Wilbrand knee.

Area of Science:

• Neuroscience
• Ophthalmology
• Human Anatomy

Background:

• The Wilbrand knee describes inferonasal crossing fibers curving into the contralateral optic nerve after unilateral enucleation.
• This anatomical feature is hypothesized to explain junctional scotomas in optic nerve lesions.
• The Wilbrand knee's existence as a normal anatomical structure is debated, with some suggesting it may be an artifact of enucleation.

Purpose of the Study:

• To investigate the presence and characteristics of the Wilbrand knee in normal human optic chiasms using advanced imaging techniques.
• To determine if the Wilbrand knee is a genuine anatomical structure or an artifact of surgical procedures like enucleation.

Main Methods:

• Utilized the anisotropic light-reflecting properties of myelinated axons for imaging.
• Acquired digital images of thin (25 µm) human optic chiasm sections from three incident angles.
• Employed pseudocoloring (red, green, blue) and image merging to visualize fiber tracts.

Main Results:

• Revealed an anomalously oriented fiber tract that reversed direction at the optic nerve-chiasm junction.
• This tract was observed in inferior sections of the optic chiasm but not in superior sections.
• Findings were consistent with the original description of the Wilbrand knee by Wilbrand and Saenger.

Conclusions:

• The study provides evidence for an anomalous fiber tract at the optic nerve-chiasm junction in normal human anatomy.
• This finding supports the original description of the Wilbrand knee but suggests its potential artifactual nature in prior studies involving enucleation.