neuro ophthalmology basics
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Basics in Neuro ophthalmology
• Introduction• Visual loss & field defects• Diplopia• Supra nuclear ocular motility disorder• Case Vignette• Painful Ophthalmoplegia & Clinical PEARLS• MCQs
Neuro-ophthalmology
• Diseases of the eye and the related neurological apparatus
• Afferent: Optic nerve, retina, chiasm, visual pathways, cortex
• Efferent: Cranial nerve III,IV,VI, ocular muscles, brain stem control centers
Vision loss
Monocular – lesion usually affects retina or optic nerve
Binocular – lesion localized to or beyond the optic chiasm
Retinal involvement – generally a/w ophthalmoscopic abnormalities
Most optic neuropathies involve visual acuity
Spared acuity raise suspicion of Pre-Retinal, Retinal or Retrochiasmal disease
Reduction in the saturation or brightness of colors may be an early sign of optic nerve disease
Look for RAPD in affected eye in unilateral cases Retina or Optic Nerve damage Swinging flashlight test
Visual field defects
Vein
Disc
Macula & Fovea
Artery
Optic cup
Features Primary Secondary Consecutive
Disc Papery white
Grey white Waxy pale
Margins Clear Blurred Normal
Cup Seen well Filled up Present
Lamina cribrosa
Prominent Not seen Not seen
Vessels in & around disc
Minimal Sheathing Attenuated
Peripheral fundus
Normal Changes + Altered Kestenbaum sign
Hemorrhage & exudates Pigmented/ degenerated
Features of optic atrophy
Anatomy and Physiology of ocular motility
BRAINSTEM NUCLEI
OCULOMOTOR TROCHLEAR ABDUCENCS
INTER CONNECTING NEURONS
EXTRA OCULAR MUSCLES
Extra ocular muscles
SR & IR• Primary action - elevation/depression (abducted eye)• Secondary action – torsion, SR - intorter & IR extorter• Tertiary action – adduction
SO & IO• Primary action - torsion, SO intorter & I0 extorter• Secondary action – depression/elevation (adducted eye)• Tertiary action – abduction
MR & LR• Adduction & abduction
DIPLOPIA
It is when more than one image ( two ) of the object of regard are seen simultaneously
1.Is the diplopia monocular or binocular?
J Neurol Neurosurg Psychiatry 2004;75(Suppl IV):iv24–iv31. doi: 10.1136/jnnp.2004.053413
DIPLOPIA
J Neurol Neurosurg Psychiatry 2004;75(Suppl IV):iv24–iv31. doi: 10.1136/jnnp.2004.053413
• Alignment of Images
──horizontal, vertical, or oblique
• Direction of gaze that increases the separation of images
• Onset and progression of the symptoms
• Exacerbating and relieving factors
• Associated symptoms
• Past medical history and family history
DIPLOPIA
EXAMINATION FOR DIPLOPIA
• Complete ophthalmological and orthoptic assessment─ for monocular diplopia
• Identify cause of misalignment in binocular diplopia• Identifying the paretic muscle(s) Subjective Tests ─ Maddox rod and Red lense tests Objective Tests ─ Corneal light reflex tests , Cover tests Three “diplopia rules”(1) Separation of images is greatest in the direction of action of the
weak muscle (2) False image is the more peripheral(3) False image comes from the paretic eye
MADDOX ROD ASSESSMENT
COVER TESTS
• Based on fixation ability Cover/uncover …detect manifest deviation, Exo/eso/hyper/hypotropia Alternate cover ….detect total deviation ( manifest + latent) ….dissociation test …..demonstrate subtle hypertropia• To measure angle of deviation….prism cover test
J Neurol (2014) 261 (Suppl 2):S542–S558
Parks three-step test
Identifying the paretic muscle in vertical diplopia
1) To determine which eye is hypertropic in the primary position RE hypertropic, one of four muscles must be paretic; right eye depressors (right SO & IR) or left eye elevators (left IO & SR )2) To determine whether the hypertropia increases in right orleft horizontal gaze, Worse on left gaze: Rt SO or left SR3) To determine whether the hypertropia is worse on head tilting
to left or right (Bielschowsky test) Worse on head tilt to right….> Rt SOJ Neurol Neurosurg Psychiatry 2004;75(Suppl IV):iv24–iv31. doi: 10.1136/jnnp.2004.053413
Hess Chart•Pictorial and reproducible record of eye movements
•Each eye is plotted in turn for the central fixation spot and targets at 15 and 30 degree eccentricity, respectively
• The smaller field belongs to the paretic eye
•Neurogenic paresis will show the largest under action inthe direction of paretic muscle and the largest over-actionis seen in the contralateral synergist
•Mechanical defects show a compressed field withoutobvious over-action.
