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((Refimprove|date=June 2020))
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'''Vertebrobasilar insufficiency''' ('''VBI''') describes a temporary set of [[symptom]]s due to decreased [[blood flow]] ([[ischemia]]) in the [[Posterior (anatomy)|posterior]] circulation of the [[brain]].  The posterior circulation supplies the [[medulla oblongata|medulla]], [[pons]], [[midbrain]], [[cerebellum]] and (in 70-80% of people) supplies the posterior cerebellar artery to the [[thalamus]] and [[occipital cortex]].<ref>((Cite web|url=https://radiopaedia.org/articles/posterior-cerebral-circulation?lang=gb|title=Posterior cerebral circulation &#124; Radiology Reference Article |first=Jeremy|last=Jones|website=Radiopaedia.org|access-date=26 April 2022))</ref>  As a result, symptoms vary widely depending which brain region is predominantly affected. 

The term 'vertebrobasilar insufficiency' may be used to describe disease in the vertebral and basilar arteries which predisposes to acute [[embolism|embolic]] events such as [[transient ischemic attack]]s (TIAs) and [[stroke]].<ref name="auto">((Cite journal|url=https://emedicine.medscape.com/article/794678-overview|title=Vertebrobasilar Atherothrombotic Disease: Practice Essentials, Background, Pathophysiology|date=10 November 2021|access-date=26 April 2022|journal=EMedicine))</ref>  Alternatively it may be used to describe recurrent symptoms which result from narrowing ([[stenosis]]) of these arteries in combination with changes of blood pressure or head position. 

VBI should not be confused with other conditions which may relate to the posterior circulation.  25% of strokes and TIAs affect parts of the brain supplied by the posterior circulation, but many of these are [[embolism|embolic]] from [[heart|cardiac]] or other sources.  VBI should also not be confused with '''beauty parlour syndrome''' which refers to strokes caused by acute arterial [[dissection (medical)|dissection]] brought on by extreme head positions, such as those maintained during hair washing.<ref>((Cite web|url=http://news.bbc.co.uk/2/hi/health/3654987.stm|title=Warning over 'hair salon stroke'|date=24 April 2004|access-date=26 April 2022|website=News.bbc.co.uk))</ref><ref>[http://www.gm.tv/articles/gmtv-today/april-2004/10432-beauty-parlour-syndrome.html] ((dead link|date=April 2022))</ref>

== Signs and symptoms ==
Symptoms relate to impaired brain function in areas supplied by the posterior circulation, as seen in [[posterior circulation infarct|posterior circulation strokes]].  However, symptoms may be far briefer than those seen in stroke.

[[Vertigo (medical)|Vertigo]] is a relatively common symptom that can result from ischemia to the cerebellum, medulla or (rarely) the internal auditory artery which supplies the vestibular system of the [[inner ear]].  While vertigo is a common feature of VBI or posterior circulation stroke, VBI only rarely presents with vertigo alone (without other neurological signs).<ref>((Cite journal |pmid = 16946161|pmc = 1779945|year = 2006|last1 = Kerber|first1 = K. A.|title = Stroke among patients with dizziness, vertigo, and imbalance in the emergency department: A population-based study|journal = Stroke|volume = 37|issue = 10|pages = 2484–7|last2 = Brown|first2 = D. L.|last3 = Lisabeth|first3 = L. D.|last4 = Smith|first4 = M. A.|last5 = Morgenstern|first5 = L. B.|doi = 10.1161/01.STR.0000240329.48263.0d))</ref>

== Pathology ==
VBI results from narrowing of posterior circulation arteries, known as [[stenosis]].  The most common cause of arterial stenosis is [[atherosclerosis]], however other pathologies such as fibromuscular dysplasia, dissection, trauma or external compression may occur.<ref name="auto"/>  Atherosclerotic plaque can rupture, resulting in a source of [[embolism|emboli]].  These emboli can cause TIAs or strokes in the areas of the brain supplied by the affected artery. 

