Approach to Ophthalmoplegia (CN3, CN4, CN6, INO, One and half), CSS, SOFS, OAS Flashcards by Chen Hee Chin

Extraocular Muscles (CN3, CN4, CN6) testing

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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Testing of saccades (gaze palsy)

Horizontal - Red ball held next to you
1A. Verical - Red ball held above you
Ask patient to alternate looking at red ball and your nose both horizontal and vertical

Vertical saccade - PSP
Horizontal saccade - INO

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What is strabismus?

Eye misalignment

Convergent strabismus - closer together than normal

Divergent strabismus - further apart than normal

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CN3 - oculomotor nerve

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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Differentiating types of CN3 palsy

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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Aberrant regeneration following complete CN3 palsy
Primary progressive oculomotor misdirection

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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Midbrain brainstem syndromes

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Differentiating ocular MG from CN3 palsy

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Differential diagnoses (causes) of CN3 palsy

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

Isolated CN3 lesion
1. Cerebral aneurysm - ICA / PcomA / basilar / PCA / SCA
2. Microvascular - diabetes, vasculitis, giant cell arteritis
3. Subacute meningitis
4. Uncal herniation
5. Pituitary apoplexy
6. Nasopharyngeal carcinoma

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

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

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CN4 - trochlear nerve (SO4) - downward gaze

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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Differential diagnoses (causes) of CN4 palsy

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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CN6 - abducens nerve (LR6) - abduction

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

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Differential diagnoses (causes) of CN6 palsy

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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Pontine brainstem syndromes

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

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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Investigations of CN3, 4, 6 lesions

MRI brain, MRA, specific CN and space, venogram
Fundoscopy
PTB workup
Vascular risk factors for mononeuritis
CTD screening
LP for chronic meningitis

Treatment of isolated CN6 palsy

Corticosteroids in compressive disease
Antiplatelet for mononeuritis, vascular

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 _____

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

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

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)

Clinical signs of INO

Impaired/slow adduction of eye on side of lesion (cardinal sign), REVERSIBLE on covering opposite eye
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)
Assessment of ocular convergence
- Preservation of convergence rules out oculomotor nerve palsy and myasthenia gravis (peripheral causes)
Long tract signs and concomitant cranial neuropathies (brainstem syndrome)
(MLF courses extensively though brainstem)

What are the causes of INO?

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

Demyelinating - multiple sclerosis (commonly bilateral)
(WEBINO - wall-eyed bilateral INO)
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)

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 __

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

What are the main structures in cavernous sinus?

CN 3, 4, V1, V2, 6
Sympathetic carotid plexus
Intracavernous carotid artery

What are the causes of cavernous sinus syndrome?

Thrombosis
Aneurysms of intracavernous carotid artery, PCom
Carotico-cavernous fistula
Tumours - meningioma, neurofibroma, NPC, mets from breast, lung, prostate
Trauma
Inflammation and infection - herpes, PTB, sinusitis, sarcoidosis, Wegener, Tolosa-Hunt

What are the clinical features of cavernous sinus lesion?

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)

What are the causes of upgaze palsy?

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

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

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

Mechanism of ophthalmoplegia in PSP

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

Chronic progressive external ophthalmoplegia (CPEO)

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 of pupil and iris muscles

Cavernous sinuses are major dural venous sinuses located: 1. Lateral to sella turcica 2. Below optic nerves/optic chiasma, and surrounds pituitary gland 3. Laterally bordered by temporal uncus It receives (drains) blood from the face via: 1. Ophthalmic veins 2. Superficial middle cerebral veins 3. Inferior cerebral veins 4. Sphenoparietal venous sinuses _Structures contained within cavernous sinus:_ A. Cranial nerves and branches 1. CN3 oculomotor nerve 2. CN4 trochlear nerve 3. CN5 V1 ophthalmic nerve 4. CN5 V2 maxillary nerve 5. CN6 abducens nerve B. Autonomic nerves - sympathetic and parasympathetic fibres of oculomotor nerve C. Internal carotid artery

