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cranialnerve6palsy-190820083542.pdf
1. Cranial Nerve 6 Palsy
DR. ARVIND KUMAR MORYA
MBBS, MS OPHTHALMOLOGY, MNAMS,
CATARACT (MICS), GLAUCOMA, PAEDIATRIC OPHTHALMOLOGY,
STRABISMUS, REFRACTIVE AND MEDICAL RETINA SERVICES,
ASSOCIATE PROFESSOR AND HEAD,
DEPARTMENT OF OPHTHALMOLOGY,
AIIMS, JODHPUR
4. NUCLEUS
LOCATION
• Lower part of Pons
• In the floor of fourth ventricle
• Either side of mid-line
• Deep to the facial colliculus
5. NUCLEUS
• ABDUCENT NUCLEUS
- Small spherical mass of multipolar neurons
- Wound round by fibres of CN VII
- Lies dorsolateral to Medial longitudinal bundle (MLB)
• PARAABDUCENT NUCLEUS
- Collection of small multipolar neurons
- Lies dorsolateral to abducent nucleus
- Connects it to opposite CN III nucleus through MLB
• ACCESSORY ABDUCENT NUCLEUS
- Lies ventrolateral to abducent nucleus
- Innervates nictitating membrane
6. COURSE
Origin
Medial to medial
lemniscus
Between scattered
fibres of pyramidal
tract in basilar pontis
Emerges at the lower
border of pons with
hypoglossal nerve
All 7-8 rootlets join at
variable distance
Pierces dura
Runs upwards,
forwards and laterally
in posterior cranial
fossa
Ascends up for 15 mm
at the back of
basiocciput and pierces
dura
Runs vertically upwards
in the posterior aspect
of petrous temporal
bone
Reaches upper border
of the bone
Bends forward under
ligament of Grubber
and superior petrosal
sinus
Enters cavernous sinus
Turns to lie inferolateral
to internal carotid
artery
Enters orbit via
oculomotor foramen of
superior orbital fissure
Runs within the muscle
cone
On the ocular surface
of lateral rectus at
junction of posterior
and middle thirds
7. RELATIONS
• AT ORIGIN
- 2 abducent nerves are 1 cm apart at the site
of origin.
- 2 vertebral arteries join to form basilar artery
in between 2 nerves.
- Lateral to its emergence is emergence of
facial nerve
- Inferior to it lies hypoglossal nerve
9. MOTOR CORTEX OF CEREBRUM
- Connected to the pre-central gyrus of opposite side via
CORTICONUCLEAR FIBRES.
- The area for eye is represented between thumb and nose.
- Stimulation leads to cortical type of movements.
PRE-CENTRAL GYRUS
10. FRONTAL LOBE OF CEREBRUM
- OCULOGYRIC AREA : Controls the voluntary
movements of the eye
- Lies in the posterior part of MIDDLE
FRONTAL GYRUS
OCULOGYRIC AREA
11. Control from frontal lobe of cerebrum
Oculogyric area
Aberrant
pyramidal tract
Crus cerebri
Verticle gaze
centre in mid-
brain B/L
Horizontal Gaze
centre
- Fibres from oculogyric area descend as aberrant pyramidal tract, in
the genu of internal capsule.
-Some fibres cross, reach the vertical gaze centre of both the sides
and end in CN III B/L
- Other fibres descend to pons para abducent nucleus (horizontal
gaze centre). Cross and end in horizontal gaze centre.
