4th Nerve Palsy Flashcards
1
Q
Features of 4th nerve palsy
A
- 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
2
Q
Aetiology of acquired 4th
A
- closed head trauma
- microvascular or mid brain stroke
- tumours - not common
- myasthenia gravis
- decelerating injury
3
Q
Aetiology of congenital
A
- 38.3% unilateral
- 10% bilateral
- anatomical anomaly of superior oblique tendon, complete absence or abnormal insertion
4
Q
Features of congenital bilateral 4th N palsy
A
- 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
5
Q
Acquired 4th features
A
- recent onset of vertical diplopia
- if over 40 and no trauma suspect vascular
- subjective awareness of abnormal head posture
- history of trauma
6
Q
Unilateral palsy features
A
- not usually torsion complaints
- hypertropia
- excyclophoria/tropia
- tilting to one side
7
Q
Bilateral palsy features
A
- 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
8
Q
Muscle sequele in 4th N palsy
A
Under action of ipsilateral SO
Overaction of contralateral IR
Overaction of ipsilateral IO
Inhibitional palsy of contralateral SR
9
Q
4th nerve pathway
A
- 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