Supranuclear Oculomotor Disorders
EYE MOVEMENTS
UNIOCULAR
DUCTION
BINOCULAR
CONJUGATE DYSCONJUGATE
VERSION VERGENCE
CONVERGENCE & DIVERGENCESACCADE, PURSUIT, VOR, OKN
FUNCTIONAL CLASSIFICATION
FUNCTIONAL CLASSIFICATION
JERKYBRINGS TARGET TO
FOVEA
WHEN TARGET IS IN MOTION
WHEN HEAD IS IN MOTION
TRACKING TARGET IN VERTICAL& HORIZONTAL
TO &FRO MOTION IN AP AXIS
BRIEF HEAD MOTION
SUSTAINEDHEAD MOTION
GAZE SHIFTING
GAZE
HOLDING
SACCADE
PURSUIT
VERGENCE
VOR
OKN
saccade“Saquer” – french – to pull Rapidly programmed eye movement, bring target into fovea• Latency-interval b/n appearance of target & onset of saccade- 200
msec• Amplitude & Velocity- Directly proportional to each other 100-700 msec• Accuracy-amount of undershoot/overshoot of target
Types of saccades
VOLUNTARY INVOLUNTARY• Visually guided Reflexive• Predictive Spontaneous• Memory guided Fast phase of nystagmus• Anti saccades
Saccade- mechanical properties
• Combination of 2 mechanical elements-
-pulse & step
• Pulse- (velocity command)- high frequency burst of neural
activity - powerful phasic contraction of EOM - overcomes
resistance of orbital tissue & inertia of globe
• Step- (position command)-sustained contraction arising from a
constant level of neural activity- keeps eye in the new position
• Integration of velocity coded into position code by neural
integrators : NPH & MVN, INC
• Premotor burst neurons: EBN : excite pulse mechanism before
saccade
• IBN: Inhibit pulse in antagonist muscles & help in moving with
contacting muscles
• Omnipause neurons: Inhibit all burst neurons, check
unwanted firing EBN IBN Neural
integratorsOmni pause
Horizontal PPRF Medullary Reticular formation
NPH & MVN Nucleus RapheInterpositus
Vertical Ri MLF Medullary Reticular formation
INC Nucleus RapheInterpositus
SACCADIC PATHWAY
DeJong's The Neurologic Examination
Abnormal saccades• Saccadic dysmetria: Cerebellar lesions
• Anti saccades: Frontal lobe/connection to basal ganglia
• Saccadic intrusions- interfere with macular fixation
- square wave jerks – spontaneous small amplitude paired saccades
with inter saccadic latency 150-200ms …..PSP, MSA, cerebellar disease
-macro square wave jerks – larger amplitude(10-40) & shorter
latency(80ms)….MS, OPCA
-ocular flutter- to & fro horizontal saccades without inter saccadic
interval… MS, cerebellar disease
-Opsoclonus(saccado mania)- conjugate involuntary large amplitude
multidirectional saccades..brainstem / cerebellar disease/
paraneoplastic
Smooth pursuit
• Slow conjugate eye movement
• To track relatively slow moving targets
(no faster than 30° per sec)
• Voluntary or involuntary
• To keep image of a moving object at fovea
• Mediated by parieto-occipito-temporal-mesencephalic pathway
• Ipsilateral control
• Latency > 125m sec
• Can track target moving up to 30˚ – 40˚/sec or 2Hz
Retinal image movement
Lateral geniculate
nucleus
Striate cortex
MT, MST, posterior parietal cortex
First descussation of horizontal pursuit pathway
Second descussation of horizontal pursuit pathway
Fastigial nucleus, medial vestibular nucleus
Cerebellar cortex
Smooth pursuit
movements
Pontine nuclei
Ocular motor nuclei (3,4, and 6)
FEF, SEF
