Acquired Nystagmus Flashcards
what is nystagmus
an involuntary rythmic oscillation of one or both eyes
direction can be horizontal vertical torsional or mixed
can be conjugate or disconguate
can be disscociated , only unilateral/bilateral
Conjugate (both eyes display same movement) or disconjugate (the eyes show different movements e.g. one eye has horizontal nystagmus and the other vertical nystagmus) eye movements may be observed.
Dissociated
nystagmus (nystagmus is of different amplitude between the two eyes) may also be noted in acquired nystagmus.
what type of nystagmus is acquired and disconjugate nystagmus more common in
acquired and disconjugate nystagmus is More common in in acquired cases
what is nystagmus a product of
product of the failure of the mechanisms which hold the eye steady
Nystagmus→ by failure to hold the eyes steady- slow phase= defective- pathway
Mechanisms to hold eyes steady:
Vestibular ocular reflex (VOR) – steady gaze when head moving
Optokinetic & smooth pursuit systems
Separate ‘fixation system’
Neural integrator (holds the eyes steady in eccentric gaze)
when systems break down causes nystagmus
Vestibular-ocular reflex (VOR) –reflex eye movements that hold images of the seen world steady on the retina during brief head rotation.
Optokinetic and smooth pursuit system – theses eye movements are produced in response to retinal image slip.
Fixation system – – ability to detect retinal image slip and programme corrective eye movements, and the ability to suppress unwanted saccades that would take the eye away from target
Gaze-holding system (neural integrator) – is a network of neurones required to hold the eyes in eccentric gaze. A constant level of fine-tuning of muscle activity is needed to counteract the elastic pull of the extraocular structures (eg fat, muscles), which would tend to return the eye toward a central position in the orbit.
If any of the above described mechanisms which normally act to hold the eyes steady malfunction, nystagmus may develop.
what is phsyiological nystagmus
Induced by
self-rotation
instilling water into ear (vestibular nystagmus)
Fine end-point nystagmus- when pt gets to end of restriction
Differentiate from pathological gaze-evoked nystagmus
A considerable number of normal individuals display a fine jerky nystagmus on extreme gaze and is described as end-point nystagmus
describe the waveforms produced in acquired nystagmus
The waveforms can be pendular, jerk, or a combination of the two.
Pendular nystagmus consists of 2 slow phases, where the eyes oscillate (swing) from one side to the other. When the sinusoid is at its right or left turning point, the retinal image of a target is placed at the fovea. (and the eye velocity is minimum).
Jerk nystagmus consists of a slow phase, in which the eyes drift and takes the target off the fovea, followed by a corrective fast phase, which brings the target back to fovea.
For a brief period of time the target is held on the fovea, which is termed the foveation period.
It is generally agreed that the slow phase resembles the pathology.
The amplitude is measured in degrees, and is defined as the peak-to-trough of the waveform.
The frequency is measured in Hertz, and is defined as the number of oscillations per second.
The Nystagmus Intensity is given by multiplying the amplitude and frequency.
how are the different types of acquired nystagmus categorised
can be separated into conjugate and diconjugate
what are the different types of acquired conjugate nystagmus
conjugate acquired nystagmus
- gaze evoked nystagmus
- periodic alternating nystagmus
peripheral vestibular nystagmus
central vestibular (upbeat nystagmus and downbeat nystagmus)
what are the different types of disconugate nystagmus
acquired pendular nystagmus
internuclear ophthalmoplegia
see saw nystagmus
convergence retraction nystagmus
describe the features of acquired pendular nystagmus
Pendular nystagmus is a to-&-fro oscillation of the eyes
Optic pathway glioma – monocular((uniocular) nystagmus may be the presenting sign in young children< 2 years (Toledano et al 2015)
what is acquired nystagmus without complaints of oscillopisa suggest
associated with anterior visual pathway defects or brainstem lesions
what is acquired pendular nystagmus associated with
Visual loss
Aetiology: trauma, retinal or optic nerve disease
Large amplitude, often vertical, maybe uniocular
Multiple Sclerosis (MS)
Disconjugate & dissociated
C/o disabling oscillopsia
See-saw nystagmus
Aetiology: lesion of optic chiasm, brainstem disease, advanced retinitis pigmentosa
1 eye rise & intort while the other eye falls & extort
what conditions are acquired pendular nystagmus associated with
Spasmus Nutans
Aetiology unknown
Onset before 18 months old
Triad of nystagmus, head nodding & torticollis
Nystagmus: rapid, pendular dissociated low amp oscillation
Nystagmus may ↓ with head nodding
Resolves clinically by ~5 years
Oculopalatal tremor (myoclonus)
Aetiology: pontomedullary infarct/ haemorrhage
Synchronised ocular & palatal oscillations- also have jaw movements – caused by haemhorrhage
describe how acquired jerk nystagmus induced by vestibular disease disease caused peripheral imbalance
defective Slow phase → corrective fast phase
Induced by Vestibular System Disease
Peripheral Imbalance
Aetiology: disease affecting vestibular organ e.g. labyrinthitis → R-L imbalance
Mixed horizontal-torsional nystagmus
Slow phase towards affected side
Fall towards affected side
VOR abnormal/ absent
C/o oscillopsia, nausea, vertigo, dizziness
describe how acquired jerk nystagmus induced by vestibulr system disease caused central imbalance issues
Central Imbalance
Vestibular imbalance → by cerebellar or medulla lesions
Down-beat Nystagmus
Fast phase down in all positions
↑ on down-gaze & often lateral gaze
Aetiology: cerebellar degeneration, cerebellar ischaemia, Arnold-Chiari malformation, drug intoxication (e.g. anticonvulsants & lithium)
Other mechanisms:
Imbalance of vertical smooth-pursuit → spontaneous upward drift
Mismatch for vertical saccade generation
how does acquired jerk nystagmus induced by vestibular system disease causes up beat nystagmus issues
Up-beat Nystagmus
Fast phase up in all positions
↑ on up-gaze
Associated with impaired vertical smooth pursuit
Aetiology: MS, brainstem tumour/ stroke, Wernicke’s encephalopathy, cerebellar degeneration, drug intoxication
Other mechanisms:
Imbalance of vertical VOR
Mismatch of saccadic generation & velocity-to-position integration
describe the characteristics of PAN and what is it caused by
period alternating nystagmus is a sympton of acquired jerk nystagmus
Periodic Alternating Nystagmus (PAN)
Horizontal jerk nystagmus
Periodically reverses direction of fast phase
Cycle: range from few seconds to 4 min
Diff Diagnosis: congenital vs acquired
Aetiology: craniocervical anomalies, cerebellar degeneration/tumour, brainstem infarct, MS, bilateral visual loss
what is gaze evoked nystagmus
induced by dysfunction of gaze holding mechanism
gaze evoked nystagmus - change in direction of fast phase depending on where they are looking
Nystagmus in eccentric gaze but absent in P.P.
Jerk nystagmus with fast phase to the right on right gaze
Jerk nystagmus with fast phase to the left on left gaze
Upbeat nystagmus in upgaze
Downbeat nystagmus in downgaze
what is the ateiology of gaze evoked nystagmus
Aetiology
Cerebellar disease, medication (anticonvulants or sedatives), alcohol
what is rebound nystagmus
Rebound nystagmus
Patients with gaze-evoked nystagmus return eyes to P.P., observe transient nystagmus with slow phase to previous gaze position (opposite)
what is the differential diagnosis for nystagmus
saccadic oscillations such as
saccadic intrusions - inappropriate saccades that intrude on steady fixation
saccadic oscillations - dysfunction of saccadic system - saccades take eyes away from the target and result in unsteady eye movements
what waveforms do saccadic oscillations produce and what do they indicate
small conjugate back to back saccades
inter saccadic interval 200msec
more than 5 degree amplitude and frequency
may be seen in healthy subjects
ateiology - progressive supranuclear palsy cerebellar disease, Parkinsons disease , ms , schizophrenia
macro swjs = more than 5 degree amplitude
inter saccadic interval (80msec)
ateiology= cerebellar disease
what are the different types of saccadic oscillations
ocular flutter
Episodic, horizontal back-to-back saccades
No inter-saccadic intervals
opscolomus (saccomdonnia)
back-to-back saccades in all directions
Aetiology: infants with neuroblastoma, cerebellar encephalitis, cancer, idiopathic
Ocular bobbing
From P.P. fast, conjugate eye movement down
After few sec slow drift back to P.P.
Aetiology: severe pontine dysfunction
These degrade Vision, cause oscillopsia and dizziness
what is volountary nystagmus
Voluntary Nystagmus
10 rapid back-to-back saccades
May be initiated by convergence
Seen in hysterical pt’s or malingers
Although careful to distinguish from Convergence-retraction nystagmus in parinaud’s syndrome
what are the aims of management and and management options
aims - treat any underlying disorder
reduce nystagmus and oscillopisa
options - medication
prisms
optical stabilisation
surgery
what is the management of acquired nystagmus
Medication
Baclofen
May ↓ down-beat, up-beat, see-saw & PAN
Clonazepan
May ↓ down-beat, see-saw & acquired pendular
3,4-diaminiopyridine / 4-aminopyridine
Randomised, controlled studies showed successful ↓ in down-beat nystagmus
Effective in some with upbeat nystagmus
Baclofen and Clonazepan first attempt of reducing nystagmus but limited success and uncontrolled studies
3,4-diaminiopyridine. Recent randomised, controlled studies has successfully ↓ down-beat nystagmus and is now recommended. Useful in cerebellar conditions
Upbeat nystagmus: recommend memantine or4 aminopyridine
Recently, gabapentin and memantine were found to be particular helpful in dampening the nystagmus, and thus oscillopsia, in patients suffering with multiple sclerosis (Shery et al. 2006).
what medication has been found to be effective in the treatment of nystagmus
Baclofen and Clonazepan first attempt of reducing nystagmus but limited success and uncontrolled studies
3,4-diaminiopyridine. Recent randomised, controlled studies has successfully ↓ down-beat nystagmus and is now recommended. Useful in cerebellar conditions
Upbeat nystagmus: recommend memantine or4 aminopyridine
Recently, gabapentin and memantine were found to be particular helpful in dampening the nystagmus, and thus oscillopsia, in patients suffering with multiple sclerosis (Shery et al. 2006).
what are gababpentine and mematine used to treat
Gabapentin
Successful ↓ in acquired pendular nystagmus caused by MS, oculopalatal tremor
Memantine
Successful ↓ in acquired pendular nystagmus caused by MS, oculopalatal tremor
May be effective in upbeat nystagmus
what are carbamazepine and immunoglobulins or prednisolone used to treat
Immunoglobulins or prednisolone
Occasionally ↓ ocular flutter & opsoclonus
how are prisms used to manage nystagmus
prisms
BDΔ may ↓oscillopsia in down-beat
BOΔ induce convergence & may ↑VA if nystagmus dampen on near fixation
BIΔ may ↓ nystagmus & oscillopsia if symptoms worsen on near fixation
how optical stabilisation used to treat nystagmus
Aim: ↓ effect of eye movement on retinal image
Principle: combine high +lenses with high –CL
100% image stabilisation not needed to o/c oscillopsia
what is the aim of using optical stabilisation and prisms to treat nystagmus
The aim is to eliminate oscillopsia by reducing the effect of eye movements and use an optical system that stabilises the retinal image. The system consists of a high power convex spectacle lens combined with a high power concave contact lens. Because the contact lens moves with the eye, it does not negate the effect of the spectacle lens. Up to 90% image stabilisation can be achieved, although less is required to abolish oscillopsia. This method may be used as a trial before Botulinum Toxin injection.
how is botox used to manage nystagmus
Botulinum Toxin
Aim: ↓amplitude of nystagmus by targeting all EOM
Retrobulbar injection (usually the eye with better VA)
Result in ↑VA & ↓ c/o oscillopsia
what is the future management of nystagmus
Medication
Clinical trials using memantine, gabapentin and 3,4-diaminopyridine/ aminopyridine
New drugs
Surgery
4 large horizontal rectus recessions
4 large vertical rectus recessions (Spielman, 2009)
Vertical Anderson Procedure (bilateral SR recessions & IR tenotomy)
Combine Kestenbaum surgery with gabapentin
Further research
>understanding of underlying mechanisms
Virtual reality
