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Year : 2019  |  Volume : 67  |  Issue : 6  |  Page : 1474--1479

An Institutional Retrospective Study of Coil Loop Herniation and its Management

Ishu Bishnoi1, Tomotaka Ohshima2, Kojiro Ishikawa2, Taiki Yamamoto2, Shunsaku Goto2, Yoko Kato3,  
1 Department of Neurosurgery, Maharaja Agarsen Medical College, Agroha, Hisar, Haryana, India; Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya, Japan
2 Department of Neurosurgery, Kariya Toyota General Hospital, Kariya, Japan
3 Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya, Japan

Correspondence Address:
Dr. Ishu Bishnoi
Assistant Professor, Neurosurgery, Room No – 18A, Maharaja Agrasen Medical College, Agroha, Haryana


Introduction: Endovascular coiling is a method of aneurysm embolization. Sometimes coil loops herniate in the lumen after deployment of the coil. It is usually seen in wide-necked aneurysms. It can cause migration of the coil and thromboembolic complications. There are different methods such as the use of a balloon, stent, and coil retriever to treat coil loop herniation. There are very few case series on coil loop herniation management. Most series are about the use of a stent/balloon for reposition. We are going to describe simple, novel techniques to treat coil loop herniation. Materials and Methods: In the last five years, 13 aneurysms out of 325 coiled aneurysms had coil loop herniation. We used three different techniques in these patients according to our selection criteria. The first technique was loop trap with another coil, the second was balloon and coil-plasty to trap, and the third was rescue stent and flow control. Results: The first, second, and third techniques were successfully used in five, five and three patients, respectively. There was a complete reposition of herniated coil and thus embolization of aneurysm in all cases. All patients recovered completely without any thromboembolic complications. Conclusions: We recommend the use of these techniques according to the proper selection criteria.

How to cite this article:
Bishnoi I, Ohshima T, Ishikawa K, Yamamoto T, Goto S, Kato Y. An Institutional Retrospective Study of Coil Loop Herniation and its Management.Neurol India 2019;67:1474-1479

How to cite this URL:
Bishnoi I, Ohshima T, Ishikawa K, Yamamoto T, Goto S, Kato Y. An Institutional Retrospective Study of Coil Loop Herniation and its Management. Neurol India [serial online] 2019 [cited 2023 Feb 3 ];67:1474-1479
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Full Text

Endovascular coiling is one of the main treatments of the aneurysm. Nowadays, coiling is performed even in wide-necked aneurysms with or without stent use. Due to this, complications of coil loop herniation, migration, and thromboembolic phenomena have been observed more frequently. One of the technical challenges is intraoperative coil loop herniation after deployment. The reported incidence of coil herniation is between 2.4 to 4.2%.[1],[2] It can be treated by reposition of coil or entrapment, and when its reposition fails or coil migrates, it is retrieved. Various devices which help in reposition of coil loops are balloon, stent, or dual placement of coil and stent.[3],[4],[5] The devices, which are used for retrieving coils, are various types of microsnares, balloon-assisted microsnare.[2],[6],[7] The interventionist usually tries to completely reposit the coil into aneurysm without any complication. At our institute, we analyzed retrospective data of the last 5 years to investigate the management and final outcomes of coil loop herniation.

 Material and Methods

In the last 5 years (January 2012–October 2017), 325 consecutive aneurysms were operated on using the endovascular approach at our institute. Of these, we found coil loop herniation in 13 (4%) aneurysms. Of the 13 patients, nine were female and four were male [Graph 1]. [Graph 2] shows the ruptured and unruptured aneurysm ratio. The average/mean age was 66.62 years. [Table 1] is depicting clinical and demographic profiles of all these patients. The average neck/fundus ratio was 1.86 [Graph 3]. These patients were treated with three different techniques. This study was conducted in accordance with the institutional guidelines and approved by the Human Research Ethics Committees. All patients gave informed consent for publication of their data and images. The techniques are 1) loop trap with another coil, 2) balloon and coil-plasty to reposit the loop, and 3) rescue stent and flow control. The inclusion criteria used for the selection of each technique in coil loop herniation patients were based on the number of herniating loops and the status of the microcatheter. Based on the loop number, the first and second techniques were considered effective for up to two loops and the third technique was effective for any number of loops. As for the microcatheter status, on the microcatheter status, the first technique was considered if the microcatheter was easy to control and not migrating out during manipulation. The second technique was considered if the microcatheter was unstable and manipulation was navigating it out of the aneurysm. Each procedure was done through femoral artery under local anesthesia. After placement of femoral sheath (8F), intravenous heparin was administered to increase activated clotting time to two times its baseline value. No extra anticoagulant was used during coil loop herniation. A separate description of each technique with a brief case summary is detailed below.[INLINE:1][INLINE:2]{Table 1}[INLINE:3]

