Carotid artery dissection presenting as exercise-induced monocular visual loss

Abstract

A man in his 60s presented to the urgent treatment centre with isolated transient monocular visual loss in the right eye soon after completing a 5 km run. He had no preceding events, no history of neck pain and no other associated symptoms. His only medical history was presumed giant cell arteritis 3 months prior. The ophthalmology team reviewed the patient urgently and retinal artery occlusion was excluded. Carotid Doppler imaging showed a total occlusion of the right internal carotid artery. CT angiogram of the head and neck vessels revealed a dissection flap immediately proximal to the occlusion. The carotid dissection was treated with aspirin 300 mg for 2 weeks followed by clopidogrel 75 mg for a minimum of 3 months. The patient was discussed with the vascular team who confirmed that no surgical intervention would be required to treat the occlusion. With the relatively simple treatment of antiplatelet therapy, the patient is making good progress with no recurrence of symptoms.

Background

Carotid artery dissection is a major cause of strokes in the young and middle-aged patients, accounting for 10%–15% of ischaemic strokes in this population.^{1 2} The pathophysiological mechanisms of this process are still unclear.³ Common risk factors however include: trauma, systemic hypertension, arteriopathies and connective tissue diseases, with the latter atraumatic types being more likely to cause complete occlusion and are less easily resolved.⁴ The classic triad of carotid dissection is pain on one side of the head, face or neck, partial Horner’s syndrome followed hours or days later by cerebral or retinal ischaemia, though only around a third of patients present with all three symptoms.⁵ We describe a case of a patient diagnosed with internal carotid artery dissection with solely transient monocular visual loss and no obvious precipitating factors preceded by short distance running.

Case presentation

A previously fit and well man in his 60s presents with monocular visual loss of the right eye lasting for 2–3 hours. Initially there was complete monocular blackout. This gradually resolved to a ‘butterfly-shaped’ central scotoma, before recovering fully. There were no associated speech, sensory and motor deficits on presentation. The patient did not lose consciousness and did not report a headache.

The patient’s only medical history is presumed giant cell arteritis, diagnosed 3 months previously by his primary care physician. At the time, the patient reported a non-radiating right temporal headache which was throbbing in character and not relieved with simple analgesia. Associated with the headache, he reported a transient loss of vision, which was momentary. At the time, he had no jaw or scalp tenderness and the temporal pulses were palpable. He was initially treated with high-dose prednisolone for a short period until his erythrocyte sedimentation rate (ESR) results returned as normal after which the steroid treatment was ceased. There was no recurrence of symptoms. Interestingly, prior to this episode, the patient had no recent history of trauma or exercise.

The patient did not take any regular medications and had no known drug allergies. He was a non-smoker and was fully independent of his activities of daily living.

His cardiovascular and respiratory examination was unremarkable. He was in sinus rhythm. On initial assessment, he reported a central scotoma in the right eye that was resolving during the consultation. He had full range of eye movements and his visual fields were intact. His speech was fluent and facial symmetry preserved. There were no other cranial nerve abnormalities. His peripheral nervous system examination did not show any abnormalities.

An urgent same day ophthalmology review was arranged which showed normal visual fields and a normal retina. He was subsequently re-reviewed in the transient ischaemic attack (TIA) clinic wherein the carotid imaging was organised. Prior to attending the clinic, the patient had a further episode of visual loss also triggered by running which lasted 15 min.

Investigations

The patient had a routine set of blood tests including full blood count, renal profile, bone profile, liver profile, thyroid function, ESR, B₁₂/folate/ferritin, iron studies, Hemoglobin A1c (HBA1C) and lipid profile to evaluate for alternative causes of visual loss. These were all normal.

His ECG showed sinus rhythm with left ventricular hypertrophy.

In the stroke clinic, the patient’s blood pressure was mildly elevated at 156/86 mm Hg and heart rate was 54 beats per minute. The mild hypertension was felt by the patient to be related to anxiety from the recurrent symptoms and reports that his home measurements are usually normal.

A carotid Doppler was performed to assess for carotid artery stenosis (figure 1). This showed complete occlusion of the right internal carotid artery with normal left internal carotid artery and normal flow in the vertebral arteries.

Figure 1.

Ultrasound Doppler showing proximal flow in the right internal carotid artery, but no distal flow.

The case was discussed with the vascular surgery team, who advised that this would not be in keeping with atherosclerotic disease in view of there being a complete occlusion of the ipsilateral artery with almost no disease in the contralateral carotid artery. A CT head and neck angiography was subsequently arranged.

CT head and neck angiography (figures 2–5) showed that there is a complete right internal carotid artery occlusion of 2.6 cm from the right carotid bifurcation up to the terminal internal carotid artery segment. There was a small dissection flap noted immediately before the occluded vessel. The right middle cerebral artery (MCA) was supplied by the contralateral internal carotid artery branch via the circle of Willis. This confirmed our suspicion that the right carotid occlusion was caused by a dissection.

Figure 2.

CT angiogram image showing a dissection flap (circled).

Figure 3.

CT angiogram image showing no flow within the intracranial internal carotid artery (circled).

