Abducens nerve (CN VI)
The abducens nerve is the sixth cranial nerve. It is the "anticipation" in this infamous mnemonic. It's course from nucleus located in the dorsal pons, to its innervation of the lateral rectus can be divided into 4 parts:
- nucleus and intra-parenchymal portion
- cisternal portion
- cavernous sinus portion
- orbital portion
Nucleus and intra-parenchymal portion
It is the most medial of the nerves emerging from immediately below the pons (facial nerve and vestibulocochlear nerve lateral to it). It courses superiorly with the anterior inferior cerebellar artery anterior to it, and the pons posterior, to pierce the dura over medial most aspect of the petrous ridge, passing through the inferior petrosal sinus in Dorello's canal. It is its oblique course and relatively fixed anchor in Dorello's canal which makes it prone to stretching when raised ICP from a space occupying lesion causes transtentorial herniation (a sixth nerve palsy is the classic lateralising sign of an extradural haematoma (EDH).)
Cavernous sinus portion
- 1. Last's Anatomy - 10th Edition - Chummy S Sinnatamby.
- 2. Clemete's Anatomy - Regional Atlas of the Human Body - 3rd Edition
- 3. Umansky F "Dorello's canal: a microanatomical study"