Nystagmus
-
Upload
susanth-mj -
Category
Health & Medicine
-
view
99 -
download
0
Transcript of Nystagmus
NYSTAGMUS
Nystagmus
Periodic rhythmic biphasic ocular oscillation with slow
followed by fast or slow phase
Slow eye movements are responsible for its genesis and
continuation
Nystagmus
Initiated by a slow eye movement that drives the eye off
target, followed by
Fast movement that is corrective (jerk nystagmus) or
Another slow eye movement in the opposite direction
(pendular nystagmus)
Mechanism of nystagmus
Aim of occular movements
to maintain foveal centration of an object of interest
Nystagmus due to distubance of
1. Visual fixation
2. Occular movements - Neural integrator
3. vestibulo-ocular reflex
Saccades
Pulse (a velocity command)
Overcoming the resistance of the orbital tissues and the
inertia of the globe, changes the position of the eye in the
orbit
Accomplished by burst neurons
Step (a position command)
Change in tonic contraction of the orbital muscles, which,
overcoming the elasticity of the orbital tissues, keeps the
eye in the new position
Accomplished by neural integrators
Horizontal saccades
Pulse
EBNs in the PPRF
↓
ipsilateral abducens nucleus
IBNs in rostral medulla
↓
contralateral abducens nucleus
Supra nuclear control
Horizontal saccades
Step
Neural Integrator
Nucleus propositus hypoglossi (NPH) and the adjacent
MVN.
↕
vestibulocerebellum, especially the flocculus and
paraflocculus
Vertical saccades
Pulse
riMLF in the prerubral field of the ventral
diencephalomesencephalic junction
upward and downward saccades and I/L torsional saccades
lateral portion concerned with upgaze, the medial portion with
downgaze
↓
B/L elevator muscles
I/L depressor muscles
Step
Neural Integrator
Interstitial Nucleus of Cajal
lies caudal to the riMLF
↓ via the posterior commissure
C/L oculomotor and trochlear subnuclei through the PC
Vertical saccades
Neural integrator depends on retinal inputs for its
calibration
Bilateral blindness may also cause an inability to hold the
gaze steady
Pursuit system
Vestibulo ocular reflex
vestibular system perceives head movement and makes
the eyeball move in the opposite direction
VOR
Connections from the anterior and posterior SCCs also
contact
Nucleus of Cajal
Important in eye head coordination in roll and in
vertical gaze holding
riMLF
Important in generating quick phases of vestibular
nystagmus in the vertical and torsional planes
Causes of Nystagmus
Result from dysfunction of
Vestibular endorgan
Vestibular nerve
Brainstem
Cerebellum
Cerebral centers for ocular pursuit
Causes of nystagmus
Symmetric, equal activity of the vestibular systems on
each side normally maintains the eyes in straight-ahead,
primary position. Vestibular imbalance causes the eyes to
deviate toward the less active side
In an alert patient, the frontal eye fields generate a saccade
to bring the eyes back toward primary position, creating
the fast phase of vestibular nystagmus.
Symptoms
Oscillopsia (absent in congenital nystagmus)
Decreased acuity
Nausea or vomiting
Vertigo
Coexisting neurologic deficits
Oscillopsia
Illusory perception of environmental movement
Four forms
1. associated with acquired jerk nystagmus (the
environment moves in the direction opposite the slow
phase of the nystagmus)
2. associated with pendular nystagmus (perceived as a to-
and-fro movement)
3. associated with SOM (jelly-like quivering)
4. associated with bilateral labyrinthine dysfunction
(continuous environmental jumping, e.g., With the
heartbeat)
Nystagmus
physiological pathological
Vestibular disorder
gaze-holding disorder
visual stabilization and pursuit mechanisms disorder
Jerk Vs Pendular
Jerk nystagmus Pendular nystagmus
Slow phase drift with rapid corrective saccade in opposite direction
Sinusoidal oscillation with slow phase in both directions and no corrective saccades
Direction is that of fast phase Horizontal or vertical
Direction of eye movement
Direction of nystagmus determined by direction of the fast
phase
According to plane of eye movement
Horizontal (right or left beating )or vertical (up or down
beating) or rotatory (clock wise or anti clockwise)
Types of nystagmus
Intensity of nystagmus: first, second, or third.
First degree nystagmus is present only wnen the eyes are turned
in direction of nystagmus. This is the weakest form ot
nystagmus.
second degree nystagmus is present when the eyes are in the
midline, increases when the eves are turned towards the side of
the slow phase.
