Differential Diagnosis in Lateral Rectus Palsy

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

Anatomical Concerns• Course of the Abducens Nerve

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.

Millar Gubler Syndrome

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

Foville Syndrome• Ipsi PPRF --> Horizontal

Gaze palsy• Ipsi CNVII --> LMN facial

paresis• contra UMN paralysis of

body• contra sensory loss of

body• internuclear

opthalmoplegia

Anatomical Consideration of the Petrous Apex

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

Intracranial Abducens

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

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

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

Superior Orbital Fissure

• Learn• Fauna• To• See• Numerous• Invertebrate • Animals

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

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