- Centre is connect to CN VI which is connected to CN III via MLB
12. Effect of stimulating various parts of oculogyric
area
STIMULUS AREA EFFECT
BILATERAL STIMULATION OF UPPER PART ROTATES THE EYE BALL DOWNWARDS
13. Effect of stimulating various parts of
oculogyric area
STIMULUS AREA EFFECT
BILATERAL STIMULATION OF LOWER PART ROTATES THE EYE BALL UPWARDS
14. Effect of stimulating various parts of
oculogyric area
STIMULUS AREA EFFECT
UNILATERAL STIMULATION OF UPPER PART ROTATES THE EYE BALL DOWNWARDS ON THE OPPOSITE SIDE WITH CLOSURE
OF EYELIDS
15. Effect of stimulating various parts of
oculogyric area
STIMULUS AREA EFFECT
UNILATERAL STIMULATION OF LOWER PART ROTATES THE EYE BALL UPWARDS ON THE OPPOSITE SIDE WITH OPENING
OF EYELIDS
16. Effect of stimulating various parts of
oculogyric area
STIMULUS AREA EFFECT
UNILATERAL STIMULATION OF MIDDLE PART ROTATES THE EYE BALL HORIZONTALLY ON THE OPPOSITE SIDE
17. OCCIPITAL CORTEX CONNECTIONS
- AREA NO. 18: PERISTRAITE CORTEX
- AREA NO. 19: PARASTRIATE CORTEX
OCCIPITAL
CENTRE
OCCIPITAL
CENTRE
SPLENIUM
OCULOGYRIC
AREA
OCULOGYRIC
AREA
SUPERIOR
COLLICULUS
HORIZONTAL GAZE CENTRE
18. EFFECT OF STIMULATION OF VARIOUS
PARTS
UPWARD CONJUGATE MOVEMENT DOWNWARD CONJUGATE MOVEMENT
19. BASAL GANGLIA
AREA 4,2,6
PUTAMEN &
OUTER GLOBUS
PALLIDUS
LENTICULAR
FASCICULUS OF
FOREL & ANSA
LENTICULARIS
NUCLEUS OF
DARKSCJWITSCH
AND CAJAL
MLB & GAZE
CENTRES
20. TRIGEMINAL NUCLEUS & CEREBELLUM
- Connected to MESENCEPHALIC NUCLEUS of trigeminal nerve
- Mesencephalic nucleus receives proprioceptive impulses from the muscles
- Mesencephalic nucleus Superior cerebellar peduncle Cerebellum (Dentate
nucleus) Oculomotor nuclei of both sides
21. MEDIAL LONGITUDINAL BUNDLE
- Connects the three oculomotor nuclei
- Helps in conjugate movement of eye
- Also connects them to :
1. Facial
2. Stato-acoustic
3. Nucleus ambiguous
4. Hypoglossal
5. Cervical segments of the spinal cord.
28. Paediatric
- elevated intracranial pressure
- pontine gliomas
- following ear or throat infections or viral illness.
•Pontine glioma.
• Brainstem gliomas are particularly common in the pediatric population, and more than 80%
arise from the pons with the peak age of onset between 5-8 years of age.
29. Paediatric
•Trauma, secondary to open or closed head injuries
Indirect pressure
on the nerve as in
passes over the
apex of the petrous
temporal bone
Secondary to
bruising or
haemorrhage
causing pressure
over the nerve
If associated with
apparently trivial
trauma, raises
suspicion with
underlying
intracranial tumour
30. Paediatric
• Elevated intracranial pressure due to shunt failure, pseudotumor cerebri, posterior
fossa tumors, neurosurgical trauma, venous sinus thrombosis, meningitis, or Lyme
disease
Downward
displacement of the
brainstem
Stretching of the
sixth cranial nerves
Tethered in Dorello’s
canal
31. Paediatric
•Intracranial tumor
• Posterior fossa tumors: such as pontine glioma, medulloblastoma, ependymoma, cystic
cerebellar astrocytoma can produce unilateral or bilateral abducens nerve palsies in
children.
• Abducens nerve palsy can also present as a postoperative complication after resection of
posterior fossa tumors in the pediatric population
32. •Meningitis
• Hanna and others found abducens nerve palsy in 16.5% of patients with acute bacterial meningitis.
Cranial nerve palsies in this setting tend to be multiple and bilateral.
35. I. Brainstem syndromes (pathogenesis)
- VI Nerve nucleus contains motor neurons that supply the lateral
rectus muscle and internuclear neurons that project via medial
longitudinal fasiculus to medial rectus subdivision of contralateral
oculomotor nucleus.
