What are the nonsurgical treatments for trochlear nerve palsy (fourth nerve palsy)?

Updated: Oct 08, 2019
  • Author: Zafar A Sheik, MD, MD; Chief Editor: Andrew G Lee, MD  more...
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Prisms may be used for patients with small deviations and diplopia without torsional component. Incomitance of deviation often limits usefulness of this therapy.

Botulinum toxin also has been studied in treatment of fourth nerve palsy. [31] It is a neuromuscular agent that acts presynaptically to block neurotransmitter release and results in muscle weakening. Use of this agent as primary therapy for fourth nerve palsy has been discouraging. However, it may be used best to correct residual deviation after strabismus surgery to delay or avoid further surgery.

BOTOX® is purified botulinum toxin A, derived from a culture of the Hall strain of Clostridium botulinum. It acts by binding to receptor sites on motor nerve terminals and inhibiting the release of acetylcholine. BOTOX® may be used for the treatment of strabismus and blepharospasm in patients 12 years and older. It is pregnancy category C.

Side effects for use in strabismus include ptosis and vertical deviation by action at extraocular muscles close to the site of injection. Injection should be performed under direct visualization during a surgical procedure or with the aid of electromyography.

Each vial of BOTOX® contains 100 units of botulinum toxin A in a vacuum-dried form. It needs to be reconstituted using preservative free 0.9% sodium chloride as the diluent. Doses used in strabismus range from 1.25-5 units, depending on the amount of deviation.

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