Neuro-ophtho Q

[golgi]

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Hi,

Just a quick Q. I am finishing up my FP rotation now and saw an interesting case involving apparent nerve palsy of the eye. This is probably something simple but I am just staring out and maybe some of you more seasoned ophthos could help me understand it a bit.

The patient was in an MVA 13 months ago and has had unremiting neck pain , especially on the left side (hit on driver's side) ever since. About 8 month's ago she noticed her left eye turns out (lateral gaze). On PE, the eye straightens out when I cover up the right eye. There's no nystagmus and she complains of H/A when I use the H-test to evaluate EOM. No PMH, no meds, no Sx.

What exactly is her problem and would the MVA have anything to do with this? Although i doubt it, would this condition be amenable to treatment?

Thanks for your help!

 

[Andrew_Doan]

Perhaps she's damaged her central fusional control? This may occur with severe head trauma which may or may not recover.

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=10623952

Acquired central fusional disruption with spontaneous recovery.
Lee MC.

Strabismus. 1998 Dec;6(4):175-179.

Moorfields Eye Hospital, London, United Kingdom

Acquired loss of central fusion occurs most frequently after severe head trauma. It has also been described as a result of disruption of binocular function by unilateral deprivation from a cataract and following mid-brain injury due to vascular lesions, tumours or abscess. Symptoms include diplopia in all positions of gaze associated with a squint of variable size. Occasionally some patients experience a spontaneous, partial recovery of fusion, which may be manipulated with strabismus surgery to minimise diplopia. Recovery of fusion may take months or even a few years to occur. We present two cases of patients who lost fusion but later regained it spontaneously with a high degree of stereopsis. Neither patient required strabismus surgery. In the first case, fusion was lost following a severe head injury which resulted in unconsciousness and a unilateral vitreous haemorrhage. The second case followed the removal of a long-standing, unilateral cataract.

___________________________
For strabismus problems, there are always these options to consider:
1) do nothing
2) prism
3) patch one eye (alleviate double vision and perhaps headaches if associated with diplopia)
4) surgery

 

[noish]

I did do a neuro-oph rotation...

So we know that basically she's got an exotropia worse in left lateral gaze. At this point you don't know if it's the left or right eye. The next thing to do is find out if the diplopia is vertical or horizontal. If it's vertical I'm thinking right away that it's a 4th (more later).

From the information given you know it's probably the obliques. Now see if it's worse in right or left head tilt. I bet it's worse in right head tilt. That would make it a right 4th nerve palsy since the right superior oblique isn't working, which is super common following accidents since it's the longest and thinnest cranial nerve. The thing is not to get sidetracked on which eye the patient is complaining about -- if they're right eye dominant and having diplopia, they'll fix with that eye even though it's the side that's been injured, so it looks like the left eye is going out.

noish

 

[Andrew_Doan]

I did do a neuro-oph rotation...

So we know that basically she's got an exotropia worse in left lateral gaze. At this point you don't know if it's the left or right eye. The next thing to do is find out if the diplopia is vertical or horizontal. If it's vertical I'm thinking right away that it's a 4th (more later).

This is a good thought. Keep in mind, however, a CN 4 palsy will give you a hypertropia that is worse in the contralateral direction of gaze not an exotropia.

You eluded to the three-step-test that maps out CN palsy for vertical diplopia.

For a right superior oblique palsy, there is a right hypertropia in primary gaze that is worse in left gaze and right head tilt.

In contrast, a left superior oblique palsy, there is a left hypertropia in primary gaze that is worse in right gaze and left head tilt.

An easy way to remember it is right is right, left, right and left is left, right, left.

Here's a link to explain how to do the test: http://www.homestead.com/emguidemaps/files/diplopia2.html#Parks-Bielchowsky three-step testing

Clarification needed by OP, is the deviation there all the time or does the left eye spontaneously turn out?

 

[JennyW]

___________________________
For strabismus problems, there are always these options to consider:
1) do nothing
2) prism
3) patch one eye (alleviate double vision and perhaps headaches if associated with diplopia)
4) surgery[/QUOTE]

One important modality that was not mentioned was vision therapy which can be very effcective in strabismus and head trauma.

