Rupture risk of small unruptured cerebral aneurysms

Fusao Ikawa, Akio Morita, Shinjiro Tominari, Takeo Nakayama, Yoshiaki Shiokawa, Isao Date, Kazuhiko Nozaki, Susumu Miyamoto, Takamasa Kayama, Hajime Arai

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

OBJECTIVE The annual rupture rate of small (3-4 mm) unruptured cerebral aneurysms (UCAs) is 0.36% per year, however, the proportion of small ruptured aneurysms < 5 mm is 35%. This discrepancy is explained by the hypothesis that most acute subarachnoid hemorrhage (SAH) is from recently formed, unscreened aneurysms, but this hypothesis is without definitive proof. The authors aimed to clarify the actual number of screened, ruptured small aneurysms and risk factors for rupture. METHODS The Unruptured Cerebral Aneurysm Study Japan, a project of the Japan Neurosurgical Society, was designed to clarify the natural course of UCAs. From January 2001 through March 2004, 6697 UCAs among 5720 patients were prospectively registered. At registration, 2839 patients (49.6%) had 3132 (46.8%) small UCAs of 3-4 mm. The registered, treated, and rupture numbers of these small aneurysms and the annual rupture rate were investigated. The rate was assessed per aneurysm. The characteristics of patients and aneurysms were compared to those of larger unruptured aneurysms (≤ 5 mm). Cumulative rates of SAH were estimated per aneurysm. Risk factors underwent univariate and multivariate analysis. RESULTS Treatment and rupture numbers of small UCAs were 1132 (37.1% of all treated aneurysms) and 23 (20.7% of all ruptured aneurysms), respectively. The registered, treated, rupture number, and annual rupture rates were 1658 (24.8%), 495 (16.2%), 11 (9.9%), and 0.30%, respectively, among 3-mm aneurysms, and 1474 (22.0%), 637 (20.9%), 12 (10.8%), and 0.45%, respectively, among 4-mm aneurysms. Multivariate risk-factor analysis revealed that a screening brain checkup (hazard ratio [HR] 4.1, 95% confidence interval [CI] 1.2-14.4), history of SAH (HR 10.8, 95% CI 2.3-51.1), uncontrolled hypertension (HR 5.2, 95% CI 1.8-15.3), and location on the anterior communicating artery (ACoA; HR 5.0, 95% CI 1.6-15.5) were independent predictors of rupture. CONCLUSIONS Although the annual rupture rate of small aneurysms was low, the actual number of ruptures was not low. Small aneurysms that ruptured during follow-up could be detected, screened, and managed based on each risk factor. Possible selection criteria for treating small UCAs include a history of SAH, uncontrolled hypertension, location on the ACoA, and young patients. Further large prospective and longitudinal trials are needed.

Original languageEnglish
Pages (from-to)69-78
Number of pages10
JournalJournal of neurosurgery
Volume132
Issue number1
DOIs
Publication statusPublished - Jan 1 2020

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Intracranial Aneurysm
Aneurysm
Rupture
Ruptured Aneurysm
Subarachnoid Hemorrhage
Confidence Intervals
Japan
Hypertension
Patient Selection
Statistical Factor Analysis
Multivariate Analysis
Arteries
Brain

Keywords

  • Risk factor
  • Ruptured cerebral aneurysm
  • Screening
  • Small unruptured cerebral aneurysm
  • Vascular Disorders

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

Cite this

Ikawa, F., Morita, A., Tominari, S., Nakayama, T., Shiokawa, Y., Date, I., ... Arai, H. (2020). Rupture risk of small unruptured cerebral aneurysms. Journal of neurosurgery, 132(1), 69-78. https://doi.org/10.3171/2018.9.JNS181736

Rupture risk of small unruptured cerebral aneurysms. / Ikawa, Fusao; Morita, Akio; Tominari, Shinjiro; Nakayama, Takeo; Shiokawa, Yoshiaki; Date, Isao; Nozaki, Kazuhiko; Miyamoto, Susumu; Kayama, Takamasa; Arai, Hajime.

In: Journal of neurosurgery, Vol. 132, No. 1, 01.01.2020, p. 69-78.

