Recipient artery dissection during extracranial-intracranial bypass surgery: Two case reports

Abstract

BACKGROUND

Superficial temporal artery to middle cerebral artery (STA-MCA) bypass is a valuable treatment for preventing ischemia and hemorrhage in occlusive cerebrovascular disease. Anastomosis site dissection is rarely reported among the various bypass-related complications.

CASE SUMMARY

In this case report, we describe two patients, who were 63- and 59-years-old with middle cerebral artery occlusion treated by STA-MCA bypass. During bypass surgery, the recipient M4 artery intima was dissected. We sacrificed the dissecting portion, and no complications occurred during the follow-up period. Postoperative brain imaging revealed improved brain perfusion. We report rare cases of recipient artery dissection located in the extracranial to intracranial bypass site, and we suggest atherosclerotic changes in the recipient artery and insufficient puncture as the causes.

CONCLUSION

Appropriate recipient artery selection is critical, and if dissection occurs, it is essential to sacrifice the dissecting portion quickly.

Key Words: Anastomosis site dissection; Pseudoaneurysm; Bypass; Atherosclerosis; Recipient artery; Case report

Core Tip: The pathological cause of anastomosis site dissection is not precisely understood. We present two rare cases of recipient artery dissection during superficial temporal artery-middle cerebral artery bypass. In order to take appropriate action when these cases occur, more case studies are needed on the causes. We proposed the atherosclerotic change of the recipient artery as the cause.

INTRODUCTION

Superficial temporal artery to middle cerebral artery (STA-MCA) bypass is one of the direct revascularization procedures used to prevent ischemia and hemorrhage in Moyamoya disease or occlusive cerebrovascular disease[1,2]. Among STA-MCA bypass complications, recipient artery dissection is a very rare phenomenon, and its pathology and appropriate treatments remain unclear[3,4]. Additionally, the literature to date has only mentioned de novo aneurysm formation in the follow-up period, not during surgery[5-7]. Here, we present two cases of cerebral arterial dissection occurring directly after STA-MCA bypass surgery.

CASE PRESENTATION

Chief complaints

Case 1: A 63-year-old male presented intermittent subjective left-arm motor weakness and dizziness suspicious of a transient ischemic attack.

Case 2: A 59-year-old male was admitted to the hospital after experiencing dysarthria, agraphia and finger agnosia.

History of present illness

Case 1: These symptoms occurred 2-3 times a week.

Case 2: The patient presented with slurred speech 2 days ago, and gradually complained of symptoms of Gerstmann syndrome.

History of past illness

Case 1: The patient had a history of hypertension, diabetes and hyperlipidemia.

Case 2: The patient was diagnosed with hypertension and did not take any antihypertensive drugs.

Personal and family history

Case 1: The patient did not drink or smoke, and had no relevant family history.

Case 2: The patient had no history of alcohol consumption. He had a smoking history of approximately 10 cigarettes/day for 30 years. He had no family history of similar disease.

Physical examination

Case 1: The patient did not present obvious motor weakness in our institution.

Case 2: The patient stuttered severely and had difficulty expressing himself, but motor weakness was not evident. The National Institute of Health Stroke Scale score was 1 in this patient.

Laboratory examinations

Cases 1 and 2: Routine clinical biochemistry showed normal results.

Imaging examinations

Case 1: Brain magnetic resonance angiography (MRA) and Digital subtraction angiography revealed complete occlusion of the proximal right middle cerebral artery (MCA) with no transdural collateral vessel involvement (Figure 1A and B). Diamox brain single photon emission computed tomography (SPECT) revealed diminished baseline perfusion and poor cerebrovascular reserve in the right frontal lobe (Figure 1C).

Figure 1 Preoperative brain image findings (case 1). A: Initial brain magnetic resonance angiography revealing right middle cerebral artery occlusion; B: Diagnostic cerebral angiography of the right internal carotid artery injection demonstrating proximal right middle cerebral artery occlusion and no transdural collaterals; C: Brain single photon emission computed tomography revealing moderately diminished baseline perfusion in the right frontal lobe; D: Moderately diminished cerebrovascular reserve in the right frontal, parietal, and temporal lobes.