Where stenosis is severe, abrupt changes in blood pressure can temporarily result in inadequate flow through the stenosis, causing symptoms that are usually very brief.<ref name="auto1">((Cite book | chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK482259/ | title=StatPearls| chapter=Vertebrobasilar Insufficiency| publisher=StatPearls| year=2019| pmid=29489229| last1=Pirau| first1=L.| last2=Lui| first2=F.))</ref>  A common cause is [[orthostatic hypotension]] which results in a fall in blood pressure when the patient changes posture and may be exacerbated by medicines (particularly [[antihypertensive drug|antihypertensives]]), dehydration and heat.  In reality, orthostatic hypotension can cause vague symptoms (e.g. [[dizziness]]) which are similar to those caused by VBI; VBI should only be considered where the stenosis is severe and/or there are focal neurological symptoms specific to the posterior circulation.<ref name="auto1"/>

VBI may also result from altered blood flow as seen in [[subclavian steal syndrome]].

VBI is described as a cause of symptoms that occur with changes to head position.  '''Rotational vertebral artery syndrome''' (sometimes referred to as Bow Hunter's Syndrome) results from vertebral artery compression on rotating the neck.<ref>((Cite web | url=https://www.webmd.com/brain/bow-hunters-syndrome | title=What is Bow Hunter's Syndrome?|website=Webmd.com))</ref>  The commonest cause is a bone spur from a cervical [[vertebra]], in combination with disease in the opposite vertebral artery.  Rotational vertebral artery syndrome is rare.

== Diagnosis ==
The diagnosis of posterior circulation stroke or TIA can be made on the basis of history and physical examination, which should include exclusion of alternative causes for the patient's symptoms and consideration of risk factors for atherosclerosis.  To confirm VBI, imaging studies of the posterior circulation can be performed.  [[computed tomography|CT]] is often the first study performed in acute stroke or TIA, as it is effective at excluding [[intracranial haemorrhage]], however [[magnetic resonance imaging|MRI]] is better at detecting ischemic strokes in the posterior distribution.  [[Computed tomography angiography|CT angiography]] and [[Magnetic Resonance Angiography]] (MRA) can be used to detect atherosclerosis and other diseases in the posterior circulation arteries.<ref>((Cite web|url=https://radiopaedia.org/articles/ct-angiography-of-the-cerebral-arteries-protocol?lang=gb|title=CT angiography of the cerebral arteries (protocol) &#124; Radiology Reference Article |first=Ahmed|last=Abdrabou|website=Radiopaedia.org|access-date=26 April 2022))</ref>  Both can over-estimate stenosis.  It is also important to remember that atherosclerosis is a common finding, and its presence does not confirm that this was the cause of the patient's symptoms.
=== Alternative diagnoses ===
VBI is often considered when a patient complains of [[dizziness]].  It is important to distinguish dizziness caused by vertigo from the sensation of being [[lightheadedness|light-headed]], as the latter is more commonly a result of other conditions.

Brief episodes of vertigo brought on by head movements are more likely to be [[Benign paroxysmal positional vertigo]].  Alternatively, [[carotid sinus|carotid sinus hypersensitivity]] can cause episodes of dizziness and collapse on head turning if the neck brushes against clothing.

== Treatment ==
The main treatment for VBI is to address risk factors for atherosclerosis such as smoking, [[hypertension]] and [[diabetes]].  Patients are often started on an antiplatelet (e.g. aspirin, clopidogrel) or occasionally an anticoagulant (e.g. warfarin) to reduce the risk of future strokes.  Where VBI is causing reproducible symptoms due to stenosis, lifestyle modification to avoid provoking factors (e.g. dehydration, standing rapidly from sitting or lying) may reduce symptoms.

Open surgical repair or [[stent]]ing can be performed to re-open stenosed vertebral arteries, and intracranial stents have also been successfully used.<ref name="pmid16497979">((cite journal  |vauthors=Marks MP, Wojak JC, Al-Ali F, etal |title=Angioplasty for symptomatic intracranial stenosis: clinical outcome |journal=Stroke |volume=37 |issue=4 |pages=1016–20 |year=2006 |pmid=16497979 |doi=10.1161/01.STR.0000206142.03677.c2|doi-access=free ))</ref>  Further research is required to determine which patients with VBI are likely to benefit.

==References==
((Reflist))

((Medical resources
|  DiseasesDB      = 29497
|  ICD10           = ((ICD10|G|45|0|g|40))
|  ICD9            = ((ICD9|435.3))
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|  OMIM            = 
|  MedlinePlus     = 001423
|  eMedicineSubj   = emerg
|  eMedicineTopic  = 834
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((CNS diseases of the nervous system))
((Cerebrovascular diseases))

[[Category:Vascular diseases]]
[[Category:Types of stroke]]

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