Nystagmus A Clinical Approach Abdullah El-Menaisy, MD, FRCS Neuro-ophthalmology & Investigation...
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Transcript of Nystagmus A Clinical Approach Abdullah El-Menaisy, MD, FRCS Neuro-ophthalmology & Investigation...
NystagmusA Clinical Approach
Abdullah El-Menaisy, MD, FRCSNeuro-ophthalmology & Investigation Service,
Dhahran Eye Specialist Hospital,Dhahran, Saudi Arabia
Nystagmus is a rhythmic biphasic oscillation of the eyes
There are three main control mechanisms for maintaining steady gaze:
1. Fixation2. Vestibulo-ocular reflex3. Gaze-holding system (neural integrator)
Mechanisms of Gaze Stability
The visual fixation mechanism: Detection of retinal image drift Programming of corrective eye movements Suppression of unwanted saccades
The vestibulo-ocular reflex: Compensates for head movements
Gaze-holding mechanism: Sustains eye at an eccentric position in the orbit against the
elastic pull of the globe's suspensory ligaments and muscles
Failure of any of these control systems will cause disruption of steady fixation
There are 2 types of abnormal fixation:1. Nystagmus 2. Saccadic intrusions & oscillations
The difference between them lies in the initial movement that disrupts fixation
In nystagmus, it is a slow drift, while in saccadic intrusions and oscillations, it is a fast movement that moves the eyes off target
Age of onset: congenital, acquired
Nature of movement: pendular, jerk
Plane of movements: horizontal, vertical, torsional
Effect of fixation block: latent, manifest, latent-manifest
Classification of Nystagmus
Pendular, Jerk
Horizontal, Vertical, Torsional
Latent, Manifest
Types
Congenital Nystagmus Spasmus nutans Monocular Vestibular Gaze-evoked Dissociated Periodic alternating
Downbeat Upbeat Convergence retraction See-saw Drug-induced Optokinetic Nystagmus
(OKN)
Congenital Nystagmus
At birth or during 4 m after birth No oscillopsia Pendular, horizontal (may be rotary or rarely vertical) May have jerk properties in end gaze Remains horizontal in vertical gaze Has null point Dampens with convergence Exacerbates with fixation Shows reverse optokinetic response Associated with high refractive error including astigmatism
Etiology: Sensory: due to disorders of afferent visual pathway - optic nerve hypoplasia - ocular albinism - Leber’s congenital amaurosis
Motor: due to efferent pathway disorder - sporadic, autosomal dominant, recessive, X-linked
Congenital Nystagmus
Congenital Nystagmus
Evaluation: Vision Pupils Fundus Refraction VEP,ERG
Treatment: Glasses, contact lenses Prism to shift null point to
primary gaze Surgery (kestenbaum) Botox injection
Spasmus Nutans
Triad of: (1) nystagmus (2) torticollis (3) head nodding Starts between 4 - 14 m Almost always resolved by 5y Pendular of low amplitude & high frequency May be horizontal, vertical or rotary May be associated by optic pathway glioma Neuroimaging is important
Monocular Nystagmus
Slow vertical pendular oscillations Due to severe monocular visual loss (Heimann-
Bielschowsky phenomenon) Can appear several years after visual loss May resolve if vision is restored May be associated with chiasmal glioma Needs neuroimaging
Vestibular Nystagmus
Peripheral vestibular nystagmus: Horizontal rotary Horizontal in different directions of gaze Amplitude increases when eyes move in the direction of
fast phase (Alexander’s law) The fast phase is opposite to site of the lesion Patients fall towards the site of the lesion Associated with vertigo, hearing loss or vomiting Causes includes: labyrinthitis, vestibular neuritis, Meniere’s
disease, migraine, benign positional vertigo (BPV)
Central vestibular nystagmus: Pure torsional nystagmus Asymmetric Vertical in primary position Change direction in different gaze positions Causes include: pontine & cerebellar lesions (stroke, tumor,
MS,…..)
