Cerebral Vascular Reserve assessment with acetazolamide (Diamox)
by Dr. L.P. Riccelli, MD
How it works: CT perfusion with acetazolamide (Diamox) consists of a baseline CT perfusion scan of a portion of the brain, followed by injection of acetazolamide (a vasodilatory agent), and then a post acetazolamide CT perfusion scan of the same area. Normally, if blood flow to the brain is decreased, the vessels for that area will expand to maintain adequate oxygen flow, up to a maximum limit. The extent to which this can occur beyond baseline is the cerebrovascular reserve. CT Perfusion with acetazolamide allows assessment of the cerebrovascular reserve.
Equipment: Perfusion studies are usually performed on a Philips 64 or 256 channel CT scanner. OHSU is an ACR accredited CT facility.
Benefits: The study is used to evaluate cerebrovascular reserve, which can help determine the risk of future stroke. The study is often used to help determine which patients might benefit from interventions designed to increase blood flow beyond a very narrow or occluded vessel.
Exam Preparation: Exam preparation is the same as for a CT perfusion study, with additional screening for any potential contraindications to acetazolamide. Additional lab work of sodium and potassium levels are necessary if not performed within two weeks. Potential contraindications to acetazolamide include: Sulfa/sulonamides, severe renal dysfunction, cirrhosis/severe liver disease, adrenocortical insufficiency, hyponatremia, and hypokalemia. A nurse or technologist will interview you for contraindications, and an IV will be placed. Usually labs will be needed prior to the study.
What to Expect: A baseline perfusion scan is performed, followed by injection of acetazolamide over several minutes. It takes about 15 minutes for acetazolamide to have its maximal effect. A post acetazolimde perfusion scan is perfomed about 15 minutes after injection. Because of this time between scans and the additional time necessary for screening and possible lab work, the amount of time spent in the department will likely be between 1 and 2 hours.
Severe reactions to a single dose of acetazolamide are rare; however, more common reactions that are usually self limited can include brief numbness around the mouth, paresthesias, malaise, and headache.
Adverse reactions to contrast materials are uncommon, but can range from mild to severe. Severe reactions very uncommon. Further information about the risks and benefits of x-rays and contrast material can be found at http://www.radiologyinfo.org/en/safety/index.cfm
Louis P. Riccelli, MD
Associate Professor of Neuroradiology
- AJNR Am J Neuroradiol 30:876–84 _ May 2009 _ www.ajnr.org
- AJNR Am J Neuroradiol 27:1876–81 _ Oct 2006 _ www.ajnr.org
- Radiology 2004; 231:632-644