Cavernous sinus contents (mnemonic)

The cavernous sinus contents (structures within the sinus proper and also in its lateral wall) and their relative positions can be recalled with the following mnemonic:

• O TOM CAT

Consider a coronal view of the cavernous sinus.

'O TOM' are the first letters of components of the lateral wall of cavernous sinus considered vertically, from the top to the bottom. CA are the first letters of the structures located within the sinus. CA continues virtually at the level of the T of 'O TOM'. So that the T represents the point of conjunction of the two words. See Figure 1 for further illustration.

Mnemonic

• O: oculomotor nerve

• T: trochlear nerve
• O: ophthalmic branch of trigeminal nerve
• M: maxillary branch of trigeminal nerve

• C: internal carotid artery
• A: abducens nerve
• T: trochlear nerve

Remember two things:

1. the mandibular branch of the trigeminal nerve is not associated with the cavernous sinus since it has descended vertically through the foramen ovale underneath the trigeminal ganglion (Gasser ganglion), which is anatomically posteriorly to the cavernous sinus
2. the maxillary branch of the trigeminal nerve is external but immediately adjacent to the lateral wall of the cavernous sinus, which becomes important in the differential diagnosis of lesions of the cavernous sinus - lesions of this nerve tends to distort the sinus rather than occupy it