General guide to the assessment of abducens palsy, referencing anatomy from the brainstem to the superior orbital fissure

1. Differential Diagnosis in Lateral
Rectus Palsy

2. CN VI
• 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

3. Anatomical Concerns
• Course of the Abducens Nerve

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.

5. Millar Gubler Syndrome

6. Foville Syndrome: Inferior Medial Pontine
Syndrome (Foville Syndrome)
• Foville’s syndrome:
Sixth nerve paresis
Horizontal conjugate gaze
palsy
Ipsilateral V, VII, VIII cranial
nerve palsy
Ipsilateral Horner’s
syndrome

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

8. Anatomical Consideration of the Petrous Apex

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

10. Intracranial Abducens
Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus

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

13. Superior Orbital Fissure
• Learn
• Fauna
• To
• See
• Numerous
• Invertebrate
• Animals

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