Collateral Circulation of the Brain

2 Sources of Collateral Circulation of the brain

  1. extracranial source
  2. intracranial route




  • a=facial a. with ophthalmic a.
  • b= maxillary a. with ophthalmic a.
  • c = middle meningeal a.with ophthalmic a.
  • d=  middle meningeal with dural artery
  • e= occipital with dural artery through mastoid foramen
  • f=occipital with dural artery through parietal foramen





  • a=pcomm a.
  • b=ACA and MCA (leptomeningeal anastomoses)
  • c=PCA and SCA (leptomeningeal anastomoses)
  • d=tectal plexus (PCA and SCA)
  • e=anastomoses of distal cerebellar arteries
  • f=acomm a.



  • a=pcomm a.
  • b=ACA and MCA (leptomeningeal anastomoses)
  • c=PCA and SCA (leptomeningeal anastomoses)
  • d=tectal plexus (PCA and SCA)
  • e=anastomoses of distal cerebellar arteries
  • f=acomm a.



*divided into primary or secondary collateral pathways


Primary collaterals = arterial segments of circle of Willis

  • Anterior COW
    • interhemispheric blood flow across Acomm
    • reversal of flow in proximal ACA
  • PComm supply either direction (ant / post)
  • Proximal PCA at posterior COW


Secondary collaterals = ophthalmic artery and leptomeningeal vessels

  • reversal of blood flow within ophthalmic artery
  • anastomoses between distal major cerebral arteries
    • between ACA and MCA
    • between MCA and PCA
    • between PCA and ACA
  • distal branches of cerebellar arteries (links vertebral and basilar segments)
  • leptomeningeal and dural arteriolar anastomoses with cortical vessels


Other collaterals less commonly encountered:

  • tectal plexus (supratentorial branches of PCA with infratent branches of SCA)
  • orbital plexus (ophthalmic artery with facial, middle meningeal, maxillary and ethmoidal arteries)
  • rete mirabile caroticum (ICA and ECA)




  • a=pterygoid plexus
  • b=deep middle cerebral vein
  • c=inferior petrosal sinus and basilar plexus
  • d=superior petrosal sinus
  • e=anastomotic vein of Trolard
  • f=anastomotic vein of Labbé
  • g=condyloid emissary vein
  • h=mastoid emissary vein
  • i=parietal emissary vein
  • j=occipital emissary vein




Liebeskind, D. S. “Collateral Circulation”. Stroke 34.9 (2003): 2279-2284. Web.

CSF WBC Correction for Traumatic Tap

If peripheral WBC is normal, then use ratio of 1:500 or 1:750.

If peripheral WBC abnormal, then use the following formula:

  • WBCcsf = WBCblood x RBCcsf / RBCblood
  • or  WBCc * RBCb = WBCb*RBCc
  • or WBCc/RBCc = WBCb/RBCb

The result is the number of artificially introduced WBCs.

True WBCcsf is then calculated by subtracting the artificially introduced WBCs from the actual WBCcsf


“WBC Correction For Traumatic Tap – Labce.Com, Laboratory Continuing Education”. N.p., 2016. Web. 17 Aug. 2016.

Anticoagulation in Patients with Brain Metastases


  • Anticoagulate in patients with brain tumors and VTE except if risk of ICH is high: i.e.
    • melanoma mets
    • renal cell carcinoma mets
    • choriocarcinoma mets
    • thyroid carcinoma mets
  • treat x 3-6 months; long term if malignant gliomas
  • LMWH recommended versus warfarin
  • If risk of ICH high:
    • IVC filter if significant residual brain mets
    • if mets already removed / treated effectively and medical condition too unstable – anticoagulate

DVT Prophylaxis:

  • do not anticoagulate except in post-operative period
  • use SCDs with post-op LMWH or UFH 12-24 hours after surgery
  • cotninue prophylaxis until ambulation resumed



Uptodate. “Anticoagulant and antiplatelet therapy in patients with brain tumors.” Accessed 08/12/2016.

Lyman GH, Khorana AA, Falanga A, et al. American Society of Clinical Oncology guideline: recommendations for venous thromboembolism prophylaxis and treatment in patients with cancer. J Clin Oncol 2007; 25:5490.


MRI: Meningioma

MRI Classic Findings in Meningioma:

  • focal, extra-axial mass
  • dural-based, presence of dural tail
  • mottled appearance (highly vascular)
  • CSF cleft (high T2 signal for CSF, pial vessels, hypointense dura)
  • homogenous on CT/T1
  • T1 = hypointense; T2 = hyperintense
  • T2W / FLAIR shows brain edema



Dynamed.  “Meningioma.”  Accessed 08/10/2016.