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Case of the week 59 ( June 2012 )
Left sixth Nerve Palsy


19 years old man complaining of acute onset of double vision started 3 months ago after car accident , Both CT and MRI brain and orbit were normal

   
 

 See video of this patient
 


The diagnosis of  6th Nerve Palsy should not present any difficulties :

  1.There is marked limited abduction of the paretic eye .

  2.The greatest esotropia occurs on attempts to abduct the paretic eye .

  3. Most patients will complain about double vision in lateral gaze and assume a compensatory face turn in the direction of the paralyzed muscle

Several recent studies have addressed that in non-traumatic unilateral  cases 78% experienced spontaneous recovery  by 24 weeks

herapy

In determining whether a patient with acute paralytic strabismus will require therapy during the recovery period which may be as long as 6 munths, one must establish the extent to which the paralysis interferes with comfortable single binocular vision.

The eyes rarely move more than 15 degrees from the primary position during normal use. Diplopia occurs in extreme positions of lateral  gaze is tolerated by most patients. Like our patient here  with a paretic left 6th nerve palsy, he may be comfortable with his eyes in primary position and in right gaze but he experiences diplopia only in lt gaze.

A slight head turn toward the left may eliminate the need to move the eye into that position, in which case therapy obviously is not required. However, what is easily tolerated by one patient may not be acceptable to another.

 Indications for therapy are the presence of diplopia in the practical field of fixation and inability to maintain single binocular vision without a conspicuous anomalous head posture.

In desperate situations in which single binocular vision cannot possibly be restored by any means, occlusion of one eye, preferably the sound eye, is a last resort to create visual comfort for the patient.

Several methods have been advocated to prevent secondary contracture of the antagonist of a paretic muscle in lateral rectus paralysis . The antagonistic muscle ( MR ) could be injected with  botulinum toxin .

Examination of the patient after 6 months of the onset of head injury will reveal the extent to which the lateral rectus muscle may recover ( partial or full recovery ) , according to the finding data at that time , the surgical plan - if needed - could be done.

A maximal recession-resection procedure suffices in most instances of incomplete 6th nerve paralysis to restore a useful field of single binocular vision and to eliminate the head turn.

 For a complete paralysis  I prefer to transpose the temporal half of each vertical rectus

muscle.  The Jensen muscle union is less frequently performed now than only a few years ago since it has been shown that this procedure does not necessarily protect against anterior segment ischemia .



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