DR IMRAN JAVED,

MBBS, FCPS.

INTERNATIONAL FELLOW

DR IMRAN JAVED,

MBBS, FCPS.

INTERNATIONAL FELLOW

VERTEBROBASILAR INSUFFICIENCY &

SUBCLAVIAN STEAL SYNDROME.

VERTEBROBASILAR INSUFFICIENCY &

SUBCLAVIAN STEAL SYNDROME.

ANATOMICAL REVIEWANATOMICAL REVIEW Vertebral artery Arises from the proximal subclavian artery.Ascends through the transverse foramina of the

first cervical vertebra. Passes posteriorly around the articular process

of the atlas to enter the skull through the foramen magnum.

The two vertebral arteries join each other at the level of the pontomedullary junction to form the basilar artery.

The vertebral artery gives rise to anterior and posterior spinal arteries, the posterior inferior cerebellar artery and branches to the medulla

Vertebral artery Arises from the proximal subclavian artery.Ascends through the transverse foramina of the

first cervical vertebra. Passes posteriorly around the articular process

of the atlas to enter the skull through the foramen magnum.

The two vertebral arteries join each other at the level of the pontomedullary junction to form the basilar artery.

The vertebral artery gives rise to anterior and posterior spinal arteries, the posterior inferior cerebellar artery and branches to the medulla

ANATOMICAL REVIEWANATOMICAL REVIEWBasilar artery Formed by the two vertebral arteries joining each

other in the midline. Ascends along the ventral aspect of the pons.Ends at the ponto-midbrain junction where it

divides into two posterior cerebral arteries.It gives rise to anterior inferior cerebellar artery,

superior cerebellar artery and numerous paramedian, short and long circumferential penetrators.

The internal auditory (labyrinthine) artery arises from the basilar artery in about 20 % of the population whereas in the remainder it arises from the anterior inferior cerebellar artery.

Basilar artery Formed by the two vertebral arteries joining each

other in the midline. Ascends along the ventral aspect of the pons.Ends at the ponto-midbrain junction where it

divides into two posterior cerebral arteries.It gives rise to anterior inferior cerebellar artery,

superior cerebellar artery and numerous paramedian, short and long circumferential penetrators.

The internal auditory (labyrinthine) artery arises from the basilar artery in about 20 % of the population whereas in the remainder it arises from the anterior inferior cerebellar artery.

ANATOMICAL REVIEWANATOMICAL REVIEWPosterior cerebral artery (PCA) The basilar artery ends by dividing into the two posterior

cerebral arteries. They encircle the midbrain close to the occulomotor

nerve at the level of tentorium cerebelli and supply the inferior part of the temporal lobe and the occipital lobe.

They anastomose with the posterior communicating arteries to complete the circle of Willis.

Many small perforating arteries arise from PCA to supply the midbrain, the thalamus, hypothalamus and geniculate bodies.

In fifteen per cent of the population, the PCA is a direct continuation of the PoCA, its main blood supply then comes from the ICA rather than from the vertebrobasilar system

Posterior cerebral artery (PCA) The basilar artery ends by dividing into the two posterior

cerebral arteries. They encircle the midbrain close to the occulomotor

nerve at the level of tentorium cerebelli and supply the inferior part of the temporal lobe and the occipital lobe.

They anastomose with the posterior communicating arteries to complete the circle of Willis.

Many small perforating arteries arise from PCA to supply the midbrain, the thalamus, hypothalamus and geniculate bodies.

In fifteen per cent of the population, the PCA is a direct continuation of the PoCA, its main blood supply then comes from the ICA rather than from the vertebrobasilar system

PHYSIOLOGY OF BLOOD FLOWPHYSIOLOGY OF BLOOD FLOWBrain uses approximately twenty percent of the body's

blood and needs twenty-five percent of the body's oxygen supply to function optimally.

Blood flow in a healthy person is 54 milliliters per 1000 grams of brain weight per minute.

There are 740 milliliters of blood circulating in the brain every minute. 3.3 milliliters of oxygen are used per minute by every 1000 grams of brain tissue.

This means that approximately 46 milliliters of oxygen are used by the entire brain in one minute.

During sleep, blood flow to the brain is increased, but the rate of oxygen consumption remains the same.

Brain uses approximately twenty percent of the body's blood and needs twenty-five percent of the body's oxygen supply to function optimally.

