Differential diagnosis of SO/SR, bilateral SO, BHTT

Question 1

To know …

Answer 1

SO palsy and contralateral SR palsies
Unilateral and bilateral IV nerve palsies
Unilateral and bilateral VI nerve palsies

Question 2

Sequelae of RSO - Right hyper (R/L)

Answer 2

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

Question 3

Sequelae of LSR- Left hypo (R/L)

Answer 3

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

Question 4

RSO

Answer 4

Ptosis- absent
AHP- down, turn and tilt left
History - Trauma
Deviation- ESO
Diplopia and V deviation- Max leave depression
Symptoms- greater for near
BHTT +ve

Question 5

LSR

Answer 5

Ptosis- L ptosis if lesion before splitting
AHP- head up, turn and tilt left
History- non specific
Deviation- EXO
Diplopia and V deviation- Max lasso depression
Symptoms- greater for distance
BHTT -ve

Question 6

If ptosis present rules out

Answer 6

SO involvement

Question 7

Bielchowsky head tilt test- BHTT use

Answer 7

To differentiate between RSO and LSR

Question 8

BHTT method

Answer 8

Patient fixes target at 3m- because not favouring any muscles
Tilt head to the right
Observe right eye for elevation
Alt CT to check if increase in R hyper deviation
PCT with prism tilted right, then in primary position & tilt left (tilt prism the same amount as head)
Increase in R hyper deviation of >5PD noted

Question 9

Results of BHTT

Answer 9

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 in SO palsy so it does not eliminate the diagnosis.

Question 10

BHTT explanation

Answer 10

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 11

Bilateral/ unilateral IV nerve palsy

Answer 11

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

Question 12

Masked bilateral IV nerve palsy findings

Answer 12

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 13

Bilateral IV nerve palsy

Answer 13

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

LSO u/a
RIR o/a
LIO o/a
RSR u/a

example HESS- Asymmertical - greater SO under action on RE AND its asymmertical - greater SO under action on RE

Question 14

Unilateral IV nerve palsy

Answer 14

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

Question 15

Characteristic of bilateral IV nerve palsy

Answer 15

AHP- head down
CT- no/ small
OM- reversal of HT, V eso >25D
Field of BSV- BSV upper field
Torsion- >10 degree exyclotorsion

Question 16

Characteristic of unilateral IV nerve palsy

Answer 16

AHP- Head down, Head turn to affected side, Head tilt to unaffected side
CT- HT to affected eye
OM- HT max on contralateral depression
Field of BSV- BSV upper ipsilateral field
Torsion- <10 degree exyclotorsion

Question 17

Bilateral IV features - Kushner (1988)

Answer 17

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 18

Torsional ranges for bilateral IV

Answer 18

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

Question 19

Masked bilateral palsy

Answer 19

Think of possibility of bilateral case in all SO palsies unless proven otherwise

Look for subtle clinical signs

Warn patients with SOP pre-op of possible reversal

Question 20

Unilateral VI nerve palsy muscles

Answer 20

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

Question 21

Bilateral VI nerve palsy muscles

Answer 21

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

Question 22

Characteristics of bilateral VI nerve palsy

Answer 22

AHP
CT- eso deviation
OM – full muscle sequelae
PCT- eso deviation no difference between bilateral and unilateral
Hess

Question 23

HESS IN

Answer 23

PP

Question 24

Consider

Answer 24

differential diagnoses even in what appear clear cut cases

consider aetiology and where lesion would be/is. Remember anatomy 4th nerves cross 6th nerves don’t.

Question 25

TO DO

Answer 25

Practice BHTT including PCT with tilt
Reading
Von Noorden & Campos p198-9, 437-8
Ansons & Davis p90-2, 376-87, 392
Leigh & Zee p407-9, 427-9