ICA - Supraclinoid segment mirror aneurysms: case report and review of the literature

Clinical History

A 65-year-old female patient presented with right sided ptosis, anisocoria and right-sided subarachnoid haemorrhage of Hunt & Hess scale Grade 2, visualized in MRI. Digital subtraction angiography was obtained to diagnose the reason for the haemorrhage and to establish a plan for appropriate treatment.

Imaging Findings

Diagnostic four vessel DSA revealed two symmetric saccular aneurysms at the C7 area of the internal carotid artery (at the location of origin of atresic posterior communicating artery); the right one was 4 mm/10 mm (medium sized) ruptured and the left one 1 mm (small) unruptured.

The right-sided aneurysm showed diverticles (daughter sacs), which are characteristic of rupture, and also coiling of the right-ruptured aneurysm was diagnosed.
On right femoral arterial approach, coiling of the right-sided aneurysm was done using GDC 360 SR 4 mm x 8 cm, GDC soft 4 mm x 10 cm, Matrix ultrasoft 3 mm x 20 cm and GDC soft SR 2 mm x 8 cm. The aneurysm was totally occluded.

The left-sided aneursym was unruptured, hence coiling was not performed. Patient was discharged with GOS grade 5.
Follow-up with DSA was planned to be done in six months.

Discussion

Multiple bilateral aneurysms account for 12.9% in angiographic series and 22.7% in autoptic series, as shown by a large review of 27 series of brain aneurysms. [1] About 25% of them occur in symmetrical localisations of the same right and left artery (mirror aneurysms), with an incidence ranging from 2.7% to 7.1% (average 4.2%).

Bilateral mirror-image aneurysms mainly affect female patients in the sixth decade. [2, 3] They occur with a high frequency at the internal carotid (intracavernous and bifurcation) artery, as well as at the middle cerebral artery (bifurcation) (up to 98% of the cases). [4]
Although various nomenclature classification systems defining the segments of the ICA exist in literature, we will refer to the one proposed by Bouthillier et al [5], because it uses a numerical scale in the direction of blood flow but also takes into account anatomical information and clinical considerations for neurosurgical practice. In this system, the ICA is divided into seven segments according to their adjacent anatomical structures and the compartments they traverse: C1, cervical; C2, petrous; C3, lacerum; C4, cavernous; C5, clinoidal; C6, ophthalmic; and C7, communicating.

Classification of cerebral aneurysm based on size
Small: 1 mm – 4 mm
Medium: 4 mm to 10 mm in diameter
Large: 10 to 25 mm in diameter
Giant: >25 mm in diameter.
Of all aneurysms, 95% are less than 25 mm in diameter; i.e., only 5% are "giant".

Hunt and Hess scale [6] is one of the grading system used to classify the severity of a subarachnoid haemorrhage based on the patient's clinical condition.

Although the incidence of ruptured cerebral aneurysms is relatively small, when rupture occurs, morbidity and mortality are exceptionally high. The understanding of the pathological and physiological forces driving aneurysmal pathogenesis and progression is crucial. When there is a ruptured aneurysm, endovascular coiling should be done as early as possible due to re-bleed rate within 1st day (2-4%), 2 weeks (about 25%) and 1st year (95%).[7].

A recent large scale study suggests that the annual risk of haemorrhage from small incidental aneurysms is substantially lower than previously thought and the risk of elective intervention higher. [8, 9]. So for small incidental aneurysms it is better to avoid elective intervention.

In summary, by mirror cerebral aneurysms we indicate two aneurysms in the same patient and at the same location in the cerebral vasculature but symmetrical with respect to a sagittal plane. [10]. Treatment with endovascular coiling should be done for ruptured aneurysm, which is symptomatic due to subarachnoid haemorrhage.

Differential Diagnosis List

Final Diagnosis

Internal carotid artery - supraclinoid segment mirror aneurysms

URL:	https://www.eurorad.org/case/10379
DOI:	10.1594/EURORAD/CASE.10379
ISSN:	1563-4086