Optimal first coil selection to avoid aneurysmal recanalization in endovascular intracranial aneurysmal coiling

Key points:

  • To investigate factors related to an optimal 1st VER for endovascular coiling.

Coiling, simple or balloon-/stent-assisted, is an endosaccular technique of treatment and a long-term follow-up is mandatory: the problem of aneurysmal recanalization remains and according to a systematic review, recanalization occurs in 20.8% of patients. The volume embolization ratio (VER) has recently been reported to be associated with aneurysmal recanalization. It is a general consideration that the choice of the 1st coil (1st VER) is important to obtain a high VER. In this paper, published online January 27, 2017, Authors investigated factors related to an optimal 1st coil choice. Obviously only normal size aneurysms (3-10 mm) were considered, because small aneurysms need only small coils and large/giant aneurysms have large volume, but large-volume coils have never been developed.

Neki H, KohyamaS, Otsuka T et al. analyzed 609 angiographic images of patients with intracranial normal size aneurysms, treated with coils in Saitama Medical University International Medical Center, Saitama, Japan, between January 2010 and December 2014. They calculated aneurysm volume, coil volume, VER, and 1st VER.


Aneurysm volume height x length x width x 𝛑=6
Coil volume (primary diameter)² x length x 𝛑=4
VER (%) (total coil volume/calculated aneurysm volume) x 100
1st VER (%) (first coil volume/calculated aneurysm volume) x 100

In the original research are available details about endovascular procedure, patients and aneurysm characteristics. The first coil was selected primarily to match the minimum aneurysmal diameter. The larger primary diameter coil (inch) was selected as a priority in the same first loop diameter coils (mm). Angiographic outcome immediately and at the follow-up (6-months and 1-year) was assessed according to the Raymond scale.

RROC (Raymond-Roy occlusion classification)

Class I complete obliteration
Class II residual neck
Class III residual aneurysm

At the multivariate analysis the factors associated with recanalization were:

  • Ruptured aneurysms

  • Maximum aneurysm size.

  • 1st VER <10.0%.

  • VER <33.0%

In conclusion, it is a general consideration that the cut-off VER value for inhibition of aneurysmal recanalization is 33.0%, but this paper gives great importance to 1st VER, depending on the 1st coil selected, like a novel predictor of recanalization. Authors calculated the relationship between the 1st VER and VER, concluding that:

  •  A 1st VER of 17.5-20%, allow to achieve significantly greater VERs. 

  •  The VER was proportional to the 1st VER when it was <15%. 

  •  Compartmentalization can occur when the 1s VER is >20%, and massive coil insertion is impeded by an excessively longer first coil. 

See also
FCP (Framing Coil Percentage)
Ishida W, Sato M, Amano T, Matsumaru Y. The significant impact of framing coils on long-term outcomes in endovascular coiling for intracranial aneurysms: how to select an appropriate framing coil. J Neurosurg. 2016 Sep;125(3):705-12. doi: 10.3171/2015.7.JNS15238. Epub 2016 Jan 8.
Useful resource
AngioCalc – is dedicated to providing quality resources for the management of aneurysms and features an online calculator that calculates cerebral and peripheral aneurysm volume and percent packing volume after coil embolization.


– Neki H, Kohyama S, Otsuka T, Yonezawa A, Ishihara S, Yamane F. Optimal first coil selection to avoid aneurysmal recanalization in endovascular intracranial aneurysmal coiling. J Neurointerv Surg. 2017 Jan 27. pii: neurintsurg-2016-012877. doi: 10.1136/neurintsurg-2016-012877. [Epub ahead of print]

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