In third degree nystagmus, nystagmus is present in all
three eye positions
Types of nystagmus
Amplitude of the nystagmus beat
large amplitude, small amplitude or medium amplitude
depending upon the
excursion of eyeball during the nystagmus.
Clinically irrelevant
Types of nystagmus
congenital or acquired
Acquired most often by abnormalities of vestibular input.
Congenital form with afferent visual pathway
abnormalities
Types of nystagmus
Acquired VS congenital
Feature Acquired Congenital
Form Pure sinusoidal variable
Different in two eyes Frequent Rare
Direction Omnidirectional –vertical, circular, elliptical
Horizontal, uniplanar,
Rarely vertical or
torsional
OKN reversal Never Frequent
Oscillopsia Frequent Mild
Clinical classification of nystagmus
Monocular
Binocular asymmetric or dissociated
(Involve mainly one eye)
Binocular symmetric
(involve both eyes symmetrically)
Monocular and Asymmetric Binocular Eye Oscillations
Monocular visual deprivation or loss
Monocular pendular nystagmus
Internuclear ophthalmoplegia and its mimickers
Spasmus nutans and its mimickers
Partial paresis of extraocular muscles
Restrictive syndromes of extraocular muscles
Superior Oblique Myokymia
Acquired Monocular Visual Loss
small, slow vertical pendular oscillations in the primary
position of gaze
may develop years after uniocular visual loss (Heimann-
Bielschowsky phenomenon) and may improve if vision is
corrected
Acquired monocular pendularnystagmus
Multiple sclerosis
Neurosyphilis
Brainstem infarct (thalamus and upper midbrain)
INO and in pseudo-INO syndromes
nystagmus in the abducting eye contralateral to a MLF
lesion
nystagmus beating in direction of abduction
occurs in midline lesions in the dorsal part of the brain
stem affecting MLF between the abducen nucleus on one
side of the brain with the oculomotor nucleus
tumors and vascular lesions may also cause
Epileptic Monocular Horizontal Nystagmus
Focal seizures originated in the occipital lobe contralateral
to the involved eye
forme fruste of the Sturge-Weber syndrome
Monocular DBN
Acute infarction of the medial thalamus and upper
midbrain
Pontocerebellar degeneration ( due to dysfunction of the
ipsilateral brachium conjunctivum)
Triad of
1. Head nodding
2. Nystagmus
3. Abnormal head
posture
Spasmus nutans
Spasmus nutans
Onset in the first year of life
Remits spontaneously within one month to several years
(up to 8 years) of onset
Sinusoidal nystagmus intermittent, asymmetric or
unilateral
High frequency and small amplitude with a shimmering
quality
Usually horizontal but may have a vertical or torsional
component
Must consider tumor of the optic nerve, chiasm, third
ventricle, or thalamus
Superior Oblique Myokymia
Paroxysmal, rapid, smallamplitude, monocular torsional-
vertical oscillation
Caused by contraction of the superior oblique muscle
predominantly on the right side
Difficult to detect with the unaided eye and is more easily
detected with a direct ophthalmoscope
Reported with adrenoleukodystrophy, lead poisoning,
cerebellar astrocytoma, dural arteriovenous fistula, and
microvascular Compression
Respond dramatically to carbamazepine or gabapentin
Bilateral symmetric eye oscillations
Disconjugate
(eyes moving in opposite directions)
Vertical disconjugate
See-saw nystagmus
Horizontal disconjugate
Convergence-retraction nystagmus(nystagmus retractorius)
Divergence nystagmus
Repetitive divergence
Oculomasticatory myorhythmia
Conjugate
(both eyes moving in same direction)
See-saw Nystagmus
cyclic movement : while one eye rises and intorts, the
other falls and extorts; the vertical and torsional
movements are then reversed, completing the cycle
See-saw Nystagmus
Usually pendular
See-saw jerk nystagmus → brainstem lesions affecting the
mesodiencephalon or lateral medulla
Represents sinusoidal oscillations involving central otolith
connections, especially the INC
May also be partly due to an unstable visuovestibular
interaction control system
See-saw Nystagmus
Congenital see-saw nystagmus
lack the torsional component or even present with an
opposite pattern (i.e., extorsion with eye elevation and
intorsion with eye depression)
Etiologies of See-Saw Nystagmus
Parasellar masses
Brainstem and thalamic stroke
Multiple sclerosis
Trauma
Arnold-Chiari malformation
Hydrocephalus
Syringobulbia
Paraneoplastic encephalitis (with testicular cancer and anti-Ta antibodies)
Whole brain irradiation and intrathecal methotrexate
Septo-optic dysplasia, retinitis pigmentosa, and cone degeneration
Congenital see-saw nystagmus
Convergence-retraction nystagmus
repetitive adducting saccades accompanied by retraction
of the eyes into the orbit, occur spontaneously or on
attempted upgaze
elicited by Sliding an optokinetic tape downward in front
of the patient's eyes
