Effect of intrathecal FK506 administration on intraorbital optic nerve crush: an ultrastructural study

Trauma to the optic nerve caused by fractures of the midface and (or) skull base has been simulated by an optic nerve crush injury model. Because the intraorbital segment of the optic nerve is surrounded by subarachnoidal cerebrospinal fluid and dura mater, we aimed to study the influence of intrathecal tacrolimus (FK506) administration after optic nerve crush injury and to determine its role in optic nerve protection or sparing after injury.

Experimental study.

All optic nerves of the animals were included in the study.

A total of 48 female Wistar rats were randomly divided into 4 groups (control, sham operated, FK506 treated, and vehicle treated). In vehicle- and FK506-treated groups, intrathecal catheter implantation and crush injury to the intraorbital part of the optic nerve were performed and then the animals were treated intrathecally. The optic nerve samples were harvested on the 30th postoperative day. Optic nerve appearances were analyzed qualitatively.

Light and electron microscopic evaluations revealed that numerous damaged myelin residues were present in the vehicle-treated group, whereas fibres of the optic nerve showed a well-shaped appearance in the FK506-treated group.

We propose that such an intrathecal administration route and small-dose regimen should be used to obtain lesser immunosuppression and neurotoxicity and higher protection or sparing after injury.