- Adjacent structures that may be affected :
1. Oculosympathetic central neuron: I/L Horner’s syndrome.
2. PPRF: I/L Conjugate gaze palsy
3. MLF: I/L INO
4. Pyramidal tract: C/L Hemiparesis
36. The brainstem syndromes:
1. Millard Gubler syndrome:
CN VI paresis
I/L CN VII paresis
C/L Hemiparesis
2. Raymond syndrome:
VI Nerve paresis
C/L Hemiparesis
3. Foville’s syndrome:
Horizontal conjugate gaze palsy
I/L V, VII, VIII paresis
I/L Horner’s syndrome
37. II. Subarachnoid space syndrome
(pathogenesis)
Raised ICP/
Haemorrhage/Inflammation/
Tumours/Infection
Downward displacement of
brainstem
Tethering of CN VI
CN VI Palsy + Papilloedema
+ Visual field defect
38. III. The Petrous apex syndromes
1. Gradenigo syndrome:
- Due to localized inflammation or extradural abscess of petrous apex following complicated
otitis media
- Clinical findings:
A. VI Nerve palsy
B. I/L Decreased hearing
C. I/L Facial pain along distribution of CN V
D. I/L Facial palsy
39. The Petrous Apex Syndromes:
2. Petrous bone fracture:
- Base skull # following head trauma
- Potential cranial nerve involvement: V, VI, VII, VIII
- Haemotympanum
- Mastoid ecchymosis
- CSF Otorrhoea
- Battle’s sign
3. Pseudo-Gradenigo’s syndrome:
- Nasopharyngeal carcinoma: serous otitis media Obstruction of the Eustachian tube and
invasion of cavernous sinus Causing VI nerve paresis
40. The Petrous Apex Syndromes:
- Cerebellopontine angle tumour: may cause VI nerve paresis and other clinical findings,
including:
A. Decreased hearing
B. VII nerve palsy
C. V nerve paralysis
D. Ataxia
E. Papilloedema
41. IV. The Cavernous sinus syndrome
- Association of CN III, IV, VI
- Carotid occulosympathetic plexus
- Optic nerve and chiasm
- Pituitary gland
42. V. The Orbital Syndrome
- Proptosis is an early sign
- Conjunctival congestion and chemosis
- Optic nerve may appear normal, oedematous or atrophied.
- Trigeminal signs limited to ophthalmic division
43. VI. Isolated VI Nerve Palsy
- Seen as post-viral neuropathy in young and ischemic mononeuropathy in adults.
- Rule: Ocular motor cranial nerve palsy in young : greater likelihood of neoplasm and in older
patient greater likelihood of ischemic mononeuropathy.
46. Signs
1. Limitation of abduction
2. Esotropia in primary position
3. Uncrossed horizontal diplopia : increased towards paralysed side, horizontal displacement of image, vertical
displacement in adduction , field of binocular vision constricted on affected side.
4. Slight face turn towards the side of diplopia
5. Early incomitant deviations ( Secondary > Primary)
6. Late comitant deviations
7. Then incomitant deviations (Primary > Secondary)
48. HISTORY
- Chief complaint:
Inward deviation of eyes
Diplopia in acquired cases
Face turn on same side
Associated complaints of headache or hearing loss
- History of presenting illness:
Age of onset
Mode of onset: Acute or chronic
Diplopia: Type/Worse in gaze/ less or absent for near
Head posture: Face turn on I/L side
49. HISTORY
- Past history:
Febrile disease: Viral illness
Diabetes Mellitus
Raised ICT
Trauma
Cerebral Palsy
- Past surgical history : Neurosurgical procedure
51. Examination
9. Special test:
Cover test
Past pointing
Diplopia charting
Binocular function : Worth 4 Dot test , Bagolini’s striated glass, Maddox rod, Synaptophore
Hess Charting
Force duction test
Active force generation test
52. SYSTEMIC EXAMINATION
- Blood Pressure
- Cranial nerve examination : V, VII, VIII
1. CN V: Sensory – Pin prick to test facial sensation, Corneal reflex test Motor- Palpating
masseter when patient clenches teeth, asking patient to open mouth against resistance
2. CN VII: Assymetry of facial movements, Taste in Anterior 2/3rd of tongue
3. CN VIII: weber’s test, Rinne’s test
53. OCULAR EXAMINATION :
1. Visual acuity: Hampered if the deviated eye fails to fixate leading to amblyopia
Assessed using Snellen’s chart, Jaeger’s chart
2. Abnormal Head posture: Face is turned to the affected side.
3. Ocular motility: Esotropia in primary position( due to relatively unopposed action of medial
rectus, characteristically worse for distance.
