NEUROIMAGING / DSA

Balloon Test Occlusion (BTO)

Created 29/04/2021, last revision 16/04/2022

  • acute internal carotid artery (ICA) occlusion is associated with a high risk of ischemic neurological deficit (20-49%) (Seet, 2012)
    • in a metanalysis of 20 studies on patients with ICA occlusion, the annual stroke risk was 5.5% (2.1% ipsilateral). Those with hemodynamic compromise on functional imaging had a stroke risk of 12.5% (9.5% ipsilateral)
    • the clinical course of ICA occlusion is variable, from asymptomatic lesions to devastating strokes (Klijn, 1997)
  • the balloon test occlusion (BTO) is performed to see whether an artery can be temporarily or permanently closed without significantly affecting the brain perfusion
  • if the BTO is well tolerated, the risk of subsequent ischemia is considerably lower
    • pharmacologically induced hypotension during BTO further increases the test sensitivity

Indications

  • functional test in patients scheduled for ICA occlusion (inoperable aneurysms, glomus tumor, intracranial  tumors, tumors in the ENT region)
  • the Matas test was performed earlier (external CCA compression during angiography); it was replaced by more sensitive balloon test occlusion (BTO)
Balloon test occlusion (BTO)
Balloon test occlusion (BTO) - collaterals M4, A4

Procedure

Patient preparation

  • allergy premedication (if required)
  • premedication with NIMOTOP 60mg (2 tablets) every 4h
  • insert a urinary catheter and intravenous cannula
  • start Normal saline solution at 150 mL/h at least 4h before the procedure
  • ensure anesthesiologist supervision
  • i.v. heparinization at the beginning of the procedure
    • bolus of 5000-7000 IU of undiluted HEPARIN (1 – 1.4 ml)
    • dilute heparin – 4ml (1ml = 5000jj) + 16ml of NS (20ml solution = 20 000jj)
    • followed by i.v. diluted HEPARIN 1-3 ml/h (1000-3000 IU/h) with the target APTT 2-3x
  • flush the distal catheter section above the balloon with the normal saline + low dose of heparin
    • HEPARIN 0.5 ml (500IU) + 500 ml of NS (1ml=1IU) – cont. 60ml/h (1IU/min) [Standard, 1995]

Clinical and TCCD evaluation during procedure

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Assessment of collateral circulation

  • assess ACA (A1-A4 segments) and MCA (M1-M4 segments) contrast filling on the occluded side  (Kikuchi, 2014]
  • assess the anatomy of the circle of Willis (especially the presence and quality of ACoA and PCoA, A1 and P1 portions bilaterally)
Balloon test occlusion (BTO) - collaterals A4, M0
Balloon test occlusion (BTO) - collaterals A4, M4
The Circle of Willis - variants

Complications

  • neurological complications: 0-8.3% (average complication rate according to various studies ~ 2.2%) → more here
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