Case 1 was a 58-year-old female who presented with diffuse SAH of WFNS grade I [
Case 1. Images and intraoperative photographs obtained in a 58-year-old female who suffered SAH of WFNS grade I. (a) Head CT scan obtained on admission demonstrates diffuse SAH. (b) Oblique view of left carotid angiogram with right carotid compression, following negative CT angiogram, reveals a 2 mm saccular aneurysm at the left A1-A2 junction (arrow). (c) Intraoperative photograph of ACoA complex through left pterional approach. A small aneurysm is observed at the left A1-A2 junction. (d)The aneurysm is trapped with two aneurysm clips. Hypothalamic artery is preserved. (e) Postoperative CT angiogram shows the aneurysm is trapped and neither of bilateral A2 segments of ACA is obliterated. (f)Postoperative MRI (diffusion-weighted imaging) demonstrates no ischemic infarction. ACoA= anterior communicating artery, AN= aneurysm, L. A1= left A1 segment of ACA, L. A2= left A2 segment of ACA, Hypo= hypothalamic artery
Case 2 was a 61-year-old female of diffuse SAH with thick hematoma in the interhemispheric fissure [
Case 2. Images, and schemes of intraoperative findings obtained in a 61-year-old female who suffered SAH of WFNS grade II. Intraoperative photographs are not available. (a) Head CT scan obtained on admission demonstrates diffuse SAH with a massive clot in the interhemispheric fissure. (b) Oblique view of right carotid angiogram only reveals a minute protuberance at right A1-A2 junction (arrow). (c) Schematic picture of intraoperative findings through right pterional approach. A fragile fibrin cap (arrowhead) covers a small hole (arrow) on right A1-A2 junction. No defined aneurysm wall is observed. (d) An aneurysm clip is applied on the small hole across ACoA. A single clip is wide enough to close the small hole. (e) A coronal image of postoperative CT angiogram shows bilateral A2 segments of ACA are intact and left A1 segment of ACA is present. (f) Postoperative head CT scan reveals cerebral edema around thick subarachnoid clot and ischemic infarction of right caudate head caused by prolonged temporary clipping. However, most of ACA territory is spared. L. A1 = left A1 segment of ACA, L. A2 = left A2 segment of ACA, R. A1 = right A1 segment of ACA, R. A2 = right A2 segment of ACA
Case 3 with unilateral A1
Case 3 presented the most complex clinical course. A 66-year-old female was referred to our hospital for SAH of WFNS grade I (E4V5M6) [
Case 3. Images, intraoperative photographs, and a schematic operation plan of a 66-year-old female who suffered SAH of WFNS grade I. (a)Head CT scan obtained on admission demonstrates diffuse SAH. (b) CT angiogram of left vertebral artery reveals a 5 mm saccular aneurysm at the left P1 segment of posterior cerebral artery (arrow). (c) Three-dimensional rotational left carotid angiogram obtained when SAH recurred on the 7th day after initial SAH. A 2 mm aneurysm-like dilatation (white arrow) is observed on ACoA. CT angiogram of bilateral internal carotid artery obtained on admission (inset) reveals small dilatation of ACoA (black arrow). Retrospectively compared with the imaging on day 7, the aneurysm-like dilatation is growing. Right A1 segment of ACA is aplastic. (d) Intraoperative photograph of ACoA complex through interhemispheric approach. A fragile fibrin cap (arrow) is observed on ACoA and no defined aneurysm wall is observed. Right A2 segment of ACA winds around the fibrin cap. (e) Schematic imaging of left STA-right ACA bypass with interposition graft. The parietal branch of left STA (between dashed lines) is detached and used as the interposition graft between the frontal branch of left STA and right callosomarginal artery. (f)Intraoperative photograph of the bypass. The distal end of the interposition graft (arrowheads) is anastomosed with the right callosomarginal artery (arrow) in end-to-side fashion. (g)The aneurysm is clipped by slightly incorporating the normal vessel wall of ACoA. Hypothalamic artery is preserved both morphologically under the microscope (arrow), and optically under the indocyanine green videoangiography (arrowheads). (h) Head CT scan is obtained 7 days after the second SAH when patient's consciousness suddenly deteriorated. Intraventricular and intracerebral hemorrhage suggests the third rupture of the aneurysm. (i)Three-dimensional rotational catheter angiogram (subtracted image) reveals aneurysm-like dilatation on ACoA (arrow). Inset shows nonsubtracted image of the same angiogram, suggesting displacement of the aneurysm clip. (j) Left external carotid angiogram at the third SAH demonstrates blood flow of right distal ACA territory through patent left STA-right ACA bypass. End-to-side anastomosis between interposition graft and callosomarginal artery is indicated (arrow). (k) The aneurysm is trapped with two aneurysm clips. The proximal blue clip is applied adjacent to the origin of the hypothalamic artery (arrow). Flow signal of the hypothalamic artery under indocyanine green videoangiography is still visible but diminished (arrowheads). (l) Postoperative MRI (diffusion-weighted imaging) shows residual hematoma in the right frontal lobe, but no ischemic infarction. ACoA= anterior communicating artery, L. A1= left A1 segment of ACA, L. A2= left A2 segment of ACA, R. A2= right A2 segment of ACA
Operation commenced with bifrontal craniotomy and the interhemispheric fissure was widely opened from genu of corpus callosum to rectus gyrus. There was no clippable component at the aneurysm neck because entire aneurysmal wall was disintegrated and the virtual neck of the aneurysm was only covered with a fragile fibrin cap [