Technique 1: Loop trap with another coil

A female aged 67 years presented with incidentally detected unruptured right internal carotid artery (ICA) and posterior communicating artery (PCom) junction aneurysm [Figure 1]a, size 8 × 10 × 4 mm. She underwent coiling after informed consent. We used 8F Optimo™ as the guiding catheter, microcatheter Headway™ pre-shaped 90, micro guidewire Chikai™ 4 200-cm, coils—Cashmere™ 3 × 6, Terumo™ HyperSoft 2 × 3, 1.5 × 2, 1.5 × 2, 1.5 × 2. The first framing coil was deployed successfully [Figure 1]b. But after few seconds, two coil loops herniated in the PCom lumen [Figure 1]c. The microcatheter was secured outside but near the aneurysm neck, and the second coil was pushed over the herniating loops [Figure 1]d. The herniated loops were reposited and the second coil was completely deployed inside the aneurysm. Postoperative digital subtraction angiography (DSA) showed complete embolization of the aneurysm and preservation of the PCom lumen [Figure 1]e, and diffusion-weighted MRI (DWI) of the brain showed no ischemic complication [Figure 1]f. The patient recovered well with no postoperative complications.{Figure 1}

Technique 2: Balloon and coil-plasty

A female aged 66 years presented with ruptured right ICA and PCom junction aneurysm [Figure 2]a, size 10 × 13 × 4 mm. She underwent coiling after informed consent. We used the same catheter and guidewire. The coils used were cashmere™ 4 × 8 and Terumo™ HyperSoft 2.5 × 6, 2 × 6, 2 × 6, 2 × 4, 2 × 3, 2 × 3, and the balloon used was Scepter C™ 4 × 10. After deployment of the framing coil [Figure 2]b, its single loop herniated on its own [Figure 2]c. While the balloon was inflated for pushing the coil loop inside, another coil was also deployed along with it to push the previous coils inside the aneurysm [Figure 2]d and [Figure 2]e. The coils were completely reposited. Postoperative DSA [Figure 2]f showed complete embolization of aneurysm and preservation of the PCom lumen, and MRI-DWI of brain showed no ischemic complication [Figure 2]g. The patient recovered well and there was no postoperative complication.{Figure 2}

Technique 3: Rescue stent and flow control

A female aged 63 years presented with incidentally detected unruptured right ICA and superior hypophyseal artery (SHA) junction aneurysm [Figure 3]a, size 7 × 12 × 3.2 mm. She underwent coiling after informed consent. We used the same catheter assembly. The coil used was Cashmere™ 3 × 6 and the rescue stent used was Neuroform™ 4 × 20 mm. After deployment of the framing coil [Figure 3]b, the loops herniated into the ICA within a few seconds [Figure 3]c. We controlled flow using an Optimo catheter and prevented further herniation or migration. The rescue stent was used to trap the coil [Figure 3]d and thus keep the ICA lumen patent. Postoperatively, DSA showed complete embolization with patent lumen [Figure 3]e, and MRI-DWI of brain showed no ischemic complication [Figure 3]f. The patient recovered completely. She was kept on anticoagulant aspirin and clopidogrel to prevent stent thrombosis.{Figure 3}

All 13 patients recovered well without any temporary or permanent thromboembolic complications or dissection. We did not find any complications of the anticoagulant therapy. Postoperative MRI with DWI of the brain was done within 3–5 days in every patient and was negative in all cases. Stent patients were prescribed the anticoagulant clopidogrel for 3–6 months.


Endovascular coiling has advanced significantly in the last decade. It is now performed in any kind of aneurysm with or without the help of balloon/stent/flow diverters. The intraoperative coil complications are more common in complex, wide-necked aneurysms.[7],[8],[9] In our study, the average neck/fundus ratio was 1.6:1, which was lesser than recommended ideal fundus/neck ratio 2:1.[7],[8],[9] It was one of the reasons for using coil loop herniation in these 13 patients. Another reason was the wide-necked nature of the aneurysms (≥4 mm) in seven patients.[7],[8],[9] We have used similar kinds of coils (Hypersoft™ and Cashmere™) in most of the treated patients. This is why we did not relate the incidence of coil loop herniation with the type of coil used.

The most common cause of morbidity and mortality after coiling is iatrogenic ischemia (a thromboembolic phenomenon).[8],[9],[10] This complication can occur because of intraoperative coil migration or coil loop herniation leading to endothelial injury/dissection/dislodgement of thrombus or coil embolization of vessels. As mentioned earlier, the reported incidence of coil loop herniation is 2.4–4.2% in the literature. Our results were similar with a 4% incidence.[1],[2] The interventionist must remain fully equipped with different methods to prevent and manage coil loop herniation. The first attempt must be made to prevent coil loop herniation by using balloon or stent assistance.[3],[4],[5],[9] However, the use of balloon and stent are associated with the increase in cost and also increase in the risk of thromboembolic complications.[9],[10],[11],[12] Thus, balloon and stent use are only considered in cases of complex, wide-necked aneurysms. In most of cases, coiling itself can be considered the treatment. However, attempting coiling solely as the treatment mode can cause loop herniation after deployment. In addition, the surgeon has to fact the challenge to reposit it back in its place. The usual causes of loop herniation are wide-necked aneurysms, small-sized framing coil, push by another coil, and recoil effect.[2],[13]

In coil loop herniation management, two approaches are usually taken. Either reposit/trap it (which is the main objective) or retrieve the coil. Nowadays, there are many devices used for retrieving the coil; for example, manual aspiration, stent, microwares, the Alligator Retrieval device, Merci devices, snares, and stent retievers.[6],[14] The reposition or trapping of coil loop is done by balloon or stent.

The use of balloon by itself for reposition carries the disadvantage of recoiling after deflation of the balloon. It is considered effective if the herniated coil loop diameter is no more than 50% of diameter of parent artery.[1] Thus, stent use has been preferred over the use of a balloon in case of coil loop herniation.[1] Recently, stent use has been utilized for the retrieval of the coil.[15] However, stent use carries two important disadvantages of increased thromboembolic complications and the requirement of lifelong anticoagulant therapy for the patient. The first two techniques, which do not involve stent use, are without these complications. The advantages of first technique (loop trap with another coil) are low cost, the fact that it can be performed with the same catheter and the avoidance of stent disadvantages. The second technique (both balloon and coil-plasty) has disadvantage of using a blloon and thus increased chances of dissection/thromboembolism. But it might be more effective than using balloon by itself as the use of a second coil adds in its efficacy. The simultaneous use of a coil, along with balloon, might help for better control of the recoil effect. Thus, the chances are increased for coil loop reposition. The third technique (rescue stent and flow control) has the disadvantages of stent use, but the flow control helps in the prevention of migration of small emboli and also coil loops. Thus, the use of this technique reduces embolic and coil migration complications. We have found fair results in all patients. In the last 5 years, we have not used a coil retrieval device after using these techniques. To achieve best results, we strongly recommend the use of selection criteria for each technique.

Our study has a few limitations. We did not compare the study with pure stent/balloon use. We did not compare it with coil retrieval. However, we aimed for coil reposition and not retrieval. Till now, we have used these techniques in 13 patients only.


The coil loop herniation is a technical challenge for the interventionist. It is more common in the wide-necked aneurysm and those with a lower neck/fundus ratio. There are limited case series about management of this complication. There are many individual case reports, mostly about retrieval of a coil. We recommend that our main aim should be to reposit the coil. To achieve this aim, the techniques described above may help.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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