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CC BY-NC-ND 4.0 · Asian J Neurosurg
DOI: 10.1055/s-0045-1811243
Original Article

Clinical Features and Post-Coiling Outcomes of Symptomatic Internal Carotid Artery–Posterior Communicating Artery Aneurysms: A Case Series and Literature Review

Daisuke Wajima
1   Department of Neurosurgery, Kanazawa University, Ishikawa-ken, Kanazawa, Japan
,
Tomoya Kamide
1   Department of Neurosurgery, Kanazawa University, Ishikawa-ken, Kanazawa, Japan
,
Mitsutoshi Nakada
1   Department of Neurosurgery, Kanazawa University, Ishikawa-ken, Kanazawa, Japan
› Institutsangaben

Funding None.
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Abstract

Objective

This article aims to understand the clinical course of symptomatic internal carotid artery (ICA)–posterior communicating artery (PCom) aneurysms and the outcomes of post-coiling for unruptured symptomatic aneurysms by analyzing the anatomical imaging data and patient backgrounds of patients treated in our institute in the last 5 years.

Materials and Methods

This study enrolled 82 patients with ICA-PCom aneurysms. Anatomical factors, including age, sex, side, aneurysm dome and neck size, aneurysm depth/neck width ratio (ASPECT ratio), family history of cerebral aneurysm, history of hypertension, smoking habit, angle between aneurysm dome protrusion and ICA C2 portion, angle between ICA C2 and C3 portions, and PCom diameter, were analyzed. In the outcome analysis of coil embolization for symptomatic unruptured ICA-PCom aneurysms, we evaluated age, sex, side, aneurysm dome and neck side, ASPECT ratio, volume embolization ratio, and time from onset.

Statistical Analysis

Mann–Whitney U and Fisher's exact tests were utilized for quantitative and categorical variables, respectively.

Results

In both ruptured and unruptured ICA-PCom aneurysms, the angle between the aneurysm dome protrusion and ICA C2 portion and the angle between the ICA C2 and C3 portions were smaller in the oculomotor palsy group than in the nonoculomotor palsy group. Other factors such as age, sex, side, aneurysm dome, neck, ASPECT ratio, family history, hypertension, smoking, and PCom diameter did not significantly influence oculomotor palsy. Early coil embolization led to better recovery of neural function, with immediate intervention offering the highest chance of full recovery.

Conclusion

Overall, this study showed that sharp ICA siphon and aneurysm dome protrusion are significant factors in symptomatic ICA-PCom aneurysms. We propose that immediate surgery be recommended for patients with ICA-PCom aneurysm-induced oculomotor nerve palsy to prevent functional disability and potential aneurysm rupture.


 

Keywords

internal carotid artery–posterior communicating artery aneurysm - internal carotid artery siphon - aneurysm dome protrusion - oculomotor nerve palsy - angle

Introduction

Oculomotor nerve palsy caused by an internal carotid artery (ICA)–posterior communicating artery (PCom) aneurysm is a well-known clinical condition. Direct mechanical compression can cause partial or complete oculomotor palsy. Herein, we assessed the radiological image findings and patient demographics associated with symptomatic ICA-PCom aneurysms, reviewing the anatomical imaging findings, patient demographics, and clinical backgrounds of symptomatic ICA-PCom aneurysm cases over a period of 5 years. Additionally, we assessed the outcomes following endovascular coiling of symptomatic unruptured aneurysms.


 

Materials and Methods

Patient Selection and Study Period

Between April 2019 and March 2024, 82 patients with ICA-PCom aneurysms underwent surgical treatment at our institute, among whom 12 had a history of oculomotor palsy symptoms, while 7 symptomatic unruptured aneurysms were treated with coil embolization.


 

Imaging and Anatomical Analysis

All patients underwent digital subtraction angiography for aneurysm analysis. ICA-PCom aneurysms were analyzed using internal carotid angiography (ICAG), and the angles between the parent artery and aneurysm and between the ICA C2 portion and C3 portion were measured in the lateral view of the ICAG.

