Cavernous sinus

The cavernous sinus is a paired venous collector located at the base of the skull on either side of the sella turcica. It is part of the sinus system of the dura mater, providing venous blood drainage from the eye sockets and certain parts of the brain.

The uniqueness and clinical significance of this sinus lie in its complex structure. Unlike other venous vessels, its cavity is permeated by numerous fibrous septa and contains a number of critically important nerve and vascular structures. Also, unlike other veins, there are no valves in the cavernous sinus, which allows blood to flow in different directions depending on pressure gradients.

Anatomy and contents

Anatomically, the cavernous sinus is a “crossroads” where veins, arteries, and nerves are closely adjacent to each other.

Directly inside the sinus are:

• Internal carotid artery (pars cavernosa).
• Abducens nerve (6th pair of cranial nerves).

Its side wall contains:

• Oculomotor nerve (3rd pair).
• Trochlear nerve (4th pair).
• The first and second branches of the trigeminal nerve (V1 — ophthalmic nerve and V2 — maxillary nerve).

Clinical Significance

Due to its anastomoses with the facial veins, the cavernous sinus is a potential route for the spread of infection from the so-called “dangerous triangle” of the face. An infection in the sinus can lead to thrombosis, a life-threatening condition with a high mortality rate.

Damage to the cavernous sinus (due to thrombosis, tumour, or injury) causes a specific neurological syndrome. It includes ophthalmoplegia (paralysis of the eye muscles), loss of sensation in the areas innervated by the ophthalmic and maxillary nerves, as well as exophthalmos and eyelid swelling due to venous congestion.