caused by Mesencephalic lesions affecting the pretectal
region
Convergence nystagmus
In dorsal midbrain stroke and arnold-chiari malformation
Whipple's disease - ~ 1 hz (pendular vergence oscillations)
Divergence nystagmus
Occur with hindbrain abnormalities (e.G., Chiari
malformation)
Associated with DBN
Repetitive divergence
Slow divergent movement followed by a rapid return to
the primary position at regular intervals
Seen in coma from hepatic encephalopathy or related to
seizures
Oculomasticatory Myorhythmia
Acquired pendular vergence oscillations associated with
concurrent contraction of the masticatory muscles
Smooth, rhythmic eye convergence, which cycles at a
frequency of approximately 1 hz, followed by divergence
back to the primary position
Synchronous with rhythmic elevation and depression of
the mandible
May also have paralysis of vertical gaze, progressive
somnolence, and intellectual deterioration
Recognized only in whipple's disease
Binocular Symmetric
Conjugate Eye Oscillations
pendular nystagmus
Jerk nystagmussaccadic
intrusions
Pendular conjugate eye oscillations
Congenital nystagmus
Acquired pendular nystagmus
Oculopalatal myoclonus
Spasmus nutans
Visual deprivation nystagmus
Congenital nystagmus
At birth or in early infancy, or may emerge or enhance in
teenage or adult life, often without apparent provocation
Seldom familial and most often idiopathic
Due to metabolic derangements and structural anomalies
of the brain, including abnormalities of the eye or anterior
visual pathways
Wholly pendular or have both pendular and jerk
components
Congenital nystagmus
Slow phase with a velocity that increases exponentially as
the eyes move in the direction of the slow phase
Visual fixation accentuates it and active eyelid closure or
convergence attenuates it
Nystagmus decreases in an eye position (null region) that
is specific for each patient
Quick phase of the elicited nystagmus generally follows
the direction of the tape (reversed optokinetic nystagmus)
Latent nystagmus
Generally congenital
Appears when one eye is covered
Usually associated with strabismus
Marker for congenital ocular motor disturbance and does
not indicate progressive structural brain disease
Acquired Pendular Nystagmus
may be wholly horizontal, wholly vertical, or have mixed
components (circular, elliptical, or windmill pendular
nystagmus)
most often caused by multiple sclerosis, stroke, or tumor
of the brainstem or other posterior fossa structures
In multiple sclerosis → sign of cerebellar nuclear
involvement or result from optic neuropathy
lesion in the dorsal pontine tegmentum, perhaps affecting
the central tegmental tract
Acquired Pendular Nystagmus
Other causes of acquired binocular pendular nystagmus
include Pelizaeus-Merzbacher disease, mitochondrial
cytopathy, Cockayne's syndrome, neonatal
adrenoleukodystrophy (a peroxisomal disorder), and
toluene addiction
Windmill Nystagmus
seen in Blind patients
repeated oscillations in the vertical plane alternating with
repeated oscillations in the horizontal plane
Palatal myoclonus
continuous rhythmic involuntary movement of the soft
palate
association of pendular nystagmus (oculopalatal
myoclonus )
Palatal myoclonus
Damage to the dentatorubroolivary pathways (Guillain-
Mollaret triangle)
most often caused by multiple sclerosis or vascular lesions
of the brainstem
MRI often shows enlargement of the inferior olivary
nuclei
Binocular Symmetric Jerk
Nystagmus
Spontaneous
present in primary position
present predominantly on
eccentric gaze
Induced
Spontaneous symmetric conjugate jerk nystagmusthat occurs in primary position
Horizontal
Congenital nystagmus
Latent nystagmus
Vestibular nystagmus
PAN
Drug-induced nystagmus
Epileptic nystagmus
Torsional
Form of central vestibular nystagmus
Vertical
UBN
DBN
Vestibular Nystagmus
Predominantly a horizontal or vertical unidirectional jerk
nystagmus, often with a slight torsional component, that is
evident when the eyes are close to the central position
Does not change with the direction of gaze
More prominent when visual fixation is eliminated
Vestibular Nystagmus
Results from unilateral destruction of
Horizontal canal
Total labyrinthine
Torsional slow component causing the upper part
of the globe to rotate toward the lesioned side
Vestibular Nystagmus
Linear (constant velocity) slow phase toward the lesion
Horizontal component is diminished when the patient lies
with the intact ear down and is exacerbated with the
affected ear down
Slow-phase velocity is greater when the eyes are turned in
the direction of the quick component (Alexander's law)
Peripheral Central
Vary with head position
and movement+ +
Latency + No
Fatigue + No
Direction Fixed Changing
Effect of fixation Suppresses No
Pure vertical or torsional
nystagmusNo +
Associated symptomsSubjective
vertigo.