The following parameters were assessed: age, sex, side, aneurysmal dome size and neck, family history of cerebral aneurysm, history of hypertension, smoking habit ([Fig. 1A], [D]), the angle between the direction of protrusion of the aneurysm dome and the direction of the parent artery (ICA C2 portion) ([Fig. 1B], [D]), the angle between the ICA C2 and C3 portions (the angle between the ICA C2 portion [the line crossing the center point of C2 and the bottom point of C2, shown with white dots] and C3 portion [the line crossing the center point of C3 and the bottom point of C2, shown with white dots]) ([Fig. 1C]), the angle between the direction of protrusion of the aneurysm dome (the line along both the top point of the aneurysm dome and the center point of the aneurysm dome, shown with white dots) and the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots), aneurysm depth/neck width ratio (ASPECT ratio), and PCom artery diameter ([Fig. 1F]).

Zoom
Fig. 1 Imaging and anatomical analysis of the aneurysm. The following parameters were evaluated in the lateral view of internal carotid artery angiography (ICAG) (A, D): ① The angle between the internal carotid artery (ICA) C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) and C3 portion (the line crossing the center point of C3 and the bottom point of C2, shown with white dots) (B, E). ② The angle between the direction of protrusion of the aneurysm dome (the line along both the top point of the aneurysm dome and the center point of the aneurysm dome, shown with white dots) and the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) (C). ③ Aneurysm depth/neck width ratio (ASPECT ratio). ④ Posterior communicating (PCom) artery diameter (F).

 

Statistical Analysis

The Mann–Whitney U test was used for quantitative variables to assess the differences in the estimated data between the groups. Fisher's exact test was used for categorical variables. Results were considered significant at p < 0.05.


 

 

Results

Clinical Characteristics and Radiological Findings of Unruptured Symptomatic ICA-PCom Aneurysms

There were significant differences between unruptured ICA-PCom aneurysms in the palsy and non-palsy groups in the angle between the direction of protrusion of the aneurysm dome and the direction of the ICA C2 portion (47.5 ± 7.86 vs. 100.8 ± 29.0, p = 0.001), and the angle between ICA C2 and C3 portions (37.5 ± 8.86 vs. 77.6 ± 17.5, p = 0.047). There were no significant differences in other factors ([Table 1]).

Table 1

Features of unruptured ICA-PCom aneurysms causing oculomotor palsy

Unruptured ICA-PCom aneurysm

Oculomotor palsy (mean ± SD)

No oculomotor palsy (mean ± SD)

p-Value

Case (n)

10

37

Age (y)

70.42 ± 9.05

69.78 ± 9.10

0.858

Sex (male:female)

2:8

7:30

0.47

Side (left:right)

5:5

17:20

0.415

Aneurysm dome (mm)

7.308 ± 3.13

6.936 ± 3.43

0.589

Aneurysm neck (mm)

4.133 ± 2.30

4.645 ± 2.68

0.556

Aneurysm ASPECT ratio

1.698 ± 0.66

1.568 ± 0.513

0.573

Familial history (yes)

3

8

0.312

Hypertension (yes)

6

24

0.396

Smoking (yes)

2

8

0.458

Aneurysm dome–ICA C2 angle (°)

47.5 ± 7.86

100.8 ± 29.0

0.001

ICA siphon angle (°)

37.5 ± 8.86

77.6 ± 17.5

0.047

PCom diameter (mm)

1.925 ± 0.90

1.75 ± 0.88

0.614

Abbreviations: ASPECT ratio, aneurysm depth/neck width ratio; ICA, internal carotid artery; PCom, posterior communicating artery; SD, standard deviation.



 

Clinical Characteristics and Radiological Findings of Ruptured Symptomatic ICA-PCom Aneurysms

There were significant differences between ruptured ICA-PCom aneurysms in the palsy and nonpalsy groups in the angle between the direction of protrusion of the aneurysm dome and the direction of the ICA C2 portion (50.5 ± 3.54 vs. 97.4 ± 17.1, p = 0.004), and the angle between ICA C2 and C3 portions (31.0 ± 5.66 vs. 76.1 ± 13.5, p = 0.042). There were no significant differences in other factors ([Table 2]).

