Vertebral artery stenosis – A Comprehensive overview

Vertebral artery

The vertebral artery is typically the first major branch of the subclavian artery on both the left and right sides of the body.

The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline basilar artery. As the supplying component of the vertebrobasilar vascular system, the vertebral arteries supply blood to the upper spinal cord, brainstem, cerebellum, and posterior part of brain.

Triangle of the vertebral artery is a region within the root of the neck and has following boundaries:

·   Medial border of anterior scalene muscle (lateral)

·   Lateral border of longus colli muscle (medial)

·   Carotid tubercle (apex)

·   First part of subclavian artery (base)

The vertebral artery runs from base to apex (prior to entering the transverse foramen of 6th cervical vertebra).

It can be divided into four anatomically different segments (V1-V4), where segments V1-V3 are classified as the extracranial vertebral artery, and segment V4 is considered the intracranial vertebral artery

Once the artery pierces the dura mater, it becomes the intracranial vertebral artery. The fourth segment (V4), known as the intracranial segment, is defined from where the artery pierces the dura mater at the foramen magnum to where it joins with the contralateral vertebral artery to form the basilar artery.

Vertebral artery stenosis

 Stenosis or occlusion of the vertebral artery can occur unilaterally or bilaterally. The arterial occlusion may cause decreased artery perfusion and as a result symptoms of transient ischemic attack, such as vertigo, ataxia, diplopia, disturbance of speech, and bilateral hemianopia may occur.

  The occlusion of artery may also cause decreased perfusion of basilar artery and it may be manifested with  vertigo, dizziness, diplopia, ataxia, dysarthria, nausea, nystagmus, drop attacks, loss of consciousness,  numbness, and an increased risk of strokes or transient ischemic attacks.

 These symptoms are more prominent when the arterial occlusion is bilateral. Neck pain or headache is an important warning symptom of VAD, and the presence of a concomitant sensory level or Brown-Séquard syndrome is helpful for the early diagnosis of Spinal cord infarction[SCI] caused by VAD.

Vertebral artery stenosis can also cause  recurring syncope, headaches, recurrent stroke, palsy of cranial nerves, altered consciousness, altered function of the sensory and pyramidal tracts, cerebellar infarcts, and tinnitus.

  The proximal vertebral artery is the most prevalent location of vertebral artery stenosis [1].

Around 20% of posterior circulation ischemic strokes involve the stenosis of the vertebral artery [2].

If symptomatic VAS is left undiagnosed and unmanaged, it may result in strokes, myocardial infarctions, vertebrobasilar insufficiency (VBI), and sudden death[3].

Risk factors

·       Diabetes mellitus, hypertension, and hyperlipidemia are common risk factors for vertebral artery stenosis.

·       Cigarette smoking

·       Old age

·       Causes of arterial occlusion

·       Calcification of arteries

·       Calcification of blood vessels plays a critical role in up to 90% of atherosclerotic lesions. Calcification occurs when calcium and phosphate get deposited in  the blood vessels.

·       Blood vessels are composed of three layers. The innermost layer is the tunica intima, the middle layer is called tunica media, and the outermost layer is called the tunica adventitia. The intimal  calcification results in atherosclerosis and stenosis.

·       The intimal calcification of the vertebral artery can cause vertebral artery stenosis through atherosclerotic lesions.

·       Atherosclerotic Lesions

·       Atherosclerosis is the most important cause of vertebral artery stenosis. High cholesterol in the blood triggers atherosclerosis.

·       Atherosclerotic plaques cause lesions and the stenosis of vessels

·       Dissection lesions

·       Dissection lesions are one of the primary causes of cerebrovascular accidents in populations under 45 years old, with an approximate incidence of 10%-25%. Vertebral artery dissections are traumatic, associated with pre-existing arteriopathies, or spontaneous [4].