Blood flow in a healthy person is 54 milliliters per 1000 grams of brain weight per minute.

There are 740 milliliters of blood circulating in the brain every minute. 3.3 milliliters of oxygen are used per minute by every 1000 grams of brain tissue.

This means that approximately 46 milliliters of oxygen are used by the entire brain in one minute.

During sleep, blood flow to the brain is increased, but the rate of oxygen consumption remains the same.

Circle of Willis or Circulus Arteriosus

Circle of Willis or Circulus Arteriosus

The Circle of Willis or the Circulus Arteriosus is the main arterial anastomatic trunk of the brain.

The Circle of Willis is a point where the blood carried by the two internal carotids and the basilar system comes together and then is redistributed by the anterior, middle, and posterior cerebral arteries.

The Circle of Willis or the Circulus Arteriosus is the main arterial anastomatic trunk of the brain.

The Circle of Willis is a point where the blood carried by the two internal carotids and the basilar system comes together and then is redistributed by the anterior, middle, and posterior cerebral arteries.

COMPANSATORY MECHANISMCOMPANSATORY MECHANISMAnterior cerebral arteries of the two hemispheres are

joined together by the anterior communicating artery.

Middle cerebral arteries are linked to the posterior cerebral arteries by the posterior communicating arteries.

So brain areas continue to receive adequate blood supply even when there is a blockage somewhere in an arterial system.

If there are no problems in either system, the pressure of the streams will be equal and they will not mix.

However, if there is a blockage in one of them blood will flow from the intact artery to the damaged one.

Anterior cerebral arteries of the two hemispheres are joined together by the anterior communicating artery.

Middle cerebral arteries are linked to the posterior cerebral arteries by the posterior communicating arteries.

So brain areas continue to receive adequate blood supply even when there is a blockage somewhere in an arterial system.

If there are no problems in either system, the pressure of the streams will be equal and they will not mix.

However, if there is a blockage in one of them blood will flow from the intact artery to the damaged one.

ANATOMICAL VARIATIONSANATOMICAL VARIATIONSAs long as the Circle of Willis can maintain blood

pressure at fifty percent of normal, no infarction or death of tissue will occur in an area where a blockage exists.

Sometimes, an adjustment time is required before collateral circulation can reach a level that supports normal functioning; the communicating arteries will enlarge as blood flow through them increases. In such cases, a transient ischemic attack may occur.

Some people lack one of the communicating arteries that form the Circle of Willis. Now if a blockage develops, collateral blood supply will be compromised, causing brain damage to occur.

There are some watershed areas in the brain located at the ends of the vascular systems. Blockages in the water shed areas can cause transcortical aphasia.

As long as the Circle of Willis can maintain blood pressure at fifty percent of normal, no infarction or death of tissue will occur in an area where a blockage exists.

Sometimes, an adjustment time is required before collateral circulation can reach a level that supports normal functioning; the communicating arteries will enlarge as blood flow through them increases. In such cases, a transient ischemic attack may occur.

Some people lack one of the communicating arteries that form the Circle of Willis. Now if a blockage develops, collateral blood supply will be compromised, causing brain damage to occur.

There are some watershed areas in the brain located at the ends of the vascular systems. Blockages in the water shed areas can cause transcortical aphasia.

PATHOGENESISPATHOGENESIS

• LUMINAL OBSTRUCTION:

e.g. Thromboembolic disease.

• VESSEL WALL DISEASE:

e.g. Athersclerosis, Fibromuscular dysplasia.

• EXTRINISIC COMPRESSION:

e.g. Osteophytes, Muculofibrous compression.

• LUMINAL OBSTRUCTION:

e.g. Thromboembolic disease.

• VESSEL WALL DISEASE:

e.g. Athersclerosis, Fibromuscular dysplasia.

• EXTRINISIC COMPRESSION:

e.g. Osteophytes, Muculofibrous compression.

DIAGNOSTIC MODALITIESDIAGNOSTIC MODALITIESDOPPLER AND DUPLEX

SCANNING.SPIRAL CT SCAN

MRI & MRA

DIGITAL SUBTRACTION ANGIOGRPHY

DOPPLER AND DUPLEX SCANNING.

