The cavernous sinuses are extradural venous spaces located on each side of the sella turcica, containing within neurovascular structures that may be affected by different infectious, inflammatory, neoplastic, infiltrative and vascular pathologies. An adequate knowledge of the local anatomy helps to recognize different lesions that may occur in this area.

1- Normal anatomy

CS is a septated venous plexus surrounded by a dural fold. It is hexahedronal in shape, with a 5-7 mm transverse diameter, 5-8 mm vertical diameter and 10-15 mm anteroposterior diameter. Both cavernous sinuses are interconnected by a venous plexus named the coronary sinus and are located laterally to the sella turcica. Medially, the internal carotid artery (ICA) runs through the CS. Laterally to the ICA, the abducens nerve (VI) within CS. The oculomotor nerve (III), the trochlear nerve (IV) and the two first divisions of the trigeminal nerve (V) are located laterally within the dural wall (Fig.1). The third division of the cranial nerve V doesn’t pass through the CS and leaves the skull through the foramen ovale. CS medial wall represents the lateral limit of sella turcica. MRI does not allow an accurate visualisation of this wall (Fig.2).

2- MR imaging protocol

MRI imaging should include:

• · Thin (3 mm) T1-weighted and T2-weighted sequences in axial and coronal planes

• · FLAIR sequences in the axial plane (including brain)

• · 3D heavily T2-weighted sequences in the axial plane (e.g. CISS)

• · Contrast-enhanced T1-weighted Fat-saturated sequences in the axial and coronal planes

• · MR angiography (3D time-of-flight (TOF) or contrast-enhanced 3D angiography sequences) if ICA anomalies are suspected.

Normal cavernous sinus appears hypointense on T1- and T2-weighted images (wi) and it shows intense homogenous enhancement following contrast administration with central flow void due to the traversing ICA and filling defect posterolaterally due to the Gasserian ganglion in the Meckel’s cave (Fig.3).