M01.02.045 Venous Drainage

The venous drainage system of the head and neck is crucial for returning deoxygenated blood to the heart. This system can be categorized into three primary regions:

1. Venous Drainage of the Brain and Meninges: Managed by the dural venous sinuses.
2. Venous Drainage of the Scalp and Face: Drained by veins corresponding to arteries, emptying into the internal and external jugular veins.
3. Venous Drainage of the Neck: Facilitated by the anterior jugular veins.

Jugular Veins Overview

There are three main jugular veins responsible for draining the head and neck:

• External Jugular Vein
• Internal Jugular Vein
• Anterior Jugular Veins

1. External Jugular Vein (EJV)

Formation

• Formed by the union of:
  • Posterior auricular vein: Drains the scalp area superior and posterior to the outer ear.
  • Retromandibular vein (posterior branch): Formed by the maxillary and superficial temporal veins draining the face.

Anatomical Course

• Runs superficially in the neck, crossing anterior to the sternocleidomastoid muscle.
• Terminates in the subclavian vein after receiving tributaries like the posterior external jugular, transverse cervical, and suprascapular veins.

Clinical Relevance

• Severance of EJV: Its superficial position makes it prone to injury. If cut, air can enter the vein, causing cyanosis and obstructing blood flow to the heart. Emergency management includes applying pressure to stop air entry.

2. Anterior Jugular Veins

Characteristics

• Paired veins with variability in anatomy.
• Drain the anterior neck and empty into the subclavian vein.
• Often interconnected by the jugular venous arch.

3. Internal Jugular Vein (IJV)

Formation

• Continuation of the sigmoid sinus in the cranial cavity.
• Begins at the superior bulb and exits the skull via the jugular foramen.

Anatomical Course

• Descends within the carotid sheath, lateral to the common carotid artery.
• Joins the subclavian vein at the base of the neck to form the brachiocephalic vein.
• Receives tributaries from facial, lingual, occipital, superior, and middle thyroid veins.

Clinical Relevance

• Jugular Venous Pressure (JVP): Pulsations provide an estimate of right atrial pressure. Observed as pressure waves since there are no valves in the brachiocephalic or subclavian veins.

Dural Venous Sinuses

The dural venous sinuses are spaces between the layers of dura mater that drain venous blood from the brain and skull into the internal jugular vein.

Clinical Relevance: Cavernous Sinus

• Located adjacent to the sphenoid bone.
• Receives blood from: Superior and inferior ophthalmic veins, middle superficial cerebral veins, and the sphenoparietal sinus.
• Key Structures at Risk: Infection here can damage the internal carotid artery and cranial nerves (III, IV, V1, V2, VI).

Points to Remember

1. The external jugular vein is superficial and prone to injury.
2. Internal jugular vein pulsations reflect right atrial pressure.
3. The dural venous sinuses are important for brain venous drainage and have clinical significance in the spread of infections.
4. The cavernous sinus is a critical area where infections from the face can spread due to valveless veins.

Clinical Figures