·       Spontaneous dissections are associated with old age, whereas traumatic dissections are seen in young people. Chiropractic manipulation, spontaneous head movements, cervical trauma, oral contraception, and fibromuscular syndromes like Ehlers-Danlos syndrome type IV and osteogenesis imperfecta type I are the causes leading to dissection.

·       The process of dissections happens when the tunica intima tears, blood accumulates, and dissects in the arterial wall. As a result of the dissection, thrombosis and hematomas precipitate. The hematomas and thrombosis can result in hypoperfusion, stenosis, thromboembolism, Wallenberg syndrome, and strokes.

·       Fibromuscular Dysplasia

·       It is a hereditary vascular disease that is non-atherosclerotic and non-inflammatory and causes stenosis, thromboembolism, dissections, fistulas, hypoperfusion of cerebral blood flow, and aneurysms in any network of blood vessels.

·       Giant cell arteritis 

·       GCA is an autoimmune disorder that affects the vasculature by causing inflammation at the internal elastic membrane.

·       Bony Compression

Vertebral arteries may become stenosed or occluded due to being compressed at any point along the course of the vertebral artery [5].

·       The most common anatomical point prone to extracranial compression is at the C1-C2 level due to its association with the atlantoaxial joint and membrane.

·       Patients with atherosclerotic arterial disease and asymptomatic vertebral artery stenosis have a higher risk of posterior circulation ischemic stroke than patients without such a stenosis, but the absolute risk remains low.

Clinical presentation

·  Asymptomatic stenosis of the vertebral artery.

There is a low risk of posterior circulation stroke in patients with asymptomatic vertebral artery stenosis.

·  Subclavian  steal syndrome (SSS)

It is the occlusion of the subclavian artery, closest to the origin of the vertebral artery, results in the reversal of blood flow in the ipsilateral vertebral artery and shunting of blood from the contralateral vertebral artery into the subclavian artery.

· Vertebrobasilar insufficiency (VBI)

VBI occurs due to hypoperfusion of the vertebrobasilar arterial system resulting in vertigo, diplopia, dizziness, loss of consciousness, dysphagia, dysarthria, nausea, ataxia, nystagmus, and numbness [6].

Vertebral artery stenosis is also associated with a high risk of strokes, myocardial infarctions, and sudden death [7].

   The symptomatic presentation of vertebral artery stenosis can vary and can present with vertigo, diplopia, dizziness, nystagmus, nausea, ataxia, and numbness [6]. If vertebral artery stenosis is left undiagnosed and untreated, there is a high risk of cerebrovascular accidents, myocardial infarctions, and sudden death.

Investigations 

·       Duplex ultrasonography (DUS) is the most common and standardized test for the initial screening and diagnosis of vertebral artery stenosis (VAS) and subclavian steal syndrome (SSS) as it is a safe, accurate, non-invasive, and cost-effective diagnostic method

·       Computed tomography angiography (CTA) is a non-invasive imaging tool to evaluate vertebral artery stenosis and disease [12]. CTA is superior to DSA because it can image the extracranial portion of the vertebral artery while avoiding the potential complications of using catheter angiography.

CTA is not the best imaging technique for patients who have a history of renal disease due to the high proton intensity and radiation that it exposes patients to.

·       Magnetic resonance angiography (MRA)

It is similar to CTA, and is also a non-invasive imaging technique used to evaluate vertebral artery stenosis and disease [12]. Imaging severe stenosis of the vertebral artery, such as the ostial portion, poses a challenge for MRA. MRA overestimates the stenosis of the ostial vertebral artery; however, the use of contrast mediums resolves this challenge. Contrast-enhanced MRAs (CE-MRAs), compared to catheter angiography, yield higher-resolution images of all extracranial cervical vessels .CE-MRA also has higher sensitivities and specificities for stenosis of the extracranial vertebral artery than MRA without contrast or DUS. However, CE-MRA cannot be used with patients who have pacemakers or other metallic devices.

Management

  The chronic management by modern or conventional medicine include:

·     Antihypertensive treatment is recommended to treat hypertension by lowering blood pressure below 140/90 mmHg.

