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MRCP PACES Neurology > Approach to Ophthalmoplegia (CN3, CN4, CN6, INO, One and half) > Flashcards

Approach to Ophthalmoplegia (CN3, CN4, CN6, INO, One and half) Flashcards

1
Q

Extraocular Muscles (CN3, CN4, CN6) testing

A

Slow pursuit - Double H
- Adequate distance
- Not too fast, or else pursuit will be broken
- Hold at extreme ends to look for nystagmus
- Change hand when going the other side
- Red pin held horizontally

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2
Q

Saccades

A
  • Red ball held next to you
  • Alternative looking at red ball and your nose both horizontal and vertical

Vertical saccade - PSP
Horizontal saccade - INO

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3
Q

What is strabismus?

A

Eye misalignment

Convergent strabismus - closer together than normal

Divergent strabismus - further apart than normal

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4
Q

CN3 - oculomotor nerve

A

CN3 - occulomotor nerve
- Medial rectus - adduction
- Superior rectus - upgaze
- Inferior rectus - downgaze
- Inferior oblique - upward abduction
- Levator palpebrae superioris - elevates superior eyelid
- Ciliary ganglion - pupillary constriction
- Ciliary muscle - lens accommodation

Origin:
- Oculomotor nucleus (midbrain) - EOM
- Edinger-Westphal nucleus - constriction and accommodation
- No decussation, except:
A. LPS supplied from both sides
B. Superior rectus muscle from superior rectus nucleus from contralateral side

Deficit:
1. Ipsilateral downward outward deviation
- Unopposed CN4 and CN6 action
2. Ipsilateral ptosis (partial or full)
2A. Bilateral ptosis in nuclear CN3 palsy
3. Diplopia in all directions, maximal looking upward outward
4. Ipsilateral mydriasis (dilated) and unresponsive to light and accommodation (in surgical CN3 palsy)

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5
Q

Differentiating types of CN3 palsy

A

Fascicular vs nuclear CN3 palsy
Nuclear:
1. Bilateral ptosis (ipsilateral complete, contralateral partial)
2. Vertical deviation (eyes downward and outwards) - unopposed superior oblique muscle (CN4)
3. Bilateral elevation weakness - SR is supplied by CN3 from both sides

Medical vs surgical CN3 palsy
Surgical: affected pupil (fixed dilated) - extrinsic compression of parasympathetic nerve fibres from EW nucleus

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6
Q
  1. Aberrant regeneration following complete CN3 palsy
  2. Primary progressive oculomotor misdirection
A

Aberrant regeneration following complete CN3 palsy
Oculomotor misdirection that is abnormal and incomplete recovery after complete CN3 palsy (from trauma or PCom aneurysm)

Primary progressive oculomotor misdirection
Aberrant regeneration progressively occurring WITHOUT history of complete CN3 palsy, usually due to intracavernous meningioma

Aberrant regeneration results in:
1. Adduction of attempted upgaze
2. Lid retraction on attempted downgaze (pseudo-Graefe sign)
3. Lid retraction on attempted adduction (horizontal gaze-eyelid synkinesis)
4. Miosis on attempted adduction (pseudo-Argyll Robertson pupils)

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7
Q

Differential diagnoses (causes) of CN3 palsy

A

Isolated CN3 lesion
1. Cerebral aneurysm - ICA / PcomA / basilar / PCA / SCA
2. Microvascular - diabetes, vasculitis
3. Subacute meningitis

Combined with other CNs
1. SOF lesion (malignant infiltration): CN3, 4, V1, V2
2. Orbital apex syndrome - CN 2, 3, 4, 6
3. Cavernous sinus thrombosis: CN 3, 4, V1, V2

Midbrain lesions affecting 3rd nucleus
1. Infarct
2. Demyelination
3. Glioma
4. Metastasis

Look for:
Contralateral hemiplegia
Ipsilateral limb ataxia
Coarse rubral tremor (cerebellar and red nucleus fibre involvement)

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8
Q

CN4 - trochlear nerve (SO4) - downward gaze

A

CN4 - trochlear nerve (SO4)
- Superior oblique - downgaze abduction

Origin and course:
- Trochlear nucleus (midbrain), decussate at midbrain-pons junction, exits from posterior
- Superior oblique is hooked around a trochlear

Deficit:
1. Ipsilateral outwards and upwards deviation (extorsion)
2. Vertical and oblique diplopia (on looking down and inwards to the nose)
3. Compensatory head tilt away from affected eye
(Or head tilt towards affected side to create wider separated images to ignore - paradoxical tilt)