The patient recovered well, although she was slightly confused due to symptomatic vasospasm. However, on the 7th day after the onset of the second SAH, the patient suddenly became comatose. Head CT scan demonstrated the third ictus of SAH with intracerebral and intraventricular hemorrhage [
Her recovery of consciousness from comatose was excellent. Postoperative MRI revealed no cerebral infarction related to the surgical procedure [
Case 4 with unilateral A1
A 58-year-old female walked into our clinic with intractable dizziness and nausea for 3 days. She was undergoing dialysis for her chronic renal failure caused by familial polycystic kidney disease. She had a history of neck clipping of unruptured left middle cerebral artery aneurysm some 13 years ago at another institution. Her GCS was E4V5M6 so WFNS grade was I. Head CT scan demonstrated small amount of SAH in the interhemispheric fissure [
Case 4. Images and intraoperative photographs obtained in a 58-year-old female who suffered SAH of WFNS grade I. (a) Head CT scan obtained on admission demonstrates localized SAH in the interhemispheric fissure (arrow). (b) CT angiogram reveals a 6 mm wide-neck saccular aneurysm on ACoA (arrow). Right A1 segment of ACA is aplastic. (c)Intraoperative photograph of ACoA complex through interhemispheric approach. The aneurysm is explored with a temporary clip applied on left A1 segment of ACA. Hypothalamic artery (arrowheads) is encased in the posterior wall of the aneurysm. Minor bleeding occurs at the neck of the aneurysm (arrow). (d) Preparation of A3-A3 side-to-side anastomosis in the widely opened interhemispheric fissure from optic nerve (ON) to genu of the corpus callosum (G). Inset shows the bypass is successful. (e) The aneurysm, together with hypothalamic artery, is trapped with two aneurysm clips. (f) Postoperative CT angiogram shows the aneurysm is completely obliterated and right A2 segment of ACA is supplied through A3-A3 bypass. (g) Postoperative MRI (diffusion-weighted imaging) shows no ischemic infarction. L. A2= left A2 segment of ACA, R. A2= right A2 segment of ACA, ON= optic nerve, G= genu of corpus callosum
Operation was performed via anterior interhemispheric approach. Dissection of interhemispheric fissure between rectus gyrus and genu of corpus callosum provided sufficient exposure of the ACoA aneurysm. During dissection, left olfactory nerve was missing and A1 segment of left ACA adhered to surrounding brain tissue, suggesting ACoA had been explored in the previous operation. The adhesion was more prominent around the aneurysm, and hypothalamic artery was encased in the aneurysmal wall with glue material [
The patient revealed good postoperative recovery with no apparent ischemic change on follow-up MRI [
In this article, we describe four cases of ruptured ACoA aneurysms that were unexpectedly trapped. Very small aneurysms under 3 mm were significantly associated with incidence of unexpected trapping. Trapping with elective bypass was a reasonable strategy to prevent disastrous rerupture and substantial cerebral infarction, with acceptable long-term outcome of cognitive function.
Very small aneurysms, which are defined as aneurysms under 3 mm, are associated with higher risk of procedure-related rupture when treated by endovascular coiling and generally treated surgically.[
In our case series of SAH, A2 segment of ACA was reconstructed by bypass surgery when it was compromised by aneurysm trapping. Aplasia of unilateral A1 segment is not uncommon, and this anatomical variant is associated with high incidence of aneurysms in the region of ACoA.[
We used two types of revascularization: STA-ACA bypass with interposition graft and A3-A3 in situ bypass, when unilateral A2 segment was compromised. Each procedure has advantages and drawbacks.[
In this study, we found interhemispheric approach was more advantageous than pterional approach to maximally avoid unexpected trapping. Wider front view of ACoA provided by interhemispheric approach enables finer manipulation and various options for clipping trajectory.[
The unsolved problem of unexpected trapping of ACoA is impairment of cognitive function when perforating arteries are involved. Previous studies showed that cognitive dysfunction was more likely observed after rupture and/or repair of ACoA aneurysms, which is referred to as “ACoA syndromes”.[
Limitations of our study include the small number of patients and its retrospective approach. The high incidence of unexpected trapping might be caused by a referral bias. Coilable aneurysms might be treated in other hospitals and the patients with uncoilable aneurysms might be predominantly referred for clipping to our institute, where direct aneurysm surgery is always available. However, we believe cases described here cover most of possible causes and sequelae of unexpected trapping of ruptured ACoA aneurysms and would like to stress validity of revascularization of ACA territory when unilateral A2 is sacrificed. Future evaluations with a large number of patients are warranted to address precise incidence of unexpected trapping and proper strategy to treat ACoA aneurysms with risk factors of unexpected trapping.
Unexpected trapping was performed when ruptured ACoA aneurysms were unclippable. Very small aneurysms under 3 mm were significantly associated with incidence of unexpected trapping. Trapping of ACoA aneurysm is acceptable to obtain reasonable results as long as maximum cerebral revascularization is performed.
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