Nucleus of optic tract pathway
Pathway for horizontal smooth pursuit
Retinal image movement
Lateral geniculate
nucleus
Striate cortex
MT, MST, posterior parietal cortex
First descussation of horizontal pursuit pathway
Second descussation of horizontal pursuit pathway
Y group neurons
DentateNucleus
cerebellum
VerticalSmooth pursuit
movements
Nucleus reticularis Tegmenti
pontis
Ocular motor nuclei (3,4, and 6)
FEF, SEF
Nucleus of optic tract pathway
Ipsilateral cortical control
Pathway for vertical smooth pursuit
Lesions –smooth pursuit
• Frontal lesions – impair I/L pursuit
• Parietal lesions – decrease amplitude & velocity of I/L pursuit
• B/L occipital – abolish smooth pursuit
• MLF – vertical pursuit
• Upward pursuit – decussate in posterior commissure
• Downward pursuit – INC –
• Role of Cerebellum –
*dorsal vermis & fastigial nucleus …onset of pursuit
*paraflocculus & flocculus …sustain pursuit response
VOR
• Conjugate eye movement, moves eye equal & opposite to head
movement
• Velocity of 800 degree/sec within a brief reaction time of 15ms
• Two types: horizontal, vertical & torsional VOR
• Function: Fix retinal images during head movements
• VOR cancellation: Normal component: inactivates VOR when target
moving in same direction of head
• Semi circular canal for angular rotation
• The Otolith organ for linear acceleration
• Reflex starts by movement of head> stimulation of
vestibular sensors> VOR circuitry in brain stem> eye
velocity command
• Head rotation to right> stimulation of ipsilateral
HC>activation of right MR & left LR> eye rotates to
left
• Down ward head acceleration> stimulates both AC
• Upward head acceleration> both PC
Optokinetic reflex
• OKN : reflexive oscillation of eyes alternating slow & quick
phases, produced by movement of visual field
• Stabilizes eye during tracking of large moving visual scene
• Responsible for sense of illusionary motion while sitting in
a vehicle
• Pathway : Retina>AOT> CTT>Inferior
olive>cerebellum(which receive vestibular fibres)
Nuclear Inter nuclear Lesions
• Abducens nuclear level: Lateral gaze palsy while looking to
ipsilateral direction, VOR also affected
• PPRF: Ipsilateral horizontal saccadic palsy, VOR not affected
• MLF: Inter nuclear ophtalmoplegia
• PPRF+ MLF= One& half syndrome, VOR spared
• Abducens complex+ MLF= One & half syndrome , VOR affected
• PPRF+MLF+facial nerve nuclei: 8&1/2 syndrome
• PPRF+MLF+b/l facial nerve nuclei: 15&1/2 syndrome
Inter nuclear ophthalmoplegia
• Due to a lesion of MLF in either pons or midbrain
• Continuity b/w abducens and contra lateral oculomotor nuclei via MLF
lost
• Type 1 INO: Lesion in midbrain near convergence area, on conjugate
gaze medial rectii are affected both sides
Normal abduction, convergence also affected
• Type II INO: Lesion midway b/w 3rd & 6th nerve nuclei
Adduction is affected on both sides with normal abduction Convergence
spared
If INO is bilateral
• abduction saccades also may be slow
• Upward beating and torsional nystagmus
• Type III INO: Lesion is in relay to 6th CN nuclei
Abduction is affected in both eyes with relatively
preserved adducion
Skew Deviation
• Common supra nuclear gaze palsy, of vertical type
