Raised intracranial pressure - caused by posterior fossa tumours/idiopathic intracranial hypertension causing a downward displacement of the brainstem stretching CN VI over the petrous lip.
CN VI is medially situated and runs through the middle of the sinus in close relationship to the internal carotid artery and is therefore more prone to damage
intracavernous CN VI palsy is accompanied by a post-ganglion Horner syndrome (Parkinson sign)
CN VI palsy is joined by sympathetic branches from the paracarotid plexus.
In contrast to CN III palsy, aneurysms rarely affect CN VI, but vascular causes are common.