Neurologic signs and
symptoms of brainstem
dysfunction
Periodic Alternating Nystagmus
Eyes exhibit primary position nystagmus, which, after 60
to 120 seconds, stops for a few seconds and then starts
beating in the opposite direction
Periodic Alternating Nystagmus
Often caused by disease processes at the craniocervical
junction
May be provoked by an attack of meniere's disease
Prominent finding in some patients with creutzfeldt-jakob
disease
Mechanism
Nodulus and uvula of the cerebellum maintain inhibitory
control over vestibular rotational responses by using the
neurotransmitter GABA and over the course of
postrotational nystagmus
following ablation of these structures, the postrotational
response is excessively prolonged
So normal vestibular repair mechanisms act to reverse the
direction of the nystagmus, which may result in PAN
Baclofen, a GABA-B agonist, may abolish PAN
Periodic Alternating Nystagmus
Drug-induced nystagmus
Predominantly horizontal, vertical, rotatory, or, most
commonly, mixed
Most often seen with tranquilizing medications and
anticonvulsants
More often evident with eccentric gaze
Epileptic Nystagmus
Usually horizontal
Often associated with altered states of consciousness
Epileptiform activity ipsilateral or contralateral to the
direction of the slow component of the nystagmus
Seizure-induced ipsilateral linear slow phases → smooth
pursuit region in the temporo-occipital cortex
Seizure-induced contralateral quick phases → saccade-
controlling regions of the temporo-occipital or frontal
cortex
Purely Torsional Nystagmus
Rare form of central vestibular nystagmus
Difficult to detect except by the observation of the
conjunctival vessels or by noting the direction of retinal
movements on either side of the fovea
Purely Torsional Nystagmus
Seen with brainstem and posterior fossa lesions, such as
tumors, syringobulbia, syringomyelia with arnold-chiari
malformation, lateral medullary syndrome, multiple
sclerosis, trauma, vascular anomalies, post-encephalitis,
and sarcoidosis, and as part of the stiff-person syndrome
DBN
usually present in primary position, but is greatest when
the patient looks down (Alexander's law) and to one side
convergence may increase, suppress, or convert the
nystagmus to UBN
DBN
Causes
Occur with cervicomedullary junction disease, midline
medullary lesions, posterior midline cerebellar lesions, or
diffuse cerebellar disease
Most lesions responsible for DBN affect the
vestibulocerebellum (flocculus, paraflocculus, nodulus,
and uvula) and the underlying medulla
Intermittent DBN, accompanied by episodic vertical
oscillopsia, may be an early sign of arnold-chiari
malformation
Mechanisms
Deficient drive by the posterior SCCs
Interruption of downward vestibulo-ocular
reflex pathways, which synapse in the MVN
and cross in the medulla
Cerebellar, especially floccular and
uvulonodular, lesions by disinhibition of the
cerebellar effect on the VN
Damage to the nuclei propositus hypoglossi
and the medial VN (the neural integrator) in
the medulla
DBN
Etiologies of Downbeat Nystagmus
UBN
Usually worse in upgaze (Alexander's law)
Unlike DBN, it usually does not increase on lateral gaze
Convergence may increase or decrease the nystagmus, or
convert DBN to UBN
UBN
Causes
Damage to the central projections of the
anterior SCCs
Damage to the ventral tegmental
pathways
Lesions of the anterior cerebellar vermis,
perihypoglossal and inferior olivary
nuclei of the medulla, pontine
tegmentum, brachium conjunctivum,
midbrain, and brainstem diffusely
UBN
Primary position UBN increased in downward gaze
Due to impairment of the vertical position-to-velocity
neural integrator in the Nucleus Intercalatus Of Staderini
Structure in the paramedian caudal medulla located caudal
to the VN and to the most rostral of the perihypoglossal
nuclei (NPH and nucleus of roller)
UBN
Primary position UBN combined with binocular elliptical
pendular nystagmus
characteristic of Pelizaeus-Merzbacher disease
Bow-tie nystagmus
quick phases are directed obliquely upward with