SPIRAL CT SCAN

MRI & MRA

DIGITAL SUBTRACTION ANGIOGRPHY

DOPPLER & DUPLEX SCANNINGDOPPLER & DUPLEX SCANNINGBy using Doppler ultrasound alone,

vertebral artery origin can only be imaged

in up to 60% of subjects.

This can be improved to over 80% by incorporating the use of colour Doppler flow imaging.

Improved accuracy in estimation of flow velocities, may achieved by taking readings from both low (C5-6) and high

(C1-2) cervical regions.

By using Doppler ultrasound alone, vertebral artery origin can only be imaged

in up to 60% of subjects.

This can be improved to over 80% by incorporating the use of colour Doppler flow imaging.

Improved accuracy in estimation of flow velocities, may achieved by taking readings from both low (C5-6) and high

(C1-2) cervical regions.

Transcranial Doppler ultrasound Transcranial Doppler ultrasound To detect intracranial vertebral artery

stenosis with a sensitivity of as high as 80%, and a specificity of 80–97% when compared with DSA.

Detection of emboli from a stenosis.

Monitoring during percutaneous transluminal angioplasty (PTA) of vertebral stenosis.

To detect intracranial vertebral artery stenosis with a sensitivity of as high as 80%, and a specificity of 80–97% when compared with DSA.

Detection of emboli from a stenosis.

Monitoring during percutaneous transluminal angioplasty (PTA) of vertebral stenosis.

Helical or spiral computerized tomography angiography (CTA)

Helical or spiral computerized tomography angiography (CTA)

To image the extra cranial vertebral artery without the risks associated with catheter angiography.

Diagnostic benefit in differentiating between ‘kinked’ and truly atherosclerotic stenosed vessels.

Diagnostic value is less in acute posterior circulation ischemic stroke.

To image the extra cranial vertebral artery without the risks associated with catheter angiography.

Diagnostic benefit in differentiating between ‘kinked’ and truly atherosclerotic stenosed vessels.

Diagnostic value is less in acute posterior circulation ischemic stroke.

Magnetic resonance imaging Magnetic resonance imaging Alone can detect intracranial vertebral artery

disease.

Best used in combination with magnetic resonance angiography (MRA) to assess both extra and intracranial vertebral arteries.

MRA has a higher sensitivity for detecting basilar stenosis than either extracranial or intracranial vertebral artery disease.

An important pitfall with MRA is an over-reporting of occlusion in cases of high-grade stenosis.

Alone can detect intracranial vertebral artery disease.

Best used in combination with magnetic resonance angiography (MRA) to assess both extra and intracranial vertebral arteries.

MRA has a higher sensitivity for detecting basilar stenosis than either extracranial or intracranial vertebral artery disease.

An important pitfall with MRA is an over-reporting of occlusion in cases of high-grade stenosis.

Digital Subtraction Angiography Digital Subtraction Angiography

It is gold standard for diagnosing vertebral artery stenosis.

Stenosis at the vertebral artery origin can still be missed with standard arch

views, because of superimposition of the subclavian artery over the first segment of the vertebral artery and additional oblique views are required.

It is gold standard for diagnosing vertebral artery stenosis.

Stenosis at the vertebral artery origin can still be missed with standard arch

views, because of superimposition of the subclavian artery over the first segment of the vertebral artery and additional oblique views are required.

Medical treatmentMedical treatmentAntiplatelet therapies or

Anticoagulation. Anticoagulation with warfarin

to an INR of 1.6–1.8 with aspirin 325 mg.

Antiplatelet therapies or Anticoagulation.

Anticoagulation with warfarin to an INR of 1.6–1.8 with aspirin 325 mg.

Surgical treatmentSurgical treatmentEndarterectomy or Reconstruction.

Endarterectomy: via a supraclavicular incision with or wothout clavicular osteotomy.

Complications include lymphoceles, fistulas, vocal cord paralysis and pneumothorax.

Endarterectomy of intracranial vertebral artery stenosis involves a limited suboccipital craniotomy.

Endarterectomy or Reconstruction.

Endarterectomy: via a supraclavicular incision with or wothout clavicular osteotomy.

Complications include lymphoceles, fistulas, vocal cord paralysis and pneumothorax.

Endarterectomy of intracranial vertebral artery stenosis involves a limited suboccipital craniotomy.

Reconstruction for extracranial vertebral artery

Reconstruction for extracranial vertebral artery

Transposition of the vertebral artery:

Common or internal carotid artery.

