gms | German Medical Science

Objective: Giant intracranial aneurysms (GIA) often incorporate thrombus or calcifications, which makes direct surgical clipping or endovascular coiling difficult. Therapists usually resort to endovascular flow-diversion-stenting or surgical in- or outflow clip-occlusion in combination with a bypass for flow reversal. Since such thrombosed GIA do not immediately disappear after therapy, follow-up MR-imaging (MRI) is used to assess treatment success. However, artifacts caused by stents or clips can make an exact assessment of changes in GIA size impossible. Using changes in volumes of neighboring intracranial structures – such as the lateral ventricle volume (LVV) – as an indirect indicator of treatment success is a concept used in the treatment of stroke or brain tumors. In an effort to apply this concept to GIA therapy we used MRI data from the International GIA Registry’s data bank to describe changes in LVV in relation to GIA volume before and 1 year after surgery.

Method: 19 consecutive GIA with surgical in- or outflow occlusion alone or in combination with a bypass were included. Pre- and 1-year-posttreatment MRI were used for volumetric analysis of the GIA and the lateral ventricles. As postoperative MRI artifacts made an exact measurement of GIA volume difficult, 2 blinded investigators grouped postoperative GIA volumes by aspect as follows: “clear decrease in volume”, “slight decrease”, “volume unchanged”, “slight increase in volume” and “clear increase”. These categories were then correlated to changes in LVV.

Results: The most significant change in LVV was observed in the “clear decrease in GIA volume” group (10 cases), with an increase in LVV by 64.7% on the same side as the GIA and by 16.7% on the opposite side. The 7 cases that were categorized as “slight decrease in GIA volume” showed an increase in LVV by 16.7% ipsilaterally and by 12.7% contralaterally. The 2 remaining GIA were assessed as “slight increase in volume”. Only in this group a decrease in LVV was observed by 2.8% ipsilaterally and 10.8% contralaterally.

Conclusions: The results of this trial support the view that LVV may serve as a surrogate marker for changes in GIA volume, as LVV increased significantly when GIA volume decreased. Such indirect volume quantification is especially relevant since postoperative MRI artifacts are a common confounding factor in long-term follow-up of GIA.