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9
Q

Differential diagnoses (causes) of CN4 palsy

A

Rarely Isolated CN4 palsy
1. Diabetes (ischaemic infarct of nerve)
2. Trauma
3. Congenital

Combined with other CNs
1. SOF lesion (malignant infiltration): CN3, 4, V1, V2
2. Orbital apex syndrome - CN 2, 3, 4, 6
3. Cavernous sinus thrombosis: CN 3, 4, V1, V2

Midbrain lesions affecting 4th nucleus
1. Infarct
2. Demyelination
3. Glioma
4. Metastasis

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10
Q

CN6 - abducens nerve (LR6) - abduction

A

CN6 - abducens nerve (LR6)
- Lateral rectus - abduction

Origin and course:
- Abducens nucleus (pons)
- No decussation for main pathway
- Exits at pons-medulla junction

  • Alternate pathway: medial longitudinal fasciculus
  • Decussate to control contralateral medial rectus muscle
  • Coordinates eye movements (eg: LE abduct, RE controlled to adduct)

Deficit:
1. Ipsilateral adduction deviation
- Unopposed medial rectus muscle
2. Diplopia

On looking forward, affected eye is ADducted (MR muscle unopposed) On directional movement, affected eye fails to ABduct
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11
Q

Differential diagnoses (causes) of CN6 palsy

A

Isolated CN6 palsy
1. False localising sign
2. Raised ICP - Tumour compression
3. Mononeuritis
- Microvascular: diabetes (mononeuritis multiplex)
- Vasculitis: sarcoidosis, giant cell arteritis, multiple sclerosis
4. Ophthalmoplegic migraine
5. Trauma and fracture of skull base
6. Vertebral or basilar aneurysm
7. Gradenigo syndrome (infection of petrous temporal bone) or meningitis
8. Cavernous sinus thrombosis
9. Nasopharyngeal carcinoma infiltration of skull base
10. Superior orbital fissure lesion

Pontine lesions affecting CN6
- Infarct
- Demyelination
- Glioma
- Metastasis
(look for contralateral hemiplegia, ipsilateral weakness of upper and lower face - CN7 fibres hooking around 6th nucleus)

Combined with other CNs
SOF: CN3, 4, V1, V2
Orbital apex syndrome - CN 2, 3, 4, 6
Cavernous sinus: CN 3, 4, V1, V2, 6

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12
Q

What if the ophthalmoplegia does not fit into specific cranial nerve? (Differential diagnoses)

A

Eg: Adduction defect that is not reversible
1. Myopathies (Graves’ ophthalmopathy)
2. Oculopharyngeal dystrophy
3. Myasthenia gravis
4. Miller-Fisher syndrome
5. Orbital myositis
6. Chronic progressive external ophthalmoplegia (CPEO)
7. Trauma

vs… internuclear ophthalmoplegia (INO)
- Adduction defect REVERSIBLE on covering contralateral (abducting) eye
-+/- nystagmus of opposite eye

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13
Q

Investigations

A

MRI brain TRO SOL
Fundoscopy
PTB workup
Vascular risk factors for mononeuritis
CTD screening
LP for chronic meningitis

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14
Q

Treatment of isolated CN6 palsy

A
  1. Corticosteroids in compressive disease
  2. Antiplatelet for mononeuritis, vascular
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15
Q

Internuclear ophthalmoplegia (INO) is a disorder of __ due to defect along __
Resulting in impaired __

It is a clinical syndrome of ophthalmoplegia due to defect in _____

A

Conjugate gaze
Defect along medial longitudinal fasciculus (MLF)
Impaired adduction of affected eye

Defect in internuclear communication (MLF) between abducens nucleus and medial rectus subnucleus of contralateral oculomotor nuclueus

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16
Q

Medial longitudinal fasciculus (MLF) is a pair of well defined __ travelling through __
(located __ and __)
Function: __

A

White matter tracts, dorsomedial brainstem
(ventral to cerebral aqueduct at midbrain and 4th venticle at pons)

Function: internuclear relay between abducens nucleus and contralateral medial rectus subnucleus of oculomotor nucleus

Signals to initiate horizontal saccades or pursuit from higher cortical centre
Paramedian pontine reticular formation (PPRF) activates ipsilateral abducens nucleus
Signal transmitted to ipsilateral lateral rectus muscle via ipsilateral abducens motor neuron and concurrently to contralateral medial rectus subnucleus via MLF

(Add picture of pathway)

17
Q

Clinical signs of INO

(Add picture)

A
  1. Impaired/slow adduction of eye on side of lesion (cardinal sign), REVERSIBLE on covering opposite eye
  2. Dissociated gaze-evoked horizontal nystagmus of contralateral abducting eye
    (Herring’s law of equal innervation - increased stimulus to poorly adducting MR muscle results in concomitant increased stimulus to contralateral LR)
  3. Assessment of ocular convergence
    - Preservation of convergence rules out oculomotor nerve palsy and myasthenia gravis (peripheral causes)
  4. Long tract signs and concomitant cranial neuropathies (brainstem syndrome)
    (MLF courses extensively though brainstem)
18
Q

What are the causes of INO?

