4th Nerve Palsy

Question 1

Features of 4th nerve palsy

Answer 1

• usually bilateral
• loss of depression
• loss of incyclotorsion
• right nucleus affects left nerve
• loss of relative abduction
• AHP to affected side
• facial asymmetry
• intermittent diplopia
• long standing can accommodate a lot of vertical deviation
• excyclotorsion

Question 2

Aetiology of acquired 4th

Answer 2

• closed head trauma
• microvascular or mid brain stroke
• tumours - not common
• myasthenia gravis
• decelerating injury

Question 3

Aetiology of congenital

Answer 3

• 38.3% unilateral
• 10% bilateral
• anatomical anomaly of superior oblique tendon, complete absence or abnormal insertion

Question 4

Features of congenital bilateral 4th N palsy

Answer 4

• V pattern esotropia with hyper deviation in non fixing eye
• both eyes can’t depress
• chin depression
• positive BHHT confirms bilateral palsy on both sides
• no torsional symptoms but obvious torsion on fundus

Question 5

Acquired 4th features

Answer 5

• recent onset of vertical diplopia
• if over 40 and no trauma suspect vascular
• subjective awareness of abnormal head posture
• history of trauma

Question 6

Unilateral palsy features

Answer 6

• not usually torsion complaints
• hypertropia
• excyclophoria/tropia
• tilting to one side

Question 7

Bilateral palsy features

Answer 7

• torsional diplopia - main symptom and prevents fusion
• excyclodeviation exceeding 10 degrees
• chin depression
• reversal of hypertropia on R+L gaze
• positive BHHT on either side
• V eso pattern

Question 8

Muscle sequele in 4th N palsy

Answer 8

Under action of ipsilateral SO
Overaction of contralateral IR
Overaction of ipsilateral IO
Inhibitional palsy of contralateral SR

Question 9

4th nerve pathway

Answer 9

• lies in dorsal midbrain
• leaves brainstem in various fine roots
• pass posteriorly emerging from opposite nucleus
• rootless travel forward around midbrain to cavernous sinus
• mild trauma give unilateral palsy
• severe trauma bilateral