Pseudosubarachnoid hemorrhage sign in a patient with tetralogy of Fallot

Subarachnoid hemorrhage (SAH) constitutes a common neurosurgical emergency. Non-contrast computerized tomography (NCCT) head has very high specificity and sensitivity in detecting SAH. However, in certain conditions, the computed tomography (CT) may be falsely positive, termed as pseudo-SAH. We hereby report a rare case of pseudo-SAH in a patient with tetralogy of Fallot and discuss the possible etiopathogenesis and the pertinent literature. We present here a case of a 15-year-old male patient, who was diagnosed with tetralogy of Fallot (TOF) physiology. He presented to the cardiology outpatient clinic with complaints of dyspnea on exertion, headache, and drowsiness. The NCCT head revealed diffuse hyperdensity in the basal cisterns and sulcal spaces, which were suggestive of diffuse SAH. However, in the setting of negative CT and magnetic resonance angiography along with high hematocrit levels (84%), diagnosis of pseudo-SAH was considered. The patient was appropriately managed with beta-blockers, intravenous fluids, and serial phlebotomies. The patient underwent a palliative shunt connecting the ascending aorta to the main pulmonary artery (central shunt), following which his saturation improved, and hematocrit decreased (40%) leading to significant symptomatic improvement. Knowledge of pseudo-SAH signs is essential for the treating physician and plays an important part in the management of this patient population.