NYSTAGMUS AETIOPATHOGENESIS TYPES AND CLINICAL FEATURES

SPEAKER : KUMAR SAURABH

HISTORICAL OVERVIEW

Nystazho{Greek} Wobbly head movements of a sleepy or inebriated individual.

DEFINITIONS

Nystagmus : Involuntary,biphasic,rhythmic ocular oscillation which can be either physiological or pathological.

Pursuit : Slow and smooth movements of the eyes to follow a moving target in the environment.

Saccade : Rapid jerky movement of the eyes to bring back the image of the target on to the fovea.

CLASSIFICATION

AETIOLOGICAL CLASSIFICATION

Nystagmus

Physiological

End gaze

Optokinetic

Vestibulo-ocular reflex

Pathological

Congenital Acquired

Toxic

Neurological

Visual loss

Functional

Infantile manifest

Infantile Latent

Infantile Manifest-latent

BASED ON MANIFESTATION Manifest

Latent

Manifest-latent

BASED ON PATTERN OF MOVEMENT

Jerk

Pendular

BASED ON DIRECTION OF MOVEMENT

Horizontal

Vertical

Rotary

UPPER MOTOR NEURON (Cerebral cortex)

PRE-MOTOR NEURONS (Brain stem)

LOWER MOTOR NEURON (Ocular motor neuron, Neuromascular junction)

EXTRAOCULAR MUSCLES

CEREBELLUM

VESTIBULAR NUCLEUS

SIX LEVELS OF OCULAR MOTOR SYSTEM 1.

2.

3.

4.

5.

6.

PATHOGENESIS OF NYSTAGMUS

Upper Motor Neuron Lesion (Supranuclear)

Nystagmus

Gaze palsy

Involuntary eye movements

Lower Motor Neuron (Infranuclear)

Paralytic strabismus

CORTICAL CENTRES FOR MOTOR CONTROL

PURSUIT SACCADE

Occipital motor area

Middle temporal area (MT)

Middle superior temporal area (MST)

Frontal eye field (FEF)

Supplementary eye field (SEF)

Dorsolateral prefrontal cortex (DLPFC)

Posterior eye field (PEF)

BRAINSTEM CENTRES FOR MOTOR CONTROL

(Saccade+Pursuit)

HORIZONTAL GAZE CENTRE VERTICAL GAZE CENTRE

PARAMEDIAN PONTINE

RETICULAR FORMATION

(PPRF)

ROSTRAL INTERSTITIAL

NUCLEUS OF

MEDIAL LONGITUDINAL

FASCICULUS (riMLF)

CLINICAL FEATURESGENERAL SYMPTOMS : To-and-fro Movement of Eyes.

Reduced Visual Acuity.

Blurred or Unstable Vision.

Oscillopsia : At >8 years of age.

GENERAL SIGNS : Repetitive movements of eyes.

• Binocular or monocular

• Direction

• Waveform

• Effect of gaze

• Conjugate or dysconjugate

• Any change with change in posture.

• Periodicity

• Any associated movement.

JERK NYSTAGMUS

• Slow defoveating drift

• Fast refoveating saccade

• Direction – Fast component

• Horizontal,vertical or rotatory

• Gaze evoked : Vestibular

• Gaze paretic : Brain stem damage

PENDULAR NYSTAGMUS

•Sinusoidal,nonsaccadic

•Slow and equal velocities

•Congenital or acquired

•Horizontal,vertical,elliptical,torsional

•Involvement of pontine tegmentum mainly

•Special types :--

CONVERGENT-DIVERGENT NYSTAGMUS

Dysconjugate

Horizontal in opposite direction

Demyelinating disease

CYCLOVERGENT NYSTAGMUS

Dysconjugate

Torsional

Upper poles move in opposite direction.

PHYSIOLOGICAL NYSTAGMUS

END POINT NYSTAGMUS

Jerk nystagmus

On looking extreme lateral or upwards

Angle of gaze > 45 degrees

VESTIBULAR NYSTAGMUS

Jerk nystagmus Altered inputs from vestibular nuclei to PPRF Demonstrated by Caloric Test Cold water – Opposite direction Warm water – Same direction Cold water in both ears – Upwards Warm water in both ears -- Downwards

OPTOKINETIC NYSTAGMUS

Jerk nystagmus

Induced by moving a full visual field stimulus

Slow phase (Pursuit): Eye follows the target

Fast phase (Saccade): Eye fixates on the next target

Used for– Detecting malingerers

Testing visual acuity in young

UPBEAT NYSTAGMUS

Jerk nystagmus with fast phase upwards.

Defect : Anterior semicircular canal projections.

Lesion:Pontomedullary or pontomesencephalic junctions.

Amplitude increases on upgaze and supine posture.

Causes : Wernicke’s encephalopathy, Organophosphates and anticonvulsants, Lithium,Nicotine,Thallium.

PATHOLOGICAL NYSTAGMUS

DOWNBEAT NYSTAGMUS

Jerk nystagmus with fast phase downwards.

Defect : Posterior semicircular canal projections.

Lesion : Commissural fibers between vestibular nuclei.

Flocculus at the craniocervical junction.

Amplitude increases with lateral and downward gaze { Daroff's sign }

May be visible only with change of posture viz. head hanging.

Causes: Chiary malformation Type I,

Foramen magnum tumors,

Alcoholism,

Amiodarone,toluene,anticonvulsants

Magnesium depletion,

Vitamin B12 deficiency.

SEESAW NYSTAGMUS (SSN)

Pendular nystagmus.

One eye rises and intorts;other eye falls and extorts.

Lesion : Midbrain-thalamic junction.

