The levator-trochlear muscle. A supernumerary orbital structure

Area of Science:

• Ophthalmology
• Anatomy
• Surgical Anatomy

Background:

• Anatomical variations in extraocular muscles are uncommon.
• Understanding orbital anatomy is crucial for ophthalmic surgery and diagnosing strabismus.

Purpose of the Study:

• To describe a supernumerary extraocular muscle identified in human cadaver orbits.
• To propose a name and discuss the potential clinical implications of this muscle.

Main Methods:

• Systematic dissection of 98 human cadaver orbits.
• Gross anatomical examination and description of the supernumerary muscle's origin, insertion, and innervation.

Main Results:

• A supernumerary muscle was identified in 7 out of 98 orbits (7.1%).
• The muscle originated from the medial border of the levator palpebrae superioris.
• It inserted on the fascia near the trochlea and was innervated by the oculomotor nerve.

Conclusions:

• The identified muscle, termed the levator-trochlear muscle, is a distinct anatomical entity.
• This muscle's presence may contribute to the understanding and diagnosis of poorly understood ocular deviations.
• Further research is warranted to elucidate its precise function and clinical significance.