Surgical Management of Neurogenic Palsies Flashcards
What are the aims of surgery?
- Relieve symptoms
- Restore BSV
- Enlarge field of BSV
- Reduce / eliminate AHP
- Improve alignment
- Restore concomitance
What factors must we consider before making a surgical decision?
- Extent of muscle sequelae
- Suitability of each muscle for type of surgery
- Size of deviation in P.P. and down gaze
- Presence of horizontal/ vertical components
- Presence and amount of torsion
Paralysis / paresis - Longstanding / recently acquired
(Fusion amplitude can help) - AHP
- Forced duction test (FDT)
What are some general surgical principles?
- Consider the suitability of each muscle. If no function is present, avoid that muscle or consider a transposition procedure.
- An elevator is chosen in preference to a depressor when weakening, as diplopia is less troublesome on elevation
- Surgery may be performed in stages (to assess the outcome of each individual stage), or at one stage (dependant upon the extent of the palsy)
- Botulinum toxin may be used in conjunction with muscle surgery
- For single muscle palsies:
Where some function is present, strengthen the affected muscle
Weaken the o/a contralateral synergist
Weaken the o/a ipsilateral antagonist
Strengthen the u/a contralateral antagonist
When should we consider a transposition procedure?
- Consider the suitability of each muscle. If no function is present, avoid that muscle or consider a transposition procedure.
When weakening a muscle in surgery do we prefer an elevator or depressor?
- An elevator is chosen in preference to a depressor when weakening, as diplopia is less troublesome on elevation
What are transposition procedures?
Involves moving the whole or part of a muscle in order to change the primary or secondary action of that muscle. Whole muscle can be done on either horizontal or vertical recti muscles.
What are the names of the whole muscle transpositions?
- Knapp
- Foster (posterior fixation sutures)
What are the names of the part muscle transpositions?
- Hummelsheim
- Jensen
What is the Hummelsheim procedure? When is it used?
A transposition procedure of part of the muscle.
Used in CNVI palsy to move the temporal halves of the IR and the SR which are inserted to the LR to allow them to become abductors in leu of the LR.
Often needs to be combined with MR recessions.
Can cause an anterior segment ischaemia because of the number of muscles being worked on
What’s a risk of the Hummelsheim procedure?
Due to the number of muscles being worked on it can caused anterior segment ischaemia
What is the Jensen procedure?
A part muscle transposition procedure. The temporal halves of the IR and SR are joined to the divided halves of the LR.
Utilises transposition without disinserting the tendons of the muscles, thus maintaining anterior segment blood supply
Needs to be combined with MR recession
What is the Knapp procedure?
A full muscle transposition procedure.
Used to correct a double elevator palsy
MR & LR are detached and reinserted along medial (MR) & lateral borders (LR) of SR. This makes the LR and MR into elevators.
If an IO palsy on its own then move the LR and MR down to the IO to make them elevators.
What is the Knapp procedure used for?
To correct double elevator palsy (congenital condition, typically have a ptosis, SR and IO palsy)
What is the Inverse Knapp procedure?
Used to correct IR palsy by detaching the MR & LR and reinserting these along the medial and lateral borders of the IR
What is the Foster Technique?
A full muscle transposition surgery of the vertical recti that are then inserted at the LR.
Posterior fixation sutures (non-absorbable) are then placed 8mm behind the LR insertion which increases abducting force
What does the Foster technique improve?
Abducting force through use of posterior fixation sutures which reduces the need for surgery on the MR which means avoiding risk of anterior segment ischaemia
What surgery would you do in Duane’s Syndrome?
Foster Technique
What is the Foster Technique used for?
Duane’s Syndrome
What is the Scott Procedure being used in replacement of?
The Scott procedure is becoming increasingly popular superseding the Faden (posterior fixation suture) technique
What is the Scott Procedure?
A resection-recession procedure on a single palsy
When is the Scott Procedure used?
Used in incomitant strabismus with small deviation in P.P. and incomitance in eccentric gaze in the field of action of the paresed muscle
Used in CNIII, CNIV & CNVI palsy
What is the aim of the Scott Procedure?
Combine a large resection with recession of a single muscle (so the resection and recession is just on one muscle) will reduce the action of the over-acting yoke muscle and thus reduce incomitance
What muscle(s) do you work on using the Scott procedure in CNIII palsy?
3rd Nerve palsy - the resection-recession is on the LR