Week 3 - 4th Nerve palsy (trochlear)

Question 1

What is IV Nerve palsy trochlear?

Answer 1

• IV Cranial Nerve Palsy causes a palsy of the Superior Oblique muscle.
• Purely a motor nerve
• Unilateral/Bilateral
• Congenital/Acquired

Question 2

What are the features of IV Nerve palsy?

Answer 2

• Loss of depression
• Loss of incyclotorsion
• Loss of relative abduction

Question 3

does Superior oblique work at near or distance?

Answer 3

Near! Therefore there will be a larger deviation at near cover test.

Question 4

What is the anatomy of IV Nerve Palsy? NEEDS FINISHED (SLIDE 6)

Answer 4

• Exits midbrain at dorsal
• Right nucleus becomes left nerve, decussation
- vice versa

Question 5

aetiology for acquired 4th nerve palsy?

Answer 5

• Closed head trauma accounts for most acquired bilateral palsies and many unilateral
• Microvascular
• Midbrain stroke
• Intracranial tumours
• Myasthenia Gravis

Question 6

aetiology for CONGENITAL 4th nerve palsy?

Answer 6

• 38.3% Unilateral and 10% Bilateral
• Anatomical anomaly of Superior Oblique Tendon, complete absence, abnormal insertion or excessively lax tendon
• Autosomal dominant form of inherited congenital superior oblique palsy

Question 7

How does congenital unilateral IVN Palsy present?

Answer 7

• Patient usually presents with an Abnormal head posture in childhood but this can also be detected quite late in life
• All children with an Abnormal head posture should have a full orthoptic/ophthalmological examination to rule out an ocular cause

Question 8

How does the abnormal head posture present? (unilateral)

Answer 8

• Head tilt unaffected side
• Head turn to unaffected side
• Chin depression
• Facial asymmetry is common in congenital
- secondary torticollis

Question 9

How does IV nerve palsy present with signs, symptoms and deviations?

Answer 9

• Intermittent diplopia can be the first sign of decompensation as the child ages
• Large Hyperphoria with the Abnormal head posture and larger
- Hypertropia without the Abnormal head posture
• Deviation will usually be greater at near
• Horizontal Deviation of 8^ occurs in 10% of cases
• Excyclodeviation can be seen on fundoscopy

Question 10

How is the Bielschowsky head tilt test done?

Answer 10

• Performed at 3 metres: not isolate muscle
• Head tilted 30 Degrees to affected side; if the hypertropia increases then SO palsy is present
• Head tilt to the unaffected side should show very little difference in the deviation suggesting a Contralateral Superior rectus under action
• Positive result should be minimum 5^ difference from tilting right to left

Question 11

What is the Parks 3 step?

Answer 11

• Cover test performed in primary position

• Alternate Cover Test performed on extroversion and laevoversion to assess the greater vertical deviation
• BHHT is then performed tilting 30 degrees right and left and noting the increase in hyper deviation

Question 12

How to differentiate if the RSO/LSR Palsy?

Answer 12

• Tilt right - right eye is intorted by the superior oblique and the superior rectus
• The depressing action of the SO is balanced by the elevating action of the SR and the eye remains level
• If there is a SO Palsy the elevating action of the SR is unopposed and the hyperdeviation increases
• This is a positive result

Question 13

How does congenital Bilateral IVN palsy present?

Answer 13

• Usually a V-Pattern Esotropia with Hyperdeviation of the non fixing eye
• Chin depression
• +ve Bielschowsky on either side confirms a bilateral palsy. Reversal of the hypertropia on right and left tilt
• No torsional symptoms but obvious torsion on fundoscopy

Question 14

What is the presentation acquired IVN palsy?

Answer 14

• Recent onset of vertical diplopia
• No evidence of enlarged Vert Fusion ranges
• Subjective awareness of AHP
• History of trauma

Question 15

Unilateral palsy symptoms?

Answer 15

• Torsion is rarely complained of in unilateral palsies

• Examination is as before with a positive BHHT
• Hypertropia
• Excyclophoria/tropia

Question 16

Bilateral palsy symptoms?

Answer 16

• Torsional diplopia is the main symptom. This prevents fusion.
• Excyclodeviation may exceed 10 degrees in PP
• Marked chin depression may be seen
• Reversal of the hypertopia on right and left gaze. With a +ve BHHT on either side
• V Eso pattern

Question 17

What do you look for during the history symptoms of palsies?

Answer 17

• As with all Neurogenic palsies
• Detailed History - microvascular causes
• History of significant trauma - skull#, loss of consciousness, subdural hematoma
• Full blood count, blood sugar levels, serum lipids

Question 18

Definition of muscle sequelae?

Answer 18

• When one muscle is weak or limited muscle sequelae develops determined by Hering’s Law of equal innervation and Sherington’s Law of reciprocal innervation

Question 19

Definition of Hering law?

Answer 19

• When an impulse goes to a muscle, causing it to contract, a simultaneous and equal impulse goes to its contralateral synergist to contract by an equal amount

Question 20

Definition of Sherringtons law?

Answer 20

• When increased innervation is sent to a muscle to cause it to contract, decreased innervation goes to it’s direct antagonist, which is therefore relaxed.

Question 21

How does muscle sequelae develop?

Answer 21

• Overaction of the Contralateral synergists according to Hering’s Law of equal innervation. - Immediately
• Overaction of the Ipsilateral antagonist according to Sherrington’s Law of reciprocal innervation - Time
• Secondary inhibition of the Contralateral Antagonist with Hering’s Law. This happens because the overaction of the antagonist in the affected eye requires less innervation -
More Time

Question 22

What are the muscle sequelae in a 4th nerve palsy?

Answer 22

• Under-action of ipsilateral SO
• Over-action of contralateral IR
• Over-action of ipsilateral IO
• Inhibitional palsy of contralateral SR

Question 23

How do you Investigate Torsion?

Answer 23

• Can be measured Subjectively or Objectively
• Double Maddox Rod, Synoptophore, Torsionometer, Dulley Adaptation on Lees Screen
• Synoptophore allows you to measure the deviation and torsion together in 9 positions of gaze
•Cyclodeviation is worse on depression and a barrier to fusion

Question 24

Difference between unilateral palsies and bilateral palsies torsions?

Answer 24

• Unilateral palsies may produce 5/6 degrees of excyclotorsion, which can be fused
• Bilateral palsies typically produce excycotorsion of 15 degrees and this cannot be fused

Question 25

Difference between Unilateral and Bilateral 4th nerve palsy for AHP, BHH test, hypertropia

Answer 25

Unilateral Vs Bilateral:
• AHP: Contralateral Head tilt vs Chin depression
•BHHT: +VE Unilat vs +VE Bilat
• Hypertropia: No reversal on versions and greater than 5^ vs Reversal on versions and less than 5^

Question 26

Difference between Unilateral and Bilateral 4th nerve palsy for Excyclotropia and V pattern?

Answer 26

Unilateral vs Bilateral:
• Excyclotropia: Not symptomatic and less than 10 degrees vs Symptomatic and greater than 10 degrees in acquired palsies
• V Pattern: Uncommon vs common

Question 27

Difference between Congenital and Acquired 4th nerve palsy for Facial Asymmetry, AHP, Cyclotropia and Vertical fusion?

Answer 27

Congenital vs acquired:
• Facial Asymmetry: Common vs none
• AHP: Presents in photographs vs aware of holding head in awkward position
• Cyclotropia: Not a symptom vs sympomatic
• Vertical fusion: increased vs normal