Case 2: Brain MRA showed acute infarction involving the left MCA territory and total occlusion of the left internal cerebral artery (ICA) at the origin site. Diamox brain SPECT revealed diminished vascular reserve in the left ICA territory.

FINAL DIAGNOSIS

Case 1

Proximal right MCA occlusion was diagnosed according to brain imaging.

Case 2

Left MCA territory infarction with left ICA occlusion was diagnosed.

TREATMENT

Case 1

His neurologic symptoms recovered and were not severe, but considering the decreased perfusion, we performed revascularization with a right-sided STA-MCA bypass. The operation was performed through a single incision following the parietal branch of the superficial temporal artery and then curving toward the occipital site, including Chater’s point. A circular right temporal craniotomy was performed, and the appropriate M4 branch was selected as the recipient artery. After puncturing the recipient artery, an arteriotomy was undertaken, and the intima of the artery with sclerotic change was separated (Figure 2A). As there was no other appropriate recipient vessel, end-to-side anastomosis was undertaken using 10-0 nylon to prevent separation of the intima, media, and adventitia (Figure 2B).

Figure 2 Intra- and postoperative image findings (case 1). A: Intima and media (yellow arrow) of recipient artery dissected from the adventitia layer (black arrow) after arteriotomy; B: To prevent dissection, we performed immediate suturing to ensure that the intima and adventitia were not separated; C: Dissecting aneurysm (yellow arrow) occurred at the anastomosis site after temporary clip removal at the recipient artery; D: Pseudoaneurysm gradually progressed; E: Before further dissection, the dissected portion was trapped using a clip; F: Postoperative brain computed tomography angiography confirmed arterial anastomosis between superficial temporal artery and distal middle cerebral artery.

Unfortunately, the intima was torn during the bypass procedure despite trying to suture the recipient artery’s full thickness. After removing the temporary clip, dissection occurred in the recipient M4 artery, where the intima was separated (Figure 2C). While we considered management options, the dissection gradually progressed proximally; to prevent rupture, we trapped the dissecting aneurysm using clips (Figure 2D and E). Intraoperative indocyanine green angiography confirmed that patency was well maintained at the anastomosis site, excluding the trapping area (Figure 2F).

Case 2

The patient underwent a left STA-MCA bypass procedure. After a circular temporal craniotomy, we performed an arterial puncture of the appropriate M4 branch with a manteaux syringe. When arteriotomy was performed using a micro-scissor, the arterial wall was dissected due to atherosclerosis, and only adventitia was excised (Figure 3A and B). Intimal and medial layers remained intact. The distal margin of the dissected portion was clipped and sacrificed, and end-to-end anastomosis was performed on the contralateral normal recipient artery and STA (Figure 3C and D).

Figure 3 Intraoperative image findings (case 2). A: When arteriotomy was performed, the intima was separated from the adventitia without incision; B: The intima was additionally incised; C: We sacrificed the separated portion of the recipient artery and performed end-to-end anastomosis between the superficial temporal artery (STA) and the M4 recipient artery, where the arterial wall was not separated; D: Postoperative brain computed tomography angiography revealed anastomosis between the left STA and left middle cerebral artery with good patency.

OUTCOME AND FOLLOW-UP

Case 1

The patient had an uncomplicated postoperative course, and postoperative brain SPECT confirmed an improving state of perfusion in the right frontal lobe.

Case 2

Postoperative perfusion computed tomography showed a decreased extent of delayed time to peak perfusion in the left MCA territory with relatively well-preserved cerebral volume and flow. The patient was discharged without any complications.