Table 2

Features of ruptured ICA-PCom aneurysms causing oculomotor palsy

Ruptured ICA-PCom aneurysm

Oculomotor palsy (mean ± SD)

No oculomotor palsy (mean ± SD)

p-Value

Case (n)

2

23

Age (y)

59.5 ± 5.27

66.8 ± 9.77

0.643

Sex (male:female)

1:1

6:17

0.36

Side (left:right)

1:1

8:15

0.401

Aneurysm dome (mm)

8.32 ± 2.17

6.47 ± 3.05

0.147

Aneurysm neck (mm)

4.36 ± 0.53

4.01 ± 1.48

0.141

Aneurysm ASPECT ratio

1.890 ± 1.73

1.67 ± 0.54

0.344

Familial history (yes)

1

2

0.281

Hypertension (yes)

1

11

0.486

Smoking (yes)

1

7

0.383

Aneurysm dome–ICA C2 angle (°)

50.5 ± 3.54

97.4 ± 17.1

0.004

ICA siphon angle (°)

31.0 ± 5.66

76.1 ± 13.5

0.042

PCom diameter (mm)

2.00 ± 0.14

2.07 ± 0.68

0.274

Abbreviations: ASPECT ratio, aneurysm depth/neck width ratio; ICA, internal carotid artery; PCom, posterior communicating artery; SD, standard deviation.



 

Outcome analysis of Post-Coiling for Symptomatic Unruptured ICA-PCom Aneurysms

When comparing outcomes in post-coiling for symptomatic unruptured ICA-PCom aneurysms, patients who improved had significantly smaller aneurysm domes (5.424 ± 1.05 vs. 10.79 ± 2.11 mm, p = 0.021) and significantly fewer days from onset (0.23 ± 0.41 vs. 2.5 ± 1.33 days, p = 0.013). There were no significant differences in other factors ([Table 3]).

Table 3

Outcomes of coil embolization for unruptured ICA-PCom aneurysms causing oculomotor palsy

Complete resolution

(mean ± SD)

Partial resolution

(mean ± SD)

p-Value

Case (n)

7

3

Age (y)

65.4 ± 6.17

73.5 ± 5.43

0.14

Aneurysm dome (mm)

6.424 ± 1.05

8.79 ± 2.11

0.053

Aneurysm neck (mm)

3.542 ± 0.45

5.82 ± 0.81

0.056

Aneurysm ASPECT ratio

1.602 ± 0.23

1.88 ± 0.35

0.216

VER

25.16 ± 3.53

23.95 ± 3.47

0.267

Days of therapy performed from onset

0.23 ± 0.41

2.5 ± 1.33

0.013

Abbreviations: ASPECT ratio, aneurysm depth/neck width ratio; ICA, internal carotid artery; PCom, posterior communicating artery; SD, standard deviation; VER, volume embolization ratio.



 

Ruptured Symptomatic ICA-PCom Aneurysms

In our series, there were only two cases of ruptured symptomatic ICA-PCom aneurysms. In one case, the patient was in Hunt and Kosnik grade 1. Coil embolization was performed on the day of onset, and oculomotor palsy was completely resolved. In another case, the patient was in Hunt and Kosnik grade 4, and coil embolization was performed on the day of onset; however, the oculomotor palsy and severe conscious disturbance did not resolve.


 

 

Discussion

In previous studies,[1] [2] [3] [4] 7 to 10% of patients with unruptured ICA-PCom aneurysms exhibited oculomotor nerve palsy, and the association between ruptured ICA-PCom aneurysms and the onset of oculomotor nerve palsy was reported to be 34 to 56%.[2] [3] [4] In our series, 14.3% of patients with unruptured ICA-PCom aneurysms exhibited oculomotor nerve palsy.

In addition, previous studies[4] [5] reported that symptomatic ICA-PCom aneurysms tend to be larger and more irregularly shaped than asymptomatic ICA-PCom aneurysms. In our cases, there were no significant differences in aneurysms size.

In contrast, there were no significant aneurysm dome or neck differences between symptomatic and asymptomatic aneurysms in our cases. Another factor associated with symptomatic ICA-PCom aneurysms is ICA tortuosity. A short ICA and sharp ICA siphon may cause a short distance between the skull base and ICA.[6] Almost all projections of symptomatic PCom aneurysms, which cause oculomotor palsy, protruding from the ICA are ventral, lateral, and posterior.[4] [5] [6] In addition, such aneurysms measuring smaller than 1 cm can cause third nerve palsy when the anterior cavernous genu of the ICA forms an acute angle and the supraclinoid portion runs posterolaterally,[4] [5] [6] while the PCom is of the fetal type.[7] In our cases, a sharp ICA siphon and protruding aneurysm dome were identified as significant factors influencing symptomatic ICA-PCom aneurysm. We assume this “sharp ICA siphon and protruding aneurysm dome” directly compresses the oculomotor nerve as in [Fig. 2].

