differential diagnosis of superior oblique and superior rectus palsy

Question 1

how to differentiate between right superior oblique and left superior rectus

Answer 1

beilshowsky head tilt test

To differentiate between RSO and LSR
Method
Patient fixes target at 3m
Tilt head to the right
Observe right eye for elevation
Alt CT to check if increase in R hyper deviation
PCT tilt right, primary position & tilt left (tilt prism the same amount as head)
Increase in R hyper deviation of more than or equal to 5PD noted

Question 2

describe. the results of the bht

Answer 2

Results
If RSO palsy, right eye elevates and RHT increases on PCT = positive result
If LSR palsy, no change in position of right eye, no increase in RHT = negative result
A positive result confirms a superior oblique palsy
but
A negative result does not eliminate it.

]Tilt to one side – SR and SO intort the eye
Balance between elevating and depressing action

In SO palsy, when the head is tilted to the affected side the SR contracts more and the adduction and vertical action is unopposed due to the palsy. Therefore an increase in vertical occurs

Question 3

what is a masked bilateral 4th palsy

Answer 3

If a bilateral IV nerve palsy is asymmetric then it may appear to be unilateral

Masked bilateral IV nerve palsy

Question 4

where do asymmetric palsies mask the deviation

Answer 4

Asymmetric palsies may mask the deviation in the least affected eye

Signs of SOP appear in the normal eye of a patient after strabismus Sx for SOP in the contralateral eye.

Despite absence of signs of bilateral palsy before Sx, a palsy may be revealed in the previously unaffected eye

Important for surgical planning

Question 5

what is the difference between a unilateral and bilateral 4th nerve palsy

Answer 5

e.g. unilateral 4th in the right eye

you wouldn’t have underaction of the left superior oblique

or right inferior rectus overaction

or left inferior oblique overaction and right superior rectus underaction

Question 6

what are characteristics of a bilateral 4th nerve palsy

Answer 6

ahp - bilateral - head down

unilateral - head down , head turn to affected side , head tilt to unaffecetd side

bilateral ct - small vertical/ non

unilateral - hypertropia of the unaffected eye

om - reversal of the hypertropia v eso more than 25 dioptres for bilateral for unilateral
hypertropia max on contralateral depression

field of bsv - bsv upper field
bsv upper ipsilateral field in unilateral

torsion more than 10 degrees of excel for bilateral and less than 10 of excyclo for unilateral

Question 7

what is the difference between muscle sequelae in unilateral and bilateral 4th nerve palsies

Answer 7

unilateral

RLR u/a
LMR o/a
RMR o/a
LLR u/a

bilateral

RLR u/a
LMR o/a
RMR o/a
LLR u/a

Question 8

describe the differences in charcatersitcs between a right superior oblique and left superior rectus palsy

Answer 8

rso ptosis = absent
lsr - left ptosis

ahp - rso- head down , turn and tilt left
lsr head up turn and tilt left

history - trauma , non specific

deviation - eso in right superior oblique and exo in left superior rectus

diplopia and vertical deviation - max leave depression for right superior oblique and max leave elevation for left superior rectus

symptoms - greater for near on rso and greater for distance for left superior rectus

and a postive bht for right superior obliques and -ve. for left superior rectus

Question 9

what is the pattern of muscle sequelae

Answer 9

primary affected muscle - contralateral synergist

ipsilateral antagonist

contralateral antagonist

Question 10

what muscle sequelae develops in a right superior oblique

Answer 10

Right hyper (R/L)

RSO u/a

LIR o/a
RIO o/a
LSR u/a

Question 11

what muscle sequelae develops in a left superior rectus palsy

Answer 11

Left hypo (R/L)

Sequelae:
LSR u/a
RIO o/a
LIR o/a
RSO u/a

Question 12

what findings have been found in bilateral 4th nerve palsy

Answer 12

Kushner (1988)
reversal of HT in any oblique fields of gaze
subjective extorsion >10 in primary position
chin down posture - no tilt
bilateral fundus extorsion
small HT in primary with large HT on tilt to both sides
V pattern of >20

Question 13

what is the difference between excylotorsion on unilateral and bilateral 4th nerve palsies

Answer 13

Georgievski (1995)
Unilateral excyclo = 5.6 (range 3.7 - 8)
Bilateral excyclo = 9.6 (range 5 - 17.3)

Roper-Hall & Chung (1997)
Bilateral if cyclotorsion >15 