Home › Body Atlas › Nerves › Abducens Nerve (CN VI)

Abducens Nerve (CN VI)

nervus abducens

The abducens nerve (CN VI) arises from the abducens nucleus in the dorsal pons, runs through Dorello's canal (under the petroclival ligament at the petrous apex) to enter the cavernous sinus where it runs free within the sinus rather than in the lateral wall, then traverses the superior orbital fissure within the annulus of Zinn to supply the lateral rectus muscle exclusively. Its long intradural course makes it the cranial nerve most vulnerable to raised intracranial pressure (false localizing sign).

Region: Head & Skull

Clinical Relevance

Clinical Notes

CN VI palsy produces horizontal diplopia from lateral rectus weakness (inability to abduct the eye beyond midline in complete palsy, or reduced abduction in partial palsy). As a false localizing sign, CN VI palsy can indicate raised ICP from any cause regardless of lesion location (the nerve is stretched over the petrous apex as the brainstem is displaced downward). In Gradenigo syndrome, petrous apicitis produces CN VI palsy, retroorbital pain (CN V1), and otorrhoea. Microvascular CN VI palsy from diabetes resolves spontaneously within 3 months without investigation beyond vascular risk factor control.

Pathology

Common Injuries & Conditions

CN VI Palsy as False Localizing Sign in Raised ICP

Horizontal diplopia from CN VI palsy in a patient with headache and papilloedema indicates raised intracranial pressure as a false localizing sign from stretch of the long intradural abducens course over the petrous apex; the lateral rectus weakness resolves with treatment of the underlying cause of raised ICP and does not indicate a pontine or cavernous sinus lesion.