2. CN VI (Abducens Nerve)
• Longest subarachoid course
• Runs from brainstem in posterior fossa, through middle fossa (especially the petrous
apex) and orbit
• Lesions can affect the nerve via:
VI1: the brainstem syndrome
VI2: the elevated intracranial pressure syndrome
VI3: the petrous apex syndrome
VI4: the cavernous sinus syndrome
VI5: the orbital syndrome
4. Brainstem Sources of Abducens Palsy
• Millard Gubler Syndrome
• A unilateral lesion of the ventrocaudal
pons may involve the basis pontis and
the fascicles of cranial nerves VI and
VII. Symptoms include:
• 1.Contralateral hemiplegia (sparing
the face) due to pyramidal tract
involvement
• 2.Ipsilateral lateral rectus palsy with
diplopia that is accentuated when the
patient looks toward the lesion, due
to cranial nerve VI involvement.
• 3.Ipsilateral peripheral facial paresis,
due to cranial nerve VII involvement.
7. Foville Syndrome
• Ipsi PPRF --> Horizontal
Gaze palsy
• Ipsi CNVII --> LMN facial
paresis
• contra UMN paralysis of
body
• contra sensory loss of
body
• internuclear
opthalmoplegia
9. Petrous Apex Syndrome (Grandenigo’s
Syndrome)
• retroorbital pain due to
pain in the area supplied by
the ophthalmic branch of
the trigeminal nerve (fifth
cranial nerve),
• abducens nerve palsy (sixth
cranial nerve),[3] and
• otitis media
11. Increased Intracranial Pressure
• Brainstem displacement inferiorly
• Diffuse pressure along the subarachnoid course
• Traction on CN VI while it is anchored in Dorello’s canal
Diplopia--> Horizontal
12. Extracranial course of CN VI
Note the Abducens in within the
cavernous sinus while the CNIII, V1, V2
and Trochlear nerves are in the wall
CN VI exists the eye at the superior
orbital fissure
14. In adults, the most likely etiology of isolated sixth nerve palsy is
ischemic mononeuropathy that may be due to diabetes
mellitus, arteriosclerosis, hypertension, temporal arteritis or
anemia
Isolated 6th Nerve Palsy
15. Six Mimics of a CN VI Palsy
Thyroid eye diseases
Myasthenia gravis
Duane’s syndrome
Spasm of the near reflex
Delayed break in fusion
Old blowout fracture of the orbit
16. Duanes Retraction Syndrome
• Defect in genesis of Abducens
nucleus
• Three components”
• Defect AB duction
• Some defect in AD duction
• Palpebral fissue narrowing and
globe retraction often with
upshoot