Given the patient’s presentation to the neuro-ophthalmology clinic and prior testing, a broad differential diagnosis for optic neuropathy was considered, although giant cell arteritis and NAION were considered to be most likely. Laboratory testing showed a normal erythrocyte sedimentation rate, C-reactive protein and complete blood count. Magnetic resonance imaging with contrast of the brain and orbits revealed a 1.5 x 1.3 cm left ophthalmic segment internal carotid artery (ICA) aneurysm compressing the pre-chiasmatic left optic nerve along with the optic chiasm (See Figures 1 & 2). The patient was sent directly from the imaging center to the Wills Emergency Room, where the exam remain unchanged from her visit to the Neuro-ophthalmology clinic two weeks prior. An emergent neurosurgery consult was placed for evaluation and treatment, and the patient underwent catheter angiography and endovascular embolization.



Discussion 

The differential diagnosis of decreased vision post cataract extraction and PCIOL placement is quite broad. In this particular instance the referring ophthalmologist was concerned for NAION. One early study reported a rate of NAION annually as 10.3 per 100,000.¹ A later published retrospective analysis concluded a post-cataract extraction six-week incidence of 34.6 per 100,000 and six-month incidence of 51.8 per 100,000.² Local vasoactive peptide release and IOP fluctuation during and after surgery could result in inadequate blood supply to the posterior ciliary arteries.³ 

Figure 2. Arterial phase of catheter angiography shows saccular aneurysm arising from the ophthalmic segment of the left internal carotid artery.

Our patient was found to have an aneurysmal dilatation of the ophthalmic segment of the left ICA. Approximately 14 percent of unruptured aneurysms have been reported to present with cranial nerve deficits, subsequently leading to the diagnosis.⁴ Of these, the ICA-Posterior Communicating Artery junction aneurysms are the most common, characteristically presenting with a third-nerve palsy.⁵ ICA-ophthalmic artery junction aneurysms have been described to cause compression of the optic nerve, chiasm or both. Most commonly, vision loss is slow and progressive, but it may also be painful, mimicking an optic neuritis.⁵ Rarely, an aneurysm of the intracavernous ICA may cause vision loss if the dilatation arises from the distal portion of the artery.⁵ 

The morbidity and mortality of intracerebral aneurysms lie within the risk of rupture and subsequent hemorrhage and vasospasm. There are 30,000 ruptured aneurysms annually in the United States, with a 40- to 50-percent survival rate.^4,6 Of the remaining 50 to 60 percent, approximately 20 percent have no significant neurologic deficits.^4,6 

Ophthalmologic signs and symptoms of aneurysms include mydriasis, cranial nerve palsies, diplopia, decreased vision and pain. The “gold standard” for imaging an aneurysm is catheter angiography. However, computed tomography angiography and magnetic resonance angiography are more commonly performed due to their overall quality without the risks of traditional catheter angiography. 

 
Size and location have been noted to be two major risk factors for aneurysm rupture. The five-year cumulative risk of rupture in our patient is 14.5 percent, whereas in an aneurysm with a diameter of 7 mm or less, the risk is 0 percent.⁷ In patients with aneurysms 25 mm or larger, the risk of rupture is up to 40 percent.⁷ Additionally, aneurysmal dilation of the vertibrobasilar or posterior cerebral circulation and the basilar tip confer an increased risk of rupture.⁴ 

Treatment options for intracerebral aneurysms include observation, open microsurgical clip ligation and endovascular coil embolization.⁶ Observation is generally limited to smaller aneurysms with little risk of rupture or aneurysms located in a difficult point to access. Clipping has been best utilized for a wide-necked aneurysm and confers a 1 to 4 percent mortality rate and an additional morbidity rate of 10 to 15 percent cognitive or physical disability.⁸ Endovascular coiling, although associated with lower mortality and morbidity rates of 1 to 2 percent and 8 percent, respectively, has resulted in higher recurrence risks.⁸  REVIEW


The author would like to thank Mark Moster, MD, of the Wills Eye Hospital Neuro-ophthalmology Service, and Joshua Ehrlich, MD, of the Wills Eye Hospital Residency Program for their time and assistance in preparing this case report.



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