Research output: Contribution to journalArticle

Ikawa, F, Morita, A, Tominari, S, Nakayama, T, Shiokawa, Y, Date, I, Nozaki, K, Miyamoto, S, Kayama, T & Arai, H 2020, 'Rupture risk of small unruptured cerebral aneurysms', Journal of neurosurgery, vol. 132, no. 1, pp. 69-78. https://doi.org/10.3171/2018.9.JNS181736
Ikawa F, Morita A, Tominari S, Nakayama T, Shiokawa Y, Date I et al. Rupture risk of small unruptured cerebral aneurysms. Journal of neurosurgery. 2020 Jan 1;132(1):69-78. https://doi.org/10.3171/2018.9.JNS181736
Ikawa, Fusao ; Morita, Akio ; Tominari, Shinjiro ; Nakayama, Takeo ; Shiokawa, Yoshiaki ; Date, Isao ; Nozaki, Kazuhiko ; Miyamoto, Susumu ; Kayama, Takamasa ; Arai, Hajime. / Rupture risk of small unruptured cerebral aneurysms. In: Journal of neurosurgery. 2020 ; Vol. 132, No. 1. pp. 69-78.
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abstract = "OBJECTIVE The annual rupture rate of small (3-4 mm) unruptured cerebral aneurysms (UCAs) is 0.36{\%} per year, however, the proportion of small ruptured aneurysms < 5 mm is 35{\%}. This discrepancy is explained by the hypothesis that most acute subarachnoid hemorrhage (SAH) is from recently formed, unscreened aneurysms, but this hypothesis is without definitive proof. The authors aimed to clarify the actual number of screened, ruptured small aneurysms and risk factors for rupture. METHODS The Unruptured Cerebral Aneurysm Study Japan, a project of the Japan Neurosurgical Society, was designed to clarify the natural course of UCAs. From January 2001 through March 2004, 6697 UCAs among 5720 patients were prospectively registered. At registration, 2839 patients (49.6{\%}) had 3132 (46.8{\%}) small UCAs of 3-4 mm. The registered, treated, and rupture numbers of these small aneurysms and the annual rupture rate were investigated. The rate was assessed per aneurysm. The characteristics of patients and aneurysms were compared to those of larger unruptured aneurysms (≤ 5 mm). Cumulative rates of SAH were estimated per aneurysm. Risk factors underwent univariate and multivariate analysis. RESULTS Treatment and rupture numbers of small UCAs were 1132 (37.1{\%} of all treated aneurysms) and 23 (20.7{\%} of all ruptured aneurysms), respectively. The registered, treated, rupture number, and annual rupture rates were 1658 (24.8{\%}), 495 (16.2{\%}), 11 (9.9{\%}), and 0.30{\%}, respectively, among 3-mm aneurysms, and 1474 (22.0{\%}), 637 (20.9{\%}), 12 (10.8{\%}), and 0.45{\%}, respectively, among 4-mm aneurysms. Multivariate risk-factor analysis revealed that a screening brain checkup (hazard ratio [HR] 4.1, 95{\%} confidence interval [CI] 1.2-14.4), history of SAH (HR 10.8, 95{\%} CI 2.3-51.1), uncontrolled hypertension (HR 5.2, 95{\%} CI 1.8-15.3), and location on the anterior communicating artery (ACoA; HR 5.0, 95{\%} CI 1.6-15.5) were independent predictors of rupture. CONCLUSIONS Although the annual rupture rate of small aneurysms was low, the actual number of ruptures was not low. Small aneurysms that ruptured during follow-up could be detected, screened, and managed based on each risk factor. Possible selection criteria for treating small UCAs include a history of SAH, uncontrolled hypertension, location on the ACoA, and young patients. Further large prospective and longitudinal trials are needed.",
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author = "Fusao Ikawa and Akio Morita and Shinjiro Tominari and Takeo Nakayama and Yoshiaki Shiokawa and Isao Date and Kazuhiko Nozaki and Susumu Miyamoto and Takamasa Kayama and Hajime Arai",
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T1 - Rupture risk of small unruptured cerebral aneurysms