·    Statins with or without LDL-lowering therapy and bile acid sequestrants or niacin are used to treat hyperlipidemia by lowering LDL cholesterol below 100 mg/dL.

·      Physical activity, glucose-lowering medications, dieting, and a statin-type lipid-lowering medication are prescribed.

 ·     It is recommended that patients diagnosed with vertebral artery stenosis due to atherosclerosis or mechanical compression of the vertebral artery be placed on antiplatelet medications such as aspirin, aspirin with modified-release dipyridamole, clopidogrel, or ticlopidine to prevent strokes, myocardial infarctions, and transient ischemic attacks.

Surgical Treatment

Surgical revascularization of the vertebral artery is done via endarterectomy or reconstruction surgery. Endarterectomy is the removal of atherosclerotic stenosis in the vertebral artery and is a complex procedure with poor success rates due to the intricate location of and access to the vertebral artery

Reconstruction surgery of the vertebral artery is a technique that involves the dissection and the transposition of the vertebral artery to either the subclavian, thyrocervical trunk arteries, common carotid, or internal carotid artery.

 In one study, the combined stroke and mortality rate of proximal extracranial vertebral artery reconstruction was less than 2%, and 92% of patients experienced patency 10 years post-operation [1]. The same study found that distal extracranial vertebral artery reconstruction was less successful with a 6% combined stroke and mortality rate, and 80% of patients experienced patency five years post-operation [1].

The ideal treatment for anatomical compression of the vertebral artery by bony structures is surgical resection of the compressing structure, decompression of the vertebral artery, or endovascular treatment.

Complementary and alternative medicine

Homeopathy

It is often prescribed as an adjuvant therapy to other medications.

Homeopathic medications to manage hyperlipidaemia include :

Cholesterinum, natrum muriaticum, lycopodium, allium sativum,

Garcinia etc.

Homeopathic remedies for managing diabetes

Natrum muriaticum, phosphorus, lycopodium, syzygium, gymnema, insulinum etc .

Homeopathic remedies for managing hypertension

Amyl nitrosum, aurum metallicum, crataegus, glonoine, Lachesis, natrum muriaticum,nux vomica,veratrum album.

Medications to prevent atherosclerosis

Baryta carb, calcarea carbonicum,lac caninum, glonoine, kali iodatum,vanadium.

Lachesis-atheroma in old age

Medications to prevent stroke in predisposed people:

Arnica,bell,coffea,fluoric acid,gelsemium,glonoine,Lachesis,laurocerasus,opium,strontium carbonicum.

 Lifestyle intervention for prevention and management

·   Promote physical activity

·   Follow healthy diets such as Mediterranean, DASH diets

·   Healthy lifestyle has crucial role in reducing the impact of risk factors on cardiovascular system. Screening for hyperglycemia, hypertension and dyslipidemia is crucial. Addressing the risk factors with proper lifestyle changes and medications whenever necessary is important in preventing the incidence of vertebral artery stenosis.

References

1.    https://www.ncbi.nlm.nih.gov/books/NBK540995/

2.    https://www.physio-pedia.com/Vertebral_Artery

3.    https://pubmed.ncbi.nlm.nih.gov/15981730/

4.    https://pubmed.ncbi.nlm.nih.gov/12509646/

5.    https://pubmed.ncbi.nlm.nih.gov/9660392/

6.    https://pubmed.ncbi.nlm.nih.gov/28722857/

7.    https://pubmed.ncbi.nlm.nih.gov/24548843/

8.    https://pubmed.ncbi.nlm.nih.gov/33552342/

9.    https://pubmed.ncbi.nlm.nih.gov/21852605/

10.  https://pubmed.ncbi.nlm.nih.gov/9660392/

11.  https://pubmed.ncbi.nlm.nih.gov/15981730/

12. https://pubmed.ncbi.nlm.nih.gov/17287234/

13. https://pubmed.ncbi.nlm.nih.gov/12509646/