• Interruptions in the pathway between VN & vertical oculo motor
CN nucleus
• When a person tilts head, eye in downward direction moves
oppositely
• If brainstem lesions below the level of decussation> eye on side of
lesion will be lower eye
• If lesion above level of decussation> eye on side of lesion will be
at higher level
• Ocular tilt reaction: Pathological head tilt, inappropriate
torsional rotation & skew deviation
• Head & superior poles of both eye rotate toward lower
eye
• The higher eye is incyclotorted
• Skew deviation may occur in combination with INO
Dorsal Mid brain syndrome
• Lesions involving posterior commissure fibers projected from INC
• Occurs in dorsal midbrain region, pineal gland lesions and hydrocephalus
• Components:
1. Impaired vertical gaze
2. Square wave jerks
3. Vergence dysfunction
4. Skew deviation
5. Convergence retraction nystagmus
6. Lid retraction
7. Light near pupil dissociation
CASE VIGNETTE• 75 year old male
• C/o decreased sensation over right face along with right sided
ptosis X 15 days
• Loss of vision in right eye X 12 days
• O/E Right sided ptosis & complete ophthalmoplegia
• Absence of light perception & pupillary reaction right side
• Decreased pain perception along right V1&V2
Clinical possibility ???
Painful Ophthalmoplegia
• Orbital pain + any combination of I/L ocular motor
palsies, oculo sympathetic paralysis or sensory
distribution in V1&V2 distribution
• Localization: orbit/orbital apex/superior orbital
fissure/cavernous sinus/subarachnoid
space/mesencephalon
SITES STRUCTURES INVOLVED
MESENCEPHALON 3RD OR 4TH NERVE
SUBARACHNOID SPACE 3RD, 4TH OR 6TH IN VARYING COMBINATIONS
PARASELLAR REGION 2ND, 3RD, 4TH & 5TH NERVE IN VARYING COMBINATION
POSTERIOR CAVERNOUS SINUS 3RD, 4TH , 6TH AND ALL DIVISIONS OF 5TH NERVE
MIDDLE CAVERNOUS SINUS 3RD, 4TH, 6TH AND 1&2 DIVISIONS OF 5TH NERVE
ANTERIOR CAVERNOUS SINUS 3RD , 4TH, 6TH AND FIRST DIVISION OF 5TH
HORNERS SYNDROME ACCOMPANY CAVERNOUS SINUS PATHOLOGY AT ANY SITE
SITES LOCALIZATION
ORBITAL FISSURE 3RD, 4TH, 6TH & FIRST DIVISION OF 5TH NERVE IN VARYING COMBINATION
ORBIT 2ND , 3RD, 4TH, 6TH AND 1ST DIVISION OF 5TH
UNKNOWN ANY OCULAR MOTOR NERVE ALONE OR IN COMBINATION
DIABETES, MIGRAINE, VASCULITIS
Clinical Pearls
• Nuclear lesions of 3rd nerve result in b/l ptosis
• Nuclear lesion of 3rd nerve often result in
weakness of superior recti b/l
• Fascicular 3rd nerve palsy in brainstem associated
with contra lateral long tract signs
• Isolated 3rd nerve palsy : Most likeley lesion within
subarachnoid space, compressive/ischemic
•The compressive lesions most often affect pupillomotor fibres
• Exception: Lesion which press 3rd nerve from below
•Combination of oculomotor paresis and sympathetic denervation
almost pathagnomonic of cavernous sinus lesion
•Maxillary division of 5th nerve escapes damage at superior orbital
fissure
•Isolated involvement of either superior or inferior division of 3rd
nerve strongly suggest orbital lesion….. BUT
•4th CN palsy : Vertical diplopia, head tilt to normal side
•Combination of 6th & 12th in Nasopharyngeal Ca & Clival tumor
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