Unremarkable MRA of the circle of Willis. 3. Abnormal signal intensity in the left mastoid air cells, as described. END OF IMPRESSION: CPT CODE: 70553, 70544, 76375 UNENHANCED BRAIN CT CLINICAL INDICATION: Headaches TECHNIQUE: Contiguous 3 mm imaging from skull base to vertex without contrast administration. Images were obtained on soft tissue and bone windows/algorithms.