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Differential Diagnosis in Lateral Rectus Palsy
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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
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Anatomical Concerns• Course of the Abducens Nerve
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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.
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Millar Gubler Syndrome
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Foville Syndrome: Inferior Medial Pontine Syndrome (Foville Syndrome)
• Foville’s syndrome:Sixth nerve paresisHorizontal conjugate gaze
palsyIpsilateral V, VII, VIII cranial nerve palsyIpsilateral Horner’s
syndrome
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Foville Syndrome• Ipsi PPRF --> Horizontal
Gaze palsy• Ipsi CNVII --> LMN facial
paresis• contra UMN paralysis of
body• contra sensory loss of
body• internuclear
opthalmoplegia
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Anatomical Consideration of the Petrous Apex
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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
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Intracranial Abducens
Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus
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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
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Extracranial course of CN VINote 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
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Superior Orbital Fissure
• Learn• Fauna• To• See• Numerous• Invertebrate • Animals
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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
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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