Subclavian Artery.

Thyrocervical trunk.

COMPLICATIONS: Horners’ syndrome

Lympholcele, Stroke & Death.

Transposition of the vertebral artery:

Common or internal carotid artery.

Subclavian Artery.

Thyrocervical trunk.

COMPLICATIONS: Horners’ syndrome

Lympholcele, Stroke & Death.

VERTEBERAL ARTERY SEGMENTSVERTEBERAL ARTERY SEGMENTSThree extracranial parts & an intracranial portion.

Part one is from the origin to the point at which it enters the transverse foramina of either the fifth or sixth cervical vertebra.

Second part courses within the intervertebral foramina.

Third part behind the atlas and heading towards the foramen magnum.

The final intracranial part begins as it pierces the dura and arachnoid mater at the base of the

skull, and ends as it meets its opposite vertebral artery.

Three extracranial parts & an intracranial portion.

Part one is from the origin to the point at which it enters the transverse foramina of either the fifth or sixth cervical vertebra.

Second part courses within the intervertebral foramina.

Third part behind the atlas and heading towards the foramen magnum.

The final intracranial part begins as it pierces the dura and arachnoid mater at the base of the

skull, and ends as it meets its opposite vertebral artery.

Endovascular treatmentEndovascular treatmentEndovascular intervention, with

percutaneous transluminal angioplasty (PTA) and stenting, is a safe and effective treatment for extracranial vertebral artery atherosclerotic stenosis, especially at the vertebral artery origin.

Endovascular intervention, with percutaneous transluminal angioplasty (PTA) and stenting, is a safe and effective treatment for extracranial vertebral artery atherosclerotic stenosis, especially at the vertebral artery origin.

Endovascular treatmentEndovascular treatmentPTA alone performed for VA origin stenosis were

associated with a marked incidence of restenosis.

Advantage of primary stenting is a reduced rate of intimal dissection at the time of the procedure.

. Intracranial stenting as reported seems to be a more technically difficult procedure.

Best treatment for intracranial vertebral artery stenosis remains controversial because of uncertainty about benefits of PTA and the lack of acceptable surgical alternatives, while optimal anti-thrombotic management for intracranial stenosis is also unclear.

PTA alone performed for VA origin stenosis were associated with a marked incidence of restenosis.

Advantage of primary stenting is a reduced rate of intimal dissection at the time of the procedure.

. Intracranial stenting as reported seems to be a more technically difficult procedure.

Best treatment for intracranial vertebral artery stenosis remains controversial because of uncertainty about benefits of PTA and the lack of acceptable surgical alternatives, while optimal anti-thrombotic management for intracranial stenosis is also unclear.

SUBCLAVIAN STEAL SYNDROMESUBCLAVIAN STEAL SYNDROMEIt refers to subclavian artery steno-occlusive

disease proximal to the origin of the vertebral artery and is associated with flow reversal in the vertebral artery.

Percutaneous transluminal angioplasty has a high rate of technical success.

Carotid-subclavian bypass (CSB) with either synthetic graft or saphenous vein graft can be performed.

It refers to subclavian artery steno-occlusive disease proximal to the origin of the vertebral artery and is associated with flow reversal in the vertebral artery.

Percutaneous transluminal angioplasty has a high rate of technical success.

Carotid-subclavian bypass (CSB) with either synthetic graft or saphenous vein graft can be performed.

Vertebral artery stenosis is an important aetiology of posterior circulation stroke. Improvements in non-invasive imaging are providing better anatomical information about vertebral artery occlusive disease. This should allow an improved understanding of the natural history of this disease process in terms of its liability to cause disabling stroke and death. Until the natural history is clearer, it is difficult to evaluate specific medical treatments and interventions fully, although endovascular intervention with primary stenting for extracranial vertebral artery stenosis is a promising potential treatment.

Vertebral artery stenosis is an important aetiology of posterior circulation stroke. Improvements in non-invasive imaging are providing better anatomical information about vertebral artery occlusive disease. This should allow an improved understanding of the natural history of this disease process in terms of its liability to cause disabling stroke and death. Until the natural history is clearer, it is difficult to evaluate specific medical treatments and interventions fully, although endovascular intervention with primary stenting for extracranial vertebral artery stenosis is a promising potential treatment.

Conclusion Conclusion