Content of cavernous sinus (m: OTOM CAT - superoinferiorly and mediolaterally) Oculomotor nerve Trochlear nerve Ophthalmic nerve Mandibular nerve Cavernous segment of ICA Abducens nerve Trochlear nerve

Cavernous sinus syndrome A. CN3, 4, 6 palsy 1. Binocular diplopia 2. Ptosis - CN3 palsy 3. Impaired pupillary response (mydriasis) - CN3 palsy B. CN V1 and V2 palsy 4. Ipsilateral facial numbness and hypoaesthesia C. Ipsilateral third-order Horner's syndrome - internal carotid artery compression (difficult to appreciate given concomitant CN3 parasympathetic defect) 5. Miosis and pupillary dilatory lag _Additional features_ 1. Chemosis 2. Pulsatile exophthalmos 3. Proptosis 4. Visual loss 5. Ocular bruit over eyes _Possible etiologies_ 1. Tenderness over paranasal sinuses, or furuncles/wound over danger triangle of face (infection) 2. Weight loss, constitutional symptoms (malignancy) 3. Endocrinopathies - acromegaly, Cushingoid (pituitary) 4. Neurosurgical scars (malignancy, structural abnormalities) 5. Lymphadenopathy 6. Breast examination, abdominal examination 7. OCP use, procoagulation state - CST _Investigations_ 1. MRI brain 2. Targeted scans: CT thorax, colonoscopy, nasopharyngoscopy, etc

Causes of cavernous sinus syndrome

A. Tumours 1. Primary - meningiomas, schwannomas 2. Metastases 3. Direct compression - pituitary tumour, nasopharyngeal carcinoma B. Vascular 1. Carotid cavernous aneurysm 2. Carotid cavernous fistula 3. Cavernous sinus thrombosis C. Infection - bacterial (usually staph aureus) or fungal 1. Danger triangle infection 2. Dental infection 3. Paranasal sinusitis D. Inflammatory 1. Sarcoidosis 2. GPA 3. IgG4-related disease 4. Tolosa Hunt syndrome

Tolosa Hunt Syndrome is a rare idiopathic granulomatous inflammation of cavernous sinus, superior orbital fissure or orbital apex. It is characterised by painful ophthalmoplegia (pain + weakness of eye muscle) with facial numbness (commonly V1, less V2). Pupil may be either mydriasis or miosis. Inflammation compresses onto cranial nerves or leads to CN inflammation It is a diagnosis of exclusion after ruling out potential causes. It affects adults 40-60 years old Equally among male and female Diagnosis: MRI of brain and orbit - soft tissue enhancement; others: ESR, CRP, IgG4 levels) Ruled out investigations: ANCA, ACE, infections Treatment: corticosteroids

Superior orbital fissure is anterior to optic canal and bordered by greater and lesser sphenoid wings. It allows neurovascular structures from cavernous sinus into orbital cavity: 1. CN3 and parasympathetic fibre 2. Trochlear nerve 3. Ophthalmic nerve and oculosympathetic fibre 4. Abducens nerve (To note: no maxillary nerve) Orbital apex is the posterior confluence of four orbital walls, with optic nerve within it.

SOF syndrome and OA syndrome

A. Ocular signs 1. Pupillary abnormalities - either miosis or mydriasis 2. Ophthalmoparesis with binocular diplopia 3. Ptosis 4. Loss of corneal reflex 5. Lacrimal hyposecretion - lacrimal nerve from V1 B. Extraocular signs 6. Numbness over CN V1 territory Orbital apex syndrome: includes CN2 defect 7. Impaired monocular vision

Causes of SOF syndrome and OA syndrome

1. Commonest - trauma Other causes similar to cavernous sinus syndrome: 2. Inflammatory: Idiopathic orbital inflammation (orbital pseudotumor), GPA, sarcoidosis, Tolosa-Hunt syndrome 3. Infectious: Bacterial, fungal, sinusitis 4. Neoplasm and local extension 5. Vascular: Carotid-cavernous fistula, cavernous sinus thrombosis, ophthalmic artery aneurysm, vasculitis