Abstract 18715: Pituitary Apoplexy Following a Nuclear Stress Test

Abstract

Background: Regadenoson is an A2A adenosine receptor agonist with weak affinity for A1, A2B and A3 adenosine receptors. Regadenoson(RAD) is used in MPI in patients who are unable to undergo exercise stress test. It acts primarily by activating A2A receptors causing coronary vasodilatation and increase blood flow. RAD has gained popularity since its approval in 2008 for its longer half life, ease of administration and obviating the need to stop beta blockers prior to testing. The common side-effects are dyspnea, headache and flushing. Here we describe the first documented case of pituitary apoplexy following regadenoson stress test. Case: Our patient is a 49 year-old female who underwent RAD stress test for evaluation of CAD. Within hours of testing she developed excruciating pressure like headache in peri-orbital and frontal regions. BP was moderately elevated and physical examination, including fundoscopy was normal. CT head showed a 1.3 x 1.4 cm pituitary mass. MRI with gadolinium confirmed a sellar and suprasellar 22 x 16 x 18 mm mass with small element of acute hemorrhage and necrosis suggesting pituitary apoplexy. Patient subsequently underwent resection of pituitary mass. Pathology revealed pituitary early infarction and hemorrhage. Conclusion: RAD induced coronary and possible peripheral vasodilatation is mediated primarily by the A2A adenosine receptor (A2A-AdoR) present in the vascular wall. The A2A-AdoR is widely distributed including the cerebral circulation. The effects of RAD such as arterial vasodilatation, sympathomimetic excitation, inhibition of platelet aggregation, reduced airway hyper-responsiveness, are known to mediate through this receptor. The vasodilatory effect on the cerebral arteries is postulated as the mechanism of headaches in patients receiving RAD. Based on our case findings and mechanism of action of RAD we hypothesize that reduced blood flow in the pituitary gland from vasodilatation and rapid fluctuations in blood pressure from RAD might have precipitated pituitary apoplexy in our patient. This case illustrates that although rare, pituitary apoplexy should be included in the differential diagnosis of patients with persistent headache of more than 30 minute duration after completion of ragedenoson stress test.