 |
Department
of Ophthalmology and Visual Sciences |
VI. Ocular motility disorders
B. CN IV
C. CN VI
D. Multiple cranial nerve palsy
E. Supranuclear gaze palsy
F. Miscellaneous causes of monocular diplopia with full motility
1. Nucleus
- located in the midbrain at level of superior colliculus
-innervates contralateral SR, ispsilateral MR, IR, and IO, and bilateral levator palpebrae muscles.
-Edinger-Westphal nucleus innervates ipsilateral pupil
-lesions are rare and would cause bilateral ptosis and paresis of contralateral SR and ipsilateral MR, IR, and IO. Usually also some ipsilateral SR weakness from involvement of fibers passing through involved nucleus from the other side.
2. Fascicle
- courses ventrally through the red nucleus and exits through the medial portion of the cerebral peduncles
-lesions are usually of vascular or metastatic etiology
- causes 4 types of syndromes
a. Nothnagel
-lesion at superior cerebellar peduncle
-produces cerebellar ataxia
b. Benedikt
- lesion at red nucleus and medial lemniscus
-produces contralateral loss of sensation, rubral tremor, hemichorea, athetosis, and ballismus
c. Claude
-more extensive midgrain lesion including red nucleus and brachium conjunctivum (superior cerebellar peduncle) with features of Benedikt’s and Nothnagel’s syndromes combined
d. Weber
-lesion at cerebral peduncle
-produces contralateral spastic paralysis
3. Subarachnoid course
-susceptible to injury by uncal herniation or post. comm. a. aneurysm or meningeal infiltrative (inflammatory and neoplastic) disorders
-lesion results in CN III palsy with pupillary involvement
4. Cavernous sinus
-CN III susceptible to injury from carotid-cavernous sinus fistula, aneurysms, tumors,inflammatory (Tolosa-Hunt syndrome) and infectious processes
-results in CN III palsy as well as involvement of other cranial nerves (IV, V, VI)
5. Orbit
-CN III divides into
superior division
-innervates SR and laevator palpebrae
inferior division
-innervates IR, MR, IO, iris sphincter, ciliary muscle
6. Isolated third nerve palsy with sparing of pupils
-due to ischemia of CN III seen in DM, HTN or just old age
-occurs in older patients (> 40 y.o.)
-self-limited and resolves in 12 weeks
7. Aberrent regeneration of CN III
Pseudo von Grafe sign
-lid retraction with downgaze
-due to innervation of levator palpebrae by IR fibers
Inverse Duane’s syndrome
-lid retraction with adduction
-due to innervation of levator palpebrae by MR fibers
Pseudo-Argyll-Robertson pupil
-light-near dissociation
-due to innervation of pupillary sphincter by MR fibers
Pupillary constriction on downgaze
-due to innervation of pupillary sphincter by IR fibers
1. Nucleus
-located at periaqueductal gray matter of midbrain
-innervates contralateral superior oblique
-lesion produces hypertropia causing vertical diplopia as well as ex-cyclotorsion (12:00 position toward the ear)
-ipsilateral Horner’s syndrome may also be present due to adjacent descending sympathetic fibers in dorsal midbrain
-etiology includes hemorrhage, infarction, demyelination and trauma/surgery
2. Fascicle
- courses dorsocaudally and decussates at anterior medullary velum prior to exiting at level of inferior colliculus
-susceptible to injury by compression (eg. severe head trauma or pinealoma) resulting in bilateral CN IV palsy
-Bielschowsky test may be negative and requires double Maddox rod test for diagnosis (>10° of excyclotorsion)
3.Subarachnoid course
-long intracranial course traversing dorsal to ventral along the tentorial edge
-highly susceptible to injury from neurosurgery and head trauma
-lesion produces ipsilateral CN IV palsy (or bilateral if anterior medullary velum involved)
4.Cavernous sinus
-located in lateral wall below CN III and above CN V
-lesion produces multiple CN palsy (III, IV, V, VI) and Horner’s syndrome
5. Orbit
-enters via the superior orbital fissure to innervate the SO muscle
-CN IV can be affected in orbital apex syndrome
6. Congenital CN IV palsy
-represents 29% - 67% of fourth nerve palsy
-seen most commonly in children but can decompensate later and may present in adults (50-70 y.o.)
