4th NP Flashcards
features of 4th
→Loss of Depression
→ Loss of incyclotorsion
→ Loss of Relative abduction
Aetiology of acquired 4th
- Closed head trauma accounts for most acquired bilateral palsies and many unilateral
- Microvascular
*Midbrain Stroke
*Intracranial tumours
*Myasthenia Gravis
aetiology of congenital unilateral 4th
AHP in childhood - can also be detected quite late in life
All children with an AHP should have a full orthoptic/ophthalmological examination to rule out an ocular cause - any head tilt think 4th
→ Facial asymmetry is common in congenital palsies
→ It develops secondary to the torticollis
→ Reduction in the distance between the lateral canthus and the corner of the mouth on the side of the head posture
signs of congenital unilateral 4th
Intermittent diplopia can be the first sign of decompensation as the child ages
Large Hyperphoria with the AHP and larger Hypertropia without the AHP
Deviation will usually be greater at near - symptoms worse at near as SO works at near
Horizontal Deviation of 8^ occurs in 10% of cases ( Telander et al 2011)
Excyclodeviation can be seen on fundoscopy
what is the Bielschowsky Head Tilt Test
- Performed at 3 metres
□ Head is tilted 30 Degrees to the affected side and if the hypertropia increases then a SO palsy is present
□ Head tilt to the unaffected side should show very little difference in the deviation suggesting a Contralateral SR u/a
□ Positive result should be minimum 5^ difference from tilting right to left
what is park 3 step
Cover Test performed in Primary Position
□ Alternate Cover Test performed on dextroversion and laevoversion to assess the greater vertical deviation
□ BHHT is then performed tilting 30 degrees right and left and noting the increase in hyperdeviation
Explanation
· RSO/LSR Palsy
· 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
findings of congenital bilateral 4th NP
- Usually a V-Pattern Esotropia with small 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
findings of Acquired 4th NP
- Recent onset of Vertical Diplopia
- No evidence of enlarged Vert fusion ranges
- Subjective awareness of AHP
- History of trauma
findings of Unilateral Palsy
- Torsion is rarely complained of in unilateral palsies
- Examination is as before with a positive BHHT
- Hypertropia
- Excyclophoria/tropia
findings of Bilateral Palsy
- 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
Investigations of 4th
As with all Neurogenic palsies
→ Detailed History – microvascular causes
→ History of significant trauma – skull#, loss of consciousness, subdural haematoma
→ Full blood count, blood sugar levels, serum lipids
Orthoptic investigation of 4th
VA n+d
CT n+d with/without AHP
OM
BHTT / Parks 3 step
lees/hess
bagolini to prove bsv
PFR - horiz and vert
measure torsion with double maddox rod
how to Investigate Torsion
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
· 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
muscle sequelae of 4th - LEARN FOR ALL MUSCLES
underaction of ipsilateral SO
Overaction of contralateral IR
Overaction of ipsilateral IO
inhibitional palsy of contralateral SR
