Elsevier

World Neurosurgery

Volume 106, October 2017, Pages 74-84
World Neurosurgery

Original Article
Risk of Aneurysm Residual Regrowth, Recurrence, and de Novo Aneurysm Formation After Microsurgical Clip Occlusion Based on Follow-up with Catheter Angiography

https://doi.org/10.1016/j.wneu.2017.06.110Get rights and content

Introduction

Established guidelines for radiologic surveillance after microsurgical treatment of intracranial aneurysms are lacking in the literature because of small sample sizes, poor definitions, and heterogeneous use of imaging modalities. We aimed to propose clinically meaningful definitions for postoperative aneurysm residual, recurrence, and de novo aneurysm formation and to analyze our long-term follow-up catheter angiography results in patients with microsurgically treated intracranial aneurysms.

Methods

A retrospective review of all aneurysms treated microsurgically in a consecutive, single-surgeon series from 1997 to present identified patients with long-term follow-up catheter angiography (>1 year after surgery). Clinical and radiologic data were collected for analysis.

Results

We identified 240 patients harboring 380 aneurysms (mean follow-up time, 6.0 ± 3.3 years per patient; range, 1.0–16.8 years). Postoperative residuals were present in 16 out of 346 clipped aneurysms (4.6%), of which only 3 were left unintentionally. Two out of 16 residual aneurysms (12.5%) demonstrated regrowth, with a regrowth risk of 2.1% per year from 93.6 patient-years of angiographic follow-up. Of 326 aneurysms with no postoperative residual, 5 (1.5%) demonstrated aneurysm recurrence, with a recurrence risk of 0.26% per year from 1931.9 patient-years of angiographic follow-up. Eight de novo aneurysms were identified in 240 patients (3.3%), with a risk of 0.6% per year from 1441.9 patient-years of angiographic follow-up.

Conclusions

Microsurgically treated aneurysms have a very low risk of postoperative residuals and aneurysm recurrence. Growth of residuals and de novo aneurysm formation justify following up with catheter angiography 3 to 5 years after microsurgical clipping.

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.

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