# Fenestrated giant mastoid emissary vein, a novel finding

## TL;DR

This paper reports a rare anatomical variation of a vein in the skull, which could impact medical procedures in the head and neck region.

## Contribution

The study documents a novel extracranial fenestration of the mastoid emissary vein with detailed imaging and morphometric analysis.

## Key findings

- A large left mastoid emissary vein exhibited a fenestration 2.33 cm inferior to its foramen.
- Three deep communicating veins connected the fenestrated segment to the suboccipital venous plexus.
- The finding may influence surgical and endovascular planning in the mastoid-suboccipital region.

## Abstract

To document an extracranial fenestration of the mastoid emissary vein (MEV) and to clarify its drainage pattern and potential procedural relevance.

A 46-year-old male underwent multidetector CT angiographic evaluation of the cervical carotid system. DICOM data were post-processed in Horos using multiplanar reconstructions and three-dimensional volume-rendered images; morphometric measurements were obtained on the reconstructions.

A large left MEV (6.6 mm) exited through a single mastoid foramen situated 2.95 cm postero-supero-medially to the mastoid tip. The vein divided 2.2 mm distal to the foramen into an anterior limb (5.0 mm) and a posterior limb (1.1 mm) that rejoined 2.33 cm inferiorly, forming a long fenestration. Three deep communicating veins connected the fenestrated segment to the suboccipital venous plexus, and the distal MEV continued as the deep cervical vein.

Extracranial fenestration is a plausible variant of a prominent MEV. Recognition on CT may prevent misinterpretation as vascular duplication or pathology and may influence mastoid, retrosigmoid, and endovascular planning in the mastoid–suboccipital region.