Figure 4.

CT angiogram image showing the right middle cerebral artery being supplied by the left sided circulation (circled).

Figure 5.

Reconstructed images of the CT angiogram showing a conical shape of the right internal carotid artery with a ‘string sign’ which is supportive of a carotid dissection diagnosis (yellow arrow).

Differential diagnosis

As the patient presented with painless monocular visual loss, which was still present on arrival, a retinal artery occlusion needed to be excluded emergently. An urgent ophthalmology consult revealed a normal retinal examination.

An alternative differential diagnosis is internal carotid artery stenosis or occlusion, which was confirmed on the carotid Doppler imaging in our case through the acute stroke services.

Giant cell arteritis should also be within the differential diagnosis list and indeed this was initially felt to be the cause of the patient’s symptoms by his primary care physician. A detailed history and examination however excluded this in addition to a normal ESR.

To summarise, the patient had an ocular TIA related to hypoperfusion of the ophthalmic artery due to complete occlusion of the right internal carotid artery caused by vessel dissection. The only precipitating factor identified was that the initial symptom onset was related directly to completing a 5 km run.

Treatment

The patient was treated medically with high-dose aspirin (300 mg) for 2 weeks followed by clopidogrel 75 mg for a minimum of 3 months. As there was complete (100%) occlusion of the right internal carotid artery, no surgical options were advised. He had complete resolution of symptoms following initiation of antiplatelet therapy, however was advised to not drive for a period of 4 weeks following the latest bout of symptoms.

Outcome and follow-up

The patient’s follow-up CT angiogram 3 months post initial assessment still showed complete occlusion of the right internal carotid artery. This is not unexpected as the Cervical Artery Dissection in Stroke Study (CADISS) has shown that complete occlusion at baseline is significantly associated with residual occlusion at the interval scan—explored further in the discussion section.

Since being initiated on antiplatelet therapy, the patient has not had any further episodes of monocular visual loss. The patient agreed to monitor his own blood pressure at home and will escalate to his primary care physician if it is persistently elevated, as well as closely tracking his other cardiovascular risk factors. However, in view of the left ventricular hypertrophy seen on his ECG, we did arrange for an echocardiogram for the patient. This showed a normal left ventricle with normal ejection fraction.

Discussion

The main mechanism of injury leading to carotid artery dissection is hyperextension and twist or bend of the neck. Sports such as trampoline, diving, combat sports, skiing and snowboarding are often cited as causes for dissection.⁶ It is generally agreed that dissection is when there is a tear in the wall of the artery leading to collection of blood between layers of the artery—though there is debate over which layer is the primary site of dissection. The collection of blood causes formation of an intramural haematoma, occluding the artery, and can also embolise to cause a stroke or TIA.⁵

An analytical study published in 2017 found that out of 191 patients with carotid dissection, 23 were associated with running. Many of these were due to long distance running of 10 km or above^{3 6 7} with one case of Horner’s syndrome after a short distance run.⁸ Transient monocular visual loss occurs in around 6%–38% of patients with carotid artery dissection.⁹ An early study by Blousse et al analysed 149 patients with carotid artery stenosis. Out of these, 41 patients had transient monocular visual loss, 31 patients had coincident ipsilateral facial, head or cervical pain and 13 were with Horner’s syndrome.¹⁰ It is unclear how many of these patients had isolated transient monocular visual loss. The ocular manifestation of carotid artery dissection is not limited to transient monocular visual loss however. Even transient monocular visual loss can be further categorised into partial or complete. Previous case reports have described carotid artery dissection presenting as homonymous hemianopia with parietal lobe infarcts,¹¹ reduction in acuity and ocular motor palsies.⁹ Therefore, carotid artery dissection is an important differential to consider when patients present with visual symptoms and patients should be referred urgently to a TIA/neurovascular clinic where they will require a complete stroke work up within 24 hours. To date, there is no case report of carotid dissection presenting with partial transient monocular visual loss after a short distance run.

Work up for diagnosing carotid artery dissection currently includes Doppler ultrasonography, magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA), CT angiography or catheter angiography.⁵ Doppler ultrasound scanning has a diagnostic sensitivity of >90%, the common finding is that of high-resistance flow pattern in distal arteries. This method is non-invasive, inexpensive and widely available. However, while this method is useful in identifying an occlusion, pathognomonic features of dissection such as a dissection flap is rarely found.⁵ CT angiography and MRI/MRA is now widely used for diagnosing carotid artery dissection. Stringaris et al¹² have shown that MRI is more effective than traditional angiography. Hanning et al suggest that CT angiography is a reliable and better available alternative to MRI/MRA.¹³ However, CT is more reliant on experience with technique. The former gold standard for diagnosing carotid artery dissection is catheter angiography. This is an invasive test and carries a risk of stroke of between 0.5% and 1%. The most common finding is ‘string sign’—a long segment of narrowed lumen. With the increased availability of CT and MRI angiography, this is rarely used.⁵

Underlying causes such as connective tissue disorders are not routinely screened for in patients presenting with cervical artery dissection unless there are clear phenotypical features. The most common culprit is Ehlers-Danlos syndrome. A large study performed by Debette et al suggest that the prevalence of these as an underlying cause for carotid dissections is around 1% of all cases.¹⁴ Since our patient had no phenotypical features that raised concerns of an underlying connective tissue disorder and there was the likely trigger of a short run preceding the dissection, we did not perform a connective tissue disease screen.

