Diagnosis of right-to-left shunt with transcranial Doppler and vertebrobasilar recording

Background and Purpose - Right-to-left shunt (RLS) due to patent foramen ovale is a well-established risk factor for cryptogenic stroke and is highly prevalent in cases of migraine, cluster headache, and obstructive apnea. It can be diagnosed by gaseous-contrast transcranial Doppler, yet in a small percentage of cases it cannot be done owing to an insufficient temporal window. The aim of the study was to compare transtemporal with transoccipital approaches for gaseous-contrast transcranial Doppler for RLS diagnosis. Methods - We evaluated 183 subjects with a standard protocol for RLS diagnosis by simultaneously monitoring the right middle cerebral and vertebrobasilar circulations. Results - Vertebrobasilar recording reached high specificity (100%)and good sensitivity (83.72%) for the diagnosis of RLS after the Valsalva maneuver. For only medium and large shunts, both sensitivity and specificity reached 100%. Time to bubble appearance after injection was higher in the vertebrobasilar circulation (4.36 +/- 1.7 vs 6.77 +/- 2.5 seconds; P < 0.001). There was a positive correlation between the number of bubbles in the right middle cerebral and vertebrobasilar circulation (k=0.97). Conclusions - Transcranial Doppler with vertebrobasilar monitoring is highly sensitive and specific in detecting RLS, particularly when medium or large. It can be proposed for subjects with an insufficient temporal bone window.