-exam shows large vertical fusion amplitude (>3D)
-old photographs showing head tilt help make diagnosis
1.Nucleus
-located at the floor of the fourth ventricle below facial colliculus (fibers if CN VII loop over nucleus of CN VI)
-contains motor neurons that innervate LR but also interneurons that project ot contralateral MR subnucleus via medial longitudinal fasciculus (MLF)
-lesion results in conjugate horizontal gaze palsy
-Duane’s syndrome
-congenital absence of abduscens nucleus
-LR innervated by branches of CN III
-defective abduction and narrowing of palpebral fissure from globe retraction with adduction
-usually does not complain of diplopia
-Mobius syndrome
-congenital absence of abduscens and facial nuclei
-may also involve CN IX and XII nuclei
2. Fascicle
-courses ventrally and laterally to exit at the pontomedullary junction
-lesion usually affects other nearby structures
-Millard-Gubler sybdrome
-involvement of the pyramidal tract
-ipsilateral CN VI palsy with contralateral hemiplegia
-Foville’s syndrome
-involvement of CN VII nucleus/fasciculus, spinal tract of CN V, and sympathetic fibers
-horizontal conjugate gaze palsy, facial weakness and numbness, and Horner’s syndrome
3. Subarachnoid course
-courses upward along the clivus and is susceptible to injury by tumors, basal skull fracture, trauma, raised intracranial pressure ("false-localizing CN VI palsy")
4. Petrous pyramid
-CN VI passes through Dorello’s canal which is bounded by the petrous bone and petroclinoid ligament
-susceptible to injury from petrous bone fracture, tumors, and infectious/inflammatory processes of the middle ear
-Gradenigo syndrome
-ipsilateral CN VI palsy, with decreased hearing, facial pain and facial paralysis
-due to abscess formation in petrous apex following otitis media
-Pseudo-Gradenigo syndrome
-similar symptoms as Gradenigo’s syndrome but due to nasopharyngeal CA or cerebellopontine angle tumors
5. Cavernous sinus
-accompanied by post-ganglionic sympathetic fibers
-lesion produces multiple CN palsy (III, IV, V, VI) and Horner’s syndrome
6. Orbit
-enters via the superior orbital fissure to innervate the LR
-can be involved in orbital apex syndrome
7. Isolated CN VI palsy
-post viral
-seen commonly in young patients (<15 y.o.)
-neoplasm
-more common in younger than older patients
-need to R/O with neuroimaging study
-ischemic mononeuropathy
-seen in older patients (>55 y.o.) esp. with DM and HTN
-self-limited with recovery occuring by 6-8 weeks
D. Multiple cranial nerve palsy
1. Cavernous sinus syndrome
-cavernous sinus is a dural venous sinus which contains the internalcarotid a., CN III, CN IV, CN V, CN VI, and oculosympathetic fibers
-lesion in the cavernous sinus causes painful ophthalmoplegia, facial numbness, and Horner’s syndrome
-various etiology
a. internal carotid artery aneurysm
b. carotid-cavernous fistula
c. cavernous sinus thrombosis
d. neoplasm
e. inflammation (Tolosa-Hunt syndrome)
2. Orbital apex syndrome
-crowding of intraorbital contents due to tumor, inflammation, infection, or edema from trauma which causes injury to CN II, CN III, CN IV, CN V 1,2, and CN VI
-presents as proptosis, chemosis, ophthalmoplegia (paresis or mechanical restriction) and decreased visual acuity.
3. Myasthenia gravis
-an auto-immune disease with formation of antibodies against acetylcholine receptors
-presents as ptosis and diplopia which fluctuates and varies from day to day
-ptosis is asymmetric and worsens after prolonged upward gaze. Manual elevation of more ptotic lid results in greater ptosis of the fromer less ptotic lid due to Hering’s law.