horizontal components alternating to the right and left
probably a variant of UBN
Both downbeat and upbeat nystagmus are poorly suppressed
by visual fixation and may be exacerbated by simply
placing patient in head hanging position
Mechanism of spontaneous vertical nystagmus
Primary dysfunction of the SVN-VTT pathway
Hypoactive after pontine or caudal medullary lesions →UBN
Hyperactive after floccular lesions → DBN
Binocular Symmetric Jerk NystagmusPresent in Eccentric Gaze
Gaze-evoked nystagmus
Nystagmus due to brainstem/cerebellar disease
Bruns' nystagmus
Drug-induced nystagmus
Physiologic nystagmus
Rebound nystagmus
Convergence-induced nystagmus
Gaze-evoked Nystagmus
eyes fail to remain in an eccentric position of gaze but
drift to midposition
velocity of the slow component decreases exponentially as
the eyes approach midposition
more pronounced when the patient looks toward the lesion
Gaze-evoked Nystagmus
Leaky neural integrator or cerebellar (especially
vestibulocerebellar lesion )
Side effect of medications, including anticonvulsants,
sedatives, and alcohol
Adult-onset alexander's disease with the involvement of
the middle cerebellar peduncles and dentate nuclei
Familial episodic vertigo and ataxia type 2
Bruns' nystagmus
Cerebellopontine angle tumors
Combination of
Ipsilateral large-amplitude, low-frequency nystagmus that
is due to impaired gaze holding
Contralateral small-amplitude, high-frequency nystagmus
that is due to vestibular impairment
Physiologic or endpoint nystagmus
Benign low-amplitude jerk nystagmus with the fast
component directed toward the field of gaze
Usually ceases when the eyes are brought to a position
somewhat less than the extremes of gaze
Rebound nystagmus
Brainstem and/or cerebellar disease (e.g., Olivocerebellar
Atrophy, Brainstem/Cerebellar Tumor Or Stroke,
Marinesco-sjogren Syndrome, Dandy-walker Cyst,
Gerstmann-straussler-scheinker Disease, Adult-onset
Alexander's Disease, etc.)
Probably reflects an attempt by the brainstem or the
cerebellar mechanisms to correct for the centripetal drift
of gaze-evoked nystagmus
Convergence-evoked Nystagmus
Usually vertical (upbeat is more common than downbeat)
Seen most commonly with multiple sclerosis or brainstem
infarction
Converting downbeat to upbeat, upbeat to downbeat, or
pendular to upbeat
Induced Nystagmus
Optokinetic nystagmus
Rotational/caloric vestibular nystagmus
Positional nystagmus
Valsalva-induced nystagmus
Hyperventilation-induced nystagmus
OKN
follow objects in motion when head remains stationary
develops at 6 months of age
slow pursuit movements on direction of drum and then a
quick saccade to opposite side
OKN
Paradoxical reversal in congenital nystagmus
With unilateral hemispheric lesions, especially parietal or
parietal-occipital lesions show impaired OKN when the
drum is rotated toward the side of the lesion
Each eye can be tested separately to exclude monocular
blindness
Hysterical patients and malingerers who claim that they
cannot see, and of neonates and infants
Positional Nystagmus
Possibly related to degeneration of the macula of the
otolith organ or to lesions of the posterior SCC
After rapid head tilt toward the affected ear or following
head extension, when the posterior SCC is moved in the
specific plane of stimulation
Other causes of positional vertigo include trauma,
infection, labyrinthine fistula, ischemia, demyelinating
disease, arnold-chiari malformation, and, rarely, posterior
fossa tumors or vascular malformations
Caloric testing
While in supine. Elevtes the head 30°; this brings the
horizontal semicircular canals in vertical plane
Cold water instilled into the right ear causes the
endolymph in the right semicircular canal to cool and
sink.This movement is the same movement induced by a
rotation or the head to the left, inducing a horizontal
nystagmus directed to the left
Warm water in the same ear produces the opposite effect
Failure to respond to otolithic stimuli implies peripheral
vestibular disease.