4. Eyelid: Usually normal
54. OCULAR EXAMINATION :
5. Conjunctiva: Conjunctival injection or chemosis
6. Cornea/Sclera/Iris: Usually normal. Corneal sensations may be reduced in acoustic neuroma
7. Pupil: Usually normal
8. IOP/Lens/Vitreous/Fundus: Papilloedema
55. Cover test
- Carried out with or without abnormal head posture
- Should be done in all 9 gazes ( at least in dextro or levo version)
- Amount of deviation will be more in the direction of involved muscle.
- Should also be done with either eye fixing
61. Forced duction test
- To look in mechanical restriction due to medial rectus.
- After topical anaesthesia, the examiner passively moves in the direction opposite to the
direction in which mechanical restriction is suspected.
62. ACTIVE FORCE GENERATION TEST
After topical anaesthesia, the paralytic muscle is held with forceps.
Patient is asked to move in the direction of limited duction.
The amount of force generated by the muscle is felt as a tug by the examiner.
64. Laboratory test
Complete blood cell (CBC) count
Glucose levels
Glycosylated hemoglobin (HbA1C)
Erythrocyte sedimentation rate and/or C-reactive protein
Fluorescent treponemal antibody-absorption test, VDRL or RPR
Lyme titer
Glucose tolerance test
Antinuclear antibody test
65. Rheumatoid Factor test
MRI is indicated for the following:
◦ Patients younger than 45 years
◦ Associated pain or other neurologic abnormality
◦ History of cancer
◦ Bilateral sixth nerve palsy
◦ Papilledema
◦ Patients younger than 55 years with no vasculopathic history
◦ In the event no marked improvement is seen or other nerves become involved
An LP can be considered if MRI results are negative.
67. General treatment
• Treatment depends on etiology of the abducens nerve palsy.
• In general, underlying or systemic conditions are treated primarily.
• Most patients with a microvascular abducens nerve palsy are simply observed and usually
recover within 3-6 months.
68. Treatment for diplopia
Prisms: Base-out Fresnel prisms can be used to
help the patient maintain binocular single
vision in the primary position, but are not
usually useful due to the incomitance of the
deviation.
69. Management of diplopia
Occlusion: Occlusion using Bangerter filter or
pirate patch can eliminate diplopia and
confusion, prevent amblyopia or suppression in
younger patients, and decrease the possibility
of ipsilateral medial rectus contracture.
70. Management of diplopia
Botulinum Toxin: Botulinum toxin injections to the medial rectus of the affected eye is
sometimes used to prevent secondary contraction of the medial rectus, or during transposition
procedures to weaken the muscle not operated on.
Surgery: In general, surgical intervention is reserved for patients who have had stable orthoptic
measurements for at least 3-6 months.
71. Surgery
Strabismus surgery can be performed for persistent abducens nerve palsies that demonstrate stable
measurements over 6 months period.
Forced duction test is performed in the office or in operating room in order to assist with surgical
planning.
Types of surgery:
A. A resection of the affected lateral rectus and recession of the ipsilateral medial rectus
(recess/resect or “R and R” procedure) is performed.
B. Resection of the affected lateral rectus with a recession of the contralateral medial rectus may be
performed.
C. Various forms of transposition surgeries can be considered. Jensen, Hummelsheim, Augmented
Hummelsheim with resections +/- Foster modifications, Knapp's procedure are some of the examples.
Botulism toxin can also be used as a temporizing treatment.
72. Types of surgeries
A. A resection of the affected lateral rectus
and recession of the ipsilateral medial rectus
(recess/resect or “R and R” procedure) is
performed.
B. Resection of the affected lateral rectus with
a recession of the contralateral medial rectus
may be performed.
75. Types of surgeries
AUGMENTED HUMMELSCHEIM: BROOK’S AUGMENTATION
Resection of 4-6 mm of transposed recti.
FOSTER’S MODIFICATION :
Transposed recti are tied together 4-6 mm
posterior to insertion.
77. Surgical follow up
Patients must be managed closely postoperatively, and any residual diplopia can be managed
with prisms.
Complications
The most likely complication following surgical correction of abducens nerve palsy is the risk of
over- or under-correction, which can be managed postoperatively with prisms.
Prognosis
The prognosis for sixth nerve palsy depends on the underlying etiology. Rush and Younge
reported a recovery rate of 49.6% in 419 nonselected sixth nerve palsy cases, and a higher rate
of 71% in 419 patients with diabetes mellitus, hypertension, or atherosclerosis.
