The document discusses Fourth Nerve Palsy (SOP), which causes weakness of the superior oblique muscle. It describes the anatomy of the fourth cranial nerve and the effects of SOP, including ipsilateral hypertropia that increases in opposite gaze. Common causes are trauma, vascular issues like hypertension, and diabetes. Clinical findings are outlined, along with classification systems. Management involves investigating for underlying causes, using prisms for small deviations, and surgery like weakening overacting muscles for large deviations. Surgical techniques are provided to address specific muscle weaknesses or torsion.

1. Fourth Nerve Palsy (SOP)
SIRAJ SAFI

2. Anatomy
• The fourth (trochlear) cranial nerve supplies only the
superior oblique muscle.
• Key features
• It is a very long and slender(slim) nerve, increasing
its vulnerability.
• It is the only cranial nerve to emerge from the dorsal
aspect of the brain.
• innervating the superior oblique muscle contralateral
to its nucleus.

3. Fourth nerve
Internal carotid artery
Posterior communicating
artery
Oculomotor nerve (III)
6th nerve

4. Fourth nerve palsy:
 The most common isolated cyclovertical muscle
palsy (congenital and acquired)
 Function of the superior oblique muscle:
 Incycloduction in abduction
 Depression in adduction
 Abduction

5. Trauma
Vascular, for example hypertension.
 Diabetes
 Space-occupying lesions
Other
Aetiology

6. Fourth nerve palsy Clinical picture:
 Ipsilateral hypertropia, excycloduction,
 V. Esodeviation
 The torsional deviation increases in lateral gaze to one
side, while the vertical deviation increases on opposite
lateral gaze.
 For example, weakness of the left superior oblique results
in – VD, which increases on right gaze and excyclotropia
which increases on left gaze
 Combined vertical and torsional diplopia, increasing in
downgaze

7. Fourth nerve palsy Clinical picture:
 AHP –
typical chin depression and head tilt and face
turn to the opposite shoulder
 Bielschowsky head tilt test positive hypertropia
increases when head tilted to ipsilateral shoulder
 EOM: limitation of depression in adduction

8. Fourth nerve palsy Clinical picture:
 Muscle sequelae:
 Overfunction of ipsilateral inferior oblique
muscle
 Overfunction of contralateral inferior rectus
muscle
 Underaction of contralteral superior rectus
muscle (“inhibitional palsy of contralateral
antagonist)

9. Management:
•In recent cases ,investigation and wait till
6 months if recovery occur
•Prism for small vertical deviations
•Surgery for large decompensating vertical
deviation

10. The fields of greatest deviation should be matched to
the muscles that exert their strongest
action in those fields.
For example, if the inferior oblique muscles overact,
this should be recessed.
If the inferior oblique does not overact and the
ipsilateral superior rectus is restricted, the superior
rectus should be recessed.
If the superior oblique is lax, it should be tucked.
Management

11. Management
 If the deviation is 15 prism pd. With an
overacting antagonistic inferior oblique
muscle, then weaken the inferior oblique.

12. Generally, for large-angle deviations
with/without torsion, surgical procedures
include the following:
Weaken the overacting muscles:
– ipsilateral inferior oblique recession
– contralateral inferior rectus recession
Management

13. Management
 If the deviation is greater than 35 prism
dpt. In primary position, consider 3
muscle surgery.
 This might include recession of the
overacting antagonistic inferior oblique
muscle and vertical rectus muscle surgery
as necessary

14. For torsion, a Harada–Ito (Fell’s
modification) can be performed (Harada&Ito
1964).
In this procedure, the anterior portion of the
affected superior oblique tendon is placed
further anteriorly and laterally
Management

16. (LSOP)

17. SOP can be classified according to a grading system based on the
gaze position or positions of greatest vertical misalignment: Knapp
Classification
Class I: greatest hypertropia in opposite up oblique field
Class II: greatest hypertropia in opposite down oblique field
Class III: greatest hypertropia in entire opposite field
Class IV: greatest hypertropia in entire opposite field and across the
lower field
Class V: greatest hypertropia across lower field
Class VI: bilateral SOP
Class VII: traumatic paresis combined with Brown's syndrome

20. investigation SO SR
Cover test Hyper-deviation if
fixing with
unaffected eye
Deviation greater for
near
Hypo-deviation if
fixing with
unaffected eye
Deviation greater for
distance
AHP Chin depression Chin elevation
EOM Increase in angle on
depression
Increase in angle on
elevation
Hess Greatest negative
displacement
on depression
Greatest negative on
elevation
Extorsion common rare
Bielschowsky
head tilt test
Usually positive Usually negative

21. Investigation Unilateral Bilateral
Cover test Hyper-deviation in primary
position reflects extent of palsy
Often only slight hyper-
deviation
in primary position
EOM 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
AHP Chin depression, head tilt and
head turn
Chin depression
Torsion Slight extorsion Extorsion >10◦
Head tilt test Positive with head tilt to
affected side
Positive with head tilt to
either
shoulder
Unilateral and Bilateral SO palsy

22. THANK YOU