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Archive for the ‘stroke’ Category

In early days of  medical school we were taught there is an important vascular grade separator in the base of  brain .God  would not have created this circle (of Willis ) without any purpose  , he must have designed it for a reason.

circle of willisHow good is the circle of  Willis to prevent a stroke ?

Unfortunately , we have not answered  this in detailed manner . Obviously  it can’t prevent all strokes however , it is strongly  believed it can  abort  many of  them .My guess would be but for its presence many of episodes of TIA, syncope ,near syncope would end up in stroke with various degree of deficit.

The other factor that tests the efficiency of circle  of Willis is the acuteness of the vascular insufficiency.Chronic carotid occlusion  as expected are well  tolerated . We failed to respect  this natural hemodynamic  sharing  and indulged in so many  unilateral carotid interventions with dubious results .

Here is a paper  with fresh  knowledge from Dr  Seemant Chaturvedi ,  Miamai , Florida .Hats off to the authors.

Are the Current Risks of Asymptomatic Carotid Stenosis Exaggerated?Further Evidence Supporting the CREST 2 Trial  Seemant Chaturvedi,  Ralph L. Sacco,JAMA Neurol. Published online September 21, 2015.

Internal carotid artery (ICA) occlusion when occurring in a chronic fashion  could be as benign as a small peripheral vessel occlusion .(Of course they can be symptomatic)

For all those patients with unilateral total carotid disease , let us thank the “circle of Hope” which if regulated by God whom should we fear ?

Further reading

carotid stenting crest 1 crest 2 ACAST ACSE CEA

cartoid stenosis current management stenting

http://www.amazon.com/Carotid-Artery-Stenosis-Treatments-Neurological/dp/0824754174

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One of my patients with atrial fibrillation  recently developed a  fairly  moderate  sized right MCA stroke that resulted in dense left sided hemiplegia .He was on warfarin , but the stroke was confirmed to be ischemic,the etiology was fixed as cardio embolic .After a  smart  recovery he asked this question.

Why did the clot  from  my  heart preferred  to enter the  brain doctor ?  Is there no other place for it  to go ?

I  told him in simple terms , “It is  your destiny and  the clot’s wish”.  In fact , you are some what blessed as the clot did not enter  the left side of the brain .If it had gone, your speech would have severely affected and you may  not be asking this question to me ! It is true the clot do have other options to  embolise ,  however they are still  trouble some !

cardiac source of emboli embolus ischemic stroke animation embolic

What is the diameter of internal carotid artery , and cerebral artery ? The common size of LA appendage clot almost match with this !

It can go straight down to your leg , kidney , intestines or upper limbs .All are equally dangerous  and present dramatically . Very rarely  it can enter  coronary  arteries  bringing a heart attack rather than a brain attack .If it is going to the legs you are at risk of acute monoplegia instead of chronic hemiplegia .Peripheral embolism are very painful .Intestinal ischemia evokes a most excruciating pain one can  ever encounter !  Luckily  stroke is not painful.God is kind enough ,he foresaw  cerebral ischemia to be more common and hence  made it pain-free ! (There is no cerebral angina equivalent  !)

Having said that , I felt we should get a scientific answer to my patients query .

What determines  the destination  of these emboli in transit from heart ?

 

cardiac source of emboli embolus ischemic stroke animation embolic peripheral renal mesentric lerish syndrome 002

A large clot often fails to traverse the Aortic arch branches and invariably reach the periphery .

The dynamics of a cardiac emboli hitting the cerebral arteries can never be known in live human vascular tree. The following factors might play a role.

  • Clot size and morphology
  • Anatomy of aortic arch -Right MCA is in immediate capture  zone .
  • Arch type and curvature radius
  • Arch  branch ostial size , shape
  • Vertebral arterial embolism is rare because it  is a second order branch.
  • Dessication and disintegration of clot in  transit is possible leading to multiple destination.
  • Most shaggy looking large clots fail to enter carotid instead reach the peripheral circulation.
  • Vegetations, tumor debri behaves differently as the density and mass of emboli has a some effect on the transit velocity and momentum.

Variations in Aortic arch anatomy

aortic arch branching pattern A to Z

Image courtesy : Anatomy Atlases by Michael P. D’Alessandro, and Ronald A. Bergman, from university of Iowa. http://www.anatomyatlases.com

It is  surprising, human beings can have as many types of Aortic arch as  English  alphabets . Then,there are innumerable ways for cardiac clots to embolise too  !

 

 

 

 

 

 

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Current prescribing information cautions clearly Prasugrel should not  be used in TIA  or recent  stroke (Even in  ischemic strokes -Embolic included !)

The warning  is perplexing and illogical to me.

What is your take ?

I would imagine the following  could be  the reasons.

Prasugrel  as an  antiplatlet agent is  many fold  powerful and could convert all  strokes into hemorrhagic one .

Does Prasugrel convert a TIA into stroke instead of curing it ?

Prasugrel may worsen the stroke  in case the TIA is going to end up as stroke.

Is there any thing called hemorrhagic TIA ?

Since we do not have any mechanism to diagnose Ischemic TIA from hemorrhagic TIA ,  it is better to avoid Prasugrel . It is still a mystery ,  why  clopidogrel which acts on the same receptor and can be safely given for TIA ( pro actively)

After thought

I think Neuro physicians must answer this question . ( Cardiologists  better limit their extended geographical terrain ! )

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