The management of carotid artery dissection depends on the symptoms. Asymptomatic patients do not require intervention.⁵ The treatment of symptomatic carotid artery dissection is usually medical. The CADISS showed that antiplatelet and anticoagulation have comparable rates of recurrent stroke and death. Due to the side effect profile of anticoagulants, antiplatelets are preferentially used by clinicians. The duration of treatment should be for at least 3–6 months. The trial further showed that complete occlusion at baseline is significantly associated with residual occlusion at the interval scan.^{15 16} The European Stroke Society Guidelines expand on this by suggesting that residual arterial stenosis has a benign prognosis with no relation between this and stroke risk.¹⁷ However, in the absence of longer-term data, some clinicians may opt to continue antiplateletsindefinitely in certain individual cases depending on the risk factor profile of each given patient. Management of cardiovascular risk factors is essential.⁶ This includes monitoring of blood pressure, lipid profile and reducing the risk of developing diabetes. Surgical intervention may be required in patients presenting with subarachnoid haemorrhage or symptomatic aneurismal dilatation. Chronic carotid artery dissection has been treated by surgical reconstruction in cases where medical therapy has not been effective after 6 months.¹⁸

If diagnosed and managed promptly, the long-term prognosis of carotid artery dissection is very good, with a rate of recurrent dissection of 2% in the first month, then 1% per year thereafter.¹⁹ Paradoxically, the rate of successful treatment of complete occlusion is higher than incomplete occlusion. This is because if there is critical arterial stenosis, there is a risk of expansion into the distal and proximal regions causing enlargement of the thrombus and this can lead to embolic events.³

In the case presented, following initiation of antiplatelet therapy, the patient has not had further episodes of visual disturbance or neurological deficits. We hypothesise that our patient had transient symptoms related to either an embolic process caused by the carotid dissection or possible hypoperfusion during a period of increased cardiovascular demand when the patient was running or exercising (so called ‘cerebral claudication’) in the context of complete internal carotid artery occlusion. The patient’s right MCA is currently supplied by the contralateral internal carotid artery and therefore a strong emphasis is placed in controlling cardiovascular risk factors to reduce the possibility of a catastrophic ischaemic stroke.

The case highlights the importance of considering carotid artery dissection in short distance runners or even those with seemingly no precipitating factors. Carotid artery dissection should also be considered a differential in patients with only transient monocular visual loss, even in the absence of neck pain, facial pain and headache.

Patient’s perspective.

I was having a 2-day birthday celebration. Around midday while sitting down I felt a sensation in my right eye. Closing the left eye and looking through the right it appeared as if I was looking through a greyish mist. Eyesight in the left eye was unaffected. The effect on the right eye cleared within 1 hour. Following this I developed a headache on the right side of my head. There was no physical exercise being conducted prior to the attack.

The next day, I felt generally unwell and the headache continued. The headache was located over/behind the right eye/right temple and forehead. A pulsating pain could also be felt behind the right eyebrow area. This was the first time I had experienced a headache like this. It was unusual as normally I do not suffer from headaches. The headache could not be stopped using over the counter medications. I was subsequently seen by my opticians to investigate the greying out effect on the right eye and optomap imaging was performed which did not reveal any abnormalities. I was subsequently seen by my primary care physician who made a clinical diagnosis of giant cell arteritis and started me on a course of steroids while waiting for my ESR to come back. The steroids helped to alleviate the headache; however, my ESR returned as normal and my primary care physician stopped the steroids. My headache had resolved and the vision returned as normal so I was reassured by this although no formal diagnosis was given to me.

Three months later, while sitting in a cafe 30 min after a 5 km Parkrun, I had a second attack. My vision through the right eye was reduced to just a small area (10% of normal view) to the bottom right corner of my normal field of vision, but it returned to normal after a few hours. On this occasion, I was seen urgently by the ophthalmology team who excluded any problems in the eye itself and I was therefore referred to the stroke clinic. As the vision had improved once again, I went for a further running session prior to attending the clinic and once again I had a further visual loss lasting for 15 min. In the clinic, an abnormality was found within my carotid artery and I was commenced on appropriate medication and I have not experienced any further symptoms despite exercising regularly.

Learning points.

• Carotid artery dissection may be precipitated by low-impact exercises such as short distance running and is important to have a high index of suspicion for this.

• In all cases of suspected amaurosis fugax, patients should be referred urgently to a transient ischaemic attack/neurovascular clinic where they will require a complete stroke work up including carotid imaging. The gold standard for this would be within 24 hours.

• Symptoms of carotid artery dissection may be minimal and include isolated monocular visual loss or central scotoma.

• Urgent investigation with Doppler flow and CT angiography is recommended to assist in the diagnosis of carotid dissection.

• Antiplatelets and anticoagulants are equally as effective in the management of carotid artery dissection.

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