A 14-year-old boy with recurrent epistaxis and unilateral nasal obstruction undergoes MRI which shows a highly vascular mass in the nasopharynx with flow voids and gadolinium enhancement. Before surgical planning, which additional investigation is most appropriate to assess the feeding vessels and plan preoperative embolization?

Explanation

## Preoperative Vascular Assessment of Nasopharyngeal Angiofibroma ### Role of Digital Subtraction Angiography **Key Point:** Digital subtraction angiography (DSA) with selective external carotid artery catheterization is the gold standard for identifying feeding vessels and planning preoperative embolization in NAF. **High-Yield:** DSA provides: - Precise identification of feeding arteries (usually branches of external carotid artery) - Assessment of collateral circulation - Determination of embolization feasibility - Real-time visualization of vascular anatomy - Allows therapeutic embolization in the same session ### Feeding Vessels in NAF | Vessel | Frequency | Notes | |--------|-----------|-------| | Maxillary artery (terminal branch of ECA) | 90% | Most common feeder | | Ascending pharyngeal artery | 30% | Often present | | Sphenopalatine artery | Variable | Branch of maxillary artery | | Internal carotid artery branches | Rare | In advanced cases with intracranial extension | **Clinical Pearl:** Most NAFs are supplied by branches of the external carotid artery, making them amenable to preoperative embolization to reduce intraoperative blood loss. ### Preoperative Embolization Strategy 1. DSA identifies feeding vessels 2. Microcatheter placed selectively into feeding arteries 3. Embolic agents (polyvinyl alcohol particles, coils, or glue) deployed 4. Goal: reduce tumor vascularity by 80–90% before surgery 5. Reduces intraoperative hemorrhage and improves surgical visibility **Mnemonic: DSA for NAF** — **D**igital **S**ubtraction **A**ngiography identifies feeders for embolization. ### Why Other Investigations Are Insufficient - **Doppler ultrasound:** Non-invasive but lacks spatial resolution and cannot guide intervention - **CTA:** Good for anatomy but does not provide dynamic flow information or allow therapeutic intervention - **MRA:** Non-invasive but less detailed for small feeding vessels and does not permit embolization **Warning:** DSA carries small risks of arterial puncture, contrast reaction, and stroke; it is reserved for cases proceeding to surgery where embolization is planned. [cite:Dhingra 8e Ch 12]