AU - Ikawa, Fusao

AU - Morita, Akio

AU - Tominari, Shinjiro

AU - Nakayama, Takeo

AU - Shiokawa, Yoshiaki

AU - Date, Isao

AU - Nozaki, Kazuhiko

AU - Miyamoto, Susumu

AU - Kayama, Takamasa

AU - Arai, Hajime

PY - 2020/1/1

Y1 - 2020/1/1

N2 - OBJECTIVE The annual rupture rate of small (3-4 mm) unruptured cerebral aneurysms (UCAs) is 0.36% per year, however, the proportion of small ruptured aneurysms < 5 mm is 35%. This discrepancy is explained by the hypothesis that most acute subarachnoid hemorrhage (SAH) is from recently formed, unscreened aneurysms, but this hypothesis is without definitive proof. The authors aimed to clarify the actual number of screened, ruptured small aneurysms and risk factors for rupture. METHODS The Unruptured Cerebral Aneurysm Study Japan, a project of the Japan Neurosurgical Society, was designed to clarify the natural course of UCAs. From January 2001 through March 2004, 6697 UCAs among 5720 patients were prospectively registered. At registration, 2839 patients (49.6%) had 3132 (46.8%) small UCAs of 3-4 mm. The registered, treated, and rupture numbers of these small aneurysms and the annual rupture rate were investigated. The rate was assessed per aneurysm. The characteristics of patients and aneurysms were compared to those of larger unruptured aneurysms (≤ 5 mm). Cumulative rates of SAH were estimated per aneurysm. Risk factors underwent univariate and multivariate analysis. RESULTS Treatment and rupture numbers of small UCAs were 1132 (37.1% of all treated aneurysms) and 23 (20.7% of all ruptured aneurysms), respectively. The registered, treated, rupture number, and annual rupture rates were 1658 (24.8%), 495 (16.2%), 11 (9.9%), and 0.30%, respectively, among 3-mm aneurysms, and 1474 (22.0%), 637 (20.9%), 12 (10.8%), and 0.45%, respectively, among 4-mm aneurysms. Multivariate risk-factor analysis revealed that a screening brain checkup (hazard ratio [HR] 4.1, 95% confidence interval [CI] 1.2-14.4), history of SAH (HR 10.8, 95% CI 2.3-51.1), uncontrolled hypertension (HR 5.2, 95% CI 1.8-15.3), and location on the anterior communicating artery (ACoA; HR 5.0, 95% CI 1.6-15.5) were independent predictors of rupture. CONCLUSIONS Although the annual rupture rate of small aneurysms was low, the actual number of ruptures was not low. Small aneurysms that ruptured during follow-up could be detected, screened, and managed based on each risk factor. Possible selection criteria for treating small UCAs include a history of SAH, uncontrolled hypertension, location on the ACoA, and young patients. Further large prospective and longitudinal trials are needed.

AB - OBJECTIVE The annual rupture rate of small (3-4 mm) unruptured cerebral aneurysms (UCAs) is 0.36% per year, however, the proportion of small ruptured aneurysms < 5 mm is 35%. This discrepancy is explained by the hypothesis that most acute subarachnoid hemorrhage (SAH) is from recently formed, unscreened aneurysms, but this hypothesis is without definitive proof. The authors aimed to clarify the actual number of screened, ruptured small aneurysms and risk factors for rupture. METHODS The Unruptured Cerebral Aneurysm Study Japan, a project of the Japan Neurosurgical Society, was designed to clarify the natural course of UCAs. From January 2001 through March 2004, 6697 UCAs among 5720 patients were prospectively registered. At registration, 2839 patients (49.6%) had 3132 (46.8%) small UCAs of 3-4 mm. The registered, treated, and rupture numbers of these small aneurysms and the annual rupture rate were investigated. The rate was assessed per aneurysm. The characteristics of patients and aneurysms were compared to those of larger unruptured aneurysms (≤ 5 mm). Cumulative rates of SAH were estimated per aneurysm. Risk factors underwent univariate and multivariate analysis. RESULTS Treatment and rupture numbers of small UCAs were 1132 (37.1% of all treated aneurysms) and 23 (20.7% of all ruptured aneurysms), respectively. The registered, treated, rupture number, and annual rupture rates were 1658 (24.8%), 495 (16.2%), 11 (9.9%), and 0.30%, respectively, among 3-mm aneurysms, and 1474 (22.0%), 637 (20.9%), 12 (10.8%), and 0.45%, respectively, among 4-mm aneurysms. Multivariate risk-factor analysis revealed that a screening brain checkup (hazard ratio [HR] 4.1, 95% confidence interval [CI] 1.2-14.4), history of SAH (HR 10.8, 95% CI 2.3-51.1), uncontrolled hypertension (HR 5.2, 95% CI 1.8-15.3), and location on the anterior communicating artery (ACoA; HR 5.0, 95% CI 1.6-15.5) were independent predictors of rupture. CONCLUSIONS Although the annual rupture rate of small aneurysms was low, the actual number of ruptures was not low. Small aneurysms that ruptured during follow-up could be detected, screened, and managed based on each risk factor. Possible selection criteria for treating small UCAs include a history of SAH, uncontrolled hypertension, location on the ACoA, and young patients. Further large prospective and longitudinal trials are needed.

KW - Risk factor

KW - Ruptured cerebral aneurysm

KW - Screening

KW - Small unruptured cerebral aneurysm

KW - Vascular Disorders

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