41 Amaurosis Fugax with Carotid Occlusion

Case 41 Amaurosis Fugax with Carotid Occlusion

Glenn C. Hunter and Alwin Camancho

Fig. 41.1 Magnetic resonance angiography of the neck revealing right internal carotid artery (ICA) stump. (LVA, left vertebral artery.)

Fig. 41.2 Angiogram: (A) Right common carotid artery (CCA) injection showing internal carotid artery (ICA) distal stump (arrow) and CCA stenosis (arrow). (B) Selective external carotid artery injection showing communication between the internal and external circulation via the ophthalmic artery (arrow). (RCCA, right common carotid artery.)

Clinical Presentation

A 70-year-old man presents to his ophthalmologist with worsening vision in the right eye.
Three months previously he experienced an episode of amaurosis fugax.
A funduscopic exam shows a Hollenhorst plaque and diminished flow in a branch of the retinal artery.
He is referred for urgent neurosurgical consultation.

Questions

List the differential diagnoses.

What are the most common causes of monocular visual symptoms?

What are the most common sources of thromboembolism?

Physical examination reveals bilateral carotid bruits and a blood pressure of 145/95 mm Hg. What studies would you obtain?
A carotid duplex scan and magnetic resonance angiography (MRA) are ordered. The MRA shows right internal carotid artery occlusion with a patent external carotid artery (ECA) (Fig. 41.1). The left carotid artery appears normal.
Outline your plan of management.
During your evaluation he experiences another episode of worsening vision. What are the potential causes of this episode?
How may this episode alter your treatment plan?
In view of the results of the MRA would you order a cerebral angiogram?
A four-vessel angiogram is obtained (Fig. 41.2). Interpret the findings on the right.
What is the significance and importance of a residual stump?
You consider doing a common carotid endarterectomy and excision of the stump. What is the risk and natural history of stroke in patients who present with monocular visual symptoms versus those who present with transient ischemic attacks (TIAs)?
What are the risk factors for stroke in patients with monocular visual symptoms?
How would you treat this patient?

Answers

List the differential diagnoses.

Ocular manifestations account for 15% of transient ischemic attacks. The differential diagnoses of this patient’s symptoms include 1,2

Amaurosis fugax

Hollenhorst plaque

Retinal artery occlusion (central/branch)

Venous stasis retinopathy

Nonspecific visual symptoms
What are the most common causes of monocular visual symptoms?
- Visual symptoms in patients in this age group are most often due to thromboembolism and less often due to hypoperfusion.^3,4
What are the most common sources of thromboembolism?
- The carotid bifurcation is the most common embolic source in these patients.⁴
- Cardiac thromboembolism (valves/aortic arch), intravascular injection of talc, and steroidal suspensions are other potential sources.
Physical examination reveals bilateral carotid bruits and a blood pressure of 145/95 mm Hg. What studies would you obtain?
- The focus of the studies should be to find an embolic source. A carotid duplex scan would be the initial screening test.^2,5
Outline your plan of management.
- Admission to hospital
- Locate potential embolic sources by obtaining CT, magnetic resonance imaging (MRI), computed tomography angiography (CTA), MRA
- Exclude cardiac sources by obtaining electrocardiogram (EKG) and echocardiogram
- Specific laboratory tests: complete blood count (CBC), electrolytes, blood glucose, coagulation profile, type and screen
- Antiplatelet therapy
During your evaluation, he experiences another episode of worsening vision. What are the potential causes of this episode?
- Worsening symptoms may be due to hypoperfusion or another embolic episode.^2,3
How may this episode alter your treatment plan?
- In patients with carotid occlusion, control of blood pressure is an important consideration. Also, if the patient is not on antiplatelet therapy or is taking only aspirin, an additional agent should be added. Heparin should be considered if the ipsilateral occlusion is recent.³
In view of the results of the MRA, would you order a cerebral angiogram?
- The presence of persistent symptoms may warrant the following studies: A four-vessel cerebral angiogram allows assessment of the ECA and ophthalmic arteries and their collateral communication and will also eliminate a “string sign.”
- An MRI/ MRA may be used instead of the angiogram in patients with renal impairment, but may miss a string sign.
- MRA tends to overestimate the stenoses in general.
- CTA may be a better study, and can be obtained in a shorter time. However, it has limitations in patients with renal impairment.
A four-vessel angiogram is obtained (Fig. 41.2). Interpret the findings on the right.
- The four-vessel angiogram shows occlusion of the right internal carotid artery (RICA) at its origin, with a residual stump and antegrade vertebral flow.
What is the significance and importance of a residual stump?
- The residual stump may be an embolic source and if associated with a high-grade ECA stenosis may contribute to retinal hypoperfusion.^3,6,7
You consider doing a common carotid endarterectomy and excision of the stump. What is the risk and natural history of stroke in patients who present with monocular visual symptoms versus those who present with TIAs?
- The 3-year risk of ipsilateral stroke is 10% for patients with transient monocular blindness versus 20% for those presenting with hemispheric symptoms.⁸
What are the risk factors for stroke in patients with monocular visual symptoms?
- Risk factors include⁸
  - Age >70
  - Male gender
  - History of TIA
  - History of intermittent claudication
  - Ipsilateral stenosis (80–99%)
  - Number of collaterals on angiography
How would you treat this patient?
- The patient was treated with excision of the stump and common carotid artery (CCA) endarterectomy⁹ and angioplasty with only minor improvement in symptoms.
- Fig. 41.3 presents a treatment algorithm for patients with ophthalmic manifestations of carotid disease.