Isolated VI Nerve Palsy
Examination (Examine patient’s eyes, CNs)
 Complete the eye examination
 Rule out MG, thyroid
 Rule out Cavernous Sinus syndrome, Superior orbital fissure syndrome
 Proceed to check cranial nerves
 V, VII and VIII for CPA tumor
 XI, X, XI, XII for any base of skull lesions
 Examine upper limbs
 Hemiplegia (long tract signs suggesting brainstem)
 Cerebellar signs (CPA lesion, Miller Fisher usually truncal and gait)
 Reflexes for areflexia (Miller Fisher)
 Examine the neck for LNs and mastoid for tenderness (Gradenigo’s syndrome)
 Request
 Fundoscopy (papilloedema from raised ICP, optic atrophy for MS)
 Field testing (bitemporal hemianopia)
 Acuity (reduced in orbital lesions)
 Corneal testing for reduced sensation form V1 involvement
 BP
 Urine dipstick
 Temperature chart for fever(meningitis)
 Ask for retrobulbar pain
Presentation
Sir, this patient has an isolated right sided VI nerve palsy as evidenced by
 Convergent strabismus at primary gaze
 Failure of abduction of the right eye
 With diplopia where the image is side by side and furthest apart on rightward
gaze, with disappearance of the outer image on covering the right eye. This
suggests a right lateral rectus muscle weakness and hence a right VI nerve palsy.
There is no evidence of a III or IV or V1 palsy which may suggest cavernous sinus or
superior orbital syndrome.
There is also no involvement of the VII or VIII nerve palsy and no cerebellar signs to
suggest A CPA lesion
There are no associated CN lesions of IX to XII and no enlarged Cx LNs.
There is no fatiguibilty to suggest MG and no thyroid eye signs.
There are no enlarged LNs or tender mastoid. There is also no hemiparesis, no
cerebellar signs and reflexes are present.
I would like to complete my examination by:
 Fundoscopy (papilloedema from raised ICP, optic atrophy for MS, DM or
hypt changes)
 Field testing (bitemporal hemianopia)
 Acuity (reduced in orbital lesions)
 Corneal testing for reduced sensation form V1 involvement




BP
Urine dipstick
Temperature chart for fever(meningitis)
Ask for retrobular pain
In summary, this patient has an isolated right sided VI nerve palsy. The aetiology
includes….
Questions
What is the course of the VI nerve?
 Nucleus of CN VI located in the pons, sending motor neurons supplying the
lateral rectus muscle of the ipsilateral eye;
 also internuclear neurons that project (via MLF) to medial rectus subdivision of
contralateral oculomotor (CN III) nucleus (ie lesion of nucleus causes ipsilateral
horizontal gaze palsy)
 nerve fascicles exit the pons anteriorly and course through subarachnoid space
where it runs a vertical (upward) course, along ventral surface of pons (confined
by adjacent AICA)
 pierces dura overlying clivus, entering into Dorello's canal, contacting tip of
petrous pyramid (part of temporal bone; adjacent to mastoid air cells)
 enters the cavernous sinus after passing through the petroclinoid (Gruber's)
ligament
 runs in body of sinus (rather than lateral wall where CN III, IV, V located) along
foramen lacerum (near internal carotid artery)
 enters orbit via superior orbital fissure and shortly thereafter pierces lateral rectus
muscle
What are the causes of a unilateral VI nerve palsy?
 Brainstem (Pons)– infarct, haemorrhage, abscess, demyelinating (look for VI and
VII palsies due to close proximity)
 Aneurysm (ectatic basilar artery)
 Meningitis
 Infective – TB, Fungal, HIV, Syphilis, Lyme
 Mitotic – leptomeningeal carcinaomatosis, secondaries(NPC), lymphoma,
radiotherapy
 Sarcoidosis
 Trauma
 CPA lesions
 Petrous temporal bone (Gradenigo’s syndrome)
 Cavernous sinus syndrome
 Superior orbital syndrome
 Miller Fisher syndrome
 Mononeuritis multiplex
 DM, hypertension
 MG
 Raised ICP
NB: - most common aetiology of isolated abducens lesion is post-viral in children and
ischemia / infarction (eg diabetic) in adults
What are the causes of bilateral VI nerve palsy?
 Leptomeningeal causes (see above)
 Miller Fisher syndrome
 Mononeuritis multiplex
 MG
 Raised ICP
 Wernicke’s encephalopathy (Ophthalmoplegia, confusion and ataxia a/w
Korsakoff’s psychosis from thiamine deficiency)
What are the syndromes associated with VI nerve palsy?
Central
 Raymond’s syndrome – ipsilateral VI with contralateral hemiparesis
 Millard-Gubler syndrome – Ipsilateral VI and VII with contralateral hemiparesis
Peripheral
 Gradenigo syndrome – inflammation of the tip of the petrous bone from
mastoiditis; VI and V(gasserian ganglion therefore ipsilateral pain) and VII
 CPA
 Cavernous sinus
 Superior orbital
Congenital
 Mobius syndrome (VI with facial diplegia)
 Duane’s syndrome (Congenital absence of VI nuclei with III nuclei innervating
the lateral recti; orbit retraction on adduction and protrusion on abducting
How do you evaluate diplopia?
 Evaluation of diplopia follows 3 rules
o The double vision is maximal in the direction of gaze in the affected
muscle
o The false image is the outer image
o The false image arises form the affected eye
What is Cavernous sinus syndrome?
 Lesion in the cavernous sinus leading to
 Ophthalmoplegia, V1, Horner’s, proptosis, chemosis and pain
 Causes include carotid aneurysm, carotid-cavernous fistula, tumour and
thrombosis, Tolosa Hunt syndrome
What is superior orbital fissure syndrome?
 Lesions occurring at the superior orbital fissure leading to
 Ophthalmoplegia, V1, Horner’s, proptosis, chemosis, pain and Optic Nerve
 Causes includes meningiomas, hemangiomas and thyroid eye disease, Tolosa
Hunt syndrome
What is Miller Fisher syndrome?
 Triad of ophthalmoplegia, ataxia and areflexia
 Cs by present of anti GQ1B antibodies
 Variant of GBS
What are the causes of mononeuritis multiplex?
 Endocrine – DM, hypt
 AI – Churg Strauss, Wegener’s, PAN, Sjogren’s, RA, SLE
 Infective – Lyme, leprosy
 Infiltrative – Amyloid, sarcoid
How would you investigate?
 Blood tests
 fasting glucose, ESR, ANA, VDRL
 Imaging
 CT brain or MRI brain
 Vascular imaging if proptosis / chemosis looking for dural carotid-cavernous
fistula or cavernous sinus thrombosis
 Examine CSF (also if systemic illness, immunocompr, bilateral, other CN deficits)
 8-30% will remain cryptogenic after work-up
How would you manage?
 Education on Px if ischaemic (see below) and Ix and avoid driving, climbing high
places and operating heavy machinery
 Treat underlying cause
 Example control DM and BP
 Symptomatic treatment
 Patch
 Prism
 If chronic, chemodenervation with botox or strabismus surgery
What is the prognosis?
 most either spontaneously improve or have underlying lesion found
 ischemic palsies almost always recover completely in 2-4 months while some
recovery seen in half of traumatic cases (but take over one year)
 if no recovery over 3-6 months then suspect underlying lesion such as tumour
 few may have chronic isolated abducens palsy of unknown cause
 follow regularly looking for emergency of new localizing signs and ensure
adequate neuroimaging and ENT evaluation