Toronto Notes

Ruptured Posterior Communicating Artery Aneurysm

Tiffany Ni*, Raza Syed*, Kieran Murphy

*These authors contributed equally to this work

Introduction

Cerebral aneurysms result from an abnormal focal dilation of an artery wall in the brain and can vary in size from 0.5 mm to greater than 25 mm(1,2). While most cerebral aneurysms are silent and may be incidentally identified on imaging, aneurysmal rupture is commonly associated with subarachnoid hemorrhage (SAH), leading to a high morbidity and mortality rate(1,2).

Despite the current uncertainties surrounding the precise mechanisms by which cerebral aneurysms develop, grow, and rupture, several factors have been associated with the formation of cerebral aneurysms(3,4). Some include hypertension, age over 40, smoking, trauma to the blood vessels, and a family history of aneurysms(3).

Posterior communicating artery (PCOM) aneurysms are the second most common aneurysms overall, accounting for 25% of all aneurysms and representing 50% of all internal carotid artery (ICA) aneurysms(5). We report a patient with a ruptured left PCOM aneurysm presenting with a left subarachnoid hemorrhage.

Patient presentation

A 52-year-old woman was presented with a sudden onset of severe headache, vomiting, nuchal rigidity, and decreased conscious level. She was transported to our hospital for management of subarachnoid haemorrhage (SAH). On admission, the patient was semi-comatose with anisocoric pupils, and a Glasgow Coma Scale (GCS) score of 5. She had no past medical history of trauma, hypertension, diabetes or other diseases.

Investigations & Diagnoses

Based on the patient’s clinical presentation, the following would be included in the list of differential diagnoses(1):

• • Arteriovenous malformations

• Cavernous sinus syndromes
• Carotid/vertebral artery dissection
• Cerebral venous thrombosis
• Fibromuscular dysplasia
• Migraine and cluster headaches
• Moyamoya disease
• Pituitary apoplexy
• Stroke – ischemic or hemorrhagic
• Vein of Galen malformation

The first-line diagnostic investigations to be ordered included(6):

• conventional catheter-based angiogram (digital subtraction angiography)
• CT angiography
• magnetic resonance angiography

The repeat computerized tomography (CT) scan demonstrated diffuse subarachnoid hemorrhage (Figure 1). Digital subtraction angiography (DSA) confirmed the presence of a saccular aneurysm localizable to the PCOM on the left side (Figure 2).

Figure 1. Computed tomographic scan showing diffuse subarachnoid bleeding secondary to rupturing of the PCOM aneurysm

Figure 2. Digital subtraction angiography was performed which showcases an aneurysm originating from the PCOM

Procedure

Endovascular detachable coil embolization was performed under intravenous anesthesia. The microcatheter was navigated from the femoral artery to the left PCOM aneurysm and a microcatheter tip was positioned in the aneurysm under fluoroscopic guidance. Coil position within the aneurysm and the patency of the parent vessel were confirmed angiographically prior to every coil detachment. The left PCOM aneurysm was successfully occluded (Figure 3).

Figure 3. Digital subtraction angiography was performed following endovascular coiling of the PCOM aneurysm showing complete occlusion of the aneurysm and exclusion from circulation as well as good patency of the PCOM

One week later, follow-up CT and DSA examination was performed and revealed no abnormality in the brain parenchyma and good patency of the PCOM. The patient’s postoperative course was uneventful, and she was discharged home on the 14th postoperative day. The patient was neurologically intact at discharge.

Case Questions

What if the patient in this case was 35 years old instead? How would your treatment strategy change? 

1. endovascular coiling
2. anti-platelet medications only
3. surgical clipping
4. endovascular thrombectomy

Answer: c) surgical clipping (instead of endovascular coiling)

In endovascular coiling, a micro-catheter is inserted into the femoral artery via an initial catheter(7,8). A platinum coil is attached to the microcatheter tip. When the microcatheter reaches the lumen of the aneurysm, an electrical current is used to separate the coil from the catheter. The coil induces thrombosis of the aneurysm and is left permanently in the aneurysm.

Surgical clipping is done under general anesthesia and requires open surgery(7). The brain is gently retracted to visualize the aneurysm. A small clip is placed across the neck of the aneurysm to block the blood flow into it. Clips are made of titanium and remain on the artery permanently.

In this situation, the preferred method of treatment would be surgical clipping(9). The less invasive nature of coiling is likely to be favored in patients who are older, are in poor health, have serious medical conditions, or have aneurysms in certain locations. In patients younger than 40 years of age, the difference in the safety between coiling versus clipping is small. Therefore, the better long-term protection from bleeding may give patients with clipped aneurysms an advantage in life expectancy.

What imaging technique should be used to assess any possible residual perfusion of the aneurysm?

1. non-contrast enhanced CT scan
2. magnetic resonance angiography (MRA)
3. CT angiography
4. digital subtraction catheter angiography

Answer: d) Digital subtraction catheter angiography

Digital subtraction catheter angiography remains the gold standard for diagnosis and characterization of vascular abnormalities and in many centers, even if the causative lesion is identified on MRA or CTA and it is thought to require surgical management, a catheter study is carried out(10).

