The glomus tumor invasion of Jugular bulb is diagnosed by -

MRI – gives soft tissue extent of tumor; Magnetic Resonance Angiography (MRA) shows compression of the carotid artery whereas magnetic resonance venography shows invasion of jugular bulb by the tumor (For more details on imaging techniques used in case of Glomus tumor – see the preceding text) Remember: Preoperative biopsy is never done in case of glomus tumor as it can lead to bleeding.