A

Commonest causes:
1. Ischaemia and infarct (commonly unilateral, but there are cases of bilateral INO)

  1. Demyelinating - multiple sclerosis (commonly bilateral)
    (WEBINO - wall-eyed bilateral INO)
  2. Differentials of myasthenia gravis (pseudo-INO)

Less common causes:
3. Infections
4. Trauma and haemorrhage
5. Brainstem structural abnormalities (Chiari malformation, tumours)
6. Systemic vasculitis
7. Metabolic (Wernicke’s encephalopathy)
8. Neurodegenerative (progressive supranuclear palsy)

19
Q

One-and-a-half syndrome is the dysfunction of __
PPRF defect: unable to __
MLF defect: unable to __
Lesion can be localised to __

Resulting in affected eye difficulty __ and __; with the unaffected eye having difficulty __

Concurrent one-and-half and other cranial neuropathies are term (n + 1 and 1/2 syndromes)
- CN7 : 8 and half
- CN12: 13 and half

The cause of one and half syndrome is __

A

Both PPRF and MLF
PPRF defect: unable to initiate conjugate gaze to affected side
MLF defect: unable to adduct affected eye
Localised to paramedian region of pontine tegmentum

Affected eye difficulty abducting and adducting
Unaffected eye difficulty adducting

Causes: same as INO

20
Q

What are the main structures in cavernous sinus?

A
  1. CN 3, 4, V1, V2, 6
  2. Sympathetic carotid plexus
  3. Intracavernous carotid artery
21
Q

What are the causes of cavernous sinus syndrome?

A
  1. Thrombosis
  2. Aneurysms of intracavernous carotid artery, PCom
  3. Carotico-cavernous fistula
  4. Tumours - meningioma, neurofibroma, NPC, mets from breast, lung, prostate
  5. Trauma
  6. Inflammation and infection - herpes, PTB, sinusitis, sarcoidosis, Wegener, Tolosa-Hunt
22
Q

What are the clinical features of cavernous sinus lesion?

A
  1. Unilateral combined CN3, 4,6 palsy
  2. Sensation loss in V1 and V2 distribution
  3. Loss of corneal reflex
  4. Painful ophthalmoplegia
  5. Conjunctival congestion
  6. Visual loss
  7. Papilloedema
  8. Retinal haemorrhage
  9. Proptosis and pulsating exophthalmos (in carotico-cavernous fistula)
23
Q

What are the causes of upgaze palsy?

A
  1. Progressive supranuclear palsy
  2. Graves ophthalmopathy (with proptosis)
  3. Myasthenia gravis (fatigue on repetitive stimulation)
  4. Miller Fisher syndrome
  5. Muscular dystrophy
  6. CPEO
  7. Parinaud syndrome
24
Q

Brainstem lesion affecting CN 3/4/5/6
- Parinaud’s syndrome (dorsal midbrain syndrome)

A

Lesion of superior colliculus

Causes:
1. Pineal tumour
2. Midbrain infarct
3. Haemorrhage
4. Hydrocephalus
5. Demyelination

Clinical features
1. Upgaze palsy
2. Convergence retraction nystagmus
3. Lid retraction
4. Loss of accommodation and light reflex
5. Mydriasis

25
Q

Mechanism of ophthalmoplegia in PSP

A
  1. Descending supranuclear control of voluntary eye movement impaired
    - Initially started with vertical gaze palsy, may progress to involve difficulty in eye movement
  2. Intact oculomotor nuclei - allow patient to fixate on a point, then passively move the head (Doll’s manoeuver)
    - Eye displays full range of movements within orbit
26
Q

Chronic progressive external ophthalmoplegia (CPEO)

A

Slow progressive paralysis of EOM, usually due to mitochondrial myopathy or skeletal muscle weakness

Bilateral, symmetrical, progressive symptoms:
1. Ptosis (may be unilateral/asymmetric initially)
2. Ophthalmoplegia (months to years)
3. No involvement and iris muscles

MRCP PACES Neurology (28 decks)

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