DISCUSSION

Anastomotic aneurysm is an extremely rare complication that occurs after end-to-side anastomosis of the STA-MCA bypass[4,6,8-11]. Suggested possible causes include hypertension, increased hemodynamic stress due to artificial T-shaped vasculature, and traumatic brain injury during surgical manipulation[6,12]. This bypass-related anastomotic aneurysm is a more commonly reported complication in cardiovascular and peripheral vascular bypass surgery than in STA-MCA bypass surgery[13]. According to Potts et al[4], 24 cases of aneurysm formation at or adjacent to extracranial to intracranial (EC-IC) bypass anastomotic sites have been reported so far, and all were discovered during postoperative follow-up. The period between initial surgery and aneurysm occurrence ranged from less than one month to 21 years. No dissecting aneurysm has been reported immediately after bypass, as was described in our first case. In our second case, we did not attempt bypass because the intima was separated from the adventitia at the incision stage. If anastomosis had been performed, suturing the intima and adventitia together, a pseudoaneurysm would have occurred, as in the first case.

The cause of anastomotic dissection after STA-MCA bypass remains unclear. The causes mentioned above may explain the dissection during the follow-up period after bypass surgery. However, it is insufficient to explain dissection during surgery, as occurred in our cases. We considered intra-operative recipient arterial dissection in two aspects. First, atherosclerotic changes in the recipient artery may cause dissection. Previous studies have demonstrated that atherosclerosis is involved in intracranial dissecting aneurysms[14,15]. Atherosclerosis makes the intima fragile and prone to separation, so dissection may occur due to changes in flow after bypass surgery. This can be expressed in a schema as described in Figure 4A. After the intima is dissected, the dissection may tend to gradually proceed in the direction of the deformed flow along the fragile part due to atherosclerosis under adventitia.

Figure 4 Schema of the causes of dissecting aneurysm. A: After bypass, dissection occurred due to blood flow between the intima and adventitia, which had become fragile due to the atheroma; B: Due to intimal atherosclerotic change, the entire wall of the recipient artery is not dissected; C: Excluding the sacrificed portion, the distal area can achieve an improved perfusion effect as it receives additional blood flow from the donor artery. STA: Superficial temporal artery.

The second cause of recipient artery dissection is when the artery is not punctured to the intima before performing arteriotomy. The method of preparing a recipient artery is to puncture the artery using a small needle and then perform an arteriotomy using micro-scissors. If the entire wall is not incised at once, then the intima is separated, as described in our second case. It may be the operator’s mistake, but if there is an atherosclerotic change in the recipient artery, the intima may not be punctured immediately (Figure 4B). Therefore, when selecting an appropriate recipient artery for bypass, it is critical to check whether there are atherosclerotic changes in the arterial wall.

When a dissecting aneurysm occurs, various management methods, such as clip reconstruction, excision of the aneurysmal anastomotic site, new EC-IC bypass, and STA ligation, have been attempted[4]. The best treatment for dissection remains undetermined, but if dissection occurs during surgery, as in our two cases, another approach should be considered. The area of dissection must be sacrificed quickly before the pseudoaneurysm progresses. One may also attempt bypass surgery by selecting a new recipient artery. However, in our experience, we have confirmed improved perfusion even if end-to-end anastomosis is performed on the non-sacrificed area. We believe this is due to the existing blood flow, though the sacrificed portion is maintained, and blood flow to the bypass site may improve, as demonstrated in Figure 4C. A double barrel bypass may also be considered to improve perfusion further if other appropriate M4 artery segments are available. Due to its rarity and lack of established optimal treatment modalities, this case provides important data for future studies of dissections occurring during EC-IC bypass. To overcome the limitation of small sample size, future studies using additional data are needed.

CONCLUSION

We report two extremely rare cases of recipient artery dissection during STA-MCA bypass surgery. The most critical decision is appropriate recipient artery selection, and if atherosclerotic changes are seen, one must account for the possibility of dissection. Additionally, if arterial dissection occurs, one must sacrifice the dissected portion quickly and perform an end-to-end bypass on the remaining vessel. The outcomes using this management plan are generally good.