The 'pulsatile' sebaceous cyst: beware of a superficial temporal artery aneurysm.

True aneurysms of the superficial temporal artery (STA) are quite uncommon. Only 14 such cases are described in the literature. Ultrasound scan (USS) is an appropriate and easily accessible non-invasive diagnostic modality, as it can show both the anatomical and flow characteristics of the aneurysmal vessel. Other conditions to be included in the differential diagnosis are haematoma, angiofibroma, eroding middle meningeal artery aneurysm, abscess or a parotid mass. Operative intervention is indicated to relieve symptoms as in this case, and to prevent rupture.