Paralytic strabismus, features, importance of Hering's Law and investigations of paretic strabismus

1. PARALYTIC AND PARETIC
STRABISMUS GENERAL
FEATURES, IMPORTANCE OF
HERINGS LAW, INVESTIGATIONS
OF PARETC STRABISMUS
01/03/15
1
Presenter Pabita Dhungel
B.optometry
Institute of Medicine

2. References
1) BINOCULAR VISION & STRABISMUS –GK VON
NOORDEN
2) CLINICAL MANGEMENT OF STRABISMUS-
ELEZABETH E.CALAROSSA &
MICHAEL W. ROUSE
3) AAO- SECTION: PEDIATRIC OPHTHALMOLOGY &
STRABISMUS
4) STRABISMUS SIMPLIFIED- PRADEEP SHARMA
5) PRACTICAL ORTHOPTICS IN THE TREATMENT OF
SQUINT- LYLE AND JACKSON’S
01/03/15
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3. PRESENTATION LAYOUT
Introduction to extra ocular muscles
Few related terms
• Introduction to paralytic and paretic strabismus
Classification
Clinical characteristics
Importance of Herings law
Investigations of paretic strabismus
Summary
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4. Introduction
There are 6 extraocular muscles – 4 rectus muscles, 2
oblique muscles
5 muscles arise from the apex of the orbit, the inferior
oblique arises form the inferonasal angle of the orbit
The 4 recti muscles originate form the apex of the
orbit at the level of the Annulus of Zinn
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5. Contd....
The recti muscles are inserted in front of the ocular equator, the
obliques are inserted behind
Movements occur about 3 primary axes around the centre of
rotation – the vertical, horizontal and saggital axes
The action of a muscle depends on the angle of its plane and
the anterio-posterior axis of the eye.
 It follows that the action of the muscle may vary according the
positions of the globe in the orbit.
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6. Few related terms
Agonist= muscle producing a specific ocular
movement
Antagonist= muscle having the opposed action
Synergist = muscle having the same actions
Ipsilateral = on the same side
Contralateral = on the opposite side
Contracture = increased resistance against passive
stretching of the muscle, loss of elasticity
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7. Hering’s Law of Equal
Innervation
An equal and simultaneous innervation flows from
the brain to a pair of muscles of both eyes (yoke
muscles) which contract simultaneously in different
binocular movements
Eg. Equal and simultaneous innervation flows to:
1.RLR and LMR muscles during dextroversion
2.Both MR during convergence
3.RSR and LIO muscles during dextroelevation
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8. Sheringtons Law of Reciprocal
Innervation
concerned with the co-ordination of muscle pairs of one eye.
ie the contraction of each ocular muscle is accompanied by a
simultaneous and proportional relaxation of its antagonist.
e.g. during dextroversion , an increased innervational flow to
the RLR and LMR is accompanied by decreased flow to the
RMR and LLR muscle
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9. Sequelae of Ocular Muscle Palsy
Underaction of the primary affected muscle
Overaction of the contralateral synergist
Overaction of the ipsilateral (direct) antagonist
Underaction of the antagonist of the contralateral synergist
(contalateral antagonist)
Overaction of the ipsilateral synergist??
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10. Overaction of the contralateral
synergist
always present.
This overaction occurs when the affected eye is fixing as
a result of increased innervation being required to rotate
the affected muscle into its field of action.
Due to Herings Law an overstimulation of the
contralateral synergist follows
This is always the largest overaction in the sequelae.
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11. Overaction of the ipsilateral
(direct) antagonist
can lead to a permanent contracture of the muscle and a
loss of elasticity
If the patient fixes with the non-involved eye within a few
days a contracture will develop in the direct antagonist
muscle
because the normal contracture of the direct antagonist is
unopposed by the weak muscle.
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12. Underaction of the antagonist of the
contralateral synergist (contalateral
antagonist)
with the involved eye fixing, the movement of the eye
into the field of action of the weak muscles antagonist
requires less innervation than normal due to the
contracture.