Nystagmus Induced By The ValsalvaManeuver
may occur with Arnold-Chiari malformation or perilymph
fistulas
Hyperventilation Induced Nystagmus
Tumors of the eighth CN (e.G., Acoustic neuroma or
epidermoid tumors), after vestibular neuritis, or central
demyelinating lesions
Slow phase away from the side of the lesion (an excitatory
or recovery nystagmus)
Due to the effect of hyperventilation upon serum PH and
calcium concentration, which improves nerve conduction
in a marginally functional, demyelinated nerve
Head-shaking nystagmus
nystagmus induced by head oscillation
usually beats to the healthy side in unilateral peripheral
vestibulopathy
Perverted HSN
nystagmus develops in the plane other than that being
stimulated, that is, downbeat or upbeat after horizontal
head oscillation
in diffuse cerebellar degeneration, with focal caudal
cerebellar stroke, or with medullary lesions
signifies central vestibular lesion
Superior SCC Dehiscence Syndrome
Vertigo and nystagmus induced by sound (tullio
phenomenon) or changes of middle ear (hennebert sign) or
intracranial pressure
Caused by bony dehiscence of the superior SCC
vibration induced nystagmus
Bone conducted vibrations (BCV) of the head at low
frequencies ( 60-100 hz )
Activating probably only semicircular canals and not
otolithic afferent neurons
High frequencv (500 hz) BCV is a selective means of
activating otoliths
Delivered at the mastoids and at the midline of the
forehead at the hairline
Saccadic Intrusions
Interfere with macular fixation of an object of interest
Essential difference between nystagmus and saccadic
intrusions
Initial eye movement
Nystagmus → slow drift or slow phase
Saccadic intrusions → inappropriate saccadic movement
that intrudes on steady fixation
Lid Nystagmus
Rhythmic jerking movements of the upper eyelids
1. Synchronous with vertical ocular nystagmus
2. Synchronous with the fast phase of gaze-evoked
horizontal nystagmus in some patients with the lateral
medullary syndrome
3. Evoked by horizontal gaze in some patients with
midbrain tumors that injure the m-group of neurons
adjacent to the rimlf
4. During voluntary convergence (pick’s sign) in some
patients with medullary or cerebellar disease
Nystagmus Evaluation
Does the nystagmus involve both eyes?
Does the nystagmus involve both eyes symmetrically
Does the nystagmus cause the eyes to move in same or
opposite direction (conjugate or dysconjugate)
Docs the nystagmus occur spontaneously in primary
position
Does the nystagmus onlv occur when gaze is directed to
an eccentric gaze position
Low amplitude nystagmus mav be detected during
ophthalmoscopy; note that the direction of horizontal or
vertical nystagmus is inverted when viewed through the
ophthalmoscope.
Electronvstagmogram ENG for identifying nystagmus not
present with eyes open
Dix-Hallpike or Barany maneuver for assessing positional
nystagmus
Nystagmus Evaluation
Treatment of nystagmus
Pendular nystagmus
central (brainstem or cerebellum
Jerk nystagmus
either central or peripheral.
NYSTAGMUS SYNDROME and LOCALIZATION
Jerk nystagmus
Linear (constant velocity) slow phase
Peripheral vestibular dysfunction
Slow phase has a decreasing velocity exponential
Brainstem neural integrator
Increasing velocity exponential slow phase in the horizontal plane
Central in origin and is the usual form of congenital nystagmus
NYSTAGMUS SYNDROME and LOCALIZATION
NYSTAGMUS SYNDROME and LOCALIZATION
Downbeat nystagmus
Bilateral cervicomedullary junction (flocculus)
Floor of the fourth ventricle
Periodic alternating nystagmus
Cervicomedullary junction (nodulus)
Upbeat nystagmus
Bilateral pontomesencephalic junction
Bilateral pontomedullary junction
Cerebellar vermis
NYSTAGMUS SYNDROME and LOCALIZATION
Pendular nystagmus
Paramedian pons
Deep cerebellar (fastigial) nuclei
Seesaw nystagmus (SSN)
Mesodiencephalic junction, chiasm, disorders that disrupt
central vision
Rebound nystagmus
Cerebellum
NYSTAGMUS SYNDROME and LOCALIZATION
Brun’s nystagmus
Cerebellopontine angle
AICA territory stroke
Torsional nystagmus, jerk
Central vestibular system
Torsional nystagmus, pendular
Medulla
Thank you
The oscillations may be sinusoidal and of approximately
equal amplitude and velocity (pendular nystagmus) or,
more commonly, with a slow initiating phase and a fast
corrective phase (jerk nystagmus)
horizontal nystagmus usually (but not always) of
vestibular origin
Vertical nystagmus is usually of CNS origin
Direction -changing or direction-fixed
change in direction of nystagmus. be it when the eyes are
in a specific position or when the position of the eye is
changed indicates a lesion in the central nervous svstem.