Vestibular Nystagmus
Gaze-evoked Nystagmus
Asymmetric in right & left gaze High amplitude (< 4 degrees) Unilateral gaze-evoked nystagmus may indicate cerebellar
or brain stem lesion Gaze-evoked upbeat nystagmus commonly due to bilateral
INO When presents in horizontal & upgaze, it signifies toxic
metabolic process Brun’s nystagmus may be seen in cerebellopontine angle
lesions
Causes: lesions in - medial vestibular nucleus - nucleus prepositus hypoglossi - cerebellum - peripheral vestibular pathway
Physiological gaze-evoked nystagmus: - symmetric in different directions of gaze - has low amplitude
Gaze-evoked Nystagmus
Dissociated Nystagmus
Nystagmus of abducted eye with impaired adduction of contralateral eye
Occurs in INO due to adaptive phenomenon that attempt to increase the
innervation to the week adducting eye
Periodic Alternating Nystagmus (PAN)
Acquired or congenital Change direction every 90 sec with a rest period of 5 -10
sec May be due to degenerative process of cerebellum May associate downbeat nystagmus or skew deviation Persists during sleep & remains horizontal in vertical gaze Baclofen ameliorates the acquired form while the
congenital form can be corrected by large horizontal recti resection
Downbeat Nystagmus
Craniocervical junction lesion Other causes are hypomagnesemia, thiamine & vit B12
deficiency, phenytoin, alcohol & lithium toxicity Congenital cases show spontaneous remission Treatment by clonazepam, gabapentin, baclofen. Prism
therapy can help
Upbeat Nystagmus
Due to midbrain, cerebellum or medullary lesions 2 types: (1) a course large amplitude nystagmus increases in
upgaze (cerebellar vermis lesion) & (2) a small amplitude nystagmus in primary position (medullary lesion)
Causes are MS, infarction, cerebellar degeneration & tumors
Tobacco smoking can produce upbeat nystagmus in normal subjects when fixation is removed
Convergence Retraction Nystagmus
It is not a true nystagmus (no slow phase) Convergent saccades in attempting upgaze In pretectal dysfunction Due to cofiring of horizontally & vertically acting EOM
See-Saw Nystagmus
Pendular Spontaneous elevation & intorsion of one eye with
depression & extorsion of the other eye and the cycle is reversed
Usually due to sellar mass lesion Some patients display ½ see-saw cycle with corrective quick
phase (hemi or jerk see-saw nystagmus). It is typically due to midbrain lesion
Baclofen or clonazepam may help in treatment
Drug-induced Nystagmus
Common In horizontal endgaze & upgaze and not in downgaze Symmetric & doesn’t fatigue Medications include: anticonvulsants, sedatives,
barbiturates & phenothiazines Carpamazepine, phenytoin & lithium may produce
downbeat nystagmus Acute alcohol intoxication can cause horizontal endgaze
nystagmus (positional alcohol nystagmus)
Optokinetic Nystagmus (OKN)
A physiological involuntary reflex Elicited by moving a striped tape or drum in front of the
patient A slow phase in the direction of movement of tape or drum
& a corrective fast phase in the opposite direction
OKN is a diagnostic tool in: 1 - a reverse OKN is characteristic of congenital
nystagmus 2 - preserved vertical OKN indicates intact vision in
congenital nystamus 3 - asymmetric OKN indicates deep parietal lesion 4 - In malingerers, intact OKN means that vision is at
least CF 5 - moving the tape downwards to elicit convergence
retraction nystagmus in patients with Parinaud’s syndrome
Optokinetic Nystagmus (OKN)
Nystagmoid Eye Movements
Not pure forms of nystagmus (no slow phase) Saccades interrupt fixation Represent disorder of saccades Includes: - Square wave jerks - Ocular dysmetria - Opsoclonus - Ocular flutter - Ocular bobbing - Superior oblique myokymia
Square Wave Jerks
Horizontal saccades with intersaccadic interval Can be seen in normal individuals (> 9 jerks per min) Causes include: cerebellar disease, Schizophrenia,
Parkinson’s disease
Opsoclonus
Involuntary conjugate multidirectional saccades (saccadomania) occur without intersaccadic interval
Associated with eye blinking, facial twitching, myoclonus & ataxia
50% of children with opsoclonus has neuroblastoma Responds to tumor removal, ACTH, prednisone, gamma
globulin, plasmapheresis Other causes include: parainfectious cerebellitis or
encephalitis, paraneoplastic disease, drug induced (amitriptyline, lithium, cocaine)
Ocular Flutter
Horizontal saccades without intersaccadic interval (no vertical component)
Can be associated with ocular dysmetria Has the same localizing value & differential diagnosis of
opsoclonus
Ocular Bobbing
Quick conjugate down movements followed by slow drift back to midline
Some patients show movements in the opposite direction Reflects pontine dysfunction May be associated with horizontal gaze palsy Causes includes: stroke, tumors, toxic-metabolic conditions
or inflammatory process
Superior Oblique Myokymia
High frequency monocular oscillations produced by spontaneous firing of one SO muscle
Idiopathic, but could be due to midbrain lesion Treatment by carbamazepine, bacolfen, propranolol Muscle surgery (SO tenotomy +/- IO resection or Harado-Ito procedure)
Downbeat: cervicomedullary junction
Upbeat: pons, midbrain
See-saw: parrasellar, midbrain
Convergence retraction: dorsal midbrain
Spasmus nutans: chiasmal glioma
Nystagmus with Localizing Value
History Visual acuity Inspection Cover test Ocular motility Saccade & pursuit VOR Pupils Fundus Electronystagmography
Evaluation
History: Onset : - Birth to 4 m: congenital - < 4 m: acquired
Associated symptoms: - Oscillopsia: acquired nystagmus - Nausea & vomiting: peripheral vestibular disease - Diplopia, dysarthria, facial numbness, dysphagia: brain stem
lesions
Medications
Similar condition in the family
Evaluation
Inspection: Type of nystagmus:1. Pendular: slow phases are of equal velocity (no corrective
saccades)2. Jerk: slow & fast phases (the direction is defined by the
fast phase). In torsional nystagmus (direction is defined towards patient’s right or left shoulder)
Evaluation
Type
Plane
Fixation Block
Amplitude & Frequency
History Visual acuity Inspection Cover test Ocular motility Saccade & pursuit VOR Pupils Fundus Electronystagmography
Evaluation
Videonystagmography
Vestibular nystagmus: slow phase is linear
Congenital nystagmus: slow phase shows increasing velocity
Gaze paretic nystagmus: slow phase is declining
Thank you