Background:
Right-to-left vascular shunts are associated with brain abscess.
Case report:
We present a 47-year-old female with a cryptogenic left thalamic abscess on which Streptococcus mitis grew upon aspiration. Computed tomography of the chest with contrast agent revealed an anomalous connection between the left superior pulmonary and brachiocephalic veins. A right-to-left shunt was confirmed in a transthoracic echocardiogram study in which bubbles were injected into the left arm; this shunt had not previously been noted upon right-arm injection.
Conclusions:
We recommend aggressive evaluation for right-to-left shunts in patients who present with cryptogenic brain abscesses. In addition to imaging, this should include a bubble-based study with left-arm saline injection.