Basilar Artery Thrombosis-MRI

An adult male in sixth  decade , hypertensive, presents with loss of consciousness after prolonged intercontinental flight (Canada to India) with no deep venous thrombosis of the lower extremity or cardiac disease. MRI shows acute ischemia pons with no bleed, with MRA showing lack of flow signal of midthird basilar , possibly  due to atheromatous  thrombosis  with  Brainstem DWI  score of 6 suggesting  moderate prognosis. Case submitted by Dr MGK Murthy, Mr Hari om and Mr Sahadev Gupta.

Teaching points:

·         Basilar is formed  at pontomedullary junction

·         Most important branches are AICA, PCAs with internal auditory meatal arteries at times directly arising from it

·         Proximal and distal basilar blocks are due to embolism  usually, while middle third is typically  thrombotic

Posterior  Circulation Acute Stroke Prognosis: Early CT Score(PCASP-ECTS) is calculated with the help  of CTA source images :

(a)          Total is taken as 10 points , with 0= ischemia in all and 10 =No Ishaemia

(b)          1 point each deducted for hypoattenuation in Left/ Right Thalamus,L/R Cerebellum and L/R  PCA territory

(c)          2 points each deducted for hypoattenuation Midbrain/Pons

 A   2009  Study has suggested  pretreatment , baseline , Brain stem Diffusion weighted Imaging Score,  as independent clinical predictor for prognosis

(a)          Total  is taken as 22 points , with 0= No ischemia in posterior circulation  and 22= Whole Brainstem ischemia

(b)          No of arterial territories with abnormal Diffusion signal at each  brainstem level including  anteromedial, anterolateral, lateral, and posterior  regions  is calculated.

(c)          0-8 is allotted for medulla  and  mid brain , with pons 0-6 only.