The benefit of DSA over MRA or CTA is two-fold:

• Higher spatial resolution: better able to delineate small vessels and characterize vascular morphology (e.g. aneurysm neck and incorporation of adjacent vessels)
• Temporal resolution: contrast can be seen to wash into and out of vascular malformations, giving important information in regard to the feeding vessels (e.g. arteriovenous malformations or dural arteriovenous fistulas)

A non-contrast enhanced CT scan is commonly used as the first-line imaging modality for evaluating subarachnoid hemorrhage as it is rapid, inexpensive, and widely available.

What are the characteristics of aneurysmal subarachnoid hemorrhage (SAH)?

1. Headaches, nausea, and vomiting is always present
2. Loss of consciousness is always present
3. Patients tend to present as asymptomatic
4. Varies, specific syndromes have been associated with particular aneurysmal locations

Answer: d) Varies, specific syndromes have been associated with particular aneurysmal locations.

For example, aneurysms at the anterior communicating artery, the most common site of aneurysmal SAH (34%), have the following characteristics(11):

• These aneurysms are usually silent until they rupture
• Suprachiasmatic pressure may cause altitudinal visual field deficits, abulia or akinetic mutism, amnestic syndromes, or hypothalamic dysfunction
• Neurologic deficits in aneurysmal rupture may reflect intraventricular hemorrhage (79%), intraparenchymal hemorrhage (63%), acute hydrocephalus (25%), or frontal lobe strokes (20%)

What is the progression of aneurysmal rupture?

1. Aneurysmal rupture is typically self-limiting
2. Aneurysmal rupture results in vasodilation
3. Aneurysmal rupture typically results in SAH
4. Aneurysmal rupture results in hypernatremia

Answer: c) Aneurysmal rupture typically results in SAH.

What typically accompanies the SAH is diffuse or focal forms of vasospasm that may lead to ischemia and infarction¹¹.

Recent animal data suggest therapeutic benefit of nitrite infusions to enhance cerebral perfusion in the setting of aneurysmal SAH¹¹. This delayed complication of vasospasm is of unclear pathogenesis but most likely is due to the presence of blood and the formation of multiple substances in the subarachnoid space. Spontaneous thrombosis of an aneurysm and subsequent recurrence have been reported in a few cases.

What are possible complications of ruptured cerebral aneurysms in general?

1. Seizures
2. Hyponatremia
3. Gastrointestinal bleeding
4. All of the above

Answer: d) All of the above.

Some of the other complications of ruptured cerebral aneurysms include¹¹:

• Vasospasm
• Recurrent hemorrhage
• Hydrocephalus
• Cardiac arrhythmia, myocardial infarction, or congestive heart failure
• Neurogenic pulmonary edema, pneumonia, or atelectasis
• Anemia
• Venous thromboembolism

References

1. Jersey AM, Foster DM. Cerebral Aneurysm. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 [cited 2021 Jun 24]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK507902/
2. Cianfoni A, Pravatà E, Blasi RD, Tschuor CS, Bonaldi G. Clinical presentation of cerebral aneurysms. Eur J Radiol. 2013 Oct 1;82(10):1618–22.
3. Inagawa T. Risk factors for the formation and rupture of intracranial saccular aneurysms in Shimane, Japan. World Neurosurg. 2010 Mar 1;73(3):155–64.
4. Etminan N, Buchholz BA, Dreier R, Bruckner P, Torner JC, Steiger H-J, et al. Cerebral aneurysms: Formation, progression and developmental chronology. Transl Stroke Res. 2014 Apr;5(2):167–73.
5. July J. Surgery of Posterior Communicating Artery Aneurysm. In: July J, Wahjoepramono EJ, editors. Neurovascular Surgery : Surgical Approaches for Neurovascular Diseases [Internet]. Singapore: Springer; 2019 [cited 2021 Jun 24]. p. 87–92. Available from: https://doi.org/10.1007/978-981-10-8950-3_11
6. Cerebral aneurysm – Symptoms, diagnosis and treatment | BMJ Best Practice US [Internet]. [cited 2021 Jun 24]. Available from: https://bestpractice.bmj.com/topics/en-us/490
7. Kim K-H, Cha K-C, Kim J-S, Hong S-C. Endovascular coiling of middle cerebral artery aneurysms as an alternative to surgical clipping. J Clin Neurosci. 2013 Apr 1;20(4):520–2.
8. Kim YJ, Song KY. Endovascular Coiling of Multiple (More than Four) Intracranial Aneurysms. Interv Neuroradiol. 2004 Mar;10(1):75–81.
9. Molyneux A, Kerr R, Stratton I, Sandercock P, Clarke M, Shrimpton J, et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial. Lancet Lond Engl. 2002 Oct 26;360(9342):1267–74.
10. Chen SH, Sur S, Sedighim S, Kassi A, Yavagal D, Peterson EC, et al. Utility of diagnostic cerebral angiography in the management of suspected central nervous system vasculitis. J Clin Neurosci Off J Neurosurg Soc Australas. 2019 Jun;64:98–100.
11. Chen J, Li M, Zhu X, Chen Y, Zhang C, Shi W, et al. Anterior Communicating Artery Aneurysms: Anatomical Considerations and Microsurgical Strategies. Front Neurol. 2020;11:1020.