-diplopia pattern is variable and may appear as cranial nerve paresis, supranuclear motility disorder, or complete ophthalmoplegia
-associated systemic symptoms weakness and fatigue, dysphagia, hoarseness of voice, dysarthria, and dyspnea
-diagnostic tests include
a. Tensilon test
-test dose of 2 mg edrophonium chloride (Tensilon) is injected followed by 8 mg slowly injected starting 1 minute later
-positive test if ptosis and ocular motility improves
-common side effects include diaphoresis, lacrimation, abdominal cramping, nausea, vomiting, salivation, syncope
-rare but serious complications include bradycardia and respiratory arrest
-antidote is atropine sulfate (but symptoms are usually over by the time this can be administered)
b. Sleep test
-patient rests and closes eyes for 30 minutes
-positive test if ptosis and ocular motility improves after rest period
c. Ice pack test
-ice pack is placed over closed eyes for 2 minutes
-ptosis improves because neuromuscular transmission is enhanced in the cold
4. Multiple sclerosis
-autoimmune disorder causing demyelination of the CNS
-affects primarily young adults (25-40 y.o.) and women greater than men (2:1)
-incidence increases with increasing latitude from the equator
-presents as multifocal neurologic deficits separated by space and time
-may present as myriad of neuro-opthalmologic deficits but commonly manifests as optic neuritis,bilateral INO, CN VI or CN VIII palsy, and nystagmus
-MRI shows demyelinating plaques
-corticosteroids used for acute attacks
-interferon and other immunomodulators being investigated for long-term treatment
5. Thyroid ophthalmopathy
-causes inflammation of extraocular muscles thereby impairing/restricting motility
6. Chronic progressive external ophthalmoplegia
-usually presents as bilateral asymmetric ptosis before adolescence which progresses to external opthalmoplegia
-rare diplopia due to symmetric nature
-may have weakness of orbicularis, facial muscles, arms legs, and chewing
-etiology is mitochondrial abnormality in extraocular muscles
-serum CK may be elevated
-EM shows ragged red fibers seen on H&E to be abnormal aggregates of malformed mitochondria
7. Botulism
-cholinergic blockade due to botulinum toxin
-may be acquired from food, wound infection or birth
-ocular findings include ophthalmoplegia, ptosis, and dilated poorly reactive pupils
-systemic symptoms are nausea vomiting, and generalized weakness
Gaze centers
Horizontal
CN VI / pontine paramedian reticular formation (PPRF)
Vertical
rostral interstitial nucleus of the MLF (RiMLF)
interstitial nucleus of Cajal
Supranuclear inputs
Visual
calcarine cortex
superior colliculus
Non-visual
frontal eye field
vestibular system (semicircular canals)
Horizontal gaze disorders
1.Internuclear ophthalmoplegia (INO)
-lesion in MLF disconnecting ipsilateral CN III, medial rectus subnucleus from contralateral CN VI / PPRF
-results in inability to adduct the eye ipsilateral to the lesioned MLF with nystagmus of contralateral abducting eye
-usually orthophoria in primary gaze
-etiology
MS, vertebrobasilar insufficiency, AVM, tumors, and inflammatory diseases
(INO is thought to be uncommon from brainstem vascular disease since there is collateral flow to the dorsal brainstem from long circumferential vessels and most lacunes occur in the ventral brainstem in the distribution of the short penetrating arteries medially.)
2.WEBINO
-walleyed bilateral INO
-exotropia in primary gaze with inability to adduct either eye past midline
-rostral MLF lesion with involvement of CNIII nucleus
3. Unilateral horizontal gaze palsy
-lesion of CN VI nucleus and/or PPRF or supranuclear pathways from contralateral cerebral hemisphere
4. One and a half syndrome
-lesion of CN VI nucleus / PPRF and ipsilateral MLF
-ipsilateral conjugate gaze palsy
-contralateral INO
5. Fisher syndrome
-variant of Guillain-Barre that involves only brainstem and cranial nerves
-results in unilateral or bilateral ophthalmoplegia with ataxia and areflexia
-self-limited and usually follows a viral illness
CSF examination shows elevated protein but no pleocytosis
Vertical gaze disorders
1. Tonic deviation
-upward oculogyric crises occurs in post-encephalitic Parkinsons’s disease
-can also be seen in comatose patients
-tonic upgaze indicates bilateral cerebral/cerebellar lesions
-tonic down gazeindicates bilateral thalamic bleed or infarct
-tonic downgaze can also occur in metabolic encephalopathy
2. Parinaud’s syndrome
-lesion in dorsal midbrain
-characterized by
- supranuclear paresis of vertical gaze with intact vestibular-ocular reflexes
-ptosis
-light-near pupillary dissociation
-skew deviation
-convergence retraction nystagmus
-etiologies
congenital aqueductal stenosis
pinealoma
head trauma
vascular formation
long standing multiple sclerosis
basilar CVA
3. Progressive supranuclear palsy
-progressive conjugate paresis of gaze which presents initially as decreased downgaze
-also exhibits nuchal rigidity and seborrhea as in Parkinson’s disease but no resting tremor and head is retracted rather than bent forward as in Prkinson’s disease (simian posture)
-has OKN "drift sign", normal Doll’s eye, and normal Bell’s response
-associated with progressive dementia and death usually in 5 years
4. Downgaze palsy
-rarely isolated
-lesion in RiMLF rostral to CNIII and dorsomedial to red nucleus
5. Skew deviation
-lesion in internuclear connections involved in vertical gaze
-produces ipsilateral hypotropia in lower brainstem lesion
-ipsilateral hypertropia in pontine and midbrain lesions
F. Miscellaneous causes of monocular diplopia with full motility
Astigmatism
Cataracts
Peripheral iridectomy
Macular disease