DSA (Digital Subtraction Angiogram)

DSA is a catheter angiogram of the vessels supplying the brain.

It is done under local anaesthesia, via the transfemoral route, on a cathlab containing special DSA & ‘roadmap’ software’ & takes just 20 to 30 minutes.

It is different from angiography of other organs such as the heart or limbs in that the machine subtracts the skull, brain, CSF, meninges etc from the image, making the contrast flowing through the blood vessels stand out. Thus it is highly accurate & detects abnormalities in blood vessels which are in the sum- mm range. It is a real-time study which does not involve any reconstruction as in MR angio or CT angio.  Also views are taken in different projections after cannulating all vessels selectively so that maximum dynamic information is gathered about the pathology. Maneuvers like cross- compression are done to ascertain cross-flow across the circle of Willis.

The common indications of DSA are:

  • ALL patients of Subarachnoid hemorrhage (SAH)
  • Patients of TIA or  ischemic stroke in whom either Doppler or MRA have detected extracranial or intracranial atheromatous disease.
  • Patients with recurrent / crescendo TIAs in the same territory
  • Suspected carotid or vertebral artery dissection when MRI is inconclusive
  • Patients with intracerebral bleed when an underlying AVM is suspected (young patients, peripheral location of the bleed, no evidence or history of hypertension, recurrent bleeds in the same territory etc.)
  • Suspected venous sinus thrombosis when MRI is inconclusive.
  • Highly vascular CNS or ENT tumors when pre-op embolisation is required.

DSA is still the gold standard for most of these indications and modalities like MR angiogram or CT angiogram are compared to DSA to establish their efficacy.