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