Jen

 

[noish]

SR IO IO SR
IR SO SO IR
OD OS
(drawing for the 3-step test)
Right? So if there's an XT, you circle IO and SO on both sides. And if there's a, say, right hyper you circle IR and SO for OD, and IO and SR for OS. And if it's worse on right head tilt you would circle SR and SO for OD, which points to a right 4th. Sorry for the poor explanation, but I'm trying to reason why I thought you could have a 4th with an exotropia.

A superior oblique palsy will give you the inability to look down and in. So you will get an XT from it as well as a hyper. That's why the vertical diplopia is never truly vertical. So if the left eye "goes out" on left lateral gaze, it could be from an inability of the right to look down and in, and the patient is fixing with her right eye. Or am I misunderstanding the 3 step test?

Vision exercises only work for something like a congenital palsy that is slightly decompensated. A palsy from an accident will usually require surgery.

noish

 

[Andrew_Doan]

Noish,

The 3-step is used for vertical diplopia only. If the patient has anything other than a hypertropia or hypotropia, then the 3-step test is not used.

Step 1: identify which side the hypertropia is on. If it is on the right, then you circle the right IR & SO and the left IO & SR. These are the muscles that can be weakened to produce a right hypertropia.

Step 2: For a right hypertropia, you then ask if the right hypertropia is worse in right or left gaze. Let's say the right hypertropia is worse in left gaze, then you circle the right IO & SO and the left SR & IR. The 'patient's left sided set of muscles' on the H-diagram are circled.

Step 3: Tilt the head and ask what makes the hypertropia worse. If it's the right SO palsy, then the patient will complain that tilting the head to the right will make the vertical deviation worse. You then make a diagonal circle in the direction of the tilt: right SR & SO and left IO & IR.

In the test above, notice the hyperdeviation is on the right side and is worse in left gaze and with a right head tilt: Right, Left, Right. This maps out to the Right SO muscle.

To understand why this occurs, you must know the primary, secondary, and tertiary functions of the muscles. The SO is mainly an intorter and depressor (rotate eye towards the nose and brings the eye down), and the SO is a weak abductor (brings the eye out). A palsy of the SO results in the inability to rotate the eye in and to depress the eye when the eye is in adduction (turned towards the nose). Because of the physics of how the SO is attached to the globe, it depresses the eye the best when the eye is looking in. This is why a SO palsy will give the patient the inability to "look down and in". A SO palsy doesn't generally result in the eye turning out. Also remember that the tertiary function of the SO is to turn the eye out, so if anything, the eye should be turned in slightly. However, the tertiary function of the SO is so weak compared to the lateral & medial recti, a horizontal deviation is not appreciated.

To confirm the SO palsy, the head tilt is used. When you tilt the head to the right, the left eye extorts and right eye intorts to maintain visual fixation. When you tilt your head, the image is fixed because the eyes are dynamic and adjusting. In a right SO palsy, if you tilt the patient's head to the right, the left eye extorts fine but the right cannot intort due to the SO palsy. The other intorter for the right eye is the right SR (this is why the right SO & SR are circled on the H-diagram); however, the SR is a stronger elevator than intorter. Thus, for every degree of intortion by the SR, there is several fold degrees of elevation; as a result, the patient's vertical deviation is worse when the head is tilted towards the SO palsy due to overaction of the right SR.

In the H-diagram, the muscle that receives 3-circles is the muscle that is weak.

 

[Andrew_Doan]

I've included a drawing of the 3-step test for a right superior oblique palsy.

Step 1 - Green

In primary Gaze:
The depressors for the right eye are the right IR and SO.
The elevators for the left eye are the left SR and IO.

Step 2 - Blue

In left gaze:
The elevators/depressors for the right eye are the right IO and SO.
The elevators/depressors for the left eye are the left SR and IR.

Step 3 - Red

In right head tilt:
The intorters of the right eye are the right SO and SR.
The extorters of the left eye are the left IO and IR.