Original ArticleRisk of Aneurysm Residual Regrowth, Recurrence, and de Novo Aneurysm Formation After Microsurgical Clip Occlusion Based on Follow-up with Catheter Angiography
Introduction
Currently, there are no established guidelines for radiologic surveillance after microsurgical treatment of intracranial aneurysms. Various groups have recommended long-term angiographic follow-up for patients with residual and/or multiple aneurysms,1, 2 but published studies have been limited by small sample size and relatively short follow-up periods,2, 3 which then lead to inaccurate estimations of the risk of aneurysm regrowth, recurrence, and de novo aneurysm formation. Although a recent report included 758 aneurysms with 5295.7 patient-years of radiologic follow-up with computed tomographic angiography (CTA) or catheter angiography,1 verification of its findings is necessary because CTA has lower sensitivity (71%) and specificity (94%) for identifying residual and recurrent aneurysms than catheter angiography.4, 5 In addition to these sources of error, differences in reported regrowth, recurrence, de novo aneurysm formation, and hemorrhage rates could be due to interobserver variability. Moreover, the rarity of aneurysm regrowth, recurrence, and de novo aneurysm formation makes best practice recommendations difficult, especially working within the financial constraints of the healthcare system.
We have maintained a prospective database of intracranial aneurysms treated microsurgically at our center for 20 years. In this study, we aimed to propose and validate clinically meaningful definitions for postoperative aneurysm residual, recurrence, and de novo aneurysm formation, and to document our experience with long-term follow-up for patients with microsurgically treated intracranial aneurysms using catheter angiography.
Section snippets
Inclusion Criteria
This study was approved by the institutional review board and performed in compliance with Health Insurance Probability and Accountability Act regulations. A retrospective review of all aneurysms treated microsurgically by the senior author (M.T.L.) between July 1997 and September 2016 was performed to identify patients with long-term follow-up catheter angiography (>1 year after surgery). In total, 240 patients out of 2700 patients (9%) had catheter angiography more than 1 year after surgery.
Clinical and Radiologic Data
Patient Population
We identified 240 patients harboring 380 aneurysms with ≥1 year of angiographic follow-up (Table 1). The mean follow-up time was 6.0 ± 3.3 years per patient (range, 1.0–16.8 years). Ninety patients (37.5%) presented with SAH, and 139 patients (57.9%) presented with multiple aneurysms. Our cohort included 52 (13.7%) large (≥10 mm), 11 (2.9%) giant (≥25 mm), and 32 (8.4%) fusiform aneurysms, and 23 (6.1%) recurrent or residual aneurysms from prior microsurgical clipping or coil embolization.
Need for More Standardized Terminology
Prior studies have consistently described divergent natural histories associated with “completely” and “incompletely” occluded aneurysms on early postoperative angiography. However, in the absence of a more precise, clinically useful, and widely used definition of “incomplete” ligation, it is difficult to synthesize single-institution findings and to accurately prognosticate or convey risks. In their review of the literature, Thornton et al. identified only 2 articles providing a more precise
Conclusion
Microsurgically treated aneurysms in experienced hands have a very low risk of postoperative residuals (4.6% including intentionally left residuals; <1% unintentionally) and aneurysm recurrence (1.5%). Growth of residuals (2/16; 12.5%) and de novo aneurysm formation (3.3%) justify long-term follow-up with catheter angiography 3 to 5 years after microsurgical clipping.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.