Faster and smaller on upgaze;

Slower and larger on down gaze.

Ceases in darkness.

Acquired SSN: Suprasellar tumors,

Leigh’s syndrome,

Jobert’s syndrome

Congenital SSN : Achiasmia.

GAZE EVOKED NYSTAGMUS

Jerk nystagmus.

Absent in primary gaze.Appears on eccentric gaze.

Fast phase in the direction of gaze.

3-8 beats/second ,coarse.

Defect in neural integrator.

Causes : Old age, Alcohol intoxication, Cerebellar or brain stem disease, Barbiturates.

GAZE PARETIC NYSTAGMUS

Jerk nystagmus.Most common nystagmus.

Absent in primary position.Appears on eccentric gaze.

Fast phase in the direction of gaze.

1-2 beats/second, symmetrical or asymmetrical.

Causes : Brain stem damage at pontine level.

PERIODIC ALTERNATING NYSTAGMUS

Horizontal jerk nystagmus.

Present in primary position.

Crescendo-decrescendo fashion.During transition nystagmus stops or beats vertically.

90 + 90 = 180 seconds or 3 minutes (approximately).

May be congenital or acquired.

Lesion : Damage to the craniocervical junction.

REBOUND NYSTAGMUS

Horizontal gaze evoked nystagmus.

Nystagmus beats transiently in opposite direction after return to primary position. ( 3 – 25 seconds ).

BRUN’S NYSTAGMUS

Jerk nystagmus.

Bilateral, asymmetrical.

On the side of lesion :Large amplitude,low frequency oscillations.

On the opposite side :Small amplitude,high frequency oscillations.

Cause : Large cerebello-pontine angle tumor.

EPISODIC NYSTAGMUS

Paroxysmal episodes of ataxia, vertigo and nystagmus.

Lasting up to 24 hours.

Causes :Inborn errors of metabolism Basilar migraine Multiple sclerosis

ICTAL NYSTAGMUS

Occurs during refractory seizures.

Mostly horizontal ; may be vertical.

Generally directed opposite to the site of epileptogenic focus.

LID NYSTAGMUS

Rhythmic jerky movements of the upper eye lid.

Conditions when lid nystagmus occurs:

Synchronous with vertical nystagmus Synchronous with fast phase of gaze evoked nystagmus. Midbrain tumors. During voluntary convergence in cerebellar disease

CONGENITAL NYSTAGMUS

Pendular or jerk type.

Pendular nystagmus often becomes jerk on lateral gaze.

Mostly horizontal,rarely vertical.

Increased amplitude on vertical tracking and distant fixation.

Decreased amplitude on convergence.

Increased amplitude when one eye is covered (Latent superimposition).

May be minimal at a particular point of gaze (Null zone).

Reversal of optokinetic response is characteristic.

Present at birth but may be detected later.

Good vision unless there is an afferent defect.

No oscillopsia.

Head titubation may be seen.

Causes :Autosomal recessive or X linked. Achiasmia, Achromatopsia, Albinism, Aniridia, Congenital cataract Retinopathy of prematurity, Optic nerve hypoplasia.

FEATURES OF CONGENITAL NYSTAGMUS

LATENT NYSTAGMUS

No nystagmus with binocular vision.

Nystagmus with monocular fixation with other eye covered.

Slow phase is directed towards covered eye.

Amplitude increases with abduction of fixating eye.

MANIFEST NYSTAGMUS

Nystagmus present with binocular vision.

MANIFEST LATENT NYSTAGMUS

Nystagmus present with binocular vision.

Amplitude increases when one eye is covered.

SPASMUS NUTANS

Transient pendular nystagmus.

High frequency, low amplitude.

Horizontal, vertical or torsional. Dysconjugate and asymmetrical.

May be monocular.

Spasmus Nutans Triad : Nystagmus, Torticollis, Titubation. Onset : 6 – 12 months Duration : Up to 2 years; maximum 5 years of age.

Causes : Glioma of anterior visual pathway Empty sella syndrome Porencephalic cyst.

NYSTAGMOID MOVEMENTS

OCULAR FLUTTER

Horizontal and conjugate movements.

Intermittent bursts of back-to-back saccades.

Triggered by change of posture.

Aggravated by attempt at fixation.

Defect : Loss of pause cell inhibition of burst neurons at PPRF.

OPSOCLONUS

Multivector saccadic eye movements.

Spontaneous, chaotic but conjugate movements.

Aggravated by attempt at fixation.

May be associated with myoclonic jerks of limbs and cerebellar ataxia.{ Dancing feet-dancing eye syndrome }

Cause :Viral encephalitis, Multiple carboxylase deficiency, Hyperosmolar coma, Multiple sclerosis, Neuroblastoma.

CONVERGENT RETRACTION NYSTAGMUS

Dysmetric horizontal eye movement upon attempted upward saccade.

Rapid convergence with retraction of both globes. Followed by slow divergent movement.

Cause : Co-contraction of extraocular muscles.

Seen in : Dorsal midbrain ( Perinaud’s ) syndrome.

OCULAR BOBBING

Rapid downward movement of both eyes.

Followed by slow drift back to primary position.

Seen in : Comatose patients.

OCULAR MYOCLONUS

Vertical pendular oscillations.

Frequency : 160 Hz.

Associated with similar oscillations of soft palate. { Oculopalatal syndrome }

Cause : Infarction at the pons.

VOLUNTARY NYSTAGMUS

Ocular flutter under voluntary control.

Usually horizontal.

May be vertical, torsional or cycloid.

Patient converges to initiate the ‘nystagmus’.

Can be sustained up to 30 seconds.

Familial inheritance.