• nystagmus due to vestibular lesion never changes
direction irrespective of whether the eyes are in a fixed
position or changed
Manner of occurrence
Effect of optic fixation on the nystagmus
Due to peripheral vestibular pathology decreases
Due to central vestibular pathology increases when eyes
open and decreases when closed
Although nystagmus described by direction of quick
phase, it is the slow phase that reflects underlying disorder
differentiated from saccadic intrusions and oscillations
rapid movements which take the eye away from the target
Nystagmus mav be unilateral or bilateral, but when
unilateral its rather asymmetrical rather than truly
unilateral
Localizing acquired central nystagmus: Jerk
Downbeat nystagmus
Upbeat nystagmus
Periodic alternating nystagmus
Rebound nystagmus
Bruns'nystagmus
Localizing acquired central nystagmus: pendular
Occular bobbing
intermittent often conjugate fast downward movement of
the eyes followed after a brief tonic interval by slower
return to primary position.
associated with intrinsic pontine pathology, particularly
heamorrhage tumours or infarction
in association with paralysis of spontaneous and reflex
horizontal eve movements
occular flutter
intermittent bursts of conjugate horizontal saccades
without an intersaccadic interval.
Impaired control by cerebellar fastigial nucleus especially
of horizontal saccadic system
opsoclonus
rare disorder of saccadic system
involuntary arrhythmic, chaotic, multidirectional saccades
without intersaccadic intervals
fixation continuously interrupted by multivectorial, back
to back saccades
at times seen only with ophthalmoscope
harbinger of an occult malignancy, though manv cases are
postinfectious, toxic-metabolic or idiopathic
usually neural crest tumors in children and lung, breast or
gynaecological cancer in adults
dysfunction of glycinergic omnipause neurons in nucleus
raphe interpositus
disinhibition of occulomotor region of fastigial nucleus
(FOR) in the cerebellum can generate opsoclonus
opsoclonus
Occulocephalic reflex
from first week of life
essentially represents a vestibulo-ocular reflex
Gaze-provoked nystagmus
The commonest form of nystagmus
eyes moved into eccentric gaze, especially in lateral and
up gaze
end point nystagmus
usuallv unsustained, . of low frequency and amplitude,
and not accompanied by other ocular motor abnormalities
Pathological gaze evoked nystagmus
sign of extraocular muscle weakness;, for example, in
patients with myasthenia gravis ("fatigue nystagmus").
result of central disorders that involve the gaze holding
neural network, which includes the nucleus prepositus
hvpoglossi and medial vestibular nucleus for horizontal
gaze, the interstitial nucleus of Cajal for vertical gaze, and
the vestibulocerebellum, which optimises gaze holding
Afferents to vestibular nuclei
• Semicircular canals → Superior and medial subnuclei
• Otolith organs → Lateral and inferior subnuclei
• Cerebellovestibular fibers through the inferior cerebellar
peduncle, primarily from the flocculonodular lobe
• Spinal cord
• Reticular formation
Ocular Connections
Vestibular
Nuclei
Mainly from superior and medial
nuclei
Superior nucleus projects to I/L
MLF; other nuclei to C/L MLF
CNs III, IV, and VI Nuclei
CN XI and upper
cervical nerves nuclei
Regulating movements of the eyes, head, and neck in response to
stimulation of the semicircular canals
MLF
Horizontal
semicircular canal
Anterior (superior) and
posterior canals
Abducens Nuclei &
Oculomotor Complex Oculomotor &
Trochlear Nuclei
Medial Longitudinal Fasciculus
Ocular Connections