Zoom
Fig. 2 Schema of the internal carotid artery (ICA) and oculomotor nerve. The pink line is the ICA and the yellow line is the oculomotor nerve. ① The angle between the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) and C3 portion (the line crossing the center point of C3 and the bottom point of C2, shown with white dots). ② The angle between the direction of protrusion of the aneurysm dome (the line along both the top point of the aneurysm dome and the center point of the aneurysm dome, shown with white dots) and the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots).

Oculomotor nerve disturbance can be caused by compression from an enlarging aneurysm[8] and by the irritant effect of an aneurysm.[9] However, previous reports have emphasized that both coil embolization and neck clipping for such symptomatic ICA-PCom aneurysms could ensure recovery from oculomotor nerve palsy.[10] [11] As endovascular coiling does not reduce the aneurysm mass, the possible mechanism of aneurysm-induced oculomotor palsy can be explained by pulsation stress on the oculomotor nerve and not solely by compression of the nerve.

In our case series, symptomatic ICA-PCom aneurysms were treated with coil embolization. In two ruptured cases, one had a good outcome, achieving complete resolution of oculomotor palsy after coil embolization, whereas the other case had a poorer outcome because the patient's initial Hunt and Kosnik grade was poor. Patients with unruptured ICA-PCom aneurysms who underwent coil embolization immediately after onset had good outcomes.

Timely surgical intervention is an important factor for complete oculomotor nerve recovery in both ruptured and unruptured aneurysms.[4] [8] [12] [13] In our study, immediate coil embolization for unruptured aneurysms could ensure complete oculomotor nerve recovery. Other factors, such as age, aneurysm dome and neck size, and volume embolization ratio, were not predictive of recovery from oculomotor nerve palsy. Consequently, we suggest performing immediate surgery for ICA-PCom aneurysm-induced oculomotor nerve palsy to prevent functional disability and potential aneurysm rupture.


 

Conclusion

To conclude that a sharp ICA siphon and protruding aneurysm dome are significant factors for symptomatic ICA-PCom aneurysms. In addition, we recommend immediate surgery for ICA-PCom aneurysm-induced oculomotor nerve palsy to prevent functional disability and potential aneurysm rupture.


 

 

Conflict of Interest

None declared.

Ethical Approval

This study was approved by our institutional review board.


Data Availability Statement

This study data is unavailable to access or unsuitable to post, because this research data includes sensitive or confidential information such as patient data.



Address for correspondence

Daisuke Wajima, MD, PhD
Department of Neurosurgery, Kanazawa University
Kanazawa, Ishikawa 920-8641
Japan   

Publikationsverlauf

Artikel online veröffentlicht:
21. August 2025

© 2025. Asian Congress of Neurological Surgeons. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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Zoom
Fig. 1 Imaging and anatomical analysis of the aneurysm. The following parameters were evaluated in the lateral view of internal carotid artery angiography (ICAG) (A, D): ① The angle between the internal carotid artery (ICA) C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) and C3 portion (the line crossing the center point of C3 and the bottom point of C2, shown with white dots) (B, E). ② The angle between the direction of protrusion of the aneurysm dome (the line along both the top point of the aneurysm dome and the center point of the aneurysm dome, shown with white dots) and the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) (C). ③ Aneurysm depth/neck width ratio (ASPECT ratio). ④ Posterior communicating (PCom) artery diameter (F).
Zoom
Fig. 2 Schema of the internal carotid artery (ICA) and oculomotor nerve. The pink line is the ICA and the yellow line is the oculomotor nerve. ① The angle between the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots) and C3 portion (the line crossing the center point of C3 and the bottom point of C2, shown with white dots). ② The angle between the direction of protrusion of the aneurysm dome (the line along both the top point of the aneurysm dome and the center point of the aneurysm dome, shown with white dots) and the ICA C2 portion (the line crossing the center point of C2 and the bottom point of C2, shown with white dots).