Table of Contents
- Course of the Vertebral Artery
- Branches of the Vertebral Artery
- Segments of the Vertebral Artery
- Relations of the Vertebral Artery
- Vertebrobasilar Occlusion and Vertebral Artery Syndrome
- Pathophysiology of Vertebrobasilar Occlusion
- Epidemiology of Vertebral Artery Syndrome
- Diagnosis of Vertebral Artery Syndrome
- Management of Vertebral Artery Syndrome
Course of the Vertebral Artery
This artery moves upwards and backwards just posterior to the internal carotid artery passing through the transverse foramina of the C6 cervical vertebrae. In some people it can also originate from the brachiocephalic artery or arch of aorta.
In case it originates from the aorta, it passes a little higher into the foramen transversarium at C5 level. Variations in the course of the artery can occur. It is seen that in 90% of the cases vertebral artery enters transverse foramen of 6th cervical vertebra and through C5 in 5% of cases. 2% of cases from C4 and C7 and in 1% of cases from C3 vertebra.
Branches of the Vertebral Artery
It gives off many small branches including spinal branches that supply the spinal cord in the cervical region and posterior inferior cerebellar artery (PICA). It terminates by joining with the vertebral artery from the opposite to form the basilar artery. The posterior inferior cerebellar artery (PICA) is the largest branch of the vertebral artery. It also supplies the cerebellum.
Segments of the Vertebral Artery
The vertebral artery is typically divided into 4 segments:
First segment (V1) – Pre-foraminal segment: expands from the origin of the artery to transverse foramen of C6
Second segment (V2) – Foraminal segment: expands from the transverse foramen of C6 to the transverse foramen of C2 from where it comes out
Third segment (V3) – Atlantic or extradural segment: expands from transverse foramina of C2 to the entrance from the foramen magnum into the skull after crossing the dura mater.
Fourth segment (V4) – Intra-dural segment: expands from the dura to their confluence to form the basilar artery
Relations of the Vertebral Artery
Anteriorly, the vertebral artery is related to the common carotid artery, vertebral vein, thoracic duct on left side and right lymphatic duct on the right side.
Posterior relations of the vertebral artery include ventral rami of C7 and C8, transverse process of C7 and inferior cervical ganglion.
These include inferior thyroid artery and middle cervical ganglion.
The second segment of the artery remains in the transverse foramina. The third segment starts from C2 (axis), and moves in lateral direction through C1 (atlas). As this segment moves through the cervical region, it enters into the skull by piercing the dura and arachnoid and continuing as the fourth segment.
The fourth segment unites the contra-lateral vertebral artery from the opposite side at the lower border of the pons and continues as the basilar artery.
Vertebrobasilar Occlusion and Vertebral Artery Syndrome
Atherosclerosis of the vertebral artery can lead to decreased blood flow to the tissues which it supplies. It can become the cause of vertebrobasillar occlusion leading to vertebral artery syndrome or vertebral artery dissection. These can complicate into stroke and paralysis.
Pathophysiology of Vertebrobasilar Occlusion
- Atherosclerosis is a very common disease of the vertebral artery leading to its narrowing and occlusion. Stenosis of both the arteries leads to vertebrobasilar ischemia. Development of collateral circulation is very effective even in occlusion of the vertebral artery. Vertebral artery stenosis due to atherosclerosis, carotid artery disease and intra-cerebral disease all complicate into ischaemia of the hind brain later on.
- Lipohyalinosis is the second common cause, which can lead to atherosclerosis. It leads to weakening of the wall of the vessel which eventually ruptures. This is frequently associated with hypertension. Almost all intracerebral hemorrhages occur due to rupture of small penetrating vessels.
- Embolic occlusion of the vertebrobasilar system is usually not common. Thromboembolism is common from the aortic arch, subclavian artery and vertebral arteries. Embolus from these arteries flow along the blood into the basilar artery and occlude the arterial system of the brain.
- Vertebrobasilar artery dissection has various causes and can complicate into vertebral artery disease.
- Aneurysms can also complicate into vertebral artery disease.
Epidemiology of Vertebral Artery Syndrome
Vertebral artery disease and syndrome can lead to stroke. Among the total number of stroke, 20% occur after disturbance of vertebrobasilar circulation.
Risk factors of vertebral artery disease
All these risk factors are associated with atherosclerosis and stroke:
- Alcohol abuse
- Coronary and other heart disease
- Diabetes mellitus
- Drug abuse
- Family history of stroke
- Giant cell arteritis
- Obesity and physical inactivity
- Previous stroke
Usually, occlusion of the vertebrobasilar system leads to sudden death due to stroke, or produces major disability. Focal neurological deficits are observed if smaller branches of the vertebrobasilar system are involved. The symptoms depend on the respective area of the brain involved.
Signs and symptoms of the disease depend on the etiology. Embolic phenomenon leads to sudden symptoms without any prodromal symptoms. Symptoms of vertebrobasilar strokes include:
- Vertigo – common – and this may be the only symptom
- Nausea and vomiting
- Disturbance of consciousness
- Visual disturbance (oculomotor signs such as nystagmus, diplopia and pupillary changes)
- Visual field defects
- Speech disturbance (for example, dysarthria and dysphonia)
- Sensory changes in the face and scalp
- Contralateral motor weakness (may cause a ‘drop attack‘)
- Sensory disturbance affecting pain and temperature
There may be a history of associated risk factors. Neck and occipital pain in this disease is often mistaken as musculoskeletal pain due to exertion and mechanical activity. Excessive mechanical straining can also raise the chances of vertebral dissection.
Nystagmus, cranial nerve impairment, hemiplegia and ability of touch and vibration are lost if cerebellar involvement occurs. Medial medullary syndrome and lateral medullary syndrome can also occur when the brain is involved in vertebral brain disease.
On examination, patients with vertebral artery syndrome are usually in altered state with signs of hemiparesis or quadriparesis. In some patients, facial nerve palsy with dysarthria, dysphagia and dysphonia along with some disturbance of occulomotor and pupillary structures can also occur.
Following syndromes can occur after complication due to vertebral artery disease:
- Lateral medullary or Wallenberg’s syndrome
- Medial medullary or Dejerine’s syndrome
- Cerebellar infarction
- Locked-in syndrome
- Internuclear ophthalmoplegia
- One-and-a-half syndrome
- Millard-Gubler syndrome
- Top-of-the-basilar syndrome
- Raymond-Céstan syndrome
- Foville’s syndrome
- Weber’s syndrome
- Benedikt’s syndrome
- Posterior cerebral artery occlusion
Diagnosis of Vertebral Artery Syndrome
Following investigations should be done for the diagnosis of vertebral artery syndrome:
- Baseline labs: CBC, ESR, blood chemistry, clotting and lipid profile.
- If patient is less than 45 years old, following labs are carried out to check the coagulation status:
- Lupus anticoagulant and anticardiolipin antibodies
- Antithrombin III deficiency
- Radiological investigations:
- CT scan of the brain to look for infarction and ischemic changes but most often CT scan is done in the emergency when early symptoms appear.
- MRI scan of the brain can pick ischemia more efficiently than CT scan. It is done to rule out any tumor, ischemia or any other disease of the blood vessels.
- MR angiography is done along with MRI brain scan to see the vascular lesions.
- ECG is done in all patients who are unconscious or have signs of stroke. 20% of patients with stroke have arrhythmias and roughly 2% are with previous history of MI.
- Echocardiography: It is done to pick valvular defects, vegetation and other sources of emboli, particularly in young patients with basilar artery occlusion.
- Cerebral angiography
Management of Vertebral Artery Syndrome
Patient is managed by special stroke unit with a neurologist. General measures like preventing aspiration when the patient is bedridden to avoid pneumonitis, controlling body temperature, blood sugar and blood pressure. Treating hypertension if hypertensive emergency exists. Assess all the reflexes of the patient and consider for endotracheal intubation if Glasgow Coma Scale is less and patient lacks a gag reflex.
Antiplatelet medication like aspirin is given along with intravenous heparin to manage acute stroke. Angioplasty can be done in occlusion of the vessel for stenting. Physiotherapy for mobilisation and strengthening along with chest care and bowel care are carried out when the patient is bedridden.