Therefore less innervation is supplied to the contralateral
antagonist which under-acts
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13. For example in paralysis of the
right superior rectus
underaction of right superior rectus
overaction of the left inferior oblique
overaction of the right inferior rectus
underaction of the left superior oblique
(overaction of the right inferior oblique)
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14. Introduction to paralytic strabismus
Terms paretic and paralytic often are used
interchangeably in clinical ophthalmology
Paralytic strabismus is an incomitant strabismus due
to motor deficiency of one or a group of extra ocular
muscles
Incomplete paralysis is called paresis and complete
deficiency is called paralysis, while palsy is used for
both without specifying
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15. Classification
A). Neurogenic
i) supranuclear
ii) nuclear
iii) internuclear
iv) infranuclear
- fascicular ( Main nerve trunk or subdivision)
 oculomotor nerve (III CN)
Trochlear nerve (IV CN)
Abducens nerve (VI CN)
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16. Contd...
B. Myogenic
i) nerve muscle junction lesion (myasthenia)
ii) muscle
(a) Congenital
Absence ,hypoplasia mal insertion or musculofascial
anomalies
(b) Traumatic laceration, disinertion
(c) inflammatory (myositis)
(d) Orbito- myopathies
(e) Dystrophy01/03/15
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17. Causes of neurogenic lesions
1. congenital
2. traumatic
3. inflammatory
4. neoplastic
5. ischemic
6. toxic
7.Demyelinating disease
8. idiopathic
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18. Paralytic strabismus etiology
I. Neurogenic lesions
1. Congenital hypoplasia or absence of nucleus: third
and sixth cranial nerve palsies.
2. Inflammatory lesions: encephalitis,meningitis,
neurosyphilis,peripheral neuritis (viral),infectious
lesions of cavernous sinus and orbit.
3. Neoplastic lesions.
4. Vascular lesions:HTN, DM and atherosclerosis.
haemorrhage, thrombosis, embolism, aneurysms
or vascular occlusions.
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19. Contd…
5. Traumatic lesions: head injury
6. Toxic lesions:carbon monoxide poisoning, effects of
diphtheria toxins (rarely),alcoholic and lead
neuropathy.
7. Demyelinating lesions:multiple sclerosis
II. Myogenic lesions
1. Congenital lesions. These include absence,
hypoplasia, malinsertion, weakness and musculofacial
anomalies.
2. Traumatic lesions.
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20. Contd…
3. Inflammatory lesions: Myositis (viral) , influenza,
measles.
4. Myopathies:These include thyroid
myopathy,carcinomatous myopathy,Progressive
external ophthalmoplegia
III. Neuromuscular junction lesion
It includes myasthenia gravis.
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21. Paralytic strabismus
SYMPTOMS:
1. LIMITATION OF OCULAR MOVEMENTS
2.SUDDEN ONSET OCULAR DEVIATION
3. DIPLOPIA
4.CONFUSION
5.NAUSEA , VERTIGO
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22. Diplopia
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23. DIPLOPIA-A)Uncrossed diplopia with an
esotropia. B)Crossed diplopia with an exotropia.
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24. SIGNS
Limitation of movement in the field of action of the
muscle
Difference in primary and secondary deviations
Compensatory HP
False projection
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25. Clinical characteristics
i) incomitance
variable ocular deviation in different position
which is maximum in the field of action of the muscle
(eg. In a LLR palsy esotropia is maximal in the
abduction of LE)
ii)Limitation of movement
of the eye in the field of action of the EOM( in
LLR palsy the abduction of the LE is deficient or
limited)
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26. Contd...
iii) difference in primary and secondary deviation
deviation of the squinting eye with normal eye fixing
is called primary deviation
Deviation of the normal eye with the paretic eye
fixing is called secondary deviation
In paralytic strabismus secondary deviation is greater
than primary deviation
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27. Contd...
This is because the paretic eye requires more effort
to straighten (come to the primary position to take
up fixation) and this extra effort is passed on to the
contralateral synergist, which is normal, increasing
the ocular deviation
The reverse is true for spastic strabismus i.e primary
deviation is greater than the secondary deviation
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28. differences Paralytic comitant
Age of onset Usually late Usually early childhood
Type of onset Sudden Gradual, sudden
manifestation
Precipitating
events
Usually head injury , systemic
illness
Rarely present. Even if
present no cause effect
relationship
Associated
neurological
signs
May be present None
Comitance May develop in late stages Usually present (except
in extreme gazes)
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29. Differences Paralytic Comitant
Diplopia Usually present Absent
Head posture Usually present Absent
Cyclotropia Usually present (except
with horizontal muscle
palsy)
Absent exception
associated A.V. patterns
or oblique over-actions
Sensory
adaptions( suppression-
amblyopia ARC)
Rare Frequent
Past pointing Present in recent cases absent
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30. Stages of paralytic squint
Undergoes three stages
1. Paresis of the particular muscle
2. Overaction of the ipsilateral antagonist
3. Underaction of the antagonist of the
contralateral synergist
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31. 1. First stage
The maximal deviation is in the field of action of
the paretic muscle for e.g. In a case left LR palsy,
the deviation is maximum in levoversion
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32. 2. Second stage
As the overaction of the ipsilateral antagonist
occurs the deviation overacting, the duration
increases in the dextroversion
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33. 3. Third stage
The underaction of the contralateral synergist
occurs.this is known as inhibitional palsy
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34. Importance of hering’s law
1. Secondary deviation( fixating with squinting eye)
is more than primary deviation in paralytic strabismus
This is based in hering’s law because when the patient
fixates with the squinting eye an excess innervation
is required to the paralysed muscle to fixate and the
concomitant excess supply to the yoke muscle from
the normal eye causes excess contraction leading to
more, the so-called secondary deviation
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35. Contd…
2. Inhibitional palsy
of the contralateral antagonist muscle developing in
patients with paralytic squint is based on Hering’s law
for e.g if a patient has RSO muscle paresis and fixates
with RE on object located on patient’s left, less
innervation of RIO is required to move the eye in this
gaze, because it doesn’t have to overcome the normal
antagonistic effect of RSO muscle
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36. Third nerve palsy
The III nerve divides into two branches.
 The superior branch supplies the LPS and SR
The inferior branch supplies the MR, IR and IO
muscles.
A complete lesion of the III nerve involving both
branches will result in a deficit of elevation, adduction
and depression in abduction.
There will be an accompanying ptosis and pupil
dilatation
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37. Contd...
Aetiology
Localisation of lesion
Nuclear
Nuclear III often produces bilateral defects of ocular
motility and lid function.
The levator palpebral superioris muscles share a
common central nucleus that produces
Clinical Orthoptics, Third Edition. Fiona J. Rowe.C
2012 John Wiley & Sons, Ltd. Published 2012 by Blackwell Publishing Ltd.
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38. Neurogenic disorder
 A nuclear lesion may also result in the following:
 Unilateral III with bilateral ptosis
 Unilateral III with contralateral superior rectus
underaction
 Isolated extraocular muscle palsy of inferior rectus,
inferior oblique or medial
rectus muscles (Brown 1957)
 Bilateral III with spared levator function
(Biousse & Newman 2000, Saeki et al. 2000).
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39. Internuclear
Internuclear ophthalmoplegia
 Weber’s syndrome: III and contralateral hemiplegia
due to lesion of corticospinal tract
 Benedikt’s syndrome: III and contralateral ataxia and
intension tremor
 Claude’s syndrome: Lesion of the red nucleus and III
nucleus producing an
ipsilateral III nerve palsy and contralateral ataxia
(Broadley et al. 2001)
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40. Infranuclear
Third nerve palsy may be central, sparing the pupil or
peripheral with pupil involvement.
If the pupil is spared, the cause is most likely
vascular.
When the pupil is involved, the cause is likely to be
an
aneurysm (Goldstein&Cogan 1960).
However, pupil sparing in children (unlike in
adults) may not be helpful in differentiating the causes
of the palsy and third nerve
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41. Investigation
Visual acuity
 It is necessary to lift the ptotic lid to evaluate visual
acuity.
May be reduced due to mydriasis, particularly for near
visual acuity
Cover test
 An exo- and hypo-deviation is present
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42. Ocular motility
There will be limited elevation, depression and
adduction,which may be complete or partial
limitations, depending on the extent of paresis/palsy.
The examiner should always check for the presence of
IV nerve function by asking the patient to attempt to
look down and outwards and observe for the presence
of incyclotorsion during this movement.
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43. Contd…
In case of presence of ptosis the upper lid will have
to be raised by the examiner (or an assistant) in order
to
perform the ocular motility assessment.
It is important to check for unilateral versus bilateral
signs and extent of limitations (ductions) versus
version movements.
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44. Right 3rd
nerve palsy
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45. Investigation
Hess chart
The affected eye will show a markedly constricted
field
whereas the other eye demonstrates overaction of its
muscles
Diplopia
 There will be constant diplopia unless complete
ptosis is present and blocks the vision of the affected
eye.
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46. Hess chart of right 3rd
nerve
palsy
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47. Convergence
This will be absent if the medial rectus muscle is
paralysed.
Binocular function
This is usually absent unless the III nerve paresis is
mild and partial.
Accommodation
If the underlying cause of the lesion has resulted in
pupillary dilatation, then fibres to the ciliary body are
also likely to be involved so that accommodation will
be defective.
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48. Aberrant regeneration
change in the actions of muscles supplied by the third
nerve due to regrowth of damaged nerve fibres
following complete or severe third nerve palsy
(Shuttleworth et al. 1998).
It is liable to occur when either trauma or an
aneurysm
has caused the lesion (Cox et al. 1979, Rossillion et al. 2001).
May occur from weeks to months after the onset of
the III nerve paresis.
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49. Investigation
Cover test
Combined horizontal and vertical deviations are
common.
Ocular motility
Abnormal movements often involve the eyelids and
pupils.
There may be horizontal gaze and lid synkinesis
(Chua et al. 2000)
Limited elevation and depression with globe
retraction on attempted vertical movements or
ipsilateral adduction on attempted elevation or
depression.01/03/15
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50. Contd…
Ptosis
The lid may rise on attempted depression, adduction
and occasionally abduction (pseudo-Graefe
phenomenon).
Pupil
This may constrict on attempted adduction, elevation
and depression
(pseudo-Argyll Robertson pupil).
Convergence
This may occur on attempted elevation
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51. Cyclic oculomotor palsy
This rare condition is usually congenital and
unilateral in origin
(Burian & Van Allen 1963).
It is often associated with a partial III nerve palsy with
some degree of ptosis.
 Acquired cyclic ocular motor palsy may occur
following irradiation of the skull base and is similar to
ocular neuromyotonia
(Miller & Lee 2004).
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52. Contd…
It may also be due to a compressive lesion
(Bateman & Saunders 1983).
The condition is described as having cyclical
fluctuation in two phases:
1. Paralytic phase: There is a partial III nerve palsy.
2. Miotic phase: There is convergence, lid retraction,
accommodation and pupil constriction.
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53. Single muscle palsy
1. Medial rectus
This produces an exo-deviation, which is greater for
near fixation.
2. Inferior rectus:
This produces hyper- and exo-deviation
3. Superior rectus:
This is often bilateral and may present with a V exo
pattern.
4. Inferior oblique:
This is a feature of an A eso pattern
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54. Differential diagnosis of single
muscle palsies
MR palsy : Atypical Duane’s retraction syndrome
:Uni/bilateral internuclear ophthalmoplegia
IR palsy: Myogenic (myasthenia gravis)
: Mechanical limitation (thyroid eye disease)
: Trauma (blowout fracture)
IO palsy: Brown’s syndrome
SR palsy : Trauma (blowout fracture)
: Mechanical limitation (thyroid eye disease)
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55. Double elevator palsy
This often has a congenital origin and is presumed to
be caused by a supranuclear defect.
The superior rectus and inferior oblique muscles of
the same eye are affected
 (Jampel & Fells 1968, Strachan & Innes 1987).
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56. Investigation
Cover test
There is a hypo-deviation in the primary position that
may be manifest or latent.
Ocular motility
There is limited elevation of one eye in both
adduction and abduction.
Ptosis and/or pseudoptosis may be present.
Bell’s phenomenon is usually present.
Abnormal head posture
The chin is elevated to compensate for the palsy
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57. Contd…
Binocular function
If there is only a small angle of deviation in the
primary position, this may be controlled with or
without an abnormal head posture, resulting in a
latent hypo-deviation.
In these circumstances, binocular single vision is
present.
Forced duction test
There may be full passive movement (negative result)
or it may be positive, depending on cause that is
important for surgical planning
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58. Differential diagnosis double
elevator palsy
The following conditions should be differentiated
from double elevator palsy as they will have a positive
forced duction test:
 Blowout fracture
 Thyroid eye disease
 Brown’s syndrome
 Congenital fibrosis of the inferior rectus muscle
 General fibrosis syndrome
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59. IV (fourth) cranial nerve
The IV cranial nerve supplies the superior oblique
muscle only.
 Any lesion affecting the nerve may result in
difficulties of depression, incyclorotation and
abduction of the eye
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60. Aetiology
Location of lesion
Fourth nerve palsy may be due to lesions in the
nucleus or fascicular lesions of the midbrain.
 It can be difficult to differentially diagnose nuclear
and fascicular lesions as the IV nerves decussate
immediately after exiting the nuclei and exit the
dorsal midbrain after a very short intra-midbrain
course.
The IV nerve is not only susceptible to damage as it
exits the midbrain but also is vulnerable in the
cavernous sinus and orbital apex.
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61. Contd…
congenital or acquired.
 Acquired group may be caused by the following:
 Trauma:
Particularly bilateral cases, as the IV cranial nerve is
the only nerve to arise from the dorsal surface of the
midbrain, and therefore follows a long, winding route
that renders it susceptible to injury.
 Vascular, for example hypertension.
 Diabetes.

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62. Contd…
Space-occupying lesions.
In congenital superior oblique palsy, the tendon is
usually lax and abnormally long
(Plager 1990, Plager 1992).
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63. Investigation
Case history
In congenital cases, the patients are often affected
bilaterally.
They may present with any of the following:
1. Manifest strabismus without binocular function
2. Binocular function, but there may be an abnormal
head posture, depending on the extent of
paresis
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64. Contd…
There is often facial asymmetry in congenital superior
oblique palsy consisting of shallowing of the midfacial
region between the lateral canthus and the edge of the
mouth (Parks 1958).
This is found in three-fourth of patients with
congenital palsy (Wilson &Hoxie 1993, Paysee et al. 1995).
In acquired cases, the paresis may be unilateral or
bilateral.
Bilateral case is often associated with major closed
head trauma.
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65. Contd…
Symptoms of cyclovertical diplopia are experienced,
which worsen on downgaze.
The presence of an abnormal head posture tends to
indicate more long-standing deviations.
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66. Abnormal head posture
In unilateral IV nerve paresis, the patient may present
with chin depression with face turn and head tilt
away from the affected side.
Bilateral cases demonstrate chin depression but there
may well be no face turn or head tilt unless one side is
affected more than the other.
Persistent abnormal head posture following surgery
for IV nerve palsy should be investigated to exclude
sternocleidomastoid muscle
tightness that may have developed in congenital cases
(Lau et al.2009).
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67. Cover test
The test is performed with and without the abnormal
head posture for comparison.
A latent deviation exists if a compensatory abnormal
head posture is adopted.
When the test is repeated with the head straight, the
deviation will increase and may become manifest
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68. Contd…
The affected eye shows a hyper-deviation and an
associated esodeviation.
(However, an exo-deviation may be seen if this was
present before the onset of the palsy.)
 It is useful to note that the vertical deviation is
commonly greater on near testing than for distance.
In bilateral cases, the main deviation usually tends to
be a small-angle horizontal deviation.
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69. Ocular motility
The primary underaction of the affected superior
oblique muscle results in a number of sequelae.
There is overaction of the contralateral inferior rectus
and of the ipsilateral inferior oblique muscles.
 The contralateral superior rectus shows secondary
underaction.
The combination of these muscle effects is variable
and often depends on whether or not the deviation is
long standing
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70. Left 4th
nerve palsy
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71. Contd…
In bilateral cases, a V pattern is often present.
In the presence of this, one should always suspect a
bilateral case, especially where there is an
excyclotorsion of greater than 7 and a tendency◦
towards reversal of any hyper-deviation or diplopic
images on lateral gaze
(Hermann 1981).
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72. Contd…
Convergence
This may be reduced, either due to convergence
insufficiency or the vertical deviation.
Differentiation is achieved by correcting the
deviation and seeing if convergence improves
Field of binocular single vision
The area in which binocular single vision is retained is
displaced upwards to the affected side
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73. Diplopia
The patient experiences a greater degree of diplopia
on near testing when looking down.
The diplopia is vertical and usually uncrossed.
However, if an exo-deviation is present, the
horizontal element of diplopia will be crossed
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74. Binocular function
Assessment of binocular function is carried out with
and without the abnormal head posture, if one is
present.
Binocular single vision cannot be maintained if there
is a significant degree of torsion and therefore is often
not present in acquired bilateral palsies.
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75. Contd…
Patients who maintain binocularity tend to have a
small angle of deviation associated with a congenital
palsy.
Some patients with long-standing acquired palsies
can maintain binocularity if there is a good fusional
control with an extended vertical fusion range
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76. B/L asymmetrical 4th
nerve
palsy
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77. Torsion Diagnostic prisms
Excyclotorsion is frequently present in acquired
bilateral cases.
Fresnel prisms may be used temporarily to correct the
angle of deviation.
 If the prism alleviates the need for an abnormal head
posture, then the indication is that the IV nerve was
responsible for the abnormal head posture rather
than a non-ocular cause
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78. Differential diagnosis
thyroid eye disease, ocular surgery, orbital
fracture, neurosurgery, childhood strabismus,
skew deviation, third nerve palsy, myasthenia
gravis and decompensated hyperphoria (Tamhankar
et al. 2011).
 Typically, excyclotorsion is seen in IV nerve palsy
and incyclotorsion is seen in skew deviation.
 Furthermore, the deviation in IV nerve palsy
remains when the patient is lying down whereas
skew deviation resolves on lying down (Wong 2010).
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79. Investigations unilateral bilateral
Cover test Hyper-deviation in primary
position reflects extent of
palsy
Often only slight hyper-
deviation in primary
position
Ocular motility No reversal of hypertropia or
and diplopia on lateral
versions
Slight V pattern may be noted
Reversal of hyper-
deviation
diplopia on lateral
versions
Large V pattern
Abnormal head
posture
Chin depression, head tilt and
head turn
Chin depression
Torsion Slightly extorsion Extorsion >10◦
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80. VI (sixth) cranial nerve
The VI cranial nerve supplies the lateral rectus muscle
only.
A lesion affecting the nerve will result in defective
abduction of the eye.
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81. Aetiology
The commonly recognised causes of sixth nerve palsy
include space-occupying lesions, trauma, vascular
insults and inflammation.
 Sixth nerve palsy secondary to raised intracranial
pressure is also commonly regarded as a typical false
localising sign.
Other causes have included pseudotumor cerebri
(idiopathic intracranial hypertension), post-operative
complications, viral infection, multiple sclerosis and
otitis
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82. Contd…Congenital
 Following birth trauma
 Hereditary
 Infection (maternal)
 Failure of lateral rectus development
Acquired
This differs according to age:
 Children (Afifi et al. 1992):
– Space-occupying lesions
– Infections, bacterial or viral
- trauma
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83. Contd…
– Raised intracranial pressure
– Decompensated esophoria
– Infantile esotropia with cross-fixation
– Mobius syndrome
– Duane’s retraction syndrome
 Young adults:
– Trauma
– Space-occupying lesions
– Post-viral inflammation
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84. Contd…
●– Multiple sclerosis
– Diabetes
– High myopia
– Ophthalmoplegic migraine
Older adults:
– Vascular
– Diabetes
– Space-occupying lesions
– Senile lateral rectus weakness
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85. Investigation
Case history
Birth history may be significant.
The patient may complain of horizontal diplopia,
which is worse in the distance and/or on lateral
gaze and relatives or friends may notice the presence of
squint (esodeviation) or an abnormal head posture
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86. Contd…
Visual acuity
This may be reduced if the affected eye fails to fixate
properly due to the presence of a marked deviation.
 Amblyopia will develop in children with unilateral
strabismus.
Abnormal head posture
The face is turned towards the affected side.
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87. Contd…
Cover test
An eso-deviation is present that is often greater on
distance testing.
The test should be carried out with and without an
abnormal head posture, if one is present.
The deviation increases without the head posture but
does not necessarily become manifest
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88. Contd…
Ocular motility
The primary underaction of the affected lateral rectus
results in limited abduction and is followed by a
number of sequelae.
There is overaction of both the contralateral and
ipsilateral medial recti.
There is also secondary underaction of the
contralateral lateral rectus
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89. Rt 6th
nerve palsy
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90. Contd…
Binocular function
This is often retained in the presence of an abnormal
head posture.
As the angle of deviation is often smaller for near
fixation, binocular function is usually present on near
fixation.
In cases of head trauma, fusion may have been lost.
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91. Rt 6th
nerve palsy
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92. Differential diagnosis
Duane’s retraction syndrome,
 Infantile esotropia,
 Nystagmus block syndrome
Medial wall fracture
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93. 01/03/15 93
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