Coil Breakage during Aneurysm Embolization. Case Report

Parent artery stenting as a rescue management for stretched coils during cerebral aneurysms embolization: Report of three cases and review of literature

BACKGROUND

Displacement of a stretched coil into the parent artery during intracranial aneurysm coiling is a challenging situation where the risk of acute intravascular thrombosis might be a life-threatening condition. The usual way of management is coil snaring, yet in some cases, it might not be feasible to retrieve the coil. Parent artery rescue stenting had already been described as a way of management in acutely thrombosed parent arteries during aneurysm coiling.

CASE REPORTS

We present three cases with an inadvertent displacement of the unraveled coils into the parent artery for which rescue stenting was carried out to crush the coil against the vessel wall aiming to eliminate its thrombogenic effect. Our preliminary experience is that rescue stenting of the parent artery for stretched coil could be a convenient effective option particularly in case of failed/risky snaring with no notable immediate or long-term complications.

REVIEW AND DISCUSSION

We review the reported cases of stretched coils with or without further unraveling and fracture and discuss the possible consequences, salvage methods, and clinical outcomes. Neurointerventionists should be aware of this complication and get acquainted with bailout strategies.

Evaluation of the Straightening Phenomenon of Various Types of Coils

The straightening phenomenon is known as a cause of catheter kickback in the late phase of coil embolization. The mechanism is supposed to be the relative shortage of the stretch resistance (SR) line, and it occurs when a coil is folded too small. Among many SR coils available, there should be a coil-specific tendency to cause this phenomenon. Here, we conducted an in-vitro experiment to know which coil is the most resistant to the straightening phenomenon. We developed an experimental model to reproduce the straightening phenomenon. Five different coils (Axium Prime, ED Coil, Hypersoft, SMART Coil, and Target 360 nano) of the same size (3 mm × 6 cm) were investigated for five times each. Resistance to the straightening phenomenon, which is represented by the insertion length at the onset of the phenomenon, was compared among coil types. The straightening phenomenon was successfully observed in all insertions. Insertion lengths were significantly different among coil types (p = 0.013). The insertion length of ED was the longest (mean ± SD, 27.0 ± 8.3 mm), which means the most resistant to the phenomenon. Axium was second (21.6 ± 7.0 mm), followed by Target (15.8 ± 6.9 mm), Hypersoft (13.8 ± 5.8 mm), and SMART (12.4 ± 4.7 mm). Difference between ED and Hypersoft (p = 0.037) and difference between ED and Smart (p = 0.018) were significant. ED coil was the one with the most resistance to the straightening phenomenon. Selecting the optimal coil is the key to avoid the phenomenon.

Case of a Stuck Coil in the Final Stage of Stent-Assisted Coil Embolization

Objective

We report a case in which two coils became stuck in a microcatheter at the end of coil embolization for a cerebral aneurysm.

Case Presentation

Two coils became stuck in the microcatheter at the final stage of stent-assisted coil embolization for an unruptured anterior communicating artery aneurysm. The rear end of a detached coil was near the tip of the microcatheter. The coil inserted next was pushed out of the microcatheter and pulled back into the microcatheter. Then, the rear end of the detached coil and the retracted coil meshed into the microcatheter, and became immobile. The microcatheter and these two coils were removed simultaneously, and coil embolization was finished.

Conclusion

At the end of coil embolization, the filling rate is relatively high. Insertion